Technology Survey Report on Electric Power Systemsdocuments.worldbank.org/curated/en/... · technology's success. The report will serve as a technical update for engineers generally

INDUSTRY AND ENERGY DEPARTMENT WORKING PAPERENERGY SERIES PAPER No. 11

Technology Survey Report onElectric Power Systems

February 1989

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The World Bank Industry and Energy Department, PPR

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TECHNOLOGY SURVEY

ON

ELECTRIC POWER SYSTEMS

by

Lionel 0. BartholdPower Technologies, Inc.Schenectady, New York

FEBRUARY, 1989

Copyright (c) 1989The World Bank1818 H Street, N.W.Washington, DC 20433U.S.A.

This report is one of a series issued by the Industry and Energy Department for theinformation and guidance of Bank staff. The report may not be published or quotedas representing the views of the Bank Group, nor does the Bank Group acceptresponsibility for its accuracy or completeness.

Power Technologies, Inc.

ABSTRACT

This report presents an overview of the status of today's power system technology and expectations

for future development. The report examines all the main areas of the power system -- supply

and demand, generation, energy storage, transmission lines, transmission substations, system

operation, distribution, system design, software, and utility management. Throughout the world

shortage of investment funds is requiring utilities to give greater emphasis to operational

improvements to extend plant life, improve capacity factors and effect energy conservation.

Combined cycle units (gas turbines plus waste heat boiler and steam turbine) are emerging as the

preferred generating source because of their low capital cost and high efficiency, particularly

where gas is available. These units can also be adapted to coal fueling through coal gasification

to minimize using oil as a fuel and to utilize indigenous resources. Increased environmental

concern over conventional coal thermal emissions in many countries is giving impetus to the

development of fluidized bed and coal gasification technologies to permit wider use of coal for

electricity production. Unless economic hydro is available, diesels will continue as the

predominant supply source on small systems up to about 100 MW. Public concern, low oil prices

and high capital cost will limit the use of nuclear power to only a few developing countries. It

will be many years before new technologies such as fuel cells or ocean thermal energy conversion

could be considered for the developing countries. The limit of ac transmission voltages has

levelled off at about 800 kV because dc transmission is available for long distance transmission

and the maximum generating unit size has also levelled off. There is considerable scope for

improving utility productivity through computer automation in specific areas such as generation

dispatch, distribution operation and system control optimization.


TECHNOLOGY SURVEY REPORT

ON

ELECTRIC POWER SYSTEMS

PREFACE

The report was prepared by Power Technologies, Inc. (PTI) ofSchenectady, N.Y. and is therefore based largely on PTI'sexperience, insights and opinions. While the report includes"application-readiness" ranking as well as economic comparisonsfor each technology, generalizing on either subject is risky,particularly when one considers the power of technicalbreakthroughs. Where circumstances make a technologyparticularly interesting, it is better to have the applicationstudied by experts than to reject it based on an arbitraryranking system as used herein.

TABLE OF CONTENTS


TABLE OF CONTENTS

PAGEPREFACE

INTRODUCTION

POWER PRODUCTION & SUPPLY/DEMAND BALANCE . . . . . . . I-l

A. SUPPLY, DEMAND AND TECHNOLOGY DRIVING FORCES . . . 1-l

Conservation ........................ . 1-2Control ..... . . . . . . . . . . . . . . . . . . . . . . 1-6Dispersed Generation .... . . . . . . . . . . . . . . . . . 1-7Environmental Accommodation . . . . . . . . . . . . . . . . . 1-8Expert System Application . . . . . . . . . . . . . . . . . . . 1-9Fast-Valving .1....................... . 1-9Inspection and Maintenance Scheduling .1.. . . . . . . . . . . I-10Life Extension and Plant Betterment .1... . . . . . . . . . . I-10Load Management . . . . . . . . . . . . . . . . . . . . . . I-liPerformance Monitoring . . . . . . . . . . . . . . . . . . . . 1-13Repowering . . . . . . . . . . . . . . . . . . . . . . . . . 1-14Stabilizers . . . . . . . . . . . . . . . . . . . . . . . . . . I- 14Uprating . . . . . . . . . . . . . . . . . . . . . . . . . . I- 17

B. GENERATION TECHNOLOGY OPTIONS, STATUS AND DEVELOPMENT I- 18

Coal Desulphurization and Gasification .... . . . . . . . . . I- 18Combined Cycles . . . . . . . . . . . . . . . . . . . . . . . 1-18Integrated Gasification/Combined-Cycle Power Plants (IGCC). . I-18Pressurized Fluidized Bed Combined Cycle .1.. . . . . . . . . . 1-22Combustion Turbine Plants .1................. . 1-24Gas Turbines .1....................... . 1-24Combined Cycles .1... . . . . . . . . . . . . . . . . . . . 1-28Low Grade Gas Turbine Fuels .1... . . . . . . . . . . . . . 1-28Conventional Steam Power Plants .1... . . . . . . . . . . . . I-29Cycles & Steam Turbine/Generators .1... . . . . . . . . . . . I-30Other Equipment .1... . . . . . . . . . . . . . . . . . . . I-31Diesel Generation . . . . . . . . . . . . . . . . . . . . . . . 1-32Direct Converters . . . . . . . . . . . . . . . . . . . . . . . 1-34Magnetohydrodynamics (MHD) .1............... . I-34Thermionic Generators .1....... ... .. ... .. . . I-36Fluidized Bed Combustion ........ .. .. . . . . . . . 1-37Fuel Cells .1......................... 1-39Fusion, Breeders and Fast Reactors .1... . . . . . . . . . I-45Geothermal Plants .1.......... .... ... ... . 1-46Hydroelectric Plants .1.................... . 1-47

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TABLE OF CONTENTS (continued)

PAGE

Liquid Metal Topping Cycles . . . . . . . . . . . . . . . . . . 1-48Nuclear Power .1... . . . . . . . . . . . . . . . . . . . . 1-49Ocean Current . . . . . . . . . . . . . . . . . . . . . . . . 1-51Ocean Thermal Energy Conversion .-. 5.0. . . . . . . . . . . . I-S0Solar Thermal-Electric Power Plants .1............. . I-51Solar Voltaic ...... .. . . .. . . . . . . . . . . . . . I-52Stirling Engines .... . . . . . . . . . . . . . . . . . . . I-54Tidal Power ...... .. . . .. . . . . . . . . . . . . . 1-55Waste-Burning Plants . . . . . . . . . . . . . . . . . . . . . 1-57Wave Energy Conversion .1.... . . . . . . . . . . . . . . I-56Wind Power .1..... .. . .. . . .. . .. . . .. . . . I-57

II. ENERGY STORAGE . . . . . . . . . . . . . . . . . . . . . II-I

Battery Storage . . . . . . . . . . . . . . . . . . . . . . . . II- ICompressed Air (CAES) .1.1... . . . . . . . . . . . . . . . II-2Pumped Hydro .1.1.... . . .. . . . .. . . .. . . . . . 11-2Superconducting Magnetic Storage Energy System .1.1. . . . . . . II-3

III. TRANSMISSION LINES .1.1.1.-. . . . . . . . . . . . . . . .

Compaction . . . . . . . . . . . . . . . . . . . . . . . . .-Conductors .1.1.1...................... . III-3Cryogenic Transmission .1.1.1.. . . . . . . . . . . . . . . . III-4Electric Fields .1.1.1... . . .. . . . .. . . .. . . . . . III-5Fibre-Optics . . . . . . . . . . . . . . . . . . . . . . . . . III-5High Phase Order (HPO) .1.1.1................ . III-6High Voltage Direct Current (HVDC) .1.1.1. . . . . . . . . . . III-7Inspection and Maintenance .1.1.1. . . . . . . . . . . . . . . III-8Insulators .1.1.1.... . .. . .. . .. . .. .. . .. . . III-9Monitoring Systems ..... i . . . .. . . . . . . . . . . . III- I0Shield Wires for Supply of Local Load . . . . . . . . . . . . . . III- 11Towers and Optimization ..... . . . . . . . . . . . . . . III- 12Ultra High Voltage (UHV) .................. . II11-14Underground Cable . . . . . . . . . . . . . . . . . . . . . . III- 15Uprating Lines and Rights-of-Way .1.1.1. . . . . . . . . . . . 111-17

IV. TRANSMISSION SUBSTATIONS .... . . . . . . . . . . . IV-I

Bus Configuration ..... . . . . . .. . . . . . . . . . . IV- IBuswork .......................... . IV-2

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PAGE

Capacitors ................... ...... . IV-2Gas-Insulated Substations (GIS) ................ . IV-4Grounding and Shielding ....... .. . .. .. . .. . . IV-5Instrument Transformers ................... . IV-5Protective Relays ........... ... ... .... . . IV-5Static Var Systems .......... .. ... ... .. . . IV-6Surge Arresters and BIL Specification ..... . . . . . . . . . IV-7Switchgear ......................... . IV-8Synchronous Condensers ........ .. .. .. . .. .. . IV-8Transformers and Reactors .................. . IV-8

V. SYSTEM OPERATION ........ .. .. .. .. . .. . V-1

Applications Software . . . . . . . . . . . . . . . . . . . . . V- 1Control Center Configuration ................. . V-3Control Software ........... ... ... .... . . V-4SCADA Systems ........... ... ... .... . . V-5Security ......................... . . V-6Training .......................... . V-6Wheeling of Power ......... .. .. .. ... .. . V-7

VI. DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . . . VI- I

Distribution Automation . VI- IDistribution Voltage . VI- IMinimum Cost Rural Distribution. . VI-2Surge Protection . VI-2Switchgear and Switching . VI-3System Configuration. . VI-3Underground Cable . VI-5

VII. SYSTEM DESIGN . . . . . . . . . . . . . . . . . . . . . . VII- I

Dynamic Analysis .. VII-1Fault Analysis.. . VII-2Harmonics .. VII-2Load Flow.. . VII-3Maximizing Transfer Capability.. . VII-3Planning .. VII-4

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PAGE

Production Simulation ............... .... .. . VII-6Subsynchronous Resonance .. VII-7Voltage Instability .... . . . . . ...... . . . . . . . VII-7

VIII. SOFTWARE . . . . . . . . . . . . . . . . . . . . . . . . . VIII- I

Artificial Intelligence . . . . . . . . . . . . . . . . . . . . . VIII- IData Bases .. VIII- IExpert Systems .. VIII-2Hardware Trends .. VIII-2"Product" Status of Software .. VIII-3Structure .. VIII-4

IX. MANAGEMENT & STRATEGIC TOPICS .XI-I

Corporate Modeling .. XI- IDeregulation . . . . . . . . . . . . . . . . . . . . . . . . . XI- IEnergy Modeling .. XI-2Least Cost Planning .. XI-3Maintenance Policies .. XI-3Prioritization and Structured Approaches to Complex Decisions . . . XI-4Privatization .. XI-SProductivity .. XI-6Strategic Planning .. XI-7

REFERENCES

-iv-

SECTION 0

INTRODUCTION


INTRODUCTION

This report is addressed to the engineer generally familiar with power industry

technologies, but not specialized in advanced technical fields. It is intended to

render as realistic and objective an assessment of technology as possible, avoiding

as best it can, the optimism bias that tends to color the reporting done by

researchers specific to a technology or by those with an interested position in a

technology's success. The report will serve as a technical update for engineers

generally familiar with power systems and it will cite, for key technologies and

major equipment categories:

o Current State-of-the-Art

o Research emphasis

o Application readiness

o Economic comparisons

The scope of the study did not provide for an extensive survey of the industry, so

the comments are largely derived from experience, consulting activities, and

software offered by the author's company. References are provided for those

interested in further background.

Each technology or product will be designated as one of the following "readiness'

categories:

A Successfully applied or clearly ready for economic application.

As Economically applicable in special circumstances only.

Ad Applicable following reasonably straightforward development orengineering effort.

P Suitable for experimental or demonstration prototype only

RD Suitable for research or development work

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C Concept only. Needs feasibility study before R&D commitment.

Developing countries often find advanced technologies difficult to apply due to a

weak technical support infrastructure and lack of local manufacturer support. Ir

the case of renewable power resources, for example, the power industry's (or moreaptly, its critics') enthusiasm has waned considerably as a result of very high-cost

demonstration projects, a lack of "breakthroughs," and the downturn in oil prices.

Most such sources, with the notable exception of small hydroelectric plants, were

too costly and too sophisticated for use in developing countries even before the oil

surplus. Lower oil prices suggest even greater caution in recommendation of

renewable options where economic priorities must put low cost energy supply highon the list of national priorities.1

In some cases however, they may be the best beneficiary of new technologies, e.g.

where those technologies accelerate training or protect equipment from misuse o!

lack of maintenance. This report points out where the latter is the case.

It is also important to note that advanced technologies are developed in

industrialized countries and put into application-ready form in accordance with

quality, reliability, and cost criteria appropriate to those countries. Manufacturers

and consultants who apply technology in developing countries, usually transfer it .s

is, without examining the implications a less demanding or more demanding context

have on the shape that technology should take. Many technical advances which a-e

used to improve performance could be used to reduce cost by accepting poorer

performance. Furthermore, equipment is usually designed assuming maintenance

skills and maintenance policies that are unrealistic in developing countries.

Determining the optimal cost/performance balance and the optimum overall energyplan for developing countries is a very complex issue.2 However electricity, in

some form and in some quality is often the key to reversing environmertal

degradation and to the beginnings of economic bootstrapping that will eventually

justify the quality and reliability norms familiar to the industrialized world.

-2-


Application in such countries should emphasize ongoing protection of equipment,training, and economy - the latter recognizing the urgency of near term needs andultimate integration into a more sophisticated system.

-3-

SECTION I

POWER PRODUCTION &SUPPLY/DEMAND BALANCE

Poawer Technologies, Inc.

1. POWER PRODUCTION & SUPPLY/DEMAND BALANCE

A. SUPPLY. DEMAND AND TECHNOLOGY DRIVING FORCES

Rapidly changing factors in the U.S. power generation environment, both business

and natural, are creating pressures which will significantly influence the

development and application of U.S. power generation technologies over the

foreseeable future. Many of these factors are global issues and power technologies

which are developed and applied to meet these requirements in the U.S. and other

developed countries, will be adopted throughout the world.

Utilities are showing continuing interest in operating improvements and in the

areas of: Plant Life Extension, Capacity Factor Improvement (Energy Management &

Interconnection), and Conservation. However, there are inherent constraints in these

approaches which will limit their impact on effective capacity improvements.

The current surplus in worldwide gas and oil production has produced a temporary

sense of relief for clean energy. This attitude has unfortunately slowed the

development emphasis of alternate fuel power technologies. Independent Power

Producers (IPP) tend to favor the low capital cost gas turbine options however,

utilities are hesitant in committing to long term premium energy sources and

demonstration to long term conversion to coal based fuels will be an increasingly

important requirement.

Pressures to deregulate the power generation industry is creating a new industry

entity called Independent Power Producers (IPP) in addition to the cogenerators

brought on by the 1978 PURPA legislation. These IPP envision a significant business

opportunity in providing the design, construction and operation of relatively small,

low cost, project financed generating plants (up to 200 MW). These changes are

occurring at a time when existing long range plans for capacity additions may be

insufficient to meet the unexpected higher load growth now being experienced in

the U.S. and many other countries.

-I-1 -


IPP are forecast to gain a major portion of new generating capacity over the

foreseeable future. The emphasis for these power suppliers will be on low risk,

demonstrated power technologies which can be reliably and economically applied at

smaller plant sizes. Primary near term candidate technologies are gas turbine

combined cycles, with coal gasification or coal derived synthetic fuels for future

fuel flexibility, and coal fueled fluidized bed boilers with conventional steam turbine

cycles.

Increasing concerns over the environmental impact of generation emissions and plant

siting are creating additional pressures which will also influence power technology

development trends. Emphasis on the development and application of higher

efficiency power cycles is likely to be the near trends in addressing this issue and

in reducing the rate of global heating due to CO2 production. Pressure to reduce

NO., SO2 and CO emission limits is growing, and is forecast to increase.

Although currently stagnated by public opposition, the disposal of municipal solid

waste by incineration and energy recovery is forecast to be a significant factor in

power generation by the late 1990's.

The following discussion on technologies must be viewed and assessed in light of

this background of market forces and uncertainty.

Conservation' [A]

Energy conservation is superficially regarded as a direct offset to the addition of

new generation capacity or fuel consumption, and, particularly for the most easily

achieved conservation options, a more economic alternative.

The cost and effectiveness of conservation initiatives involve major uncertainties.

Regional differences are important, as are program details. See Figures I-1 and 1-2.

-I-2-

Power Technologies, Inc.2.7

4.000 - so-w wm *wsf - MCW _ " 2.4

M _ kWhsv | _ 2.1

°kW savs

3,000 _ _ 1.8

3u000 I- 11

t 09

1,000 0

Figure I-2. Air Conditioner Demand and Energy Savings as a Result ofElcrcUtility Promotion of Energy-Efficient Units Vary Significantly

Among Utilities. (Source: Electrical World, August 1983, p.85)

1,200 -WaIWAGOWes .Mwg uas,m

1.000

I~~~~~~I3

Figure 1-2. Benefits of Electric-Water-Heater Conservation to a Utilityare a Function of Technology. (Source: Electrical World, August 1983,p.86)


Economic analyses of conservation options are difficult. It is often an

oversimplification to view conservation as negative generation. For example, the

Philadelphia Electric Company (peak demand: 6500 MW) studied eight conservation

programs:

A. "House doctor" thermal rebates

B. Commercial lighting rebates

C. High-efficiency motor rebates

D. Refrigerator rebates

E. Central air conditioner rebates

F. Room air conditioner rebates

G. Mail order conservation services

H. Third-party megawatt contracting

Figure 1-3 shows that most appear attractive on a utility investment-per-kW basis.

But Figure 1-4 shows that the overall effect of all of them is to raise average

electricity costs.

PeakReduction 240 + E

24.0 +(MW) -

16.0 +

8.0 _ A- C

-H

°-°~ + -+_+ G +++F

0 350 700 1050 1400 1750

Utility Investment (S /kW)

Figure I-3. Peak MW Reduction and Utility Investment for EightConservation Programs (Data Source: Philadelphia Electric Co. "IntegratedResource Plan")

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PeakReduction 24.0 E B

(MW) 240

16.0 +

8.0 + AC

H

0.0+ G ° F

0.00080 0.00160 0.00240 0.00320 0.00400 0.00480

Reserve Requirements Increase (¢/kWh)

Figure 1-4. Peak MW Reduction and Revenue Requirement Increase forEight Conservation Programs. (Data Source: Philadelphia Electric Co.,"Integrated Resource Plan")

Among the most highly leveraged conservation programs are:

o Thermal insulation campaigns to reduce both heating and coolinglosses, where both involve significant electrical consumption.

o Time-of-day metering, penalizing use at peak periods.

O Demand-limiting controls for commercial and industrial facilities.

O Replacement or upgrading of energy intensive industrial processes.

Conservation must always be viewed in its broadest context since increased use of

one energy form may result in a net saving in total energy or in a particularly

scarce fuel. Automation of processes, for example, may actually increase electrical

use but reduce total fuel consumption significantly.

( See also "Load Management")

-I-5-


Control . 7. 8 [A]

Power plant control represents a highly leveraged investment in plant economy,

security, and life-extension. It remains a rapidly evolving technology.

New and retrofit controls are now all digital, distributed processing systems. The

reliability of digital controls is so high that it is feasible to make the entire plant

operation dependent on control functioning. However just as early automobiles were

designed as "horseless carriages," most commercial digital controls simply replicate

their analog predecessors. The real potential of digital systems is just beginning to

be tapped. Among the new functions that digital controls allow are:

o Thermal simulation of turbines, boilers and auxiliaries either tocontrol start-up and shut-down or impose limits on operator-initiatedactions, to minimize the risk of damage.

o Simulation of the combustion process as an aid in optimizingoperating variables such as excess air, temperatures and pressures.

