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Cycling Is Bane For Power Utilities

Koteswara Rao Pothala

Head-Central Performance Monitoring & Nodal Control Centre, Lanco Power, India

pothalakrao@gmail.com, 91-9346302240

Author

Pothala Koteswara Rao , is a Mechanical engineering graduate with distinction from Andhra

University (1992). Obtained MBA while working. He is Certified Boiler Operation Engineer( BOE) ,

Certified Energy Auditor by Bureau of Energy Efficiency and got IPMA level-D certification in Project

Management.

Started his career as Graduate Trainee in NTPC (silver medallist). He has been O&M professional

with emphasis on power plant management in various organizations like NTPC, Reliance Power, KSK

Energy Ventures and Lanco Power. Got exposure to large PF fired, AFBC, CFBC and Combined cycle

plants. He has good hand in performance and commercial aspects of power generation.

Got yearlong advanced professional training at Germany in energy and efficiency management.

Visited China, Malaysia and Singapore on technical tours. Has authored more than eight technical

papers on Performance improvement, operation best practices, reliability improvement, boiler tube

failures, alarm conditions in operations, outage management , Generation cost reduction strategies,

heat rate improvement programme etc.

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Abbreviations used

APC Auxiliary Power

Consumption

AT &C Aggregate technical and

commercial losses

BAU Business as usual

BOP Balance of plant

BT Billion Ton

BU Billion Units

CEA Central Electricity Authority

C&M Capital and maintenance

CW Circulating Water

DISCOM Distribution companies

EFOR Equivalent forced outage

rates

EOH Equivalent operating hours

GCV Gross Calorific value

GDP Gross Domestic Product

ICRA Indian Credit Rating Agency

MMSCMD Million standard cubic meter

per day

MOEF Ministry of environment and

forests

MT Million Ton

NLDC National load dispatch

centre

O&M Operation and maintenance

OEM Original Equipment

Manufacturer

PGCIL Power grid corporation of

India limited

POSOCO Power system operation

corporation limited

PPA Power Purchase Agreement

PTCC Power and

telecommunication

coordination committee

R&R Rehabilitation and

resettlement

RLDC Regional load dispatch

centre

ROW Right of way

SEBI Securities and Exchange

Board of India

TOOP Turbine outage optimization

program

VOM Variable Operation and

Maintenance costs

USD United States dollar

YOY Year on Year

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Cycling Is Bane For Power Utilities

Abtract:

India is a land of abundant resources but ill

managed due to complex matrix of reasons.

Though there is a wide gap between supply

and demand, supply is restricted due to

political reasons and non-realisation of bills.

Units are forced to cycle with load following or

shutdowns on account of non-availability of

coal, transmission bottle necks and other

reasons . The Plant Load Factor of India has

been declining from 75.08% in 2010-11 to

69.95% in 2012-13.

This paper discusses various reasons for cycling

in India with emphasis on coal and transmission

bottle necks. It also covers effects and damages

inflicted by cycling in power plant equipment.

Introduction:

There lies ~9% peak deficit and ~8% energy

deficit in India despite its being world’s

� 4th

largest energy consumer after US,

China & Russia,

� 3rd

largest economy in terms of GDP

(Purchasing power parity 2011) after US

and China,

� 2nd

fastest growing economy in the

world after china.

Deficit scenario in the medium term will

continue. According to estimates by CEA /

ICRA, the peak and energy deficit are

projected to the 12% and 6% respectively by

the end of Twelfth Plan period, while Crisil

has projected a reduction in peak deficit to a

level of 4% by FY2015.

The Plant Load Factor of India has been

declining from 75.08% in 2010-11 to 69.95% in

2012-13.

The main reasons for energy gap in India is

due to inadequate fuel supplies, slippage in

capacity addition, transmission/open access

constraints and high aggregate technical and

commercial losses (AT & C) losses in the

country. And the Irony is that, even with

such wide energy gap, power utilities are

forced to do cycling.

If one observes the generation loss statistics

during the last three years, it is increasing YOY

as given in table-1 below. These losses are

attributed to causes beyond the control of

generator. Forced outages and extended

planned outages also contributed to generation

loss, but these are within control of generators

and could have been avoided or minimised.

