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Page 1 of 14
Cycling Is Bane For Power Utilities
Koteswara Rao Pothala
Head-Central Performance Monitoring & Nodal Control Centre, Lanco Power, India
[email protected], 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.
Page 2 of 14
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
Page 3 of 14
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
Page 4 of 14
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.
Page 5 of 14
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)
Page 6 of 14
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
Page 7 of 14
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
Page 8 of 14
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
Page 9 of 14
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
Page 10 of 14
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
Page 11 of 14
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
Page 12 of 14
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.
Page 13 of 14
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
Page 14 of 14
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.