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Workshop March 31st Drafting Team met with ERCOT Market Participants and provided detailed information on the proposed draft variance. Drafting Team met with ERCOT Market Participants and provided detailed information on the proposed draft variance. Held halfway through 30 day comment period. Held halfway through 30 day comment period. Tools in the form of Excel Spreadsheets provided with Draft posting for use in the evaluation of Resources to the draft variance. Tools in the form of Excel Spreadsheets provided with Draft posting for use in the evaluation of Resources to the draft variance.
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BAL-001-TRE-01BAL-001-TRE-01ERCOT CPS2 R2 WaiverERCOT CPS2 R2 Waiver
Regional VarianceRegional VarianceApril 16, 2009April 16, 2009
Sydney NiemeyerSydney Niemeyer
Work ProductWork Product Draft standard consistent with SAR on which it Draft standard consistent with SAR on which it
was based.was based.
include requirements concerning frequency response contained in the ERCOT Protocols, section 5
include Requirements, Measures, and Levels of Non-Compliance sections
FERC determined that the minimum frequency response needed for reliability and requiring appropriate generators to have specific governor droop to be a more stringent practice than requirement R2 in BAL-001-0
Workshop March 31stWorkshop March 31st Drafting Team met with ERCOT Market Drafting Team met with ERCOT Market
Participants and provided detailed Participants and provided detailed information on the proposed draft information on the proposed draft variance.variance. Held halfway through 30 day comment Held halfway through 30 day comment
period.period. Tools in the form of Excel Spreadsheets Tools in the form of Excel Spreadsheets
provided with Draft posting for use in the provided with Draft posting for use in the evaluation of Resources to the draft evaluation of Resources to the draft variance.variance.
Goals of the VarianceGoals of the Variance Reliability Impact.Reliability Impact.
Improved frequency profile will increase Improved frequency profile will increase probability that frequency will be near probability that frequency will be near 60.000 Hz when a perturbation occurs.60.000 Hz when a perturbation occurs.
Improved frequency stability even with an Improved frequency stability even with an increase in variable generation.increase in variable generation.
Support for Voltage and Automatic Voltage Support for Voltage and Automatic Voltage Regulators by supplying appropriate Regulators by supplying appropriate energy delivery during perturbations.energy delivery during perturbations.
Goals of the Variance, Goals of the Variance, continuedcontinued
If an electrical island forms within If an electrical island forms within the ERCOT Interconnection, this the ERCOT Interconnection, this variance will provide the best variance will provide the best probability of both islands surviving.probability of both islands surviving. Resources, through correct frequency Resources, through correct frequency
response, will know immediately the response, will know immediately the correct action to take to balance the correct action to take to balance the generation to the demand of each generation to the demand of each island.island.
Interconnection Changed in Interconnection Changed in Source of Frequency Source of Frequency Response after 2001Response after 2001
Retirement of many conventional steam units.Retirement of many conventional steam units. Many had mechanical fly-ball governors that had Many had mechanical fly-ball governors that had
various amounts of deadband.various amounts of deadband. These Resources provided linear frequency These Resources provided linear frequency
response once the deadband was crossed.response once the deadband was crossed. Installation of many Combined Cycle Units.Installation of many Combined Cycle Units.
All had electronic/digital governors with deadband All had electronic/digital governors with deadband capabilities.capabilities.
Most deadbands were set at the maximum allowed Most deadbands were set at the maximum allowed setting of +/-0.036 Hz.setting of +/-0.036 Hz.
To meet the 5% droop performance characteristic To meet the 5% droop performance characteristic they were encouraged to have non-linear response they were encouraged to have non-linear response to overcome deadband region.to overcome deadband region.
LOAD-FREQUENCY CHARACTERISTIC
59.8
59.85
59.9
59.95
60
60.05
60.1
60.15
60.2
50 70 90 110 130 150 170 190
GENERATION (MW)
FREQ
UEN
CY
(HZ)
Unstable configuration Between 59.964 and 60.036 HZ, there is no solution the governors can find.
Comparing September 2008 vs March 2008 profile of frequency in 5 mHz bins
00.010.020.030.040.050.060.070.08
Sep-08 Mar-08
Existing +/-0.036 Hz allowable deadband
ERCOT ACE +/- 237.6 MW
CPS2 10 minute average
ACE Limit = 143.2 MW (0.0217 Hz)
Due to the small amount of frequency response within the deadband, MW needed in Resource movement to return to schedule frequency is much less than ERCOT ACE.
Frequency ResponseBased On
Droop Setting and Deadband
-150.00
-100.00
-50.00
0.00
50.00
100.00
150.00
59.50 59.55 59.60 59.65 59.70 59.75 59.80 59.85 59.90 59.95 60.00 60.05 60.10 60.15 60.20 60.25 60.30 60.35 60.40 60.45 60.50
Hz
MW
Cha
nge
Droop Setting 5.00% Ideal Performance adj for limiting factor Minimum Standard Performance Droop %
Deadband Setting
0.01667 Hz
745.00000Capability (MW)
Comparing November 2008 vs March 2008 profile of frequency in 5 mHz bins
00.010.020.030.040.050.060.070.080.09
Nov-08 Mar-08
ERCOT ACE +/- 110 MW
Proposed +/-0.0166 Hz allowable
deadband
CPS2 10 minute average
ACE Limit = 143.2 MW (0.0217 Hz)
Smaller deadband on Resources provides resistance to frequency change sooner. This results in three things 1) Overall frequency response needed from the Resource is less. 2) ERCOT ACE more closely represents the MW needed to return frequency to schedule. 3) Greater frequency stability.
Frequency ResponseBased On
Droop Setting and Deadband
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
16.0%
18.0%
20.0%
59.50 59.55 59.60 59.65 59.70 59.75 59.80 59.85 59.90 59.95 60.00 60.05 60.10 60.15 60.20 60.25 60.30 60.35 60.40 60.45 60.50
Hz
Dro
op
Droop Setting 5.00% Ideal Performance Droop % Minimum Standard Performance Droop %
Deadband Setting
0.03600
Hz
745.00000Capability (MW)
Droop Characteristic of Resource with 5% Droop setting and +/-0.036 Hz Deadband
Frequency ResponseBased On
Droop Setting and Deadband
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
16.0%
18.0%
20.0%
59.50 59.55 59.60 59.65 59.70 59.75 59.80 59.85 59.90 59.95 60.00 60.05 60.10 60.15 60.20 60.25 60.30 60.35 60.40 60.45 60.50
Hz
Dro
op
Droop Setting 5.00% Ideal Performance Droop % Minimum Standard Performance Droop %
Deadband Setting
0.01667
Hz
745.00000Capability (MW)
Droop Characteristic of Resource with 5% Droop setting and +/- 0.0166 Hz Deadband
Draft Regional Variance Draft Regional Variance Future DirectionFuture Direction
Drafting team will meet on May 4 to Drafting team will meet on May 4 to begin the process of responding to begin the process of responding to the Industry comments received.the Industry comments received.
Modify Draft Variance based on Modify Draft Variance based on Industry guidance.Industry guidance.
Request second posting for Request second posting for comments once modifications are comments once modifications are complete and have team consensus.complete and have team consensus.