O Optimum start-up and shut-down logic for pulverizers, boiler feedpumps, fans, etc.

o Performance monitoring of plant components, including analysis ofperformance data and maintenance recommendations.

o Simulation of turbines and boilers, initially for precommissioningcheckout of controls and later for operator training. Checkoutsimulators allow replication of emergencies that would not be a partof shakedown in full-scale plant tests. They also speed up plantcommissioning.

o Increased use of automation augmented by expert system application.

These extensions to control functions represent logical, cost-effective enhancements

to the "stripped down" controls which unfortunately resulted from an intensely

competitive power plant market. They also represent a good example of where

developing countries have a greater need for "stretch" technology than industrialized

countries. In the latter, skilled and experienced operators plus a well estahlislL;d

maintenance infrastructure already assure reasonable care and support of fJIan

-I-6-


equipment. In developing countries plants are more apt to be misoperated, incipientproblems less likely to be detected, and maintenance more difficult. Thus theinherent power of digital control and automation should be used to the fullest toguide operation and protect equipment.

Fibre-optics are increasingly popular in plant control communication. They arerugged and virtually insensitive to noise which often plagues electrical controlwiring in plants.

Disnersed Generations [A]

"Dispersed' generation refers here to a variety of power plants, usually in the rangeof a few kW to hundreds of MW, not necessarily owned by a conventional utility,but connected to the utility network at the subtransmission or distribution level.This includes installations which make use of waste heat or steam produced in thegeneration process (cogeneration). Cogeneration may offer efficient use of scarcefuel in many countries.

Dispersed plants have become increasingly popular for a variety of reasons,including the economies sometimes achieved through combining generation with theindustrial processes, and laws which require utilities to purchase excess power atrates favorable to the seller.

The trend is encouraged by emphasis on deregulation, i.e. the concept that anyorganization should be free to build and operate power generating facilities,competing with the utility and others to supply load.

Dispersed generation need not involve any new power generation technology. Itdoes, however, involve new challenges at the system and institutional levelincluding:

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O Adapting a transmission network to an unknown pattern ofgeneration, considering transmission line thermal capability, stability,and protective relay coordination.

o Operation of a system where some of the generation is not undercentral control.

o Providing reliable back-up to generation which is neither plannednor controlled centrally.

o Anticipating and providing for system effects inherent in somedispersed generation, e.g. harmonic generation, and reactive powerdemands.

o Accommodation of safety problems inherent in some remotegeneration sites.

Most experts consider the further development of independent generating plantsinevitable, encouraged in part by the difficulty in gaining approval for conventionalutility plants. However, any country adopting a policy that encourages dispersedgeneration should thoroughly study the system challenges inherent in that policy,particularly the need for close communication and cooperation between independentgenerators of power and the utility system to which that generation is connected.

(See also "Wheeling'" in Section V.)

Environmental Accommodation [A]

Electrostatic precipitators and baghouses are commonly used for removal ofparticulate matters from fuel gases. Most utilities prefer precipitators except wherespace is at a premium.

"Scrubbers," using limestone to remove sulphur-dioxide from flue gas, are nowuniversally applied to coal-fired plants in industrialized countries. They increasethe equipment first cost of a plant by about $150-250/kW, almost double the plantmaintenance cost, increase the heat rate, and will reduce availability somewhat.

Scrubbers also use a great deal of water - up to 1 gallon per minute per MW.

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?odwcw Technologles, Inc.

TEilese disadvantages weigh against application of scrubbers in developing countries

JJ zere environmental priorities suggest better application of financial resources.

Nitrous oxides (NO.) are not affected by scrubbers and can best be controlled by

bur ners which minimize excess air. However thermal nitrogen fixation by ammoni

i..jection is another technology gaining industrial application popularity.

Cooling towers, either natural or forced draft, have changed very little. They are

of en called for in developed countries through concern over heating rivers or

lakes, and in developing countries simply for want of adequate cooling water.

(See "Conservation")

ExDert System ADDilcatlon [PI

Expert Systems, now in the prototype stage, have been developed to improve plant

performance, enhance operational safety and supplement equipment maintenance.

This capability may be particularly important in developing countries where

operating and maintenance expertise is not generally available. Expert system

applications include:

o automated analysis of equipment performance trends to identifyand/or implement changes to operating procedures to improveperformance

o identify longer term maintenance requirements and timing

o alarm diagnostics for safe operator reactions

o sequence of event analysis and resolution.

Fast-Valvinll [A,,]

Generators are deliberately tripped on some systems to preserve stability. As an

alternative, output on reheat units can be cut very quickly by intercept or bypas

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valve operation. Fast-valving is not widely used, though many plants are capable of

applying it.

Insvection and Maintenance Scheduling [Al

Performance monitoring and inspection during overhaul are increasingly important

inputs in establishing what maintenance needs to be done. Newly introduced

performance monitoring systems, designed for retrofitting as well as for new plants,

warn of individual plant component degradation. Once maintenance is undertaken,

modern inspection procedures correct operating practices and establish the timing of

future maintenance work.

Once maintenance needs are known, either to restore efficiency or avert possible

breakdown, maintenance scheduling software is increasingly used to optimize the use

of down-time and to evaluate the economic trade-off between maintenance cost and

improved efficiency.

Life Extension and Plant Betterment3 [A.]

Power plant life extension and plant betterment programs have been encouraged by

the dearth of new plant construction in industrialized countries. Experience gained

through such efforts, while still very limited, will be very useful to countries the

world over.

Older, less efficient plants are often relegated to cyclical operation, thereby

increasing wear and the need for refurbishment. Life extension amounts to (I)

increasing reliability and longevity of aging components and (2) improving

efficiency to bring old plants back to economic usefulness. Many fossil-fired plants

built in the 1950's, for example, can be refurbished for costs in the range of $200

to $400 per kW, increasing efficiency by as much as 10% in the process.

-I-10-


Life extension and betterment efforts generally consist of the following steps:

1. Performance tests to determine the current status of all equipmentand instrumentation.

2. Specification of a "Design Change Package" (DCP) addressing bothequipment changeout or rebuild and improvements in operatingprocedures.

3. Implementation of changes, testing, and recommissioning.

Steps I and 2 represent major efforts in their own right, ranging from thorough

inspection and test of plant components, to consideration of system level objectives,

such as operational coordination with existing capacity, maintenance scheduling,availability estimates, etc.

Recommended improvements may range from lubricating system replacement toreplacement of such major components as turbine rotors. Virtually all projects

include modernization of controls and monitoring systems.

Despite the limited experience with life extension programs, they should beconsidered a viable alternative where new construction can be postponed or

eliminated. Success is heavily contingent on the thoroughness of steps 1 and 2 cited

above, specifically on the recognition of all limitations to existing performance andlongevity.

(See also 'Performance Monitoring" and "Repowering")

Load Manaeement5 [A]

While efforts to control loads by economic incentives or direct controls go back to

the 1930's, intensive studies began relatively recently.

Shifting load from peaks to valleys, or simply shaving the peak, is very effective in

deferring capacity additions and in transferring load from high cost, inefficient

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peaking generation to economic, base load units. While each country's load pattern

is different, utilities usually find that residential load (heating, air conditioning, and

water heaters) represent the best aggregate opportunity for load control, but the

most complex to implement due to the large number of small control points.

Adjustable commercial and industrial load, while smaller contributors to overall

load swings, are larger, easier, and more often implemented targets of load

management systems.

For example, Figure 1-5 shows the effects of an aggressively-marketed storage

heater program on the winter daily load curve of a West German utility.

900

Hamburg Electric Works Daily Load Curve - Typical January Day

Figure I-5. Impact of Storage Heating

-I- 12-


However time-of-day rates have not always had the desired effect on consumption

patterns. This has made evident the importance of understanding consumer

response. In some developing countries availability and cost of meters suitable for

time-of-day charging is a barrier.

Less than 1% of U.S. load is controlled for peak-leveling purposes. Most of present

control is "direct," i.e., controlled by the utility without customer action. The least

common is "local control," (controlled at the customer side of the meter with no

utility intervention), and intermediate in popularity are "distributed controls,"

(controlled with inputs from both). Radio is the most common communication

medium, though power-line carrier (PLC), telephone, and cable TV circuits have also

been tried.

Load management is a very important option for any country with capacity

limitations or high peaking energy costs - if it has significant controllable loads. It

should not be undertaken without thorough understanding of customer response and

of system issues ranging from the effect on maintenance scheduling to adequacy of

and access to communication links.

(See "Conservation")

Performance Monitoriny [A]

The need for accurate and timely monitoring of power plant performance is driven

by higher fuel prices and the need to keep older plants in useful service.

Component monitoring permits the plant operator to:

o Identify controllable operating problems and ensure efficientoperation.

o Use component performance as a guide to maintenance planning.

O Compare component performance with guarantees.

-I-13-

Fower Technologies, Inc.

O Develop meaningful incremental production costs to aid in systemeconomic dispatch.

Modern plant performance monitoring systems include a comprehensive set of

performance calculations. They supplement and work in parallel with power plant

operating computer systems. Calculated performance indices and warnings of

substandard operation are sent to the plant's computer system for display or alarm.

While a relatively new technology, monitoring systems should be considerce for

plants in developing countries where extending life and identifying the need for

maintenance or incipient equipment damage is unusually important.

(See "Life Extension" and "Plant Betterment")

Rgowerina [Al

'Repowering" involves replacing the fuel-handling and boiler systems of a steam

turbine with a gas turbine and Heat Recovery Steam Generators to fet!rm a

combined cycle plant. Candidates for repowering projects are usually non reheat

units in the range of 100 MW. Repowering improves heat rate and cepacity

substantially. The technology is mature, so this option should be care'Aly

considered where candidate plants exist. The repowering of existing boiler/-! tam

turbine plants with supplementary fire gas turbines can also be a viable power

option.

(See also "Combined Cycle" and "Life Extension.")

Stabllzers16, 17 [A]

Low frequency oscillations with periods of one to three seconds may de"'elop

between machine groups on systems where electrical distance is long for the pc ;ver

-I-14-


being transmitted. Those oscillations in active and reactive power, and voltage may

be sustained or growing leading to what is know as dynamic instability.

This problem has long been mitigated with the use of "stabilizers" providing

supplementary inputs to the excitation systems of the problem generators.

Virtually all generator manufacturers supply stabilizers designed for their particular

excitation systems. Tuning and maintaining analog type stabilizers has been a

problem. If detuned they can make oscillations worse. That prospect, in fact, has

led some utilities to leave stabilizers disconnected.

Within the past several years digital, microprocessor base stabilizers have been

introduced using standard voltage and current inputs thus making them suitable to

any type of excitation system. The new generation of stabilizers does not need

retuning with system changes and is simpler to maintain.

Stabilizers are important adjuncts to systems which are subject to dynamic

instability, as is often the case with the 'stretched" state of systems in developing

countries. They provide the least expensive means of increasing transmission

capability in systems limited by dynamic stability.

-I-1S-


I~~~ ~ ~ ~~~~~~~~~ , I ISetacted Top Ratio

Oulput of Shp Algorithm

GENERATOR POWER OUTPUT

NoSlFbills r

0 1.0 2.0 3.0 4.0 5.0

TIME tsECO.OSI

Figure 1-6. Effect of Power System Stabilizer on Dynamic Stability

Figure I-7 is an example of the effectiveness of supplementary stabilizing through

excitation control.

0O REItat'l machin angle s.,ngs follo. 3m short Circb n

Mai uJ bUof tramums on circuit

10 Srlem u dbil al iONtumbers on cu,,,es id*nV)r the ma:hints.

0

.30

-tiO

0 TIME SEQTESCE30 Relati,,i macbice mngt swinp for sume dislurbanct.

20 System usumei to ts,* stali: exciulion *yulems

10 LDd stabilizers on xal units

10

-I-16-


UDratinz [A]

There are some opportunities where replacement of turbine steam path components

will result in increased power output. This results from the increased efficiency of

the new parts. As an example, a majof U.S. turbine manufacturer has a replacement

last stage which will improve performance by 1.2%. This must result in increased

output of the same amount. This can only be realized if the units generator has the

capability of the increased power.

Uprating can be accomplished in other ways depending on the original constraint on

the maximum output of a unit. Design of a unit should be based on the turbine-

generator as the limiting factor. Many units built in the 1950's had excessive

capacity margin in the turbine generators. This resulted in other plant components

being the output limiting factor. Replacement of limiting auxiliaries can often

provide unit uprating.

-I- 17-


B. GENERATION TECHNOLOGY OPTIONS, STATUS AND DEVELOPMENT

Coal Desulphurization and Gasification4 [Ad]

The high costs for the treatment or removal of SO2, NO. and particulate matter

from flue gas with commercial systems creates a financial incentive for technologies

which can mitigate these effects. Coal desulphurization by acid leaching, catalytic

and noncatalytic nitrogen fixation, and many other techniques are being developed

and used.

The entrained gasification concept being developed by Texaco, Shell, Dow, and

others, is receiving the highest priorities. Gasification systems with capacities over

1000 tons per day and used in commercial service have been in operation for several

years.

Coal gasification is a key technology in the future use of fossil fuels for power

generation. In addition to the ability to "deep clean" the fuel gas, gasification

provides a valuable synthesis gas which can be utilized as a chemical feedstock for

a wide variety of petrochemical products. These products include clean synthetic

fossil fuels from coal, such as methanol and synthetic oils. Gasification may also

play a major role in reducing fossil fuel combustion C0 2 emissions since the fuel

gas may be shifted and the concentrated CO2 chemically removed to produce a

hydrogen fuel.

Combined Cycles

Integrated Gasification/Combined-Cycle Power Plants (IGCC)3' 4 [Ad]

Combining Gasification with a Combined-Cycle plant provides additional efficiency

opportunities by integrating process waste heat in the cycle. Coal gasification is a

particularly promising concept since contaminants are concentrated in high pressure,

-1-18-


low gas volume flows which can be economically treated to high degrees of

cleanliness. The resulting clean fuel is ideal for application in large advanced gasand steam turbine combined cycles with efficiencies of 40%.

Air blown gasifiers produce a low-Btu fuel gas from the reaction of coal, steam, and

air. An intermediate-Btu gas results when oxygen is used in place of air. Combined

cycle gasifiers would operate at high pressure to produce a fuel gas adaptable togas turbine firing after appropriate cleanup to remove particulates, sulphur andother deleterious components. Steam is also produced in the gas cooling process and

can be integrated with the combined cycle steam system. Figure 1-8 presents aschematic and sample heat balance for such a gasifier used in conjunction with agas turbine and condensing steam turbine combined cycle power plant. Thisconfiguration is similar to the 100 MW Coolwater Demonstration project, utilizingthe Texaco entrained gasifier, which has been operating since 1984.

-I-19-


LOSSES

13 UNITS

HHV COAL.WATER GASIfiER S UNITS100 UNItS LAND up

E LAN-U OXYG EN LOSSES4 UNItS , Y SS UNITS (AUXILIAR IES)

O UNITS POWER

LOSSES OXY GE

13 UNITSi8 UPNITSr

Fuel: Coal

Variables: Process TemperatureSteam Turbine Exhaust Pressure

Range: 80 MW - 500 MW

Advanced Art Gasifier, Gas Cleanup, Gas TurbineSystem Integration

Figure I-8. Integrated Gasifier-Gas Turbine

-1-20-


The progressive generation concept whereby combined cycle plants, initially installed

and operated on natural gas or oil, can be refuelled with clean coal gas when the

fuel supply economics warrant is an attractive power generation expansion conceptwhich is being utilized to obtain natural gas permits for these plants.

The major advantages of IGCC are:

- High efficiency (35% to 40%, including gasification)

- Capability to attain very low levels of SO2 and particular emissions

- Solid wastes only 40% of a pulverized coal plant, 25% of an AFBCplant

- Capable of phased construction

- Uses coal.

- Uses only 50% of the water requirement of a conventional steamplant with cooling towers.

Disadvantages include:

- Costs are comparable to conventional coal 1,500$/kW

- Complexity

- Limited operating experience

- Land area required (300 - 600 acres for 500 MWe)

- Large water requirement.

Since none of the IGCC technologies are particularly new or exotic, all have been

tried in service, and prototype IGCC operating experience has been favorable, IGCC

plants should be considered a viable current alternative, particularly where water

and land area are not limitations, where coal is plentiful, where staged investment

is desirable, and where environmental compatibility is important.

-1-21-


Pressurized Fluidized Bed Combined Cycle [A.]

A second means of utilizing coal for a gas turbine system is the pressurized

fluidized bed system illustrated in Figure 1-9. The gas turbine functions as a

supercharger pressurizing the PFB and supplying all of its air for coal combustion.

The gas turbine expands the combustion gases from 17000 F to 9150 F. The PFB bed

temperature is held at 17500 F by the simultaneous combustion of coal and heat

transfer to inbed steam generating tubes. Dolomite fed into the bed captures the

sulphur from the coal. American Electric Power is constructing a 70 MW

demonstration plant utilizing this concept which should be in operation by 1990.

Configurations of the PFB with high temperature air-cooled imbedded tubes are

presently uneconomical since high alloy tube materials are required that would

greatly increase the cost as compared to steam generation.

Improvement to cycle heat rate is marginal (one or two points) due to the relatively

small amount of gas turbine topping power as compared with other combined cycle

approaches.

-1-22-


75% 1460 P, 100M f W

lOOY; 1750 F 11% fEEDWATER t I E _6 OE

COAL Avance Ar FB asceau

MODULE 17090F

600 Ff~ CYCLONESI 0% -10 °%

AIR 600 F' 4~49%e STACK +

AIR \13% i/GS OTHERCOM IN 9% POW ER LOSSES

Fuel: Coal

Variables: Process Temperature,Steam Turbine Exhaust Pressure

Range: 13 MW - 600 MW

Advanced Art PFB, Gas cleanup

Availability: 1 990

Figure I-9. Pressurized Fluidized Bed

Advanced development includes the PFB and the gas cleanup or gas turbine erosion

protection means. System integration and control would also require development.

-1-23-


Combustion Turbine Plants

Gas TurbInesl 2 13 [A]

The gas turbine is a thermally versatile component which may be installed in a

variety of configurations to satisfy both power and, for cogeneration applications,

process heat requirements. Each configuration has a distinct efficiency and output

characteristic, and depends on the base firing temperature and pressure ratio of the

gas turbine under consideration as can be noted in Figures 1- 10 and 1-11.

In each example, the fuel higher heating value (HHV) is counted as 100 units. A

latent heat loss of 6 units (oil), is deducted at the combustor. Regeneration

improves cycle efficiency by exhaust heat recovery with compressor discharge as

compared to the simple cycle. The steam injection gas turbine (STIG) increases its

power and efficiency by the expansion of steam through the turbine, but reduces

the process heat available. In the combined cycle shown, the HRSG produces steam

at a pressure and temperature appropriate for expansion through a steam turbine for

process use. A condensing steam turbine would increase power output by 15 units as

compared to 10 for a noncondensing cycle.

-I-24-


HHV FUEL 8 UNITS AIR 0 UNITS POWER100 UNITS LATENT POWER X 36 UNITS

48 ITSS L 1 UNIGASTURBINE ERA-

GE REGENERATIVERCENRTo~~~~~~~~~~O

UNITS LOSS

AIR ~ ~ 6 U NT OE 2UISFO A UBN

LOSS ~ ~ ~ ~ ILATIENT 1 UNIT

33UITS 1 NT

AIR 0 UNITS 1 UN

PROCESS HRSG LOSS

5 UNIS t NITSLOSS UN|10INIT

HEAT 1 UNIT HHV48 UNITS

T7 UNIT S ....

IMCYLE STACK LOSS LOSS 36 UNITSCYCLE I3UN7T4 HSGI UNITS 1I UNo. PROCESSSTEAM SYSTEM 3UHNEAT

Figure IREGENERATIVE CYCLE

STACK LOSS20 UNITS

AIR 0 UNITS ~~POWER 82 UNITS FROM GAS TURBINE

TOR 1UNIT.*..HRSG42 UNITS

83 ~~~~~~~~~POWER6 UNITS UNITS LOSS ~ ~ ~ ~ ~ ~ 0 UIT

23 UNITS HHV FUEL ~~~~STACK LOSS

21 UNITS I~gUNIS ENRA

STEAM~~~~~~~~~~STA

INJECTED ~~~~~~~~~~~~~~LOSSSTACK LOSS GAS TURBINE 1 UNITCYCLE 37 UNITS COMBINED CYC'LE1 PROCESS

H EATSTEAM SYSTEM 31 IUNITS

Figure I- 10. Gas Turbine Configurations

-I-25-


Using clean fuels, the total temperature at the first stage would be 23000 F for

advanced air-cooled units and could rise to 26000 F for advanced water-cooled

units. Current state-of-the-art gas turbines operate at about 18500 F firing residual

oil and 20500 F firing distillate oils or natural gas fuels.

Simple cycle and STIG combustion turbines are an attractive option for peaking duty

on most systems. Maximum rating will probably stabilize at 150 MW. Gas turbine

technology is advancing at a rapid pace relative to the conventional steam plant

cycle. Units operating at 2300°F will be going into commercial operation starting

in 1989. Cycle options such as regeneration, gas reheat and compressor

intercooling, offer further improvements to heat rate but their cost and

complication make the approach of increased turbine firing temperature and

application of advanced steam reheat cycles for combined cycles, the preferred

concept.

Research in gas turbines includes the following:

o Increasing efficiency by raising first stage firing temperatures fromtoday's practice of beyond 23000 F by cooling the first stage withair bled from the compressor.

o Dry combustion development to achieve lower Nox and CO emissionswithout steam or water injection.

O High temperature materials and coating technology development toallow use of wider range of fuels and higher firing temperatures.

-I-26-


42 - ,i~ STIG 15%SSH/,./ AC ZKX0F

4oL /STIG 10% SN

f 12 AC 22000!12

10 Tp 10 14

12 16tc AC 14

EUIS &11is I IsSTIG 10% SATRC WC p , AC220001

36 ~~~~14 AS 1212 1 12 1C

16~~~~1

z~ ~~~~h *I' o10P 7 c SMPXY2'34L 1

|C AC 2HCOO- s - 222000!A 12

M. RC WC32 BASIE ~ 12 26000!

tO 10 10F I 20000C SC SIMPLE CYCLE

3 0~7S0 AC AIR COOLEDWC WfATER COOLED

SC AC (NO HASG) RC REGENERATIVE CYCLESTIG STtAM INJIEC "ED CYCLE

S ~~~~SN SUPERHSATED STEAMSC AC SAT SATURATED STEAM'

28 ~~~~2200011

a REGENERATOR IFF!CTIVINFSS

22' 700 120 140 160 .,0 =!0

SPIECIFIC CUTP1UT KWV L3hlSEC;

Figure I- lI

Gas Turbine Performance Map

-1-27-


Combined Cycles3 [A]

A steam turbine cycle can make use of a gas turbine's waste heat, in a "topping

cycle" arrangement, and currently achieve heat rates below 7800 Btu/kWhr (HHV)

at full load.

Combined cycle plants incorporating 150 MW advanced gas turbines are commercially

offered at heat rates below 7500 Btu/kWHR. These plants incorporate factory

assembled module components and have low installed cost. Because of gas turbine

modularity and ability to control air flow, low heat rates can be maintained across

most of the load range for larger plants.

Combined cycle plants can be built in stages, the steam system being postponed

until the extra capacity is needed. Combined cycles represent a mature technology

which should be considered seriously where new low cost capacity additions are

required and gas and liquid fuels are available.

Low Grade Gas Turbine Fuels [A]

Crude oil, residual, and some distillates contain corrosive components and as such

require fuel treatment equipment. In addition, ash deposits from these fuels result

in gas turbine deratings of up to 15%. They may still be economically attractive

fuels however, particularly in combined-cycled plants.

Sodium and potassium are removed from residual, crude and heavy distillates by a

water washing procedure. A simpler and less expensive purification system will do

the same job for light crude and light distillates. A magnesium additive system may

also be needed to reduce the corrosive effects if vanadium is present.

"Higher Heating Values - see "Gas Turbines."

-I-28-


Fuels requiring such treatment must have a separate fuel-treatment plant and a

system of accurate fuel monitoring to assure reliable, low-maintenance operation of

gas turbines.

Research continues on the direct use of micronized coal, however there does not

appear to be any concept which would result in a successful breakthrough with this

technology.

Conventional Steam Power Plants1 0 [A]

Coal, oil, and gas-burning conventional power plants continue to be the mainstay

capacity additions for most countries. Fossil-fired plants are designed both for

base-load and cycling duty.

Steam pressures and temperatures peaked about 1960 in the U.S. at 5,500 psi and

1 200°F, respectively. Both overstretched the technology and caused serious

availability problems. Pressures for supercritical units retrenched to 3,500 psi,

10500 F but the "advanced coal-fired power plant," resulting from a major EPRI

study, calls for 4,500 psi and double reheat, anticipating full-load heat rates

approaching 8,000 BTU/kWhr. Steam temperatures for this design will be 1050°F.

The cost of new coal-fired plants will range from $1,500 to $2,000 per kW

installed, depending on location, size and, more specifically, environmental

compatibility requirements.

For pulverized coal plants up to 15% of the cost goes for pollution controls where

environmental restrictions limit air discharges and where low sulphur coal is

unavailable. Heat rates for modern plants are in the order of 9,000 Btu/kWhr.

Typical plants require I acre of land per MW of capacity.

New Oil and Gas-fired plants will likely incorporate combined cycles, but with some

reluctance due to fuel costs and fuel supply uncertainty.

-I-29-


Cycles & Steam Turbine/Generators 18 [A]

Steam turbine development slowed considerably in the mid 1970's due to world

energy supply concerns and subsequent recession. U.S. load growth dropped from its

historic 7%/year level to less than 2%/year, leaving a drought in new U.S. plant

orders. In addition, the heavy focus on nuclear generation in the late 1960's and

early 1970's shifted large steam turbine development away from large turbines with

advanced steam conditions to large nuclear turbines operating under saturated steam

conditions.

Current focus in steam turbine activity is on performance upgrading of existing

units and the supply of relatively small state-of-the-art units for combined cycle

and cogeneration applications.

Reduced load growth and the anticipated increase in power supplied by cogenerators

and independent producers in the U.S., indicates that in the near term U.S. power

plants will incorporate smaller steam turbine units (eg. 200 MW) with no more than

state-of-the-art reheat steam conditions, (eg. 24000F/1000 0F/1000 0F).

With the current world concerns toward nuclear based power, and the long term

availability of oil and gas fuel, there is likely to be some continued emphasis on

larger more efficient coal power plants, incorporating advanced steam conditions.

Major world equipment manufacturers continue to explore material development,

turbine and plant designs for advanced steam cycles. A 700 MW double reheat

supercritical cycle is currently under construction by the Chubu Electric Power Co.

in Japan. Further improvements to Rankine Cycle efficiency will be marginal. If

sufficient growth in coal based generation develops there will be renewed incentive

for large steam turbines incorporating advanced steam conditions if such plants can

demonstrate economy of scale with advanced technology.

-I-30-


Generator technology has remained reasonably stable over the past decade. Stators

on large machines are water-cooled, whereas hydrogen cooling of rotors is

commonplace. Water-cooling of rotors has been used in China, but is not likely to

be applied by western manufacturers.

The escalation in generator unit size foreseen in the early 1960's, while proven

unrealistic in retrospect, led to interest in cryogenic generators. It was argued

that their losses would be lower, their size smaller, and their electrical

characteristics more apt to keep systems electrically stable. Research was terminated

in the U.S., largely due to the realization that generators were already highly

efficient, that units were getting smaller rather than larger, and that the stability

advantage was probably not worth complexity and reliability issues introduced by

cryogenic cooling equipment.

Development of advanced technology generators has virtually stopped. Current sizes

with hydrogen and water cooling appear suitable for units in the foreseeable future.

Higher temperature cryogenic technology may revive advanced development in the

next decade.

Other Equigment [A]

Power plant auxiliary equipment has not changed substantially over the past decade.

However utilities now undertake more careful risk analysis to determine the degree

of redundancy or overrating. Industrialized countries, where system reliability is

critical, generally minimize the chance that plant output will be lost or curtailed

due to the failure of one pulverizer, boiler feed pump, etc. Developing countries,

while perhaps more tolerant of down time, may have an even greater incentive for

redundancy due to long repair cycles.

Probably the most important technical change in auxiliaries is the introduction of

electronics for variable speed operation of AC induction motors. This has made

-I-31-


drives for fans and pumps more reliable by substituting speed control for motor-

operated hydraulic valves and fluid couplings. Retrofitting forced and induced-draft

fans on boilers, for example, allows better flow control and minimizes the risk of

boiler "implosions," following inadvertent fuel cut-off.

Boiler manufacturers are now working on two-stage pulverizers to produce

"micronized' coal, recognizing that the finer coal means less ash, greater

efficiency, due to lower excess air requirements and more complete coal combustion,

and fewer particulates in the flue gas. This work is largely developmental and most

suitable for industrialized countries.

Diesel Generation 9 [A]

Slow speed (450 rpm) diesel engines burning residual oil are typical of larger power

installations. The diesel has had a substantial growth in power output by increased

supercharging and aggregating up to twenty cylinder configurations up to 40 MW.

Diesel advancement has been evolutionary which is expected to continue. Higher

supercharge with intercooling, and charge air cooling, could permit up to 50 percent

increase in power output per cylinder. Truly revolutionary steps, such as the

adiabatic diesel with ceramic parts or the slow speed coal-burning diesel, will

require prolonged development to meet the standards of diesel reliability and low

maintenance expense. These latter are considered to be a generation beyond the

advanced diesels that will be ready for commercial application before 2000.

Figure 1-12 presents a heat balance schematic for the diesel engine. The advanced

diesel efficiency is only slightly higher than state-of-the-art diesels.

-I-32-


PROCESS HEAT6 UNITS

INPUT PROCESS HEAT_ ~~100 UNITS 25 UNQITS

115" *ts135*F 39 UNITS , STACK LOSS

AIR COOLER DIESEL 9 300 F0 UNIT S |I o | >L ISE 0' 37 UNITS ELECTRIC

* | _ ~~OTHER230'F _2500 F LOSSES

4 UNITS

14 UNITSPROCESS HEAT

Fuels: Residual (Distillate)

Variable: T Process2 MW to 15 MW

Advanced Art: Higher Supercharge2500 F Jacket CoolantGreater Efficiency

Figure I-12. Diesel Cogenerator

-I-33-


Diesel Generators, remain a reliable, low initial cost, short term power source.

These advantages are bought at the cost of use of restricted types of fuel and

relatively high maintenance requirements.

The maturity, modularity and simplicity of field installation makes diesel technology

a predominant choice for small remote systems of 100 MW or less.

The medium speed diesel efficiency is comparable to modern gas turbines but are

limited to much lower combined cycle efficiencies. Diesel waste heat may be used

for hot water, space heating, etc.

Diesel generators play an important role as local reserve, particularly where the

transmission tie is radial or of margin reliability for other reasons.

Direct Converters

Maunetohydrodvnamics (MHD) [P]

Figure I- 13 is a schematic for a coal fired Open Magnetohydrodynamic (MHD) cycle.

There are variation of this cycle including closed inert gas and liquid metal. This

concept offers the potential of efficiencies of 50% when combined with a Rankine

Cycle power plant. Although MHD has received considerable support for many years

and prototype experiments of key components such as the MHD generator channel,

continue at MW scale, the practical achievement of a reliable large commercial

design is many years away. The obvious complexity of this concept questions the

overall power cost and reliability of such an approach. Gas turbine cycle "topping"

approaches which simplify the configuration and improve potential reliability, have

gained stronger support.

-I-34-


A C Powe to T(onslormer

o d r ICverttf S I06 1 .O02$ 1D C Po. 0.01'.1 R cti, C , P

X? "I 2 0 rl* Reoctor~fedwo,,Keoor

| iK2CO i MHD | S sioc g - O

Dried D i _ __ _ff URPul"rizedL ir H eo-8trf

cool,¢nk 00 rsdeh_ h;7

_~~~~~~~~n ;Reheqh Plssue _ ol 1D riiwiter|

Fiir Ire - 1. O

-1-35 E Aos -_

= r . ; o i e t Fe rd.otr Heolers~~ i i Inlerrmed ole ~~~~~~~~~~And So ler feed Pumps

Stoeri Condootor Sta cilaillasnorn

Condensate_ \ t Celn

Schematic Diagram of Open Cycle MHD

Figure 1-13. Open Cycle MHD Cycle

-1-35-


Thermionic Generators [RD]

The thermionic steam generator is illustrated in Figure 1-14. Pulverized coal is

burned in primary air and hot recycle secondary air. Radiant and convective heat

exchange to the high temperature thermionic emitters at 1600 K drive direct current

electricity and heat energy to the thermionic collectors. The thermionic collectors

use heat pipes to discharge heat to the combustion air flow. The combustion gases

flow out of the radiant furnace zone, heating the low temperature thermionic

elements with 1300 K emitter temperature, then heat exchange with steam

superheater and steam generator surfaces. Preheated secondary air is used for

staged combustion of the pulverized coal. NOX limitation is achieved by this means.

The secondary steam generator brings the stack gas to 3000 F. Flue gas

desulphurization is applied to limit sulphur emissions. Residual oil could be

substituted for coal as fuel. This is particularly suitable for small ratings. Steam

conditions of 1465 psia, 1000° F are producible in this system. Condensing steam

turbine bottoming is used to increase power output.

-I1-3C-


fUEL 1000

STACK LATENT HEAr SICONOAAY AIR 1OO0f

6 ° t M3 2 'ET I NPUTS 11t36.2 .203

MISCELLANEOUS , LU

AC a153.7 ^Xo25 30OANS * 13o\ETAC * 140.7 145.1

p I 120.1 I

SECONDARY AIR GOOF 4PRIMARY AIR 540F

0590.6

TO300F AMBIENTAsi RF ~~~~~ZERIO SASE

FOR HEATINTO STEAM SENSIBLE STACK BALANCE

(Power 248) LOSS AT 300Fn5OlLEA M.

Figure 1-14. Thermionic-Steam Heat Balance Based on 1000 Btu Coal HHV

Although this concept has the attraction of eliminating high temperature rotating

equipment, a thermionic power system has not been demonstrated to date and

requires extensive development to achieve the performance level of Figure I-14.

Fluidized Bed Combustion3' 4 [A.]

In fluidized-bed combustion, fuel is burned and its sulphur recaptured in a single

process, as contrasted with conventional boiler combustion where a scrubber

removes the sulphur from flue gasses. The fuel, which can be a wide variety of

solid materials, limestone (the 'sorbent"), and air are simultaneously injected into a

'bed" of intent solids. The combustion occurs in a high temperature (1500 to 16000

-I-37-


C) turbulent bed of solids which acts as a fluid. Due to the solids mixing and

contact with the heating surfaces, heat is transferred from the fluid combustion bed

to water tubes at rates much higher than in a conventional boiler. Particles (the

sorbent-sulphur mixture) are removed from the vessel for separation and ash

recycle, and from the flue gas by precipitators or baghouses.

These plants utilize conventional steam cycles therefore, efficiency levels are

comparable to coal fired power plants.

The "bubbling bed" AFBC is the most technically mature of the various types, and

involves lower bed air velocity. Northern States Power Company and TVA

(Tennessee Valley Authority) are currently testing 115 MW and 160 MW versions of

this concept. The "circulating bed" AFCB, continuously transports and recycles bed

material to separation cyclones. This type of fluid bed requires higher air velocity,

but shows somewhat more promise for high capacities and eliminates troublesome

bubbling inbed tube problems. Smaller scale demonstrations have been done with

pressurized fluidized bed combustion (PFBC). The marginal potential efficiency

improvement, when integrated with an expander gas turbine, and inherent technical

problems with turbine solids flow and hot gas cleanup, put it in the longer range

category. American Electric Power is building a 70 MW PFBC plant which should be

operational in 1990.

Commercial units are being offered in the U.S. at 106 lbs/HR steaming capability by

Pyropower and Combustion Engineering. Pyropower has had a 130 MW unit in

operation at Colorado UTE Co. for over a year and is working with Black & Veatch

on the design and construction of a 100 MW power plant at the Trona, California

site of Kerr McGee. Circulating fluid beds will likely dominate near term solid fuel

power generation application in sizes from 100 MW to 200 MW. Reheat capability is

also being offered. AFB technology offers ability to efficiently burn wider range of

solid fuel types in the same boiler but has marginal economic advantage (if any)

over conventional coal boilers with flue gas treatment systems and is at an

economic disadvantage where stack treatment is not required. Ability to

-I-38-


simultaneously burn clean industrial wastes, sludges and biomass fuels is asignificant technology advantage over conventional grate or suspension type boilers.

Fluid bed SO2 emissions are comparable to dry scrubbers (90% +) and NO. emissions

less than conventional boilers due to lower combustion temperatures. However, this

technology produces an ash which has leachable characteristics. This will require

development for siting where tight standard exist.

Major application hurdles for this technology are:

o Cost (approximately $1,500/kWe for capital and 17 mills/kWh forfuel). Further scale up can be anticipated.

o Although initial results are encouraging with availabilities in the 80%range, system reliability base must be developed

o Long plant lead time

o Siting of solid fuel plants

This technology is receiving heavy industry support with many commercial projects

in the 50 to 100 MW range, currently planned by IPP.

AFBC should be regarded as a technology beyond a 100 MW scale, although is still

in a prototype stage at this scale. This technology will find application in countries

where national priorities rank control of atmospheric sulphur discharge high or have

difficult or multiple solid fuels to utilize.

Fuel Cellsh [P]

Fuel cells produce direct current by the electrochemical reaction between oxygen

and hydrogen, the latter extracted from a hydrocarbon fuel (usually natural gas) by

a 'fuel processor." There is no combustion in the traditional sense.

-I-39-


Hydrogen, fed into an electrolyte of phosphoric acid, generates negative charge at

the anode and positive at the cathode. Water is the only byproduct of the reaction.

Individual cells are connected into series 'stacks' ranging from 200 to 700 kWe, a

number of stacks comprising a fuel cell power plant. Stacks must be replaced after

about four years at full power output.

Fuel cells also require inverters to convert dc to ac. This adds to the initial cost,

maintenance cost, and inhibits application as a small, sole source plant in isolated

locations.

PDFC Fuel cells have been applied in demonstration programs with prototypes up to

5 MWe having been demonstrated. Commercial type units could range up to 25 MW.

The fuel cell component conversion efficiency can be over 40%,, the total generation

system efficiency, including hydrogen production, steam cycle waste heat recovery

and dc/ac power conversion can produce power at more than 50% from fossil fuel.

There are many varieties of fuel cell processes, however, the leading candidates

are:

phosphoric acid (PAFC), 2500 C

- molten carbonate (MCFC), 6000 C

- solid oxide (SOFC), 11000 C

Each of these concepts have unique development problems which must be solved

before commercial status can be achieved.

The PAFC has a high first cost ($2500/kW) projected for larger MW units. MCFC

must be integrated with a steam bottoming cycle to produce 50% efficient power at

the 250 MW size level.

These systems are relatively complex with many subsystems which require close

integration. This will tend to keep fuel cell power a higher cost option. Solid oxide

-I-40-


(SOFC) technology is still in an experimental stage and requires extensive

development before commercialization.

The molten carbonate fuel cell operates at a temperature of 13000 F. Figure 1-15

presents a schematic and heat balance for a coal-fueled molten carbonate fuel cell

energy conversion system. The pressurized coal gasifier effluent gases are cooled by

an HRSG en route to the gas cleanup system. The fuel gas that is not consumed in

the anode (A) side of the fuel cell at 2000 F is burned with supplementary air in

the catalytic burner. These combustion gases with excess air provide the necessary

oxygen on the cathode (C) side of the fuel cell. The recirculation loop has an

HRSG, a blower, and a hot gas bleed-off to the expansion gas turbine. The gas

turbine exhaust passes through an economizer to be cooled to the minimum stack

temperature of 300° F. The aggregate net ac power produced is 41.4% of the fuel

energy of which 6.3% is produced by the gas turbine generator. The aggregate steam

production from all HRSG sends 47.*% heat to the steam turbine.

The simplified system would be used for a small distillate-fired molten carbonate

fuel cell. The distillate would be processed in an autothermal reformer with air and

steam to form synthetic fuel gas. That stream would be cooled in an HRSG and then

passed through a zinc oxide reactor to reduce sulphur to below 1 ppm.

-I-41 -

Power Technologles, Inc.

(Power 17%)

ST EA..J 1MLL N Ou HA

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MOLTEN CARUONATE PUEL CELL

Fuels: Coal, Distillate

Variables: Process Temperature 2000 F to 5000 F

Advanced Art: Molten Carbonate Fuel CellGasifiers, System Integration

Availability: 1990

Figure 1-15. Molten Carbonate Fuel Cell

The phosphoric acid fuel cell operating at 3750 F is shown schematically in Figure

1-16. The fuel gas at the anode is hydrogen. The distillate fuel oil must be

processed through a zinc oxide reactor to remove any trace sulphur. The zinc oxide

consumption results in a high operating expense. The reformer burns spent anode

fuel gas and some distillate oil as its heat source and uses the bulk of the distillate

fuel as a chemical feedstock. There is extensive heat exchange at the reformer that

heats the incoming fluid streams and cools the effluent gas streams. The shift

reactors produce a high concentration of hydrogen in the fuel gas stream. The stack

gases are cooled to 1000 F in order to recover and recycle water in the system.

The cleanliness of the exhaust products (e.g., 02, H20) is an environmental

advantage.

-1-42-


Although the fuel cell operates at a nominal 3250 F to 3750 F level, other heat

exchangers operate a temperatures up to 7500 F. Process steam can be produced at

temperature levels from 1600 F to 6000 F to the extend of 0.17 of the fuel energy.

FUEL

HEAT oo%| {STAC K

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Phosphoric Acid Fuel Cell

Fuel: Distillate - Desulfurized

Variables: Process Temperature (600 F to 6000 F)

Range: I MW - 10 MW

Advanced Art Phosphoric Acid Fuel CellShift ReactorsSystem Integration

Figure I-16. Phosphoric Acid Fuel Cell

-I-43-


The fuel cell's primary advantages are:

- Low environmental impact

- Relatively high fuel efficiency (40%-44%)

- Ease of waste heat recovery

- Flexible module size.

Its disadvantages include:

- Uncertain maintenance and availability data

- High capital cost (Est. at $3,000/kWe at present)

- Requires premium fuels and "fuel processor"

- Specialized technology

- Required premium fuels and "fuel processor'

- Not suitable as the sole supply on isolated systems

- Requires high grade fuels (H2, natural gas, etc.)

The long range role of fuel cells will become increasingly clear as small prototype

plants gain experience. It is not currently a practical technology for developing

countries, other than on an experimental or familiarization scale.

Figure I-17 compares the cost and efficiency of several advanced combined cycle

coal fired systems. The dash line indicate the performance of large state-of-the-art

supercritical coal fired steam plants. It will be noted from this comparison that only

the integrated gasification gas turbine combined cycle indicated a cost of power

reduction potential vs. the state-of-the-art steam plant. It would require a coal cost

of over $5.00/106 Btu for MHD to compete with the steam plant.

-I-44-

Power Technologles, Inc.

I. A Liquid Meal

Iner Ges l Suprcrltical CO2Ful Cells Low F Iner 60 _ Trsture \ .t. ,'i \ ~~~~~Fuel Calls High _ _ meal Vapo

I MMDTemperature Topping

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pen Cle bs Turbine CombinedCoal Cost

85¢/106 Btu

0 AD~~~~~~~~~~~~ Oerall Etldcinqc III

Figure 1-17. Advanced Energy Conversion Systems

'Range" of Results

Fusion. Breeders and Fast Reactors [R]

Research in fusion, breeders and fast reactors still receives considerable funding in

industrialized countries. Breeder and fast reactor concepts have been demonstrated

at various scale in the U.S. and foreign countries. Further application of this

technology depends on the timing and fate of nuclear energy for power generation.

Fusion has yet to demonstrate a sustained reaction. Furthermore, researchers have

-I-45-


yet to address methods for handling the heat produced by a fusion reaction. These

problems, plus the uncertain economics of fusion generation, put it in a 30 to 40

year time frame and even then leave a question as to its long term applicability.

Geothermal PlantsM [A - Single flash, P - dual flash, binary]

Geothermal plants are useful only where special geological conditions entrain high

temperature brine close to the earth's surface. Heat is removed by "flashing" a

portion of the brine into steam to operate a turbine. Typically, less than 15% of the

thermal energy is convertible to power.

Commercial single-flash geothermal plants reflect a mature technology which

goes back many decades. Newer technologies attempt to improve efficiency and

make lower grade heat sources economic. "Dual flash" plants, for example, extract

the heat in two successive tanks, one at high pressure, the other at lower pressure.

Unused brine, plus condensate from the steam, are pumped back into the earth to

maintain reservoir pressure.

The dual flash process requires a lot of cooling water (typically 3 Million gal/day

for a 50 MWe plant). The most serious technical obstacle is scale formation in and

corrosion of flash equipment and plant piping due to noncondensable gases and

entrained solids in the brine.

Where conditions favor geothermal, typical dual-flash plants will be rated about 50

MWe and will require only about 20 acres.

An alternative binary cycle technology uses the brine to vaporize a secondary fluid

with a lower boiling temperature, which in turn drives a turbine generator. Binary

cycles return all the brine to the reservoir and therefore produce less air pollution.

They are more efficient, but more complicated, more costly and use even more

-I-46-


water than the dual flash plant. The first binary plant prototypes were put into

operation in the U.S. in 1986.

Advantages of Geothermal are:

- Low fuel and operating costs

- Small land requirement

- High plant factor.

Disadvantages are:

- Useful only in special locations, i.e., site-specific

- High survey & feasibility study and field development costs

- High cost (est. between $1,500 to $2,000 per kWe)

- Large cooling water requirements.

- Environmental discharge constraints primarily on H2S.

- High maintenance of equipment.

- Lower availability compared to other types of power generators.

Geothermal generation is a practical option where geological conditions provide a

basis for it. Single flash plants represent a mature technology while dual flash and

binary cycles should be regarded as technologies to watch, pending operating results

from present prototypes.

Hydroelectric Plants14 [A]

Both the electrical and civil technologies supporting hydro electric plants are well

developed and well understood. Advances have been made in control, monitoring,

-I-47-


protection and other aspects of electrical design. Units as large as 700 MW have

been installed in the U.S.S.R.

China's success with relatively low-technology hydro plants in the range from

several hundred kW to ten MW, gave impetus to the idea, now popular in the U.S.

and Canada too. Many of these plants use induction generators and require very

little maintenance. Where they serve mostly local load, power is distributed at

generator voltage.

Hydro plants in any size range are more expensive than fossil-fired plants. However

since much of the cost is labor, and much of the hardware can be locally

manufactured, many developing countries have made small, unsophisticated hydro

plants an important part of electrical development plans. China has over 90,000 such

plants and India has encouraged their development as well.

Many irrigation projects could be retrofitted with small hydroelectric generators.

Liauld Metal Tonxnlz Cycles [Ad]

Combined cycles for power generation may be configured utilizing a variety of

technologies other than gas turbines. This includes: MHD, liquid metals, fuel cells,

etc. Liquid metal topping cycles have been under study for many years. These

topping cycles utilize liquid metal working fluids having a high vaporization

temperature which provides for heat absorption and conversion at higher average

cycle temperature level while maintaining high steam conditions in the steam

bottoming cycle. Liquid metal cycles can utilize such metals as mercury, sodium and

potassium. A successful demonstration plant was built and operated by American

Electric Power Company in the 1950's. However, the evolution of the supercritical

steam cycle and high efficiency gas turbine combined cycles diminished the

advantages to be gained with the more complex and expensive liquid metal combined

cycles.

-I-48-


Nuclear Power [A]

Three basic technologies remain useful in nuclear generation. They are (1) the

Pressurized Water Reactor (PWR), (2) the Boiling Water Reactor (BWR), and (3) the

Heavy Water (CANDU) reactors developed and applied in Canada. In addition,

several industrialized countries operate breeder reactors to reprocess fuel and some

research continues on high temperature gas-cooled reactors (HTGR).

BWR and PWR technologies remain at what appears to be an economic standoff. The

Candu reactor is somewhat less efficient and has the extra expense of heavy water,

but has built an enviable record of availability due, in part, to the fact that it can

be refuelled on line.

Politicization of nuclear power in the U.S., England, Germany, Sweden, Austria and

many other countries, has virtually stopped consideration of new plants and put

pressure on decommissioning of existing plants. This trend is not universal,

however. France now derives over 70% of its power from nuclear plants and has

become an international leader in nuclear technology. The U.S.S.R. also continues

with an active nuclear program, as does Japan, Korea, and Taiwan. The long term

future of nuclear is not clear, but two factors which may have a very important

bearing are:

1. An end to the current low price levels of oil.

2. Attitudes less antagonistic to nuclear.

3. Concern over global heating due to CO2.

Nuclear technology continues to develop and will likely one day be a major source

of world electricity supply. Current costs of new plants range up to $5,000 per kW,

fuel costs being from 50% to 60% of that for a similarly sized coal-fired plant.

-I-49-


Ocean Thermal Energv Conversion14 [All

Scientist have long sought to take advantage of thermal gradients in the ocean for

electric power generation. While the available energy is very impressive, the

temperature differential is very limited - usually less that 200C (370F). Serious

experiments in taking advantage of this gradient began in 1926, but with limited

success. Present technology shows somewhat more promise, but is still considered

uneconomic by most experts. There are two basic Rankine cycles which take

advantage of this source:

1. Open Cycle

Open cycles use the water vapor generated by first degassing warmwater, then reducing its pressure (flashing) in an evaporator, theresulting steam being used to power a turbine. The condenser useswater from a greater depth. Warm water and cold water pumps, aswell as vacuum pumps, are required to maintain the continuous flowconditions in the evaporator and condenser.

Very large, slow turbines are needed to generate significant amountsof power. Plans for such turbines use light weight materials such asfibre-reinforced plastics.

2. Closed Cycle

A closed cycle permits use of a high vapor pressure fluid, such asammonia. Ammonia equipment and process technology is welladvanced by virtue of experience in refrigeration and in chemicalmanufacturing. However very little experience exists with ammoniaturbines.

Among the technical challenges of OTEC cycles are:

o The cold water pipe is very difficult to install andmaintain.

o Platforms accessible to cold water tend to bedifficult to install.

o Heat exchangers tend to get fouled by marine life.

-I-50-


The best economic case for OTEC plants can be made by locating the plant wherewarm discharge water from a conventional plant can be used. Even under thosecircumstances OTEC plants tend to be very expensive to build and maintain.

While several small OTEC plants have been built in Japan and Hawaii, it is not, atthis stage, a practical technology for developing countries.

Ocean Currenll' [R1

Ocean currents have been used in low-energy applications since medieval times,normally mounted on bridges and used to pump river water to nearby towns.

While a variety of schemes have been proposed for electric power generation, themost popular is a series of low-speed water turbines, tethered to moorings at thebottom of a river or sea channel. Most proposals involve relatively small levels ofpower, and the technology must be regarded as largely experimental.

Solar Thermal-Electric Power Plants3 [P], [R]

The most efficient method for converting the sun's incident energy into thermalenergy useful for production of electricity is by concentrating it at one centralreceiver by means of mirrors ("heliostats"), at the focal point of each of manyparabolic dish, or along a 'solar trough." In each case the collecting mechanism iscaused to track the sun, and the concentrated heat energy is transmitted to aturbine, either as the sole energy source, or to supplement a gas-fired turbine.

A 10 MWe prototype central receiver system has operated in Southern Californiasince 1982. Parabolic troughs, a more mature technology, have also been built atratings appropriate to commercial application, although economically justifiedthrough tax incentives.

-1-51 -


Another form of thermal-electric conversion uses a solar pond, relying on three

layers of water, each of different density by virtue of its salt content. The high

density of the bottom layer (highest in salt content) prevents its normal rise to the

top as it gathers heat. The entrapped heat can cause the temperature of that layer

to reach 2270F, sufficient for transfer, by means of an intermediate fluid, to a

power-producing turbine generator. A 5 MWe prototype solar pond plant has been

built in Israel, and several small ones in the U.S. for direct heat use. The

technology is well established.

There are many variations of the above principals, though most are characterized by

the same general advantages and disadvantages, the former being:

- No fuel cost

- No air pollution.

The disadvantages are:

- High and uncertain capital cost

- Uncertain maintenance cost

- Limited prototype experience

- Low capacity factor

- Large land requirements.

Solar thermal power generation is not likely to be an important commercial source

for at least the next decade or two. The R&D and prototype funding needed to

firmly establish costs are very high, considering current estimates of economic

value.

(See also 'Solar Voltaic")

-I-52-


Solar Voltalc3 [P]

Photovoltaic semiconductor cells convert sunlight directly into direct current. Cells

are grouped into modules, the output from which is fed to an inverter to produce

alternating current at commercial voltage and frequency.

The simplest, "flat plate" solar configurations are less efficient than systems which

use lenses to concentrate sunlight to a smaller but more intense surface.

Concentrator systems which follow the sun with a two-axis tracking system might

come closest to economic feasibility, realizing capacity factors as high as 30% to

35%, and conversion efficiencies from 12% to 20%, depending on location. The best

case for photovoltaic generation is for centralized plants up to 20 MWe. Even for

this case, capital costs are uncertain, - currently ranging about $5,000 per kWe,

with projections as low as $2500 per kWe peak in areas of greatest sun intensity.

Land estimates span an even broader range, from 40 to 370 acres, for such a plant.

Recent progress in the reliable and cost effective production of high conversion pV

cells using integrated circuit techniques, has greatly improved cell density and

offers potential for commercialization. More basic technology and production

technique breakthroughs are needed before significant power generation application

is realized.

The advantage of photovoltaic generation include:

- No fuel cost

- Minimal water requirements

- No emissions or solid wastes.

Major disadvantages are:

- High capital costs

-1-53-


- Intermittent solar supply

- Very high land use.

While further technical developments and mass production could certainly improve

the economics of solar voltaic generation, this technology is not likely to be a

significant source of economic energy at least for the next decade or two.

(See also "Solar Thermal-Electric Power Plants")

Stirline Eneines [Ad]

The stirling cycle uses a helium closed cycle which approached Carnot efficiencies.

Burners atop each cylinder are supplied with highly preheated air. Within the

cylinder are dual pistons, the lower drives the crankshaft, the upper provides

helium compression and helium expansion. The displacer piston surges the helium

through an external regenerator and through a helium heater and heat rejection

heat exchanger. As noted in the heat balance scxhmatic of Figure I- 18, the 35%

engine efficiency is significantly reduced to about 28% when all system components

are included.

An industrial-size stirling engine beyond 500 kW is a significant development. Unit

sized could be in the range of 500 kW to 2 MW. Combustion of coal would

represent a further significant development effort.

-I-54-


COMBU A.ST5OUL.OR 1140ATE

1O P 1472. 1E A t2F !OG

aEo .INO| COCLANL *. *Li CYCLE

PIREN£ATIR PET T s F

+|^ ~~~~1 4% ,S.-ACX

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ADVYANCEO ART; INOUSTRIAL STIRLING CYCLEAIR PAEH"TIA TO 120OFCOAL EURNER HEAT EXCHANGE)

Figure 1-18. Stirling Cycle

The advantages of slower speed engines and hydrogen working fluids could improve

efficiency by approximately 2%. The increased size and weight would appreciably

increase the cost at no increase in power output. The stirling cycle concept doesnot appear to be a major contender for future power generation.

Tidal Powers1 [Al]

Means of harnessing the power of tides for useful work go back to the 12th

century, since which time a number of ingenious schemes have been used, including

the recapture of potential energy of a heavy mass, floated to the top of a platform

at high tide.

-I-55-


Modern tidal power applications, the largest of which is a 240 MWe station in

France, involve at least one storage pond (two if continuous output is required),one or more dams, a sluice system, and a power house. One of the larger projectproposed is in the Bay of Fundy, where engineers have shown a potential ofbetween 1,000 and 4,000 MWe. In England, however, schemes in the range from7,000 to 13,000 MWe have been considered. These schemes may involve either single

or double effect operation, i.e. extraction of energy either at lowering tide or at

both rising and lowering tide.

The technologies associated with tidal power are all well known. In fact a tidalplant is very similar to a run-of-river hydro plant. Apart from the normalenvironmental issues associated with large civil engineering projects, tidal power

may also affect certain tidal ecosystems.

Tidal power is limited mainly by its high cost and the limited number of sites whereboth tidal and coastal geographic conditions are suitable. It will have very limiteduse for electrical generation in developing countries, though may, on much smaller

scale, be useful for its traditional role as a drive for mills.

Wave Enerev Conversion's [R]

The prospect of exploiting wave energy has fascinated engineers for at least 100

years. Dozens of innovations have been proposed and tested on a small scale,including:

o Hydraulic pumps, driven by wave perturbation of an air-filledcylinder.

o A cam-shaped "duck" which rotates with wave action, acting againsta gyroscope to drive a hydraulic pump.

O A "sea clam' consisting of several flexible bags configured to usewave action to force air into a turbine.

-1-56-


O A barge, large enough to straddle several waves, under whichvariations in air pressure are captured by a number of cylinders,rectified, and used to drive an air turbine.

o A series of hinged barges, the relative tilting of which is used todrive hydraulic pumps.

o Wave amplifying channels, built into the shore-line, which causewater to spill over into a reservoir which, in turn, drives a low-head hydro plant.

o Vertical "flaps," anchored to the sea-bottom, whose forward andbackward rocking energy is capture by a hydraulic damping device.

o Hydraulic pumps driven by the rising and falling action of floats.

O Dome-shaped wave focusers, directly couple to a low-speed turbinegenerator.

It is too early to gauge the usefulness of wave energy, but early experiments

indicate that it is a very high-cost option, both in terms of initial and maintenance

expenses. Of the options tested, the wave amplifying channels appear the most

economic, though they require special shore-line features. Visual, ecological, and

navigational impacts may also be impediments.

Waste-Burnina Plants 19 [A]

Plants up to 50 MW have been built to burn solid refuse, from which non-

combustibles and toxic materials have been removed. Incinerators for municipal

solid wastes have been commercially operated for many years. Problems with

combustion, slagging, corrosion, surface fouling, unsteady power production and low

availabilities are inherent with the nature of and wide variations in fuel

constituents.

The steam turbines and power cycles associated with these fuels generally employ

low technology components (750 psig, 750°F nonreheat steam conditions). Material

-I-57-


improvements and power cycle configurations which allow increased steam conditions

(to 900°F) with supplemental fuels are possible and have been proposed.