Table-1 Break up of energy loss on external

causes.(Source: CEA Annual reports)

S.

No

2010-

11

2011-

12

2012-

13

REASON BU BU BU

1 Shortage of

coal

8.4 11.6 12.25

2 Wet/poor

coal quality

17.4 17.9 5.42

3 Backing

down/shut

down (Low

schedule)

13.7 15.3 13.37

4 Transmission

constraints

3.7 3.92 1.93

5 Gas

shortage

28.27 36.71 73.09

Total Loss

BU

71.47 85.43 106.06

Plant cycling refers to the operation of electric

generating units at varying load levels: frequent

shut downs/ start ups, part load operations on

various reasons.

Effects of cycling are more predominant in units

that are designed for base load operation.

(figure-1)

Base-load units are those which operate

continuously, typically for 6000+ hours per

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year, close to their maximum rated output,

except when they are offline for maintenance.

Figure-1 (Cycling definition –depiction)

Power Plant O&M costs are competing with

inflation rates and often crossing them due to

cycling and other inefficiencies in the system.

Cycling is of two types, uninteruupted cycling

and cycling with hold time. (figure-2)

Figure-2 (Types of cycling)

A start up or load change may lead to thermal

stresses of such magnitude that the elastic

limit of the material is exceeded locally. The

effect of hold time on the fatigue cycles will

depend on the position, the length of hold

time, the material, and the temperature.

Reasons for cycling

Reasons for cycling are numerous. The

cycling reasons most of the time are external

to the generator.

Let us look at some significant ones.

A. Frequent shut downs and start ups due

to one or more of the following reasons.

a. Reserve shut down due to coal non-

availability

b. Reserves shut down due to grid

limitations Forced outages

c. Forced outages

d. Equipment failures (part load)

B. System load requirements ( Schedules)

a. load following, and

b. grid limitations like inadequate

evacuation capacity, low demand,

transmission line congestions etc

c. Extended planned outages

C. Input conditions

a. Major changes in CW water

temperature

b. Water non-availability

c. Poor quality of water available

d. Coal supply shortage

e. Coal quality inferior than design

D. Legal and regulatory reasons

a. Improper PPAs

b. Litigations

c. Compliance issues

E. To harness renewable energies , during

times of their availability

F. Merit order operation.

All of them can be put in to three broad

baskets a) Availability and reliability issues

b) Coal non availability c) evacuation

problems.

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Cycling – why it is bane for power utilities

Every power plant is designed and operated

differently. But cycling has detrimental effects on

all types of machines and which are unique to the

machines.

Thermal differential stresses from cycling result

in early life failures in addition to penalties

incurred in parameters like heat rate, auxiliary

power consumption, specific oil consumption,

DM water consumption and parameter

deviations during ramping up / ramping down

operations.

Cycling also affects reliability, availability and

generation of the plant.

Asset management of power plants must

include all the costs including cycling costs

some of which are often latent and not clearly

recognized by operators . The aim should be

the least cost option ensuring safety and

reliability of the plant. Figure-3 illustrates how

cycling shortens equipment life.

Figure-3

Cycling – Costs

Damage from cycling operations can be limited

to acceptable rates, but unit specific damage

mechanisms must be well understood to

manage and reduce the damage rates.

Total Cost of Cycling consists of following

incremental costs

• Maintenance and Capital Spending

• Cost Due to Forced Outages

• Long-Term Heat Rate Impacts

• Operational Heat Rate Impacts

• Hot, Warm, and Cold Start Costs

• Startup Auxiliary Power and Chemicals

• Startup Fuel and Manpower

• Capital Cost Impacts Due to Unit Life

Shortening

• Base-load Variable operation and

maintenance (VOM) costs

The typical costs due to cycling are reflected

almost 60% in boiler area, 30% in Turbine area

and 10% in BOP , Electrical and Control area put

together as depicted in figure-4

Figure-4 (typical distribution of cycling effects)

Heat Rate Impacts

• Cycling’s effect on heat rate is the

greatest for small coal units.

• Newer, combined cycle units as well as

simple cycle gas fired units see a much

lower impact.

