Electrical Power Generation, Transmission, Storage and Utilization Ray Findlay IEEE 2002 President...

Electrical Power Generation, Transmission, Storage and

Utilization

Ray Findlay

IEEE 2002 President

McMaster University, Canada

r.findlay@ieee.org

Robert K.Green, President & CEO of UtiliCorp United

• “The utility of the future is multinational, carries its expertise into emerging parallel businesses, has the flexibility and willingness to unbundle, adapts readily to new structures and concepts, goes beyond its traditional borders to grow, and is an expert manager of risk.”

What’s in the Future?

• Global power

• Privatization

• Consolidation

• Deregulation

• Free market competition

• Emphasis on capital, investment strategy and economics, including cost reduction

Technical Requirements• Generation: need the lowest cost generation

available to meet demand

There are many factors involved in this process, complicated, not only by technical considerations, but also by political considerations:

Environmental considerations

Maintenance and operating costs

Inefficiencies as a result of transmission

Regulatory issues

Some Elements of the Competitive Power Market

• Energy network owners - transmission• Energy traders• Energy brokers• Mechanisms for exchange• Wholesale energy pricing• Cost of energy trading• Energy service providers - distribution • Retail operations - supply• Marketing services

Challenges• Aging infrastructure• Maintenance & scheduling• Power Quality & harmonic distortion• Advances in machine & drive design• Reducing transmission loss• System complexity• Networked generation distribution• Business VS engineering decision-making• Educational issues

Opportunities

• Generation asset management

• Efforts to optimize utilization of generation facilities according to market demand

• Incentive to increase efficiencies of power plants and systems

• Incentive to rationalize maintenance schedules to minimize downtime

• Improvement of communications among suppliers, and of monitoring systems

Transmission/Network Grids, A Problem

• Unbundling the transmission grid from both the generation and delivery creates a problem - by definition it must be a monopoly.

• Need to ensure open access

• Need for regulation and oversight

• Need for maintenance & development of more capability as required

• Danger of fragmentation, congestion, tariffs, scheduling difficulties, etc.

The Retail Environment

• Role of the retailer

• One, two, how many bills?

• Wholesale versus retail

• Large customers versus small customers

• Multiple service opportunities: gas, electricity, water, financial services (credit)

• Methods of pricing for retail delivery– fixed term pricing– spot market pricing– regulated, capped or open access pricing

Control

• With large, multi-connected systems inter-tying substantial areas of the globe, communication and control become problems

• Dedicated communication lines

• Internet operation and control

• DC generation/conversion transmission versus AC generation and transmission

CoGeneration• Issue of small plants

* Methane* Wind power* Solar power* Tidal power

• Interconnections as a virtual plant• Control issues• Specialized components

Power Quality• Harmonics• Distortion: power electronic loads, adjustable

speed drives & switch-mode power supplies• Electromagnetic compatibility• Component magnetics: machines, transformers,

ACSR, etc.• Power factor: displacement power factor versus

true power factor

Power FactorDisplacement power factor:

PFd = Cos (/VfIf)

True power factor:

PFt = P/(VrmsIrms)

For 100% THD on current, the maximum true power factor will be about 0.71

Measuring Power Quality

• Total harmonic distortion Irms/I1

• True power factor

• Communications influence w2Ii2/Irms

• Crest factor Vpeak/Vrms

• There are several other special purpose power quality indices.

Harmonic Sources

• Saturable devices include electrical machines, transformers, some transmission conductors, and fluorescent lights with magnetic ballasting

• Power electronic (switching) loads include switch-mode power supplies, PWM converters, voltage source converters, fluorescent lighting with electronic ballasting, computers, etc.

• Although not strictly a source, a resonant system can exacerbate harmonics - systems containing both capacitance and inductance. An example is an inductive load with power factor correction.

Voltage Sags in a Multisource Environment

• Motor starting, transformer energizing, faults and load switching can all lead to voltage sag.

• Normal clearing time for a fault is 2 or 3 cycles

• Clearing for a motor start can take 10 cycles

• For a load switch/transformer energize, it can take 25 - 50 cycles

Voltage Sag MitigationStrategies

• Reduce the number of faults. This can be accomplished by upgrading equipment

• Improve the system. Loads susceptible to faults should be multi-sourced. Use high-impedance grounding with Y transformers to reduce the effects of a single phase to ground fault

• Interface between system and load - installed additional equipment. Dynamic voltage restorer.