Justification for waste-burning plants rests in part on their waste-disposing

function. They are difficult to justify solely on economics where land-fills are

available.

Wind Power3 [Al]

Experimental wind turbines have been built up to 1 MWe, though most have been in

the 100 kWe range, clustered into "wind farms' to centralize maintenance and

operating support, take advantage of a good location, and minimize environmental

impact - primarily noise and visibility.

Wind farms occupy large land areas, probably in excess of a thousand acres for a 20

MWe capacity plant. Capacity factors are also low, usually below 20%, making the

land per kW unusually high.

The cost of wind power in moderately large farms is estimated at between about

$1,300 and $1,900 per kWe, though these costs must be viewed with an awareness of

the low capacity factor that can be expected. Operating costs are estimated in the

range from 10 to 25 mills/kwHr.

Advantages of wind power include:

- No fuel requirement

- Minimal ecological impact- Remote, isolated operation is feasible

- Short delivery time.

-I-S8-


Disadvantages include:

- High (often sophisticated) maintenance burden

- Large, specialized land area requirements

- Low capacity factor ... need for energy storage method

- High initial cost.

Wind energy should be regarded as suitable only for experimental or highly

specialized applications, e.g. in isolated locations where fuel transport costs would

otherwise be very high, where intermittent operation (e.g. for pumping load) is

acceptable, and where maintenance access is not difficult.

U.S. activity in wind power subsided with elimination of state and federal subsidies.

-I-59-

SECTION 11

ENERGY STORAGE


II. ENERGY STORAGE

Battery Storaze2 0 [R]

Large scale storage of electricity by batteries has been the subject of industry

research for almost twenty years. Schemes ranging from static batteries such as the

familiar lead-acid units, to circulating reactant systems resembling a complex

chemical plant have been explored. Most have a cycle efficiency between 65% and

75%, similar to pumped hydro.

Battery storage is an attractive option technically since it can be used in small

sizes, permitting "local" storage, and because the charge\discharge cycle can be

reversed quickly enough to allow the battery to stabilize the system during dynamic

swings. It is expensive and, at least in the case of lead-acid cells, cycle life

requires replacement every 8 to 16 years. Zinc-chloride and other battery options

may ultimately have longer life and lower cost, but are still in an early

developmental stage. The cost of battery storage is increased by the fact that a

rectifier/inverter is needed to convert from ac to dc or vice versa.

The overall economics of battery storage are generally unfavorable. For example, a

recent study of a peak-shaving battery system for a subway system (ideal by virtue

of two sharp daily peaks and high electricity demand charges), showed that the

costs outweighed the benefits.

Battery storage is a technology worth following, since a breakthrough in battery

storage technology could profoundly influence utility loads and utility system

structure.

ComDressed Air (CAESWS [AJ]

Compressed air is an interesting storage medium because of its synergy with the gas

turbine combustion cycle. About two thirds of a gas turbine's output is used in its

-II-1 -


air compressor, one third being available for the electrical generator. If a

generator is run as a motor during off-peak periods, the compressor can pressurize

a reservoir which can later substitute for all or part of the compressor requirement

during the generation cycle. The result is up to three times the output of the

original turbine, paid for of course by the energy used in pressurizing the

reservoir. Efficiency is further enhanced by using turbine exhaust heat to preheat

air discharged from the storage chamber.

The storage reservoir may be in hard rock caverns, salt caverns, or in an aquifer.

Except in the latter case, a compensating pressure water reservoir is needed to

maintain constant pressure in the cavern.

In addition to a suitable reservoir, CAES plants must have access to water in the

amount of about 2,000 gallons per day per MWe.

Although the elements of a CAES plant are well proven, none have been built in

the U.S. A successful 290 MWe demonstration plant has been operating since 1978

at Huntrof, Federal Republic of Germany.

While most of the individual components of a CAES are commercially available,

there is significant uncertainty associated with this technology as a system. Its

performance at a specific site is uncertain and it appears expensive compared to

other options.

Pumped Hydro20 [A]

Pumped hydro represents the mainstay of storage technologies, but is limited to

regions where terrain permits economic reservoir construction. Pump/discharge

efficiency of most pumped storage plants falls in the range from 65% to 75%. Cost

varies considerably, depending on geographic conditions. Unit sizes suitable for

utility application will generally be larger than 100 MW. Heads of at least 300 feet

are preferred. "Turn-around" time is an important measure of any storage scheme.

-11-2-


To go from full pump rating to full generation rating or vice-versa, usually takes

from 30 to 40 minutes for pumped storage plants.

Pumped hydro using underground storage has been proposed, but would require

relatively large storage ratings to be economic, e.g. 1000 MW. Apart from higher

construction costs and difficult maintenance access, operating characteristics of

plants using underground storage are estimated to be the same as an above ground

plant.

In a station at La Rance, France, pumping has been combined with tidal effects to

give efficiencies above 100%. The plant pumps sea water at high tide and

generates at low tide.

Sunerconductine MaRnetic Storage Enerey System20 [R]

A superconducting magnetic energy storage system stores electrical energy in the

magnetic field produced by a circulating current in the winding of a magnet. Typical

overall efficiencies are believed to be in the range from 80% to 90%, considering

refrigeration and ac/dc conversion loss.

Superconducting storage is very expensive, requires a lot of land, and is fraught

with technical problems. It is a technology to watch, however, both because of the

impact that local storage capability would have on system design and operation, and

because of recent dramatic advances in high temperature superconductivity.

-II-3-

SECTION III

TRANSMISSION LINES


III. TRANSMISSION LINES

Compaction21 [As]

The past decade's transmission line research has included emphasis on compact

construction to reduce transmission line cost, lessen visual impact, and to make

maximum possible use of available rights of way. The most dramatic reductions in

spacings have been at 115-138 kV where traditional clearance specifications were

established long before technical requirements were clearly understood and before

probabilistic flashover calculations were accepted.

Demonstration lines have been built with spacings as low as 0.9 meter at 138 kV

(Figures III-I and III-2) and about 2 meters at 230 kV. Typical compact

construction has allowed more spacing - usually 1.5 m at 115 and 3 m at 230 kV.

Reductions in spacing at 345 kV and higher are also being proposed, but since

conventional spacing is largely limited by surface gradients on the conductors,

compaction above 345 kV involves unusually large conductor "bundles."

Where long low voltage lines are to be built in developing countries, reduced phase-

phase spacing will also provide a significant advantage in lower reactance. For

example, a 230 kV line with compact spacing and twin conductors can offer the

same load-carrying capability as some conventionally designed 345 kV lines ... an

example of where modifications of design practices can be appropriate for

developing countries, because many such countries have no ice problem and because

occasional outages due to wind motion of conductors may be acceptable, compact

line designs may be particularly attractive.

(See also "Uprating")

- III- 1-


Figure III-1. Prototype Compact 138 kV Line - Horizontal

' /

Figure III-2. Prototype Compact 138 kV Line - Delta

-111-2-


Conductorsl° [A]

Purchase and installation of transmission line conductors typically represent a third

of the total construction costs of a transmission line, and must therefore be

approached with great care. There are a variety of aluminum conductor types, the

most common of which is ACSR (Aluminum Conductor Steel Reinforced), in a variety

of stranding configurations. All-aluminum conductors and various aluminum alloy

conductors are available. Difference in conductor cost, strength, weight, and

domestic availability will effect the best choice. That choice will also interact with

the tower type. Joint conductor/structure optimization software has become an

important adjunct to line design.

Line designers normally select a conductor size that balances initial cost (conductor

and tower support requirements) equal the present worth of losses over the life of

the line. At voltages above 230 kV, corona effects may force a somewhat larger

than economic conductor, or cause the optimum cross-section area to be subdivided

to comprise a "bundle" of several conductors. In developing countries, some

applications will favor lower initial cost, higher losses, and higher electrical

gradients (noise).

Conductor temperature calculations are also critical to conductor application.

Temperature depends on the balance between heat inputs, principally ohmic and

solar heating, and heat losses due to wind and radiation. Maximum allowable

conductor temperature is governed by loss of life, by the risk that conductors will

sag to unsafe limits, or both. Since conditions vary along the right-of-way, the limit

is set by the span assumed to have most adverse conditions.

Aluminum alloys used in most overhead conductors suffer some permanent loss of

strength above 750C, a loss that depends on both temperature and time of exposure.

Since most utilities allow a 10% loss of strength over the life of a line, strict limits

are placed on emergency loading to respect that threshold.

-III-3-


Because of recent progress in the understanding of temperature and loss-of-life

characteristics, many utilities have increased power flow limits. Countries with

limited economic means should pay special attention to thermal criteria to assure

that assumptions are appropriate to their circumstances.

New lines which would benefit from very high overload capability should consider

conductors specifically designed for high temperature operation. In SSAC (Steel

supported aluminum conductor), the aluminum strands are pre-annealed, so the

temperature limit (in the order of 250°C) is set by the risk of damaging the

galvanizing on strands of the steel core.

(See also "Monitoring," "Low Cost Transmission," and "Tower Optimization")

Cryo2enic Transmission [RI

Research has been done on cryogenic transmission cable both in the superconducting

range (initially in the liquid range 40 Kelvin, now possibly approaching room

temperature) and in the "resistive" range (liquid hydrogen temperature 20°K to

liquid nitrogen, 800 Kelvin). While attractive in concept, the idea had two important

hurdles. The power levels necessary to justify cryogenic cables (2,000 to 10,000 MW)

are simply too large for practical systems to accommodate, recognizing that several

parallel cables would be needed to accommodate the failure of one. In addition, the

practical difficulty of maintaining a distributed refrigeration system at such low

temperatures suggested poor availability and high risk.

Recent breakthroughs in "high temperature" superconducting materials have

reawakened interest in application for power transmission. Yet the research

timetable, uncertain economics, and inherent reliability obstacles, suggest that

superconducting applications in the power field, if ever commercially attractive,

will first occur in concentrated installations or equipment.

(See "Energy Storage" and "Generators")

-III-4-


Electric Fields [A]

There has been considerable recent study of the effects of 60 Hz electric and

magnetic fields produced by transmission lines. Means for preventing electric

shock hazards have long been known, but of more recent interest is the prospect

that those fields could have adverse health effects.

Literally hundreds of studies of electric and magnetic field effects have been done,

none showing any physiological link between high fields and disease or injury. A

small statistical correlation was shown between proximity to distribution lines and

the incidence of leukemia in children but:

o The experiments are suspect to challenge insofar as objectivity isconcerned.

o Other experiments, involving people with unusually high exposure tofields, show no correlation.

o Magnetic fields in most household, school, and commercialenvironments far exceed those found under transmission anddistribution lines.

Thus there is no substantial evidence showing harmful electric or magnetic fields

associated with overhead or underground transmission or distribution lines. They

should not be a factor in deciding on their construction, other than necessary to

prevent electric shocks by induced voltages on nearby objects.

Fibre-Optics 7 5 [A.]

Fibre Optics are already widely used in communications and in equipment

applications. Of particular current interest is their incorporation into the center of

shield wires on electric power lines. Several manufacturers will supply such shield

wire and considerable field experience has now accrued.

-111-5-


Fibre optics have far greater signal capacity and immunity to noise and to surges

than carrier current systems, and are usually much less expensive than microwave

links.

Early suspicions that lightning strokes would damage the fibre-optic link appear ill

founded. To the author's knowledge, there has been no instance of such damage.

As with any fibre-optics installation, maintenance and repair demand specialized

tools and skills. Apart from those considerations, fibre-optic ground wires should be

regarded as a viable application where a transmission right-of-way is to be used for

communication or relaying.

(See "Control")

Hih Phase Order (HPO)22 [P]

It was demonstrated in the 1960's that increasing the number of phases from the

traditional three to either six or twelve, allowed unusually high loading on a

relatively narrow right of way; experimental circuits have since been built and

tested using both six and twelve phases. Six-phase line is pictured in Figure III-3.

L~~~~~ A

Figure 111-3. Experimental Six-Phase Line

-III-6-


Because HPO produces lower conductor electrical gradients for the same spacing, it

also appears useful in uprating double circuit three phase lines where the conductor

would otherwise be too small. Economic studies have shown cases where savings in

losses alone would justify the conversion to six-phase. In the U.S. serious

consideration is being given to conversion of a 115 kV double circuit line to six

phase operation for that reason.

Economics show HPO to be competitive with UHV for very large transfers of power.

Some developing countries have shown interest in HPO since it would allow the

same transfer at a lower voltage than three phase, permitting use of domestically-

made equipment.

This technology should be considered quite tentative until prototype lines have

demonstrated satisfactory performance.

Hkih Voltaue Direct Current (HVDC)2 3 [A]

HVDC has seen wide spread, successful application over the past two decades. It has

proven a valuable recourse in systems where:

o Transmission distance causes the lower cost of dc overhead line orunderground cable to justify the added expense of HVDC terminals.

O The power transfer that is economically justified is less than theac capacity needed to connect two systems stably.

o Characteristics of the two connected systems are incompatible, e.g.differences in frequency.

o The damping capability of HVDC is valuable in maintaining stable actransfer.

Most HVDC lines have been justified on the basis of one or more of the above

arguments. While few are based solely on distance economics, it is of interest to

note that, at a cost of about S50/MW per terminal, the "break even" distance for dc

-III-7-


from 350 to 450 miles of overhead line and from 20 to 40 miles of underground or

undersea cable.

In some cases dc has been applied "back-to-back," i.e., as an asynchronous coupler

without any dc transmission line at all. This is useful where there is a frequency

difference, a strong incentive to limit fault current or to control exchange between

systems. Back-to-back dc costs about 85-90% as much as two independent separated

terminals. Of course this application fails to take advantage of the inherently less

expensive transmission that could be interposed between rectifier and inverter

terminals.

When power must be tapped off along a transmission corridor, ac transmission has

the advantage of flexibility. However, modern controls make multi-terminal HVDC

feasible when the economics justify intermediate HVDC taps. One multiterminal

system has been commissioned in Europe. A five terminal HVDC system is under

construction in North America.

In theory, small series taps could be inserted in a dc line, but planners are

reluctant to jeopardize the reliability of a major tie just to gain access to the line

for a small level of power. The cost of smaller taps tend to be disproportionally

expensive.

HVDC is now entirely based on thyristor technology. When large Gate-Turn-Off

devices become commercially available at attractive prices, cost reductions will be

possible in converter stations.

Inspection and Maintenance [A]

Transmission line inspection has been made much easier through the use of aircraft,

particularly in colder climates where thermographic inspection methods are

applicable. Such an inspection is particularly important prior to significant

-III-8 -


increases in line loading. Thermographic methods allow the user to identify bad or

poorly made splices and dead ends.

X-ray equipment, put into the proximity of the conductor with a hotstick, may be

used to locate strand breaks due to excessive aeolian vibration. If such damage is

found, vibration dampers may be installed to prevent further deterioration.

Live-line-maintenance is now common for voltages up to and including 500 kV. The

cost of equipment and training necessary for safe and effective live-line work is

usually more than offset by the value of continuity of service for the maintained

line. Training courses and conferences specific to live-line work should be made

use of by utilities beginning live-line programs or extending them to higher

voltages.

Novel construction methods involving live line techniques can be used for a line

remaining in service. For example, temporary bypass structures or sections of

cable can be used while the main structures are rebuilt or replaced.

(See also "Monitoring," "Uprating")

Insulators [Al

Basic porcelain suspension insulators have changed very little in the past several

decades. Their glass counterparts have won increased acceptance, though not

uniformly. Most U.S. utilities still fear the susceptibility of glass to shattering

when hit by rifle fire. Countries who have used quality glass insulators regard them

as a reliable option.

Fiberglass insulators have evolved as another reliable alternative to porcelain, as in

Figure 111-4. Several manufacturers have demonstrated success with units having

significantly better electrical performance than their porcelain counterparts.

Improved power frequency (contamination) performance in kV per length of insulator

-III1-9 -


is possible with synthetic insulators compared to porcelain. These advantages are

particularly important in uprating, where clearances are limited, or in regions

subject to atmospheric pollution. Because they are relatively new, utilities are well

advised to use only those fiberglass units that have extensive field experience,

accepting units of newer design only on a prototype or experimental basis.

Figure III-4. Non-Ceramic Insulator

Monitoriun Systems 25 ' 26 [RD to A.]

Monitoring of transmission lines will become an increasingly important technology,

albeit mainly confined to industrialized countries and to prototype service over the

next decade. Instrumentation ideas range from a "doughnut" current transformer

-111-10-


and instrumentation unit to robots traveling on the conductors. Doughnuts are

already marketed, robots mainly in the conceptual stage.

Real-time conductor thermal rating is high on the list of application possibilities

[III(5)]. The thermal capability of a line is based on relatively conservative

assumptions of ambient temperature, wind, and solar radiation. Knowing actual

conditions, including conductor temperature, would allow greater power flow under

most circumstances. Skeptics argue that hot spots, e.g. joints, clamps, broken

strands, or areas of atypical weather, minimize the value of readings taken at

several discrete points. Nevertheless it is very likely that monitoring will be used

increasingly, not only to assess operating state, but also to detect anomalies in sag,

hot spots, insulator defects, and corona levels.

Instrumentation and real-time thermal ratings are becoming important options for

underground transmission cables, technically, because of the high thermal inertia and

economically because of the high cost of installing new cables.

Relevance to developing countries is minimal, both because of the stage of

technology and the fact that most lines in developing countries are stability or

voltage-limited, rather than thermally limited.

(See also "Maintenance & Inspection")

Shield Wires for SuDily of Local Load27 [Al]

In many developing countries, high voltage transmission lines pass through villages

which are not yet electrified or which depend on very high cost sources of power,

and whose demand does not justify a step-down substation. Shield wires can be

used as a low cost means of transmitting power to such locations, particularly

where this purpose is anticipated at the tinre the line is built.

-III-ll-


The simplest means of doing this is by simply using the shield wire as a single-

phase distribution circuit with a ordinary distribution step-down transformer at local

loads. Inductive coupling from the phase wires can also be used as a source of low

voltage power up to about 100 kW. The fact that the shield wires are energized

does not diminish their shielding effectiveness. However the distribution circuit must

be designed very carefully, recognizing both electrical and safety considerations.

Where clearances permit, the more conventional alternative of "underbuilding" a

distribution or subtransmission circuit on existing towers should also be considered.

Towers and Ontlmization2 4 ' 28 [A]

The past twenty years has seen major strides in the design of towers and in the

optimization of structures and conductors as a single mechanical system. Towers

have evolved to allow the use of cables for tension loading-receiving rigid members

for compression and bending loads. Figure III-5 shows a traditional steel lattice

self-supporting tower and a more recently developed "rope suspension" tower. The

use of guyed towers requires somewhat greater right of way and may present

problems in rugged terrain, but the cost savings can be significant. Experience

with guyed towers goes back almost 50 years and shows that, properly designed,

they are as reliable mechanically and as sabotage-resistant as self-supporting towers.

The optimization of transmission lines involves the consideration of all the major

cost factors simultaneously. The major determinants of transmission line cost are:

conductor size, type, and tension; tower design, placement on the right-of-way, and

minimization of high cost dead-end and heavy angle tower types; predicted electrical

loads over the life of the line; and environmental and reliability limits. For

example, in flat terrain, the use of higher conductor tensions [29, 30], made

possible with special conductors such as SDC, T2 or SSAC, or by the application of

vibration dampers, can reduce the number of towers per kilometer and/or allow the

use of shorter towers. If environmental restrictions on radio noise are reduced it

may be possible to reduce the size of conductor required and thus save both on

-III-12-


conductor material cost and on the cost of supporting towers and hardware. Joint

optimization of all line cost variables can reduce the cost of lines well below the

cost of lines designed by traditional methods.

65'i 36'

in 4 44'6'

TP1

Figure III-5

-III-13-


Several advanced computer programs have been introduced for overall line

optimization. They have proven very successful in reducing cost.