• Moreover, plant heat rate is commonly

monitored and plant operators often

make capital investments to improve the

heat rates of their power plants. This

results in frequent replacement of

components damaged by cycling.

• Typically each start up penalizes heat

rate by 0.44% in a large coal fired power

plant.( figure-5)

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Figure-5 ( Heat rate degradation curve)

Heat rate degradation due to ageing and other

reasons is cyclic in nature. Typically 70 to 80%

of the degradation is recouped during each

major overhaul.( figure-6)

Figure-6 ( Heat rate degradation curve)

Heat rate deteriorates with decreasing loading

factor as shown in the figure-7.

Figure-7 ( Heat rate vs loading factor)

Auxiliary power consumption increases with

decreasing loading factor as shown in the

figure-8.

Figure-8 ( APC vs loading factor)

Reliability Impacts [EFOR]

Considering 30 years as life of boiler, major

maintenance at half life and renovation capital

investment at full life renovates the availability.

(figure-9)

Figure-9 (Availability vs maintenance)

Load Following and Ramping Costs

• significant load following and

• shallow load following.

• Load following has three effects

o Seasonal Effects

o Time or Aging Effects

o Cycling Effects

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Startup Fuel Input and Other Costs

Table-2 ( start up oil requirement)

Unit size Startup Oil Consumption (kL)

Hot Warm Cold

200-250 20 30 50

500 30 50 90

660 40 60 110

Typical trend of start ups in India per unit is 7-9

per annum. The distribution is as below:

Cold 2

Warm 3

Hot 4

Damage mechanisms due to cycling.

Load cycling and start ups have significant

damaging effect as depicted in figure-10,

proportional to the down time.

During each shut down/ start up the boiler,

steam lines, turbine, and auxiliary components

go through unavoidably large thermal and

pressure stresses, which cause damage. This

damage is worse for high temperature

components due to creep-fatigue. While

cycling-related failures may not be noted

immediately, critical components will

eventually start to fail. Shorter component life

expectancies results in higher plant equivalent

forced outage rates (EFOR).

The magnitude and impact depend on the

amount of creep damage present and the

specific types and frequency of the cycling.

Different damage mechanisms in different

parts of power plant / different equipments

on account of cycling are given in table-3.

Table-3 Damage mechanisms

DAMAGE MECHANISMS

Part Primary Damage Mechanism

Boiler

Water

walls

Fatigue

Corrosion fatigue due to outages

oxygen and high starts up oxygen

Chemical deposits

Boiler

Super

heaters

High temperature differential and

hot spots from low steam flows

during startup, long term

overheating failures

Boiler

Reheaters

High temperature differential and

hot spots from low steam flows

during startup, long term

overheating failures, tube exfoliation

damages IP turbines

Economiz

er

Temperature transient during

startups

Boiler

Headers

Fatigue due to temperature ranges

and rates, thermal differentials tube

to headers

LP

Turbine

Blade erosion

The Hot/Warm/Cold start cost is the

additional cost attributed to each

additional on/off cycle.

Additional fuel input cost for start ups.

The same is true for other start cost inputs

like water, chemicals, additives and

auxiliary power.

Typical oil consumption for each start up

cold/warm/hot is given in table-2

Figure -10

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Part Primary Damage Mechanism

Turbine

shell &

rotor

clearance

Non uniform temperatures result in

rotor bow and loss of desired

clearance and possible rotor rubs

with resulting steam seal damages

Feed

water

Heaters

High ramp rates during starts, not

designed for rapid thermal changes

Air

Heaters

Cold end basket corrosion when at

low loads and start up, acid dew

point

Water/Ch

emistry /

Water

Treatmen

t

Cycling results in peak demands on

condensate supply and oxygen

controls

Effects of Cycling on Boiler

Accelerated Boiler Failures Due to Cycling

• Boiler Seals Degradation

• Tube Rubbing

• Boiler Hot Spots

• Drum Humping/Bowing

• Downcomer to Furnace Sub cooling

• Expansion Joint Failures

• Superheater/Reheater Tube Leg Flexibility

Failures

• Superheater/Reheater Dissimilar Metal

Weld Failures

• Startup-Related Tube Failures in

Waterwall, Superheater, and Reheater

Tubing

• Burner Refractory Failure Leading to Flame

Impingement and Short-Term Tube

Overheating

Effects of Cycling on Turbine

Turbine Effects Due to Cycling

• Water Induction to Turbine

• Increased Thermal Fatigue Due to Steam

Temperature Mismatch

• Steam Chest Fatigue Cracking

• Steam Chest Distortion

• Bolting Fatigue Distortion/Cracking

• Blade, Nozzle Block, Solid Particle Erosion

• Rotor Stress Increase

• Rotor Defects (Flaws) Growth

• Seals/Packing Wear/Destruction

• Blade Attachment Fatigue

• Disk Bore and Blade Fatigue/Cracking

• Silica and Copper Deposits

• Lube Oil/Control Oil Contamination

• Shell/Case Cracking

• Wilson Line Movement

• Bearing Damage

• Reduced Life

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Effects of Cycling on Chemistry

Cycling effects on Chemistry

• Corrosion Fatigue

• Oxygen Pitting

• Corrosion Transport to Boiler and

Condenser

• Air, Carbon Dioxide, Oxygen Inleakage

(Require NH3 Countermeasures)

• NH3 - Oxygen Attack on Admiralty Brass

• Grooving of Condenser/Feedwater Heater

Tubes at Support Plates

• Increased Need for Chemical Cleaning

• Phosphate Hideout Leading to Acid and

Caustic Attack

• Silica, Iron, and Copper Deposits

• Out of Service Corrosion

Effects of Cycling on Electrical & Control

systems

Cycling Effects on Electrical

and Control System

• Increased Controls Wear and Tear

• Increased Hysteresis Effects that Lead to

Excessive Pressure, Temperature, and Flow

• Controls Not Repeatable

• Motor Control Fatigue

• Motor Insulation Fatigue

• Motor Insulation Failure Due to Moisture

Accumulation

• Motor Mechanical Fatigue Due to

Increased Starts/Stops

• Wiring Fatigue

• Insulation Fatigue Degradation

• Increased Hydrogen Leakage in Generator

• Fatigue of Generator Leads

• Generator Retaining Ring Failures

• Generator End Turn Fatigue and Arching

• Bus Corrosion When Cool (i.e., low amps)

• Breaker Fatigue

• Transformer Fatigue Degradation

Effects of Cycling on Human interface

related activites

Increased Risk of Personnel Errors Due to

Cycling

• Implosion

• Explosion

• Low Water in the Boiler

• Water Induction into the Turbine

• Low Load Instability

• Improper Valve Alignment

• Other Man/Machine Interface Problems

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Coal Shortage crippled power generation in

India

One of the major contributors for cycling in

Inida has been coal shortage. If one looks at

Coal mining in India , it started way back in 1774

in Raniganj Coal field at western bank of river

Damodar. Coal production has risen from 33

MT in 1951 to 600 MT at present . Present Coal

shortage ranges between 64 to 81 MT by

various estimates. Experts say that this shortage

could be met by increasing productivity in

mining.

India has Coal resources of about 267 billion

tonnes of which proven reserves are about

106 billion tonnes. According to industry

sources, Coal requirements for the power

sector is projected to reach to about 800 mt by

FY 2017 and increase to 1070MT by FY2022.

However, domestic coal supply is projected to

increase to 554 Mt by FY 2017 and 756MT by

FY2022. Total Coal imports are projected to

reach about 200 million tonnes by FY2017.

Various reasons for Coal Shortage in India are:

Environmental: MOEF Environmental

restrictions in no go areas has stalled or delayed

considerable number of mining projects.

Social : Acquiring land is becoming more and

more difficult as the owners of land are not

willing to part with the land also they are

sceptical of governments rehabilitation and

resettlement (R&R) pograms.

Logistics : 50 % of coal is transported through

rail but the railways routes are over saturated.

Also there is limited connectivity between mine

heads and railway loading points

Infrastructure related : Domestic coal

productions are stagnant over last three years

due to lack of technology up gradation and

shortage of skilled manpower

Opening coal mining for private participants:

There has been scams and delays in coal block

allocations to private parties who could have

brought best technology and industrial

practice in coal mining. Out of the 100 blocks

allocated to private companies with

geographical reserves of 17.93 Billion tonnes

production has commenced in 23 blocks

only.

Wet and Poor Coal Quality

Each Boiler is designed for a range of coal

quality (Worst coal, Design coal, and Best Coal

for example one 600 MW Coal based plant is

designed for 5900 kCal/Kg GCV with 15 %

moisture and less than 10 % of ash. The worst

coal GCV is 5350 kCal/Kg and best coal GCV is

6250 kCal/Kg. When the boiler is fed with coal

out of this range or of different moisture its

efficiency is affected. For each 10 % moisture

change 1% boiler efficiency change is observed

and For each 200 kCal/Kg GCV change 0.1 %

boiler efficiency change is observed

Therefore the quality of coal should confirm to

design coal range, Due to non-availability of

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required range coal utilities are forced to fire

Inferior quality coal. It not only penalises the

efficiency but also aggravates equipment wear

and tear and Increase in auxiliary power

consumption.

Traditionally quality of domestic coal supplied

from mines starts deteriorating from the month

of March till end of monsoon season. Therefore

coal procurement strategy should be such that

good quality coal should be procured and

stacked before onset of monsoon, so that the

same can be blended during such times.

In a study it was established that it is better to

procure High GCV coal at a little higher cost

than procuring low GCV coal at low prices.

This is because the effective cost per 1000 kCal

heat value works out to be cheaper than

inferior coal brought at lower cost due to

additional latent ash and moisture

transportation costs and resultant heat rate

loss and increased auxiliary power in the plant.

Best practices in coal stockyard management

are to be practiced to avoid coal degradation

due to wetting, rain, moisture absorption and

spontaneous combustion.

Various studies carried abroad and in India have

confirmed that coal degradation in the yard is

not linear. In a coal GCV degradation study

carried out at one of the imported coal based

plant , revealed that one third of the GCV loss is

observed in first two weeks after mining, one

third in next two months and the remaining one

third in rest of the period in a year. For example

at a site if the GCV loss observed is 300 kCal/kg

in a year , 100 kCal/kg is typically lost in first

two weeks, 100 kCal/kg in next two months and

remaining 100 kCal/kg in the rest of the year.

However the magnitude of the GCV loss is site

specific, depends on yard compaction, yard

management practices, environmental

conditions like windage , relative humidity,

rainfall etc.

Impacts of Imported Coal

Financial viability:

Power projects based upon imported coal

(mainly from Indonesia) are affected badly. The

new mining law in Indonesia provides for

annual alignment of coal prices with

international rates. Also it mandates that

Indonesian coal producers must allocate 24.2 %

of their annual production for domestic use.

Around the same time Australia also imposed

mining law to impose a carbon levy. Most of the

coal rich countries started changing their laws

and imposing new taxes to encash the demand

opportunity. So all the firm price projects

became unviable.

Delay in capacity addition abroad

The developers who have the responsibility of

mining and transporting are delaying the

project till the environment is financially

favourable to them.

Cost pass on to Customers

In metropolitan cities Discoms (like in New

Delhi) are procuring power at higher cost and

passing on the cost to consumers.

Power transmission “The Real Bottleneck”

The next major cause contributing to cycling in

India is transmission bottlenecks.

The transmission grid is presently

experiencing problems on account of

insufficient interregional transfer capacity

which is hampering the increasing volume of

traded power as also encountering problems

pertaining to increasing short circuits levels,

operational voltage excursions due to

fluctuating reactive balance and grid stability.

Power transmission networks are vital arteries

of the power value chain. Against India’s GDP

growth of 5 % in 2012-13 the energy demand

has seen a 7 % Y-O-Y growth. During 2012-13

power shortages in India accounted for GDP

loss of USD 68 Billion (0.4% of GDP). In the last

five years the power generation capacity has

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grown by 50 % whereas transmission capacity

has increased only by 30 %. As many as 120

transmission projects have faced delays

because of land acquisition problems and

delays in clearances from all stakeholders like

Forest department, aviation department,

Defence and PTCC .This is despite electricity act

2003 empowers the licensee with right of way

(ROW) under the telegraphic act 1885. Time

taken from concept to commissioning (5-6

years) is much longer than global standards

must be optimised to around 40 months. The

level of innovation and technology must be

upgraded. Clearance process and redressal

mechanisms should facilitate fast

implementation rather than hinder the process.