• Improve the load equipment

Power Acceptability

• To ascertain power acceptability we can use power acceptability curves that measure the sensitivity of the load against voltage sags or over-voltages. The curves are logarithmic for time duration to recovery against change in voltage.

• Rectifier loads are particularly sensitive to voltage sags

DeRegulation & Generators

• Particular utilities have standard requirements (called grid codes) for generators before the generator can connect to the grid.

• However, between utilities there is, as yet, no consistency among the grid codes used.

• Once requirements in a utility are established they may be historical and may revolve around the weakest link in the utility system.

• This may cause problems for some units that may be required to conform to the weakest link grid codes. (Extreme frequency deviations, extreme VAR limits, etc.)

Resulting Problems

• Result is inconsistent standards in delivery• May result in more expensive units to meet the codes• In some areas of operation can lead to extreme

anomalies in operation, for example may never operate in the leading PF range.

• Difficulties in matching overall system requirements to generator capacity.

• Although the machines may be capable of producing the power they may be penalized for not operating in the extremes - hence leading to more expensive power.

New Technologies

• To develop a rational maintenance schedule we need to make us of new technologies, for example monitoring partial discharges of the stator windings of generators.

• Some insulation materials have predictable partial discharge behaviour which may make it possible to determine the state of the winding, as well as the specific aging mechanism.

• By keeping a record of PD activity it is then possible to develop a rational maintenance schedule.

• This type of monitoring can be set up as an intelligent system to warn of impending winding failure.

Partial Discharge Tests

• Pulse peak magnitude

• Pulse polarity

• Repetition rate

• Phase location

• Plotted results:

• Pulse height analysis

• Pulse phase analysis

• Trends

From these plots we can determine:• The overall degradation of the stator winding• The partial discharge activity: the maximum

magnitude of pulses with a particular repetition rate• The trend of partial discharge activity which yields

the progression of insulation aging• Analysis of the pulse phase plot can pinpoint the

location of the activity - slot or endwinding • Pulse patterns reveal the nature of the partial

discharge activity, including the predominant sources.

Winding Deterioration Factors

• Voltage switches and variations• Operating conditions• Fluctuations in load• Mean operating voltage level• Winding temperature• Humidity• Aging• Winding displacement in slot - fit

Web-Based Monitoring and Control• The web presents an opportunity for system automation

and control.• For large deregulated systems information transfer

plays a large part in determining success.• This gives rise to the concept of an on-line System

Control and Data Acquisition System (SCADA) .• When combined with an interactive energy

management system, we have an effective operating system over long distances and between systems.

• To take advantage of this possibility will require substantive changes in individual SCADAs, as well as a very cooperative approach to selecting standards

longitudinal flux

circular fulx

current direction

current in steel core

current in aluminum wires

An ACSR Conductor

54 aluminum conductors in three layers19 steel conductors, two layers over a single wire

M HT

EMRC

Predicts conductor behaviour over the life time by introducing statistical distribution of system loads, ambient temperature, and rise of conductor surface over ambient

COOLTEMP

Heat transferModel

ElectromagneticModel

ComplexPermeability

Data

COOLTEMP

Radial ConductionModel

Layer’stemperature

Avg.steeltemp.

Avg.aluminium

temp.

Mechanical Model

Pretensioningvariables

Stringing variables

Running-out variables

AluminiumStress

Annealing

Creep

Sag

Horizontal Tension

Steel Stresscurrent

Conductor dimensions

Complex Layer’sCurrent

Mag. Field Strength

I

I

Cicular inductances

Resistances

Longitudinal inductances

Loop inductance

total

total

d

j(I +I +I + koI )k ln[Do/(Do-d)]s i m o

j(I +I +I + kiI )k ln[(Do-d)/Dm]s i m o

j(I +I +koI )k ln[Dm/(Dm-d)]s i m

j(I +I +kiI )k ln[(Dm-d)/Di]s i m

j(I +koI )k ln[Di/(Di-d)]s i

j(I +kiI )k ln[(Di-d)/Ds]s i

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