responsive reserve service deliverability review september 15, 2011 1
DESCRIPTION
Congested Responsive Reserve Service Capacity SCED will utilize congested RRS capacity last. Congested RRS capacity will continue to provide Primary Frequency Response even while congested. Governor In-service and free to respond to all frequency deviations outside Governor Dead-Band. During EEA-2A and 2B, RRS Capacity on Generators will be utilized to maintain frequency at 60 Hz. During EEA- 3, RRS Capacity on Generators will be utilized to maintain frequency above Hz. 3TRANSCRIPT
Responsive Reserve Service Deliverability Review
September 15, 2011
1
IntroductionResponsive Reserve Service Capacity as it
relates to congestion and its deliverability.Responsive Reserve Capacity during the
February 2nd EEA event.The potential affect of Responsive Reserve
Service capacity that is not frequency responsive.
Responsive Reserve Service allocation limits on a single Resource, is the 20% capacity limit correct?
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Congested Responsive Reserve Service CapacitySCED will utilize congested RRS capacity last.Congested RRS capacity will continue to provide
Primary Frequency Response even while congested.Governor In-service and free to respond to all
frequency deviations outside Governor Dead-Band.During EEA-2A and 2B, RRS Capacity on Generators
will be utilized to maintain frequency at 60 Hz.During EEA- 3, RRS Capacity on Generators will be
utilized to maintain frequency above 59.80 Hz.
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Percent of 5 minute intervals in a month when transmission constraint was affecting # of resources carrying RRS
Month-Year AVG Number of Resources carrying RRS
Max Number of Resources carrying RRS
Min Number of Resources carrying RRS
1-10 Resources 10-20 Resources
20-30 Resources
Greater than 30 Resources
sum
Dec-10 31 44 (1.20% intervals >35)
13 (0.067%<20) 12.34% 5.42% 10.21% 7.59% 35.56%
Jan-11 29 39(1.63% intervals >35)
15 (0.201%<20) 17.70% 3.90% 10.79% 2.48% 34.87%
Feb-11 44 85 (1.88% intervals >80)
23 (0.174%<25) 18.97% 2.88% 9.54% 14.99% 46.37%
Mar-11 37 48 (24.30% intervals > 40)
23 (5.63% < 30) 8.20% 1.11% 1.38% 11.04% 21.73%
Apr-11 37 54 (4.98% intervals > 45)
23 (3.34% < 30) 33.90% 6.31% 7.68% 7.22% 55.11%
May-11 34 47 (3.93% intervals > 40)
19 (0.0112% < 25)
26.72% 10.62% 13.80% 9.01% 60.15%
Slide provided by ERCOT, Constrained = Resource LMP more than $0.50 below system lambda.
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1. 5 minute sampled data
2. Telemetered Responsibility used to determine number of
Resources carrying RRS
3. 1% duration generally converts to roughly ninety 5-minute
intervals (31 days month)
4. The number of resources carrying RRS may include up to 13
resources in Synchronous Condenser (Hydro)5
During the February 2nd EEA event.
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59.50
59.52
59.54
59.56
59.58
59.60
59.62
59.64
59.66
59.68
59.70
59.72
59.74
59.76
59.78
59.80
59.82
59.84
59.86
59.88
59.90
59.92
59.94
59.96
59.98
60.00
60.02
60.04
60.06
60.08
60.10
5:35 5:40 5:45 5:50 5:55 6:00 6:05 6:10 6:15 6:20 6:25 6:30 6:35
Hz
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
MW
Frequency ERCOT Total Physical Reserve
Wednesday, February 02, 2011
Frequency 59.80 Hz
Physical Reserve = 850 MW
Physical Reserve = 450 MW
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During Short Supply PeriodsResponsive Reserve Service capacity can
decrease to very low levels during EEA 2 and 3 events.
August 4 EEA 2B event, RRS capacity decreased to levels just below 1000 MW.
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That is not frequency responsive.
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RRS Capacity that is not Frequency ResponsiveIf allowed, increases risk of UFLS significantly.If constrained, non-frequency responsive
capacity may never be utilized.With grid Primary Frequency Response
depending totally on Load Dampening, frequency would be extremely sensitive to any imbalance. (If all RRS was not frequency responsive).
Frequency could reach 59.300 Hz before capacity could be utilized by SCED and waiting on delivery. (Ten minute product vs. frequency responsive product).
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Load RRS Gen Total Load Dampening RRS Capacity Resource LossDampening PFR PFR Contribution Contribution to ReachMW/0.1 Hz MW/0.1 Hz MW/0.1 Hz MW MW* 59.400 Hz
Summer -166 -191 -357 996 1000 1996 MWWinter -73 -191 -264 438 1000 1438 MW
Summer -166 0 -166 996 0 996 MWWinter -73 0 -73 438 0 438 MW
*MW less than normal minimum 1150 MW on Generators due to SCED dispatching some of the capacity as energy.If RR Ancillary Service is not required to be frequency responsive.
Recent Operation During EEA Step 2A and 2B Emphasizes An
Important DifferenceRegulation Up Service was fully deployed.Load Resources were fully deployed.SCED Up Capacity was limited to the
capacity of un-deployed Responsive Reserve Service from Generators.
MW loss size assumes a starting frequency of 60.000 Hz. 11
SummaryResponsive Reserve Service capacity that
does not respond to changes in frequency, increases the risk that a relatively small Resource trip during short supply events will trip UFLS.
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Deliverability during sudden, extreme events (May 15, 2003).
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20% Capacity Limit per ResourceThe Governor of a Resource will deploy 20%
of the capacity of a Resource if frequency deviates -0.600 Hz plus the Governor Dead-Band.At 59.364* Hz, the Governor will deploy 20% of
the capacity of a Resource with a 5% Droop setting.
Even if fully constrained by SCED, full RRS should be deployed by the Governor before the first stage of UFLS, 59.300 Hz, is reached.
* Originally the RRS was intended to protect 59.40 Hz and did not include Governor Deadband. Using the maximum Governor Deadband of 0.036 Hz this number now comes out to be 59.364 Hz.
Resource Performance May 15, 2003May 15, 2003 loss of 3434 MW and 59.29 Hz Point
C and 59.46 Hz Point B. During the first minute of the event:16 Steam units responded with average 0.655 P.U.
performance. (65.5 % of expected response)13 Combustion turbines responded with average
0.660 P.U. performance. (66% of expected response)Generators responding correctly provided 14% of
their capacity on average in less than one minute. 5 steam units provided 18% or greater. 2 combustion turbines provided 18% or greater. 5 combustion turbines provided 16% or greater. 2 steam units provided 16% or greater.
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SummaryIs the 20% allocation limit correct for
maximum deliverability during sudden, extreme events?
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