ENERGY AUDIT AT RINFRA DAHANU
THERMAL POWER STATION
(250 X 2 MW UNIT)
CENTRAL POWER RESEARCH
INSTITUTE, BANGALORE-560080
MERC CONTRACT TO CPRI
 INVESTIGATION
INTO PERFORMANCE
OF DTPS R-INF
 PERIOD: 2 MONTHS FROM 22.01.2010
 TOR: RATING OF THE UNITS
PERMISSIBLILITY OF MW OVERLOADING OF
THE UNIT ABOVE THE MCR VALUE
DE-RATING/UP-RATING OF THE UNITS
FACT FINDING OF UNIT CAPACITY &
HISTORY
TESTS ON UNITS & CONSTRAINTS
DESIGN CAPACITY/
RATING OF DTPS






INSTALLED DURING BSES PERIOD 1995
TAKEN OVER BY R-INFRA IN 2003
NO MAJOR CHANGE IN HARDWARE SINCE
IDENTICAL TO OVER 25 250 MW UNITS INSTALLED
ALL OVER INDIA INCLUDING PARLI, PARAS & TATA
TROMBAY.
SAME DESIGN REPLICATED IN ALL UNITS. THEY ARE
OF STAND 250 MW DESIGN OF BHEL
PG TEST, INSTALLATION MANUALS, NAME PLATES,
CAPACITY TESTS OF EQUIPMENT AND C & I
INDICATE UNITS ARE OF 250 MW CAPACITY.
Margins provided by OEM
 Continuous
peak plant load duty (over
and above the 100 % unit MCR rating)
is denoted equipment wise as follows:
 Boilers: BMCR (boiler MCR) rating
 Turbines: VWO (valve wide open)
rating
 Generators: MVA (apparent power)
rating
 Generating transformers: MVA
(apparent power) rating
Margins over 250 MW




DTPS units have operating margins of:
8 % steam flow in the boiler side (BMCR flow)
5 % power output on the turbine side (VWO
flow)
16 % on the generator side (capability curve)
23 % on the generator transformer side.
These margins are provided in all 250 BHEL
supplied units including those at Paras Unit 3,
Parli Unit 6 and Tata Trombay Unit 8 as
elaborated in the text. MARGINS CAN BE FULLY
USED CONTINUOUSLY PROVIDED PARAMETERS
ARE NOT EXCEEDED. OEM HAS IMPOSED
RESTRICTIONS ONLY ON OPERATING
PARAMETERS OF INDIVIDUAL EQUIPMENT AND
NOT ON MW MARGINS
BOILER MARGINS
Sl. No.
Unit particulars-boiler
Dahanu 250 MW
Units 1 & 2
UNITS
NCR
BMCR
MARGIN
Design
t/h
746.60
805
1.08
CE/BHEL
t/h
736.20
810
1.10
CE/BHEL
t/h
738.21
810
1.10
CE/BHEL
t/h
736.20
810
1.10
CE/BHEL
t/h
652
700
1.07
CE/BHEL
6
Chandrapur 210 MW
Unit 3
t/h
652
700
1.07
CE/BHEL
7
Bhusawal 210 MW
Unit 3
t/h
654
700
1.07
CE/BHEL
t/h
652
700
1.07
CE/BHEL
Khaperkheda 210 MW
Unit No 4
t/h
624.23
690
1.11
CE/BHEL
Chandrapur 500 MW
Unit 7
t/h
1540
1670
1.08
CE/BHEL
1
2
3
4
5
8
9
10
Paras 250 MW Unit 3
Parli 250 MW Unit 6
Tata Trombay Unit 8
Nasik 210 MW Unit 5
Koradi 210 MW Unit 7
INSTALLATIONS at SL. Nos.5-10 are old
Plant load (active power or MW) dependent
and plant load independent parameters:
 Majority of the quality parameters like
temperature, pressure (except for variable
pressure operation), voltage, etc., are designed
by the OEM to be nearly constant and first
order load independent for the load range of 60
% UMCR to through maximum load and
changes are only second order.

However, the quantity parameters like flow,
current, etc. are directly proportional to active
power (MW) or plant load or machine loading.
As energy efficiency increases these quantities
decrease in magnitude for a given output.
OEM DEFINITION OF:
 CONTINUOUS PEAK
 LIMITED TIME PEAK PARAMETERS
 Continuous
peak
parameter:
purposefully set for achieving the
maximum performance or output from
the machine.
 Peak
parameters for limited periods:
time limits in s /min /h in one excursion
as well as total time in the lifetime of the
equipment. Occurs because of system
operational transients or constraints or
faults or system mismatch.
Sl.
No.
1
2
3
4
5
Partic
ulars
at 100
%
BMCR
condit
ions
Units
Dahan
u 250
MW
Paras
250 MW
Parli 250
MW Unit
6
Nasik
210 MW
Unit 5
Chandr
apur
210
MW
Unit 3
Bhusawa
l 210 MW
Unit 3
Koradi
210
MW
Unit 7
Khaper
kheda
210
MW
Unit No
4
Chandra
pur 500
MW Unit
7
Desig
n coal
GCV
kcal/
kg
3700
3400
3400
5000
4445
5100
5000
3500
3500
Annua
l
avera
ge
GCV
kcal/
kg
3966
3652
3608
3422
3170
3235
3642
3354
3170
Total
heat
to
boiler
Mcal
/h
599.
4
611.7
527.34
536
533.4
531.42
527.5
515.5
5
1215.9
Total
fuel
quanti
ty
t/h
162
179.9
155.1
107.2
120
104.2
105.5
147.3
347.4
Restri
ction
on
BMCR
to
GCV
%
less
No
No
No
Yes
No
Yes
Yes
No
No
Variation of Steaming rate with boiler efficiency at
constant coal consumption and constant GCV
Steaming rate, t/h
810
800
790
780
770
760
750
740
80
82
84
86
88
Boiler efficiency, %
SIMULATED FROM ACTUAL DATA
90
Coal consumption, t/h
Variation of coal consumption with boiler efficiency
at a constant boiler steaming rate and constant
GCV
164
162
160
158
156
154
152
150
80
82
84
86
88
Boiler efficiency, %
SIMULATED FROM ACTUAL DATA
90
Dependence of unit loading (MW) on the coal quality
280
y = -4E-05x 2 + 0.351x - 465.57
R2 = 0.7627
Unit load (MW)
270
260
250
240
230
3300
3500
3700
3900
4100
4300
Coal GCV (kcal/kg)
SIMULATED FROM ACTUAL DATA
4500
Heat loading rate (Million kcal/h) in the boiler
Heat loading rate (106 kcal/h)
640
620
600
design
580
Operating
560
Linear (design)
540
Linear (Operating)
520
500
480
235
240
245
250
255
260
265
270
Plant load (MW)
SIMULATED FROM ACTUAL DATA
275
TURBINE MARGINS
Sl. Unit particularsNo. Steam turbine
UNITS
TMC
R
Dahanu 250 MW
Units 1 & 2
MW
MARGIN
Design
250 262.82
1.05
Seimens
MW
250 264.78
1.06
Seimens
MW
250 264.78
1.06
Seimens
MW
250 264.78
1.06
Seimens
MW
210 213.30
1.02
Russian
6
Chandrapur 210 MW
Unit 3
MW
210 215.80
1.03
Russian
7
Bhusawal 210 MW
Unit 3
MW
210 215.00
1.02
Russian
MW
210 215.80
1.03
Russian
Khaperkheda 210
MW Unit No 4
MW
210 221.70
1.06
Seimens
Chandrapur 500 MW
Unit 7
MW
500
1.05
Siemens
1
2
3
4
5
8
9
10
Paras 250 MW Unit 3
Parli 250 MW Unit 6
Tata Trombay Unit 8
Nasik 210 MW Unit 5
Koradi 210 MW Unit 7
VWO
524.40
TURBINE MARGINS
Sl.
No.
Unit particulars
- Steam turbine
UNITS
TMC
R
VWO
MARGIN
Hitachi
1
MW 210
222.00
1.06
MW 210
222.00
1.06
MW 210
221.70
1.06
MW 210
215.60
1.03
Mitsubishi
2
Siemens
3
Russian
4
Steam input to turbine,
t/h
Variation of steam input with turbine heat rate
at constant power output
VWO: 800 t/h
765
760
755
750
745
740
735
1920
1940
1960
1980
Turbine heat rate, kcal/kWh
SIMULATED FROM ACTUAL DATA
2000
Variation of power output with turbine heat
rate at constant steam input to turbine
Power output, MW
VWO: 800 t/h
264
262
260
258
256
254
1920
1940
1960
1980
Turbine heat rate, kcal/kWh
SIMULATED FROM ACTUAL DATA
2000
TURBINES
DTPS has be able to maintain good MW load ability
on the machine within the OEM margins and
without exceeding any OEM parameter limits
by:



Maintaining
high
turbine
efficiency (turbine heat rate
deviates from design by only 4.4
kcal/kWh)
Strictly
maintaining
water
quality parameters as per OEM
guidelines
Minimizing auxiliary stack, vent
and
gland
sealing
steam
requirements in the turbine.
Sl.
No.
MW at
pf =
0.85
MARGIN
MW at
pf=0.85
pf=0.99 to 0.99
Unit particularsGenerator
MVA
rating
Dahanu 250 MW
Units 1 & 2
294.0
250
291.18
1.16
294.1
250
291.18
1.16
294.1
250
291.18
1.16
294.1
250
291.18
1.16
247.0
210
244.59
1.16
6
Chandrapur 210 MW
Unit 3
247.0
210
244.59
1.16
7
Bhusawal 210 MW
Unit 3
247.0
210
244.59
1.16
247.0
210
244.59
1.16
Khaperkheda 210 MW
Unit No 4
247.0
210
244.59
1.16
Chandrapur 500 MW
Unit 7
588.0
500
582.35
1.16
1
2
3
4
5
8
9
10
Paras 250 MW Unit 3
Parli 250 MW Unit 6
Tata Trombay Unit 8
Nasik 210 MW Unit 5
Koradi 210 MW Unit 7
TESTS ON UNITS
Maximum load- 265.5 MW: 2292.7kcal/kWh
 100 % UMCR- 252 MW: 2299.13 kcal/kWh
 F-GRADE LOAD- 2326.2 kcal/kWh
MAXIMUM LOAD REACHED WAS 240 MW
Design: 2230.60 kcal/kWh
Achieved: 2293 kcal/kWh
EVEN AT 268 MW NO PARAMETER HAS
EXCEEDED OEM LIMITS ; DTPS CONTROL
SET POINTS ARE BELOW OEM LIMITS

Loadability




Combining all the margins provided by the OEM,
R-Infra has been able to load the unit to 268 MW
against the design value of 250 MW.
Maintaining this load is not harming the life of the
unit as the DTPS has ensured that all parameters
are kept within OEM limits.
High loadability is made possible by high energy
efficiency or low unit heat rate which enables the
parameters not to exceed their limits.
OEM MANUALS DO NOT SPECIFIC ANY UPPER
LIMITS ON MW LOADING OR MW OVERLOADING
ABOVE 100 % UMCR RATING, OEM MANUAL
SPECIFIES
CONTINUOUS AND LIMITED TIME
LIMITS ON OPERATING PARAMETERS OF B,
T,G,GT, ETC.
Remaining life
Units 1 & 2 have been commissioned in Jan
and March 1995 and have completed 15 years
of service and nearly 1,20,000 operating
hours.
Acceleration of life expenditure takes place
due to parameter excursions into the limitedtime-overload-regime for long periods, due to
frequent cyclic loading, due to frequent
transients with high ramping rates. Scrutiny
of operation and parameters indicates that the
DTPS has avoided operation in these life
limiting regimes thereby preserving the
longevity of their assets. The cyclic operations
are far lower than their design values.
We are here
Remaining
Life
(h, years)
Ө
Ө > 45˚
poor
Ө=45˚
Normal
Real time years
<45
˚
Good
Remaining life
Considering a total engineering life of 35
years of service or 3,00,000 operating hours
the physical (actual) life expenditure of both
units is expected to be 40 %. Except for
generator, where the life expenditure is 50 %
(remaining life= 50 % or 14 years), the
remaining life of other components matches
roughly with the physical life expenditure.
This indicates that acceleration of life has not
taken place. The low degradation rate
coupled with the high loading on the plant
also leads to the conclusion that the
equipment are healthy and factors in the
nature of non-repairable damage are not
present. UNHEALTHY EQUIPMENT CANNOT
BE LOADED AT ALL
Degradation
The CPRI test TG HR is showing a
degradation rate of 0.13 %/year.
The degradation is 2.0 % of the
DHR
LOW LEVEL OF DEGRADATION
INDICATES THAT THE EQUIPMENT
ARE HEALTHY AND NO NEGATIVE
EFFECTS OF MW LOADING
BEYOND 100 % UMCR
Up-rating/de-rating
The maximum load on Unit 1 was 268.7 MW and
on Unit 2 was 266.0 MW in 2009 & in 2010. Uprating or de-rating of the unit has been studied
and it is concluded that the unit capacity is 250
MW and the present maximum plant loading of
268 MW is sustainable only because of high
boiler, turbine and generator efficiency; and
external factors like coal quality being 600
kcal/kg higher and high power factor of 0.99.
The sustainability may not be long lasting.
The PG test by OEM is for 250 MW, these units are
identical to several 250 MW units, grid code
2005 stipulates a margin over the 100 % UMCR
rating. Considering these facts it is concluded
that the up-rating of 250 MW to 260 or 265 MW
may not be sustainable in terms of availability
as well as loadability in the future.
CONCLUSIONS




SCRUTINY OF RECORDS INDICATES UNIT CAPACITY IS
250 MW IDENTIAL TO OTHER 250 MW UNITS SUPPLIED
BY BHEL.
OEM MARGINS IN BOILER, TURBINE, GENERATOR AND
GENERATOR TR HAVE BEEN FULLY MADE USE OF TO
ACHIEVE LOADABILITY OF 268 MW WELL WITHIN OEM
PARAMTER LIMITS.
OEM MARGINS CAN BE FULLY USED CONTINUOUSLY
PROVIDED PARAMETERS ARE NOT EXCEEDED. OEM HAS
IMPOSED
RESTRICTIONS
ONLY
ON
OPERATING
PARAMETERS OF INDIVIDUAL EQUIPMENT AND NOT ON
MW MARGINS. OEM PARAMTERS ARE NOT EXCEEDED BY
DTPS.
TESTS INDICATE ANNUAL UHR OF:






265.5 MW - 2293 kcal/kWh
100 % UMCR- 252 MW: 2299.13 kcal/kWh
F-GRADE LOAD- 2326.2 kcal/kWh
MAXIMUM LOAD REACHED WAS 240 MW
Design: 2230.60 kcal/kWh
Achieved STATION DATA : 2293 kcal/kWh
CONCLUSIONS


UPRATING OF THE UNIT HAS BEEN STUDIED.
SINCE THE UNIT IS OF 250 MW STANDARD
DESIGN OF BHEL, THE MARGINS ARE BEING
UTILIZED
BY
ENERGY
EFFICIENCY
IMPROVEMENTS, HIGHER GCV OF COAL AND
HIGH POWER FACTOR. THESE CIRCUMSTANCES
MAY NOT BE SUSTAINABLE ALL THROUGH THE
LIFE OF THE UNIT.
GENERATORS AND GTS ARE QUITE HEALTHY
AND NORMAL. REMAINING LIFE IS ALSO GOOD.
NO IMMEDIATE RISK FOR 16-20 khours AS PER
THE
RLA
REPORTS
OF
ABB
&
ERDA.
CONSIDERING THE CRITICALITY OF LOAD
HANDLED BY DTPS AND CONSIDERING THAT
THERE ARE NO SPARES WITH OTHER MEMBERS
OF MAHARASHTRA GRID FOR 250 MW THESE
CAN BE CONSIDERED.