Tower/conductor optimization, and the use of lighter, more efficient towers

represent a very attractive technology for developing countries. It is ironic that the

poorest countries tend to be the most conservative in terms of structure design and

conductor choice.

Ultra High Voltaee (UHV)3' [A]

Beginning with 345 kV, each new voltage was preceded by major research and

demonstration projects. The progression in voltage levels was quite steady until the

introduction of 800 kV in the Eastern U.S., Canada, and Brazil in the 1960's and

1970's. In the mid 1960's, intensive research began on "Ultra High Voltage" (UHV),

i.e., voltages above 1000 kV, primarily in the U.S., the U.S.S.R., Italy, and Japan.

Several lines have been built and operated in the U.S.S.R. where large blocks of

power must be transmitted long distances to load centers. Several were proposed in

the Western U.S., but are no longer seriously considered. Despite solution of all

critical technical problems and demonstrated economic advantage for large blocks of

load, it now seems quite unlikely that UHV will see much further application, the

reasons being:

o Growth in maximum transmission line rating correlates closely withgrowth in the output of power plants. The latter growth stoppedabout 1970 and has, in fact, reversed. Thus the function that wouldhave been served by UHV has not materialized. (See Figure III-6)

o Despite extensive research on the effects of electric fields, publicconcern remains strong enough to raise doubts as to whether a UHVline could be built in a developed country even if the need arose.

o HVDC technology has matured to the point where large powertransfers, where they are required, are usually better served byHVDC than by UHV. Where synchronous (AC) ties are needed, High-Phase-Order may also one day compete with UHV three-phase,serving the same transfer need at lower line-to-ground voltage.

(See also "HVDC" and "High Phase Order")

-III-14-

Power Techmologles, Inc.

10000

0z

cc _ _ 4 F u _LARGEST GENERATOR

_ - _ -_ _ LARGEST PLANT SIZE_ _ _ -__- S.I.L. OF HIGHEST

TRAN SMISSION10 ~~~~VOLTAGE

1880 1900 1920 1940 1960 1980 2000 2020

YEAR

Figure 111-6

Undermround Cablell3 2 [A]

Underground transmission cable, used primarily in metropolitan areas or underwaterlinks, is primarily:

o Pipe-Type cable, in which an oil-filled steel pipe houses three phasesof power cable.

o Direct burial self-contained cable, where each phase or all threephases are built for direct burial without a pipe. This cable may beinstalled in duct, if required.

-III- 1S-


O Extruded cable, which resembles the self-contained cable but uses apolythene insulation similar to distribution.

Pipe-Type cable has been popular in the U.S. because of its high reliability and

ease of maintenance. Direct burial cable predominates in Europe. Both have

traditionally used oil-impregnated paper for insulation. Extruded cable, the newest

approach, is used throughout the world too. Originally limited to distribution, it has

progressed upward in voltage to the point where France has considerable experience

with no failures at 220 kV (other than a dig-in) and now has installations at 400

kV.

The three basic cable design approaches cited above should be considered as viable

competitors. The best choice in a particular case will depend on the specifics of the

application and on financing since pipe-type cable is manufactured principally in

the U.S. and both self-contained and extruded cable for transmission voltages, only

outside the U.S.

Among the more innovative transmission cable technologies are:

o Forced cooling, wherein water or oil is circulated to remove heatfrom the duct, pipe or ground environment. This is a reasonablysound, well-developed practice, though limited in application to caseswhere high thermal rating or uprating warrants the expense.

o Flexible gas-insulated cable is being developed, largely through U.S.(EPRI) research funding, but is likely to serve only specialapplications, and only then after considerable further work.

o PPP (Paper-Polypropelene-Paper) insulated cable is a very promising,near-range technology that promises to reduce cable system cost andincrease thermal ratings. While initially aimed at pipe-type cable, itis also applicable to self-contained cable. While PPP splices havebeen used for over ten years, PPP cable prototypes are just nowbeing installed. PPP technology is understood in most cable-producing countries.

O Temperature-monitoring is particularly useful for thermally-limitedcable since the thermal time-constant of the environment is verylong.

-III-16-


The three basic cable design approaches cited above should be considered as viablecompetitors. The best choice in a particular case will depend on the specifics ofthe application and on financing since pipe-type cable is manufactured principally in

the U.S. and both self-contained and extruded cable for transmission voltages,

principally outside the U.S.

UDratine Lines and Rights-of-Wav10 ,33 [A]

The uprating of existing circuits (or rights-of-way), either in terms of voltage orcurrent, probably represents the most cost-effective of all methods for improving

transmission capability.

In the U.S. a number of 138 kV lines have been satisfactorily uprated to 230 kV-

some with no change in either conductor or insulation system. Most uprating hasconcentrated on overhead lines but underground cables have been modified to

increase power transfer by as much as 34% as well.

Voltage uprating is feasible because insulation and clearance requirements are nowbetter understood and the need for large design margins is correspondinglydiminished. This change has been reflected in revisions of design codes.

The most attractive opportunities for voltage uprating occur in the range fromabout 50 kV through 230 kV where:

o The conductor is large enough to operate at the next higherstandard voltage.

o Clearance to ground and to the tower will, under present codes anddesign practices, be adequate for the next higher standard voltage.

o Insulation is adequate for the next higher voltage or can be replacedby insulators that are.

o The change-over can be accommodated by the system itself,considering:

-III- 17-


- The ability of the system to operate while the line isout of service, if removal from service is necessary.

- The loss of the circuit to the lower voltage network.

- The convenience of terminations at the upratedvoltage, e.g. by virtue of the higher voltage alreadybeing used at one or both terminals.

- The uprated circuit's ability to relieve a power flowlimitation by virtue of the changed system impedancematrix.

The feasibility of voltage uprating, where limited by switching surge levels, can be

accommodated by upgrading or replacing circuit breakers by breakers with surge

control resistors.

Sometimes insulator or hardware changeout can be done without removing the line

from service. Utilities have also bypassed sections of line with temporary structures,

rebuilding the removed section, moving the bypass further along, and ultimately

rebuilding the entire line. It has been suggested that this could also be done with

cable bypasses, though in both cases a thorough analysis of the technical and safety

issues must be made.

Sometimes voltage uprating would be attractive but for too small a conductor, i.e.,

excessive corona at the uprated voltage. This limit is sometimes overcome by either

reconductoring or adding a second conductor to each phase. Doing either would

normally require structural reinforcement of the existing towers.

In one case, a utility will convert a double-circuit 138 kV line to 230 kV by

simultaneously converting it to six phase. The latter reduces the electric gradient

on the conductor.

Voltage uprating of an existing line will greatly increase its load carrying capacity.

Doubling the line voltage quadruples the surge impedance loading and doubles the

-III-18-


thermal capacity. However, the actual increase in transfer of course is determined

by the overall system configuration and generation dispatch.

Increase in current carrying capacity can be accomplished by a number of methods,

the most expensive of which is reconductoring. A far less expensive alternative is

the use of dynamic thermal ratings as described in the section on line monitoring.

Another uprating method simply utilizes existing materials less conservatively. For

example, actual measurement of the breaking strength of conductors has shown that

ACSR conductors with 15% to 20% steel by area can experience temperatures in the

range of 1 50°C for several weeks with little or no loss of strength. Maximum

conductor temperatures may then be increased from more conservative temperatures

of 75°C-95°C in order to increase the line rating.

Thermal rating of certain lin-es limited by conductor say at heavy load, have been

increased by 10% to 30% or more by a careful route survey and selective increases

in the clearance of certain critical spans through the addition of towers or the

raising of existing towers.

A careful study of weather conditions along the right-of-way can also provide a

basis for using less conservative weather parameters in a conventional thermal

rating calculation. Increases of 5% to 15% are possible using this approach.

Uprating of rights-of-way are of particular interest in countries where new rights-

of-way are scarce. Rebuilding on an existing right-of-way can often increase the

capacity of that right-of-way by a factor of ten or more.

Uprating remains one of the most underutilized methods for increasing the transfer

capability in developing countries.

(See "Compaction" and "High Phase Order")

-III-19-

SECTION IV

TRANSMISSION SUBSTATIONS


IV. TRANSMISSION SUBSTATIONS

Bus Configuration [A]

The progression from (1) Ring Bus to (2) Breaker-and-a-half to (3) Double Breaker,

Double Bus schemes (See Figure IV-1) generally represents a progression in

increased reliability34 and increased cost. While the breaker-and-a-half scheme is

clearly the most common and the best compromise, there will be applications where

the alternative schemes should be preferred. In developing countries, for example,

the cost savings with ring bus schemes may be more important than the reduced

reliability.

(a) Ring Bus (b) Breaker and a Half

(c) Double Breaker, Double Bus

Figure IV-1. Different Bus Arrangements

-IV-1-


In any case the reliability/economics tradeoffs, particularly important in developing

countries, can now be analyzed with the aid of substation reliability software.

Buswork [A]

Bus current rating should generally be coordinated with the highest future current

level anticipated on any one bus section. This may require bus rating substantially

higher than present requirements, but the penalty for over-rating bus work will

appear very small compared to the cost of rebuilding an existing substation to

accommodate system growth

The dire consequences of bus faults make careful mechanical design of high voltage

buswork extremely important. Some utilities now prefer rigid tubular bus, supported

by post insulators to the traditional suspended bus design. The former provides a

lower, more compact, "cleaner" looking station. However rigid bus has much tighter

engineering tolerances than suspended designs and makes it easier for mechanical

failures to cascade within the station. For this reason, substations which do not

demand a particularly low profile for aesthetic reasons and which may be subject to

a lack of precision in engineering or workmanship, will more safely be candidates

for suspension bus.

CaDacitors1 0 [A]

Capacitors often represent the most economic recourse in improving system transfer

capability and voltage quality. Shunt capacitors, now cost roughly $5 per kVAR

(installed) at distribution voltage and $16 per kVAR at transmission voltages. Series

capacitors cost roughly $12 to $15 per kVAR installed.

Series and shunt capacitors, now almost universally made with polypropelene film,

rather than paper, often represent the most economic way to enhance the capability

of transmission systems. In many instances, judicious use of the capacitors may

postpone the need for new lines. Shunt capacitors, more widely applied than series,

-IV-2-


increase transfer capacity by supplying extra reactive power. Series capacitors

simply make lines electrically "shorter." Both have important roles and should often

be used in combination.

Shunt capacitors are often switched (sometimes more economically on a transformer

tertiary) to accommodate changes in line loading. Where rapid response and fine

control are not necessary, switched capacitors often make an economic alternative

to static var control systems.

Capacitor switching may pose some unusually difficult requirements on switchgear,

particularly when banks are switched in parallel or "back-to-back." Any application

of capacitors should examine not only new breakers but also existing breakers

whose duty may be made more severe by adding capacitor banks.

Capacitor fusing is also a debatable issue, most European manufacturers favoring

internally-fused units (fuses on each "pack" within a capacitor can) which afford

maximum protection but which give no indication of having blown. U.S. suppliers

favor external fusing. While there are arguments for either practice, care should be

taken when internally fused capacitors are part of a tuned circuit, e.g. in a

harmonic filter, since an unknown fuse blowing can detune the bank and cause

serious problems.

As more and more shunt capacitors are added to improve transfer, systems tend to

approach voltage instability. Before approaching that point, it's usually prudent to

use some degree of series compensation.

Series capacitors, traditionally used on long, heavily loaded lines, are useful even on

compact systems if the latter are reactance or stability-limited. Series capacitors

need to be bypassed in the event of a close-in fault, lest the high voltage drop

across the capacitor's reactance cause it to fail. The advent of metal oxide arresters

gave a two-fold boost to the series capacitor option. They make application simpler,

and improve both the margin and reliability of protection. Rigid specifications for

-IV-3-


oxide arresters are important, since not all manufacturers have had equal success in

oxide protector application.

The problem of sub-synchronous resonance (SSR) was a barrier in the widespread

application of series capacitors. With development of new analytical toolsJ5 36

37, this problem can be studied and appropriate solutions can be implemented.Hence, this barrier has been effectively overcome.

Experts now discuss the prospect of thyristor controlled series capacitors toincrease stable transfer limits by modulation of series system reactance.

Gas-Insulated Substations (GISl 8 [A]

SF6 -insulated substations are useful in areas where the cost of land is high, the

environment is harsh, severe contamination problems exist, or where there is simply

no space for conventional stations. They occupy about one eighth the space of open

stations, but may even be cost-competitive where space limitation is not a problem.GIS also requires more specialized maintenance. GIS has been successfully applied

up to 500 kV. While there have been experiments with compact HVDC stations, GISfor dc should be regarded as being at the experimental or prototype stage.

Surge arresters presented a particularly difficult problem for early GIS gear, but

metal oxide arresters solved that problem by eliminating the need for internal arc

discharges. As with any oxide protector application, specifications should be quite

careful and rigorous.39

While GIS should be regarded as a mature technology, research is now focused on

the effect of very steep-fronted waves such as those generated by the operation of

disconnect switches.

-IV-4-


Groundlin and Shielding4 0 s5 [A]

Substation grounding and the shielding of control and instrument leads are poor

places to seek economies. A quality installation in either case will prevent

operating problems and the need for rework many times the original cost. The

principles of grounding in substations are well established and set forth in the

references.

Fibre optic control leads, now successfully applied in some substations, offer an

excellent way to finesse interference problems and the need for shielding. Prior to

using this technology however, utilities should have specialists trained in fibre-

optics repair and maintenance.

While some substations have operated satisfactorily with minimal shielding of

instrumentation and control wiring, it is generally advisable to use only shielded

cables unless a utility already has considerable satisfactory experience with

unshielded wiring.

Instrument Transformers IAI

Instrument transformers, potential and current transformers have changed very little

in the past several decades, even though a number of radical departures from

traditional instruments have been studied and the subject of experimentation. While

still in its infancy, optics based instruments appear likely eventually.

Protective Relays IA)

Protective relays respond to faults, overloads, voltage, instability, or other

difficulties, either isolating equipment or splitting the system. Most new relaying is

solid-state or microprocessor-based, though mechanical relays still find an

important market - principally where a new line is to match several that were built

when mechanical relays were the way to do things. No dramatic improvement in

-IV-5-


relay (or breaker) speed is likely since present 2-cycle speeds are close to the

inherent time needed to diagnose system malfunctions.

Relay application remains one of the most sophisticated aspects of system

engineering and one of the most leveraged areas of system investment. Relay

reliability and dependability is a matter of concern to utilities the world over.

Nuisance trips represent one of the most common and most serious outage causes

for many systems - normally because relays were not properly specified, maintained,

or because the system is being used in a manner not anticipated at the time the

relays were installed.

Some system planners feel that investments in protective relaying, including the

supporting communications systems, represent by far the lowest cost way of

improving system reliability and safe transfer limits. Optimizing relay system

investment does not mean adding relays, however, but rather opting for high quality

elements and selective use of redundancy and voting logic.

Relaying is a discipline in which developing countries will do well to develop

application and maintenance skills.

Static Var Systems36 [Al

Static Var Systems now costing roughly $20 per kVAR installed, have all but

replaced synchronous condensers as controlled reactive power sources. If properly

applied they can enhance stability and eliminate rapid voltage fluctuations. They are

cheaper, easier to maintain, and generally respond faster than synchronous

condensers.

A decade ago there was quite a variety of SVS options available.41 Present day

SVS is usually a thyristor switched reactor, a thyristor switched capacitor or a

combination of these with fixed mechanically switched capacitors. Use of SVS on

transmission voltage levels involves a stepdown transformer to 10 kV - 20 kV range.

-IV-6-


It is also possible to connect SVS to the power transformer tertiary taking care

that the tertiary rating allows this.

SVSs now represent a mature technology - one that is very important to full

utilization of many voltage or reactance-limited systems.

(See also "Capacitors")

Suree Arresters and BIL Specification IAl

Metal oxide surge arresters provide much lower protective levels and higher current

discharge capability than their gapped predecessor. In theory, this allows use of

equipment with lower impulse strength (BIL) and lower switching surge strength

(BSIL) than before. In practice, most utilities prefer to stay with insulation strength

they have used before, accepting protective margins much higher than the 15% to

20% which have proven a good rule in the past.

It is also wise, though not common, to undertake replacement programs of older,

gapped arresters, thus giving extra protection to older insulation that may have an

actual strength lower than presumed rating.

Recognizing the protective characteristics of Zinc Oxide arresters, present

transformer insulation levels, according to IEC standards, generally fall in the

following range:

Maximum Switching LightingSystem Impulse ImpulseVoltage Withstand kV Withstand kV

(SIL) (BIL)

300 kV 750- 850 850-1050362 kV 850- 950 950-1175420 kV 950-1050 1050-1425525 kV 1050-1175 1175-1550765 kV 1300-1550 1425-2400

-IV-7-


Switchgear 37 . 42 [A]

There have been few important improvements in circuit breakers or disconnect

switches in the past decade. SF6 now dominates the high voltage circuit breaker

market, though oil breakers are still manufactured up to 230 kV. SF6 breakers are

moving down in voltage rating to address the 38 kV market while vacuum breakers,

dominating the low voltage and industrial market will probably push above 38 kV to

compete with SF68. Air, as an interrupting medium, has virtually vanished above

utilization voltages.

Operating times have stabilized at three cycles up to 400 kV with two cycles as an

option at 400 kV and standard for higher voltages. One cycle breakers have been

built for special applications, but are seldom needed, considering the time needed

for accurate diagnosis of system faults.

Continuous current ratings for high voltage breakers are typically 2,000 or 3,000

amperes with short circuit current ratings typically ranging from 30 kA to 60 kA,

well in excess of requirements in developing countries.

Synchronous Condensers

Synchronous condensers are now seldom competitive with Static Var Systems. In

unusual circumstances they may be needed to support commutation in very weak

systems fed by HVDC lines.

(See "Static Var Systems")

Transformer. and Reactorse [A]

Transformers and reactors represent a very mature technology - one in which

dramatic changes are not likely. Thyristors will gradually replace contactors for tap-

changing, though this is still a prototype development.

-IV-8-


Volume variations in insulating oil are usually accommodated by "Conservators," i.e.

a tank with an air cushion, pipe-connected to the main tank. This works well for

slow variations in pressure but often results in tank rupture for the fast changes

associated with faults. There is considerable current interest, particularly at 500 kV

and above, in providing an air cushion within the tank to minimize damage in the

event of a fault.

Perhaps the most important current topic in transformer and reactor development is

the use of amorphous (unusually straight-grained) steel for cores. Amorphous steel

has very low losses. Quite a number of test units have been built at the distribution

level and a few for transmission application despite the increased difficulty at

higher voltages.

Introduction of amorphous-steel cores will probably be very slow and very cautious.

Their ultimate role is not yet clear and it is quite possible that the same

characteristics that reduce losses may cause resonance or overvoltage problems.

"Electrification," i.e. the build up of high static charge as a result of oil flow, is

among the more significant areas of present transformer research. Electrification,

normally associated with high velocity oil flow, is blamed for a number of

dielectric failures and has implications both in design and oil handling. Utility

engineers responsible for transformer maintenance should remain aware of this work.

Experiments have been done with gas-insulated transformers but it is unlikely that

commercial application will evolve very soon, if ever.

(See also 'Surge Arresters")

-IV-9-

SECTION V

SYSTEM OPERATION


V. SYSTEM OPERATION

The hardware, software, and communications equipment that dominate modern

control systems are no more important to system operation than carefully developed

operating policies, practices, and well trained staff. The former, however, are more

amenable to treatment in this report.

Anplications Software44 [A]

An increasingly sophisticated array of software is now available to system

dispatchers to aid their judgement in system operation and to produce information

needed for system control. Most relate to system security. They include:

Topology [Al - A means for determining, from telemetered and manually-entered data, the exact configuration of the system, e.g. which physicalbus sections form an electrical node and which line sections andtransformers form a network branch.

State Estimation [Al - Software which uses topology results and SCADAinputs (the later being incomplete, partly inaccurate, and non-simultaneous) to estimate a complete load-flow.

Contingency Analysis [Al - The process of identifying and analyzing theeffect of important operating contingencies, ranking them in order ofdecreasing severity and, in the most modern programs, suggesting actionsto reduce operating risk.

Operator Load Flow [Al - Allowing the operator to simulate steady-stateoperation of the system, opening or closing breakers, changing dispatch,etc. and note the results in terms easily understood by him. Someoperator load flows permit direct acceptance either of real-time or ofstate-estimator data.

Optimal Load Flow [PI - [A.1 - Software which goes well beyond normaleconomic dispatch to also develop a schedule of reactive power outputs,tap settings, capacitor or static var compensator (SVS) operating points.The objectives of Optimal Load Flows are typically (1) minimization ofproduction cost, (2) reduction of system losses, (3) improved systemsecurity and (4) improved voltage regulation. Optimal power flows arerarely used and where they are, generally provide the operator with astrategy (suggested changes) rather than being directly linked to thecontrol loop.

-V-1-


Hydro Scheduling IAl - Developing short-term (hours to weeks) plans foroptimum use of hydro-electric resources considering a wide variety offactors including available water, irrigation demands, load forecasts, andthermal generation costs.

Short-Term Load Forecasts [Al - Techniques for reviewing past weatherdata, load patterns and load/weather correlations to predict load profilesfor the short-term (hours to weeks) given in current weather forecasts.Long-Term Load Forecasts [Al - Procedures for developing annual andmulti-year forecasts of load given recent history, demographic patterns,and prediction of industrial production.

Unit Commitment IAl - The decision as to when specific generator unitsshould be put into or removed from service, considering power demand,security requirements, and the cost of production and standby operation.

Maintenance Scheduling [Al - Producing a frequently updated annualschedule for taking generating units out of service for maintenance, givenannual load forecasts, maintenance needs, crew and equipment availability,and multi-unit constraint.

As with many types of modern software, the above functions are available as a

package built around a common data base.

In addition to the above, it is becoming increasing popular to use what is normally

considered as "system planning" software in the control center, sometimes capable of

accepting real-time data as its initialization. This software is used by engineers

assigned to operations planning functions. Short circuit and even dynamic solutions

can be relevant to operating strategies.

It is hard to argue against the tendency, even in developing countries, to specify

state-of-the-art application programs for new control centers. Assuming the SCADA,

communication systems, and CPUs can be maintained, good application software

allows the operator to make maximum use of whatever system he is given to operate

- a requirement even more important to developing countries.

State estimation has to be treated very carefully in that regard. While it may be

very important to make the best use of known information, it is dangerous to use

state estimation without having sufficient hard data to make the estimate accurate.

-V-2-


Sparse data can lead to implied precision but mask serious inaccuracies. In fact,

one of the best initial uses of state estimation software is in the planning stages,

where the software itself is used to determine the optimum number, type, and

location of remote telemetry units (RTUs).

Control Center Confieuration [A]

Modern control center configurations are designed for a system availability of at

least 99.8 percent (cumulative failure rate of 17.5 hours per year). System

availability is a function of both the time between failures and the time to repair

and is highly dependent upon the equipment configuration. High availability is

achieved by using redundant components (e.g., computers, auxiliary memory units,

man/machine interface equipment and power supplies) arranged in various

configurations principally determined by the control system vendor. A vendor's

software subsystem design is tightly coupled to the chosen arrangement of

equipment.

Modern systems tend to employ microprocessor based communications front-end

controllers to reduce loading on the host computers. Some also use separate

interconnected microprocessor based subsystems to handle most of the display

processing.

Virtually all new systems use multicolor limited-graphic displays with special

function keyboards supplemented by light pen or trackball cursor positioning devices

as the primary man/machine interface. These are arranged in specially designed

dispatcher consoles, each with two or three CRT units. Electric utility limited-

graphic symbols are used to construct one-line diagram displays designed by utility

personnel. Full-graphic display systems, of increasing interest, represent an

emerging technology - one requiring significantly more expensive display equipment

and computers. As the technology matures over the next several years their cost

will decrease.

-V-3-


Typical systems employ "mirror image" computer subsystems with certain peripheral

equipment (e.g., communication processors, printers, and display units) connected to

one subsystem or the other via computer and manually controlled peripheral

switches. One subsystem serves as primary while the other operates in a "hot

standby" mode. The data base in the standby subsystem is periodically updated

using a high-speed computer-to-computer data link. Failover from the primary to

the standby subsystem can be both manually and automatically controlled.

Configurations are increasingly being seen where two or more host computers are

connected together and with the peripheral equipment using a local area network

(LAN) such as Ethernet. LAN configurations offer greater flexibility, improved

expansion capacities and lend themselves well to distributed processing. A single

LAN can, with very low probability, present a single point of failure; therefore,

some systems utilize two LANs to ensure the desired system availability is

maintained.

Control Software44 [A]

Some software is integral with on-line system control. Automatic Generation Control

(AGC), a relatively mature technology, allocates the total MW demands of the

system among generators, continuously matching total generation with the load,

plus interchange. On interconnected systems, measured net flows between systems

combined with frequency deviation are used to guide control action needed to

maintain frequency and scheduled interchange.

The allocation commands given to AGC are developed by "Economic Dispatch" (ED)

software which minimizes the sum of production cost and the cost of transmission

losses. Modern dispatch programs also accommodate constraints, ranging from system

security to pollution control. Normal ED software is unable to schedule reactive

power output, transformer tap positions, or changes in system configuration. Those

decisions, also important influences on losses, security, and service quality, are now

-V-4-


the subject of considerable industry development and are discussed under "Optimal

Load Flow" in the paragraph on "Application Software."

AGC and ED, supplementing a basic SCADA system, form the core of most

sophisticated control systems.

SCADA Systems4 6 [Al

"Supervisory Control and Data Acquisition" (SCADA) systems represent the nerve

system of energy control and the foundation for more sophisticated control systems.

The SCADA system includes:

o Sensors at remote points on the system, now increasinglysupplemented by distributed microprocessors or programmablecontrollers which improve the quality of data transmitted to thecontrol center and may also perform certain local functions.

o Communication link to the control center, by combinations ofmicrowave, power line carrier, and leased phone line. Radio linksand fibre-optic segments may also be used.

o Central processors for data reduction, control, and applicationsoftware functions. CPUs will often be distributed or paralleled toachieve response-time and availability requirements.

o Relational data bases, the most dramatic recent improvement inSCADA systems, allow great flexibility in displays and analysis ofdata.

o Color graphics systems, now universally used, typically high-resolution, and often replacing the traditional "mimic board."

Among the more current developments are "expert systems" applications to help

interpret operating data - particularly alarms. They will become very useful in

suppressing alarms that are meaningless, redundant, or in error.

SCADA systems are an essential part of energy control in virtually any country.

They are normally very cost-effective. In developing countries, one must be careful

-V-S-


about oversophistication and the availability of manufacturer support for complex

hardware and software SCADA elements.

(See also "Control" and "Application Software")

Securitv10 [A]

Much of the system security issue is associated with and discussed under application

software programs in "System Operation."

The broader issue includes efforts to minimize the risk of any service interruption,

of containing that interruption if it does occur, and of speeding up restoration. The

U.S. has led the development of procedures and software to minimize and contain

interruptions. The Soviet Union has put more emphasis on minimizing their

consequences and on automating restoration.

System security standards should be carefully tailored to the requirements of each

system. It is unlikely that those requirements would be the same for systems in

both industrialized and developing countries.

Training4 6 [A]

Dispatcher training is recognized as extremely important to system security.

Courses, particularly audio/visual courses, are good at teaching fundamentals, but

there is no substitute for exercises specific to the system to be operated. One of

the most popular and effective ways to train dispatchers in the real context they'll

be working, is to use a spare CRT-based console that is able to access all the

software and displays available from the main operating consoles. Data are

simulated or come from the real-time data base. Actions initiated at the training

console are not permitted to affect the real system. Actual system condition,

including those associated with past emergencies, can be loaded for access at the

training console.

-V-6-


Wheeline of Power47 [A]

Wheeling is defined as "The use of transmission or distribution facilities of a system

to transmit power of and for entities other than that which owns and operates the

lines involved." It is obviously a problem in countries which have multiple systems,

although, while as old as interconnected systems themselves, it has never been a

major issue. Networks were designed to accommodate contract flows and, to a

certain extent, inadvertent flows resulting from emergencies or equipment outages.

The movement towards deregulation and privatization has caused an increased

interest in wheeling. In the total absence of regulation, there is no control over

flows through intermediate systems and no way to plan for adequate transmission

capacity or secure system operation. The result can cause a severe economic

penalty to the intermediate system since the transmission losses (which it must

supply) are proportional to 12. Thus a company forcing a 10% increase in loading of

a line it does not own, imposes a loss increase of 21% on the intermediate utility,

irrespective of the prospect of conductor overheating, sag excess, etc. Yet it is

often in the best interest of consumers to encourage competition for generation and

to make maximum available use of transmission.

In a newly-private system, concerns over the operation and ownership of the

transmission system and future wheeling arrangements have resulted in industry

structures that associate transmission with the generating utilities in some countries

and with the distribution utilities in others. The whole issue is under debate, and

represents a particularly complex argument considering an ac system's inherent

inability to direct or regulate flows, and the difficulty in establishing fair rates for

transmission access.

-V-7-

SECTION VI

DISTRIBUTION


VI. DISTRIBUTION

Distribution Automation4 8 ,49 [A]

Automation of distribution systems addresses such functions as:

o Feeder sectionalization

o Meter reading

o Load control

o Capacitor control

o Monitoring and Data collection

The economic case for distribution automation is much debated. In making economic

comparisons, for example, it is important to compare automated systems with

manually-operated systems having extended manual control options rather than with

the inflexible characteristics of many existing systems. Where automation is a

clear-cut, reasonably long term alternative to reconductoring or power equipment

replacement programs, it can be very advantageous.

Distribution automation is an example of new technology that may actually have

more application in developing countries than in industrialized countries ...

particularly where applied to load control. Developing countries often have more

incentive for load control, both in stretching the existing transmission and

distribution systems and in accommodating generation capacity shortfalls. They are

also less sensitive to the reliability degradation inevitable with intentional load

trips.

Distribution Voltaie5 0 [A]

Distribution voltages have increased over the past several decades, initial feeling

being that 35 kV would be optimum for many high density as well as rural systems.

-VI-1-


The reliability of 35 kV systems has been disappointing, however, particularly where

a lot of underground is used. System problems such as lightning and switching

overvoltages as well as ferroresonance which were not significant at lower voltage

become more important at 35 kV, due in part to the lower insulation margins

characteristic of 35 kV equipment. While these phenomena are well understood and

easy to avoid in the engineering of transmission systems, it is impractical to try to

anticipate all possible configurations of a distribution system - hence the need for

systems which have margin sufficient to ride through them.

15 kV distribution still appears the best choice for many systems, particularly those

in developing countries. An exception is the case where rural distribution

predominates and feeders are unusually long, in which case 35 kV may be a better

choice.

Minimum Cost Rural Distribution [A.]

A variety of innovations have been used for distribution where shortages of money

or materials makes conventional systems impossible. Single phase, ground-return

systems have been used in Australia, New Zealand, Canada, and the U.S. to serve

widely dispersed rural loads. In North Carolina, for example, a 7.2 kV single wire,

ground-return system achieved its ground at the step down transformer by extending

a local ground wire one span in either direction, terminating it in a guy and screw

anchor system. In some cases steel conductors have been used.

A World Bank/CIDA financed project in the Ivory Coast included single-wire earth

return systems using Canadian experience.

Surge Protection61' 62 [A]

Metal oxide arresters, a boon to transmission applications, must be looked at much

more carefully on distribution systems. In many cases, all the advantages of a

gapless device apply. However some distribution systems, particularly those in

-VI-2-


developing countries, are subject to voltage variations which are hard to predict

precisely. Thus the risk of exceeding the continuous capacity of a gapless protector

is much higher. Where that risk is significant, it may be wiser to use a gapped

arrester, thus preventing arrester current absent a bona fide fault.

Switchzear and Switchinv53, 54, 61 [A]

Although vacuum breakers are very widely used on today's distribution system, SF6 .

promises to become a significant competitor. Distribution vacuum breakers are

usually under oil, with all the attendant oil-insulated gear problems. SF6. breakers

require no oil and have a better history of operation, reliability, and safety since

failures are not explosive.

Automatic reclosing is becoming less common in developed countries. More systems

are now underground, and it makes no sense to close on underground (presumably

permanent) faults. Also, with most fault currents reaching well beyond three or

four thousand amperes for many systems, fuses operate in one-half cycle, making it

virtually impossible to save the fuse on temporary faults by reclosing. Finally, fuse

operation interrupts just one lateral whereas reclosing interrupts the entire feeder.

With more and more sensitive loads, it is often better to accept a longer outage

time if it means fewer loads are out.

System Confieuration 5 s [A]

The five basic distribution system configurations are shown in Figure VI- 1. The

radial system is least expensive and least reliable, the spot network being highest

on both counts and appropriate only to dense metropolitan load areas. The primary

loop configuration is by far the most common in the U.S. It permits isolation of

permanent faults with minimum disruption to other loads.

-VI-3-


PRIMARY FEODRS

(1) PAOIAL

rO LC.AOS

(2) PAIMARY

LOOP~~~~~~N

( PIMARYTO rA S

NO NoT- T

DNOARY ~~~~~~~~~~~F1OTO LOAOS) SECrTvE 1CTI_E

, SPOT1 OR TO LOADS

NETWORK TRANSFORMERWITH PROTECTOR

NO* NORMALLY OPEN SWITCHOR RAEACER

Figure VI-I - Five Basic Distribution Service Systems

There has been a strong recent trend to four-wire distribution systems, their

advantages being:

o Higher, more predictable fault current, allowing better relayprotection.

o Lower BIL.

O Economy in single-phase underground laterals (no need to use twophase-wires.)

o Greater reliability.

-VI-4-


Underground Cable5 6 [A]

Virtually all distribution cable is extruded, most of it cross-linked polyethylene

(XLP). Research is now focused on improved reliability, including the prospect of

more widespread use of Ethylene Propylene Rubber (EPR) due to its good failure

record. Reducing the exposure of distribution cables to surges is also felt important

to improve reliability. Evidence attributing failures to surges, particularly in older

cables, is now very strong.

-VI-5-

SECTION VII

SYSTEM DESIGN


VII. SYSTEM DESIGN

This section will address some of the more important issues in system design. Most

are closely linked to software and, while discussed separately here, are often

addressed by "activities" within a common software package. (See Section VIII-

Software).

Dynamic Analysis57 [A]

Modern dynamic analysis requires flexibility in problem scope, time span and time

resolution. The last decades efforts at better defining machine and load model

characteristics have resulted in their very accurate simulation. Among the features

of state-of-the-art dynamics programs are:

o HVDC models, with comprehensive control simulation

o SVS models, including controls

o Frequency-dependent system models

o Extensive libraries of protective relay models, capable of beingeither "set" to operate as they would during actual systemperformance or raising "flags" to show how they would haveoperated.

o Utility modules for estimating parameters when accurate data isunknown.

o Provisions for checking excitation system models against actualexcitation system performance.

o Provisions for eigenvalue and frequency domain analysis.

Insofar as technical capability is concerned, modern dynamics programs can carry

solutions out to steady-state values with any degree of resolution in between.

Economics of computer time however, suggest special program features for "mid-

term" stability, also inherent in leading software offerings.

-VII-1-


Fault Analysis

Modern fault analysis programs will handle complex combinations of unbalanced

faults, including:

o Identification of individual ground currents

o Provision for single-pole closing

o Provisions for sizing of circuit breakers.

Harmonics5 8 , 65 [A]

It is estimated that by the turn of the century, one half the power consumed in the

United States will flow through silicon. The rapid growth in low-cost thyristor

control of lighting and motor drives in virtually all developed countries has brought

the issue of harmonics to prominence. The harmonic currents generated by static

converter controlled loads flow into the system and may damage capacitors, motors

and other equipment. The increased use of shunt capacitors for voltage and

reactive power control makes it more likely that harmonic currents will see

resonant points in the system, thus amplifying both harmonic current and voltage.

Distorted voltage waveshape can affect the timing of equipment that depends on

consistency in voltage zero from cycle to cycle. Higher harmonic currents can

induce noise in communication circuits.

The industry has responded to the problem by strengthening standards which limit

harmonic currents sent to the electric utilities by encouraging filters at major

harmonic generating loads.

Harmonic generation is often a more serious problem in developing countries than in

industrialized countries. New production facilities impose loads which, in developing

countries, tend to be large relative to local system capacity, thus making the

consequences of harmonic currents more severe. Situations of this kind should

-VII-2-


always be preceded by analyzing the harmonic effects and determining the

appropriate solutions.

Load Flow59 [A]

Load flow programs have grown dramatically in sophistication and speed. Among

recent advances are:

o Increase in representation capacity to easily accommodate extremelylarge systems, e.g. all of the Eastern U.S. or Central Europe. Thishas virtually eliminated the need for equivalents in representation.

o Increases in speed to permit automated sweeps through a large fieldof cases.

o Economic dispatch capability to replicate actual schedule ofgeneration.

O Automatic transformer tap changer action.

o Area interchange analysis.

o Automatic generation of contingency cases.

o Programmable sequence of events.

Maximizine Transfer CaDabilitv'0 [A]

Many industrialized countries have been forced to "stretch' existing transmission

systems beyond transfer levels for which they were designed. This is due to load

growth, a dearth in new line construction, and shifting generation patterns and

transfer incentives.

The challenge of maximizing transfer capability of existing systems uncovers useful

recourses in:

o Transmission line uprating

-VII-3-


O Addition or modification of substation equipment

o Changes in system operation and control

o Modifications in power plant control

o Reassessment of reliability criteria.

While these studies were inspired by a system where additions were inhibited by

regulatory or environmental constraints, they are equally applicable to systems

whose expansion is limited by financial resources or which, while committed to

expansion, must do so in as leveraged a way as possible.

Prior to committing new transmission facilities, any system would do well to go

through an exercise to see what stretch remains in the existing network through a

variety of recourses such as those cited above.

Plannine6 [Al

The system planning process traditionally consisted of:

1. Forecasting Loads

2. Developing alternative generation plans and dispatch schedules.

- Aided by sophisticated simulation of reliability andproduction cost, including plant maintenance, hydroscheduling, representation of load management, etc.

3. Identifying alternative transmission system plans capable ofaccommodating new loading levels, considering thermal ratings,voltage tolerances, and dynamic behavior.

- Now based on very accurate simulation, aided by recentresearch on machine and load modeling.

- Considering a broad array of equipment options toenhance power flow control and dynamic performance.

- Basing transmission costs on preliminary optimizationstudies.

-VII-4 -


4. "Testing" each transmission alternative against standard (severe)contingencies to assure that each alternative results in a "tough"system.

- More modern approaches go beyond "pass/fail" tests andassess the value of differences in reliability ofalternatives.

5. Selection of the minimum cost alternative.

- Considering both generation and transmission investmentand operating costs.

6. Studies of subsidiary issues, including overvoltage and protection,relaying, and communications.

Generation and transmission planning are logically coupled. Traditionally, because

of the relative investments and lead times, transmission planning tended to react to

generation planning, with distribution planning done last.

Computer programs which combine some of these steps have been developed -- e.g.,

our "TPLAN" and EPRI's "EGEAS." These cycle through menus, carry out many

analyses, and give tentative recommendations which can then be analyzed using

detailed models.

Today, in the US and abroad, new elements of planning are in the limelight. One

is the need to consider objectives of a variety of utility stakeholders: various

classes of rate payers, equity holders, creditors, the regional or national society,

etc. Related to this is the active participation of these parties in the planning

process, which is no longer the private domain of the utility. Unusual options for

customer-supplied energy sources and new utility-customer relationships are on the

table. Finally, new and critical uncertainties and risks must be accounted for.

The new planning environment, and responses to it, are discussed in Section IX of

this report.

-VII-5-


Production Simulation6 l (A]

Modern production-simulation ("production cost") programs to examine a spectrum of

time frames, ranging from short term operations planning analysis to long term

resource and strategic assessment of up to 40 years. They will simulate production

chronologically, incorporating unit commitment constraints, transactions, and unit

modeling or by handling key variables probabilistically. Such programs will

recognize multi-area transmission limitations, accommodate supply and demand side

load management strategies, storage alternatives, emissions constraints, and a

variety of other financial and operational issues.

While production simulation is most widely used by utilities in industrialized

countries, its ability to minimize production costs make it extremely helpful in

developing countries where there is flexibility in power sourcing. Table VII- I

summarizes the five principal types of production-simulation programs.

TABLE VII-I

Summary of Production-Simulation Programs

BALERIALDX MONITE QUICK ANDMETHOD CUMULANTS CARLO DIRTY DETERMINISTIC

<----------------ACCOUhNT FOR THERMAL UNIT FORCED OUTAGES----------------->

LOAD CHRONOLOGICAL PLACE-WISE USUALLY SEASONAL CHRONOOLOGICALMODEL OR LOAD- LINEAR CHRONOLOGICAL LOAD-DIRATION

DURATION LOAD-DLRATION CLRVESCURVES CURVES

RESLLTS -----------------AVAILABLE LINIT-BY-UNIT----------- AG6EGATED INDIVIDUALBY FLEL LUNITSTYPE

COMPUTER LON6 MODERATE DEPENDS ON SHORT SHORT TOTIME NUMBER OF MODERATE

GAMES

OTHER -----FAIR MCOELING OF -----> GOD MODELING MANY GOOD MODELING<--TIME-DEPENDENT EFFECTS--) OF TIME- SHORTCUTS OF TIME-

DEPENDENT EFFECTS DEPENDENT EFFECTS

CAN BE USED INACCULATE --------------CAN BE USED ON ALL SYSTEMS------------->ON ALL SYSTEMS FOR SMALL SYSTEMS

-VII-6-


Subsynchronous Resonance62' 63, 64 [A]

In the 1960's severe oscillations, capable of fracturing generator shafts, were

observed on systems using series capacitive compensation, it being found that they

resulted from a combined resonance of the system's electrical properties and the

mechanical properties of steam turbine-generators. "Subsynchronous Resonance" has

since shown itself to be a potential problem on a number of series compensated

systems.

The initial "fix" was to apply a filter tuned to damp the frequency of oscillation.

Subsequently less expensive devices were introduced to achieve damping.

Alternatively, system designers have preferred to reduce or eliminate series

capacitors on systems subject to this problem. In some systems the possibility of

SSR occurs only under several simultaneous contingency conditions considered to be

extremely improbable. In such cases the approach has been to use SSR detection

and accept the risk of having to trip generators.

Subsynchronous resonance is now sufficiently well understood to trigger very careful

study on any potential application of series capacitors. It should not be regarded as

reason to discount the series capacitor option, but merely as an extremely important

check to be made in system studies involving such application.

Voltage Instabilitv10 [A]

Voltage instability or "collapse" has gained new attention as systems have been

loaded closer to their steady-state dynamic limits. Without adequate voltage support

near load areas, a point can be reached where the reactive demands of loads cannot

be satisfied, resulting in rapid "collapse" of voltage. Once initiated, there is no

way to reverse the collapse process with loss of load. However there are methods

for gauging the systems "proximity" to collapse, both in planning and during the

course of system operation.

-VII-7-


Shunt capacitors, placed near load areas, extend the safe transfer limits of the

system but also steepen the edge between normal operation and collapse. Series

compensation helps too, without steepening that edge. Usually some combination of

the two, or with static var systems, is best.

-VII-8-

SECTION VIII

SOFTWARE


VIII. SOFTWARE

Software has become an increasingly important technology, affecting virtually every

aspect of power system planning, design, construction, and operation. An

appreciation of the changing nature of software is essential to anyone dealing with

technical, financial, or managerial aspects of electric power systems.

Artificial Intelligence [R]

Artificial Intelligence is the means by which a program, in the course of its

execution, gains and stores experience of value in later calculations. Practicability

of implementation is improving, as the Al languages (LISP, Prolog) become available

for conventional computers as well as their initial special machines.

Applications in the electric power industry are slow to appear and it seems unlikely

to see significant practical applications for several years.

(See "Expert Systems")

Data Bases [A]

Data bases, originally an inherent part of individual programs, have emerged as a

product in their own right. Modern "Relational" data bases will serve such functions

as:

o Accepting and ordering data, making unit conversions andreasonableness checks.

o Complex searching and sorting to specified requirements.

O Plotting of one variable against another, either directly from datastored or through exercise of an algorithm based on that data

o Accepting programs based on the stored data, providing a convenientuser link to that program and others similarly coupled.

- VIII- 1-


O Minimizing the effort and storage space required to establish andmaintain a date-coded general purpose data base with monitoredaccess rights and security measures.

Some data bases can be used to knit together a group of related individual programs

into a cohesive, user-friendly package. Limitation in the representational capacity of

programs that were originally designed for free-standing operation will remain

however.

Expert Systems [P]

Expert systems attempt to capture the wisdom and experience of experts and build

those inputs into software to help those with less skill. Expertise can be

incorporated directly into the program or through a question and answer procedure.

Early applications among utilities are in less sophisticated areas such as fleet repair.

The first technical applications are in areas that are largely experience based, e.g.

relay settings, training simulators, and turbine diagnostics. It is also likely that

expert systems will be used to allow those only marginally acquainted with a

technical discipline to use sophisticated programs in that discipline for the limited

scale or generalized solutions needed by the investigator or for training.

(See "Artificial Intelligence")

Hardware Trends [A]

Hardware capability and cost continue to be closely linked to software trends.

Among the key developments in hardware are:

o Speed increases continue. Sometimes measured in "MIPs" (Mega-Instructions per second), five years ago, I MIP was the cutting edgeof commercially available minicomputers. Now 10 MIP machines areoffered and 100 MIPs on the horizon.

o Costs continue to decrease at roughly 10% per year for a givenmodel, closer to 30% per year for a given compute capability.

-VIII-2-


o Office "Work Stations" consisting of small computers, intermediate incapability between a PC and a mainframe, combined with a completeperipherals package, are becoming less expensive and more popular.

O Memory costs have decreased to the point where memory's hardly alimitation in most applications. But the industry is becoming moreaware that magnetic memory has a limited life (Usually two to fiveyears without reprocessing) and that optical memory, in addition toits immense capability, has virtually no deterioration.

o Parallel processing, originally introduced in the form of specialpurpose computers, is now showing up as an integral feature ofmodern mainframes. In some of the newest computers, the parallelingof computations is an option exercised by the compiler to makemaximum use of available CPU resources.

o Although initially unattractive due to the need for special computers,except in special applications, parallel operation of multiple standardcomputers has recently been shown to be promising.

o Personal computers are virtually universal and will continue to growin popularity and power, differing less and less from what are nowconsidered "work stations."

o High resolution color graphics systems are now widely available andwill continue to drop in price.

Of paramount importance in selecting hardware for a particular application is the

degree of manufacturer support in the installed location.

"Product" Status of Software

At first, most application software was developed by users. User groups then

formed, pooling resources to maintain and improve the more successful programs.

Commercially developed software was then gradually introduced and, as is the case

with electrical apparatus, became the logical way to concentrate development and

to accommodate the growing burden of maintenance and support. The analogy to

"manufactured" products goes further than many realize. Commercial software

developers:

-VIII-3-


o Pool the most current needs and the best ideas of a wide variety ofusers, through market research and a broad industry interface.

O Through use of program "shells," develop code for ease of use, filehandling, modification, and maintenance. In the case of software,"maintenance" amounts to accommodating changes in operatingsystems, compilers, graphics and other peripheral devices, eliminationof latent errors, and alteration of algorithms for improved accuracyor extended scope.

o Avail themselves of sophisticated "Machine Tools" for manufacture-in this case software utility programs which help organize, write,optimize, maintain, and diagnose code. Similarly, software sourcecode maintenance programs keep a log which helps a manufacturermaintain and institute retrofits for old versions of a program.

O Initiated rigorous Quality Assurance and testing programs.

o Developed the equivalent of "spare parts" support - in this caseadditional modules to extend the useful scope of software.

o Instituted warranty and user support "hot lines."

o Launched major R&D programs to advance their product offering.

It is seldom economic for individual users to develop programs which are available

in commercial form.

Structure [A]

Until about 1970, most computer programs addressed a single, limited scope problem,

e.g. load flow, short circuit, stability, etc. Each called for its own input data, and

most simplified certain boundary conditions. In 1970 a pioneering program was

introduced which bundled four programs which used the same data. What used to be

separate programs became "activities" within a common program package. Data input

was simplified, problem-solving was more convenient, and fewer boundary

simplifications were necessary. Most modern software now uses this approach. In

system planning, for example, load flow, short circuit, stability, and a host of

subsidiary functions now share a common data base.

(See "Data Base")

-VIII-4-

SECTION IX

MANAGEMENT & STRATEGIC TOPICS


IX. MANAGEMENT & STRATEGIC TOPICS

Corporate Modelin26 6 [A]

Financial modeling of corporations goes back to the late 1960's, the basic idea being

to allow top management to interpret decisions (plant additions, rate policies, fuel

alternatives, etc.) in terms of their effect on the income (i.e., profit and loss)

statement and balance sheet. Early models were complex and tended to be inflexible.

This limited their usefulness. Current practice tends to subdivide models (e.g.

revenues, taxes, fuel costs, etc.,) defining an interface between them. In fact the

advent of spreadsheet software, such as Lotus 1-2-3, has made model-building simple

enough for most utilities to satisfy their own modeling problem. Some form of

financial modeling, if only spread-sheet based, is essential to effective utility

management in any country.

Deregulation6 7 [Aj]

Deregulation is a strong trend in the U.S. It is assumed that by making the

generation end of the utility business competitive, production costs will drop and a

new diversity in sources will obviate the need for many more large central plants.

No one disputes the need for singular ownership and operation of distribution and

transmission facilities within a given area. In the U.S. bidding systems for new

generation are being developed and implemented in several areas. There is also

pressure to require utilities to offer unbundled transmission service (i.e., wheeling)

and to allow the wheeling of power by larger customers as well as by utilities and

independent generators.

The benefits of deregulation are not without costs and disadvantages - among them:

o Difficulties in assuring adequate generation capacity when plantconstruction and decommissioning are dependent on market forces,recognizing the high risk and long lead times involved.

-IX-1-


O Difficulties and cost premiums associated with the conversion oftransmission systems, originally designed for a specificload/generation pattern, to one capable of accommodating a flexiblepattern of generation sources.

o Difficulties in achieving reliable operation of a system wheregeneration sources have diverse ownership and, in many cases,subsidiary purposes, e.g. steam production.

o Economies of scale, the ease and cost of pollution control, andenforcement of national fuel policies are lost, in part, withdependence on smaller, decentralized generation.

Deregulation, at least in its extreme form, should be viewed with extreme caution

prior to a clear demonstration of its advantages over assigning total power supply

responsibility, within a fixed area, to one accountable entity. It should not be

confused with "Privatization," the act of transferring state owned utilities to

private ownership.

(See "Dispersed Generation")

Enerev Modelini68 [A]

Many countries attempt, with varying degrees of sophistication, to model their

entire energy situation, from primary fuel resources to utilization. Many early

models were too complex, and buried too many assumptions to win the confidence of

decision makers. The trend has been to subdivide models into smaller, manageable

modules, allowing judgement inputs as they are used together to address larger scale

issues.

Prior to embarking on comprehensive energy modeling efforts, governments would do

well to survey the successes and failures of other countries in this field. Some of

the best work on the subject has been done by the International Institute for

Applied System Analysis (IIASA) in Vienna.

-IX-2-


Least Cost Planning6 9 70 [A]

Until the early 1970's, utility planning studies, largely centered on issues internal to

the utility, sought to minimize the present worth of revenue requirements or some

other economic or financial yardstick specific to the utility. Public awareness of

the socio-economic impact of electric power, together with new consciousness of the

environmental impact of planning choices, gave rise to a more circumspect approach

to system planning - one that optimizes the total societal cost. "Least cost

planning," as it is called, examines such issues as demand-side alternatives to

supply-side growth, affordability, value of service, etc.

Because least cost planning must compare a wide range of dissimilar alternatives,

new techniques were necessary and they have been developed.

While the issues involved in least cost planning for developing countries will be

quite different from those associated with the same process in industrialized

countries, the least cost process may be even more germane in the former. For

example, the value of electrification in building up economic infrastructure in a

developing country may actually outweigh its value as measured in revenue-

producing service.

(See also "Prioritization and Structured approaches to complex decisions)

Maintenance Policies

Maintenance policy and operator training is part and parcel of an increasingly

important tradeoff between plant design, first cost, service reliability, and

equipment life. That balance is sometimes poorly understood by those countries

least able to afford the penalties of poor balance. The objective of developing

countries should be to:

-IX-3-


O Stick to relatively simple, well-proven plant designs, avoidingfeatures that are poorly understood, marginally useful, or difficult tomaintain.

Equipment and software suppliers receive bid specificationsfrom developing countries which call for state-of-the-arttechnology and redundant designs where simple, lessexpensive, and more easily maintained alternatives wouldappear better suited.

o Stress the building of maintenance and operating skills and facilities,as opposed to reliance on excessive equipment redundancy.

Redundancy and automatic throw-over, often coupled witha large spare parts compliment, are often considered asubstitute for the lack of local maintenance skills. Yetcomplex plants cost more and are less reliable thansimple ones. Maintenance and operator training is a farbetter long range investment.

O Limit the number of qualified suppliers and technologies, thussimplifying maintenance and facilitating a rational spare parts policy.

Competitive considerations often result inengineer/constructors mixing equipment from an unusuallybroad spectrum of suppliers. That pressurenotwithstanding, specifications can be written to minimizethe range of technologies that need to be serviced, andthe number of spare parts that need to be maintainedlocally.

This does not necessarily mean low-technology solutions are best for developing

countries. It does suggest that technology be used much more selectively, and that

it not be considered a substitute for aggressive maintenance or operator training

programs where the latter is the real availability limitation.

Prioritization and Structured Anproaches to Comolex Decisions7 1

Engineers have long appreciated the power of eigenvalues in simplifying complex

response characteristics of electrical, mechanical, chemical, or other system. One

breaks the system into "orthogonal' (uncoupled) components, analvzes the problem

-IX-4-


one component at a time, and treats the whole problem as the sum of several

simpler ones.

The same general approach has been found useful in simplifying complex judgement

challenges that confront decision makers, for example, "Which prospective

structural alternatives is best for our national utility system?", "What mix of

generation will best satisfy the diverse pressures we're subjected to?," or "What's

the best portfolio of R&D projects considering that I can't fund all of them?" In

each such case there are "orthogonal" attributes that can simplify the comparison

and lend clarity and structure to the judgement call that must ultimately be made.

The problem is often less of evaluating individual options than comparing alternative

"portfolios." Portfolios are most commonly reviewed in terms of "balance" and

"robustness," balance measuring the degree to which a portfolio satisfies objective,

and "robustness" indicating the sensitivity of a portfolio to surprises in the

operating environment.

The process, relatively new, is essentially a disciplined way of addressing complex

alternatives or groups of alternatives and as such will be useful in many countries

and a wide variety of issues.

Privatization72 [A]

The past decade has seen more and more conversions of government-owned utilities

to private companies, either through vertically-integrated companies of regional

scope or of separate generation and distribution companies, or both.

The success of "privatization" hinges on better management and operational

efficiencies, stemming in turn, from financial incentives of private owners.

This move, while mainly seen up to now in developed countries, has also been

proposed as a means of revitalizing and de-politicizing national utilities in

-IX-5-


developing countries. One useful means proposed for achieving more efficient

operation is "performance contracting," a deal where private owners or operators

agree to certain economic bogeys and share in the savings achieved beyond those

norms. Performance contracting must be done with great care to assure that the

benefits are long-term.

Productivity7 3 [A]

Utilities in the U.S. and in many other countries are subject to new pressures to

improve productivity through improved methods, through automation, and through

better organization and deployment of human resources. Improvements in methods

and automation have evolved constantly and are now encouraged, in the U.S. at

least, by comparative productivity data for power plant, and line crews.

The potential for improving productivity further is apparent from the very wide

disparity in employees per installed MW among world utilities having similar systems

and internal staff scope.

A variety of approaches to human productivity have been used successfully. Most

lead to reductions in the number of management layers (vertical) and the degree of

organizational compartmentalization (horizontal). Most achieve these goals by

eliminating or farming out marginally useful or highly cyclical work, and by

increasing management spans of control, i.e. the number of direct reports.

One of the most successful and most quantitative approaches begins by building a

data base which, among other information, describing how every employee currently

spends his time. This is done by means of a "dictionary" of activities, usually

tailored to the company under study. The data base helps improve structure, improve

work flow, and allocate human resources in accordance with priorities.

To be effective, productivity improvement programs must have the support and

-IX-6-


participation of top management and must be sheltered from excessive political or

institutional constraints.

Strateeic Plannin&z4 [A]

No corporate or government entity can avoid the need for some form of strategic

planning. Experience with strategic planning suggests that whether strategic

planning is done by internal specialists, hired consultants, or is built into the

management function is less important than whether it:

o Is based on a clear statement of mission and objectives.

o Includes a realistic, dispassionate appraisal of the operatingenvironment, including its constraints.

o Fosters imaginative, and courageous thinking.

o Results in strategies that are straightforward and simply stated.

o Is a process rather than a document.

o Involves and has the commitment of top management.

Strategic planning is a judgement game. While software and modeling may provide

inputs, the strategic process itself cannot be "programed."

Utilities who have never done strategic planning would be well to sponsor internal

workshops on the method and, from that point forward, learn by doing the planning.

(See also "Prioritization and Structured Approaches to Complex Decisions")

-IX-7-

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-R-2-


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-R-4-


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(68) Enersv in a Finite World: Executive Summary, by Alan McDonald. Reportby the Energy Systems Program Group of the International Institute forApplied Systems Analysis, Wolf Hafele, Program Leader. Executive Report4, May 1981, Revised October 1981. IIASA, A-2361 Laxenburg, Austria.

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-R-6-

ENERGY SERIES PAPERS

No. 1 Energy Issues in the Developing World, February 1988.

No. 2 Review of World Bank Lending for Electric Power, March 1988.

No. 3 Some Considerations in Collecting Data on Household EnergyConsumption, March 1988.

No. 4 Improving Power System Efficiency in the Developing Countriesthrough Performance Contracting, May 1988.

No. 5 Impact of Lower Oil Prices on Renewable Energy Technologies, May1988.

No. 6 A Comparison of Lamps for Domestic Lighting in Developing Countries,June 1988.

No. 7 Recent World Bank Activities in Energy (Revised September 1988).

No. 8 A Visual Overview of the World Oil Markets, July 1988.

No. 9 Current International Gas Trades and Prices, November 1988.

No. 10 Promoting Investment for Natural Gas Exploration and Production inDeveloping Countries, January 1989.

No. 11 Technology Survey on Electric Power Systems, February 1989.

Documents

Technology Survey Report on Electric Power Systemsdocuments.worldbank.org/curated/en/... · technology's success. The report will serve as a technical update for engineers generally