Dealing with judicial system makes the process

time consuming hence legal litigations should

be avoided as far as possible.

The Country has five transmission zones

North, East, West, South & North East)

presently all are synchronously linked. The

NLDC (National load dispatch centre) and five

RLDC (Regional load dispatch centres) form a

part of POSOCO (Power system operation

corporation limited), A subsidiary of PGCIL

(Power grid corporation of India limited).

Continual support from government is

needed for private players to setup a level

playing field (Land approvals, Infrastructure

discounts, Tax holidays etc ) This is required

to drive maturity and stability. During 2012-

13 Indian energy exchange and power

exchange of India lost opportunity 1350

crores worth business amounting to 15 % of

total traded volume of power due to

transmission constraints. Plant supplying

electricity to SEBI under long term PPA lost

1.93 BU of generation due to transmission

capacity bottlenecks. Going forward the

demand side capacity is expected to further

increase with the industry moving towards

open access. Open access allows every end

user of electricity in the country to choose

from all available transmission lines thereby

increasing transmission load across the

country.

Periodic and regular Grid Backing down is

experienced by various power generating

utilities. This may be due to maintenance of

Transmission lines, Congestion in Transmission

lines in particular links between major grids,

Merit order generation, Increased hydal power

generation, Restricted Demand, Faults,

trippings, Lack of grid discipline like Overdraw /

Over Injection, Lack of coordination between

various agencies.

Gas shortage

Around 8000 MW of Gas based power plants

are severely affected by falling production

KGD6. KGD6 production steeply fallen from 69.4

MMSCMD in March 2010 to 10 MMSCMD in

December 2013 against planned 80 MMSCMD.

The gas scenario in India is bleak for variety of

reasons. For years the government has imposed

curbs on the price of natural gas which had

deterred energy majors from investing money

in exploration and production. As many as 10

power stations in Gujrat, 7 in Andhra Pradesh, 4

in nation capital and 1 big plant in Maharashtra

are stranded for lack of gas supply.

Outage management

The Availability of a power plant is defined as

A = (T-P-F)/T

T=Total hours in the period

P=Planned outage hours in the period

F=Forced outage hours in the period

The Reliability of a power plant is defined as

R= (T-F)/T

Availability and Reliability have a very major

impact on the plant economy. Minimising, if not

eliminating, the Forced outages (FO) and strictly

not spilling over the Planned outage(PO) are of

paramount importance . FO &PO are

controllable in-house unlike external factors like

Grid related and coal related issues.

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Outages planned for regulatory are OEM

suggested are need based maintenance are

called planned outages.

Zero tolerance to forced outages that too to

repetitive type of failures must be the goal.

Outages represent the second largest

expenditure (after fuel) for fossil fuel stations.

To minimised the cost and duration of planned

outages plants must optimised work task

identification, prioritization, planning,

scheduling and resource use. Effectively

planned and carried out outages minimised the

risk of shortcoming and failures and result in a

measurable success. The outage management

include business goals, scope development, pre-

outage and post-outage milestones, pre-outage

and post-outage performance testing, planning

and scheduling processes, outage metrics,

financial and scheduling tools, outage execution

and industrial safety performance.

Outage scope and plans should start early at

least 18-24 months before outage. Assign area

leads 12 months prior to shutdown.

Some Outage best practices are :

Develop a checklist of everything to consider

before the shutdown and when to consider it

a. Evaluate the effectiveness of your current

shutdown effort

b. Measure your shutdown efficiency by

benchmarking with world-class shutdown

strategies

c. Formulate good contractor relations to

further reliability

d. Unearth tools and technologies that can

smooth the process and create a backbone

for effective plant maintenance and

reliability

e. Collaborate and balance out contractor

engagement and in-house staff to obtain

an effective workflow

f. Reduce unnecessary costs incurred by

properly planning, executing and closing

your shutdown

g. Planned outages are outages planned

before hand based on OEM

Recommendations, Equivalent operating

hours (EOH) based on condition. EOH takes

into account number of running hours, cold

starts, warm starts hot starts, trips from

above or below specified levels, rate of

loading unloading and overspeeds. EPRI

specifies Turbine major overhauls every

80000 EOH in addition to this a condition

assessment is conducted giving a colour

coding- blue, yellow, red or green for level

of degradation- Some significant, severe or

good condition of major steam turbine

components.. VGB Recommends major

Turbine overhaul after 100000 EOH.

Intermittent overhauls every 25000 EOH.

In US Risk based TOOP (Turbine outage

optimization program) for power

generating TG units is used to calculate

Interval between major outages (EOH).

Normally based on risk EOH varies

between 5-12 years.

h. Risk is defined as product of probability of

failure and consequences. In India Utilities

like NTPC having planned outage of 5-7 %

Mitigation Strategies

Cycling costs may be reduced

a. by the obvious method of not cycling a

unit

b. understanding the issues and managing

the unit to reduce the damage rates

c. modifying the operation process or

procedures

d. capital or O&M projects to modify the

base load designs to be better suited for

cycling

Government + Regulator + Private Players

should work in unison to realise the following.

Backward integration

Forward integration

(Plant) RCM

Fuel –quality & quantity

Transmission DISCOMS Bills Realisation

Availability &,Reliability

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Detailed component analysis helps in taking

countermeasures that address the root cause

of the cycling damage. Some examples are:

a. Air/Gas Side Operational Modifications –

Reduces rapid transients in boiler flue

gas

b. Steam bypass – Matches steam

temperature to turbine controls start up

steam temperature in Superheater

/Reheater

c. Feedwater bypass to condenser –

Controls startup temperature ramp rates

to feedwater heaters and economizers

d. Condenser tube replacement – Improves

plant chemistry and reliability and

prevents turbine copper deposits, if the

tubes are of Cu-Ni

e. Motorized valve for startup – Reduces

temperature ramp rates in boiler and

reduces fatigue while providing a rapid

and repeatable operation of critical

components including drains.

f. Motor driven boiler feed pump –

Reduces fatigue of economizer and

feedwater heaters and allows lower

stress and faster, reliable start up

The cycling costs mitigation committee

This is to Identify cycling effects, Analyse,

Evaluate and suggest alternative action plans to

mitigate cycling costs.

It should consist of six people.

• Plant Management

• Operations

• General Maintenance

• Turbine Maintenance Expert

• Boiler Maintenance Expert

• Plant Chemistry Expert

Conclusions

If cycling is inevitable, then its impacts and

costing to be done and cycling schedules

should be made on MERIT ORDER basis.

Three pronged approach focussed to

(1) increasing productivity in coal mining,

(2) Asset management practices in plants and

(3)Revamping of DISCOMs along with

strengthening transmission networks will bail

out ill fated Indian power industry.

Power is the essential ingredient for any

economy to grow and strengthen.

All states, private players and regulatory

authorities should come together and work

towards making the power sector successful

and self sustaining beyond boundaries and

limitations.

Acknowledgements

I am grateful to authors of various articles used

in reference. My sincere thanks to engineers,

superiors and plant people who made it

possible to write this paper out of good

experiences.

References

1. CEA Annual reports 2010-11, 2011-12,

2012-13.

2. CEA Monthly Report March 2013

3. Power Plant Cycling Costs (April 2012)

by N. Kumar, P. Besuner, S. Lefton, D.

Agan, and D. Hilleman

4. Cost Analysis and Cost-Based Power

Plant Asset Management –Thermal

Power Plant Cycling Costs -Steven A.

Lefton ,Nikhil Kumar, Intertek APTECH.

5. The relationship between base load

generation, start-up costs and

generation cycling-Niamh Troy, Eleanor

Denny, Mark O’Malley.

6. INDIAN POWER SECTOR news

7. POWER magazine-articles

8. Author’s technical papers on reliability,

coal GCV degradation etc.