Lessons Learned from 2011 Southwest Cold Weather Event

OPERATIONS LESSONS LEARNED: 2011 Tamme R. Chilton Tamme R. Chilton Real Time Operations Training, CenterPoint Energy

OPERATIONS LESSONS LEARNED: 2011 While extreme cold weather events are not common in the Southwest, they do occur every few years. These events create significant impact in terms of dollars and human hardship. Many utilities have already undertaken improvements in light of their experiences during the February 1 5, 2011 event. *Source: Outages and Curtailments during the Southwest Cold Weather Event of February 1 5, 2011 2 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 Some corrective actions implemented to improve winter operations include: Document minimum operating ambient temp on all generating and transmission facilities Inspect generating and transmission facilities for areas where water could collect and freeze Provide operators with more information and tools to aid in implementing rolling blackouts, as well as communicating with local agencies regarding outaged areas Train operators annually in winter- specific awareness, and conduct periodic drills to maintain their skills Review and modify Protocols as needed *Source: NERC Event Analysis Cause Codes Southwest Cold Weather Event of February 1 5, 2011 3 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 OBJECTIVES Given a winter storm event: Identify precursors Determine actions necessary to maintain system reliability 4 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 1 Precursors: Coldest Texas weather since 1989 Single-digit temps Sustained winds with 30-40 mph gusts ERCOT winter peak demand 56,344 MW 5 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 2 Initial conditions: Senior Operator @ each group will Supervise Evaluate your system Review applicable procedures for Generation/Transmission/ERCOT preparations Determine general course of action 6 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 2 Monitor expected path of Extreme Cold Weather Review Emergency Operating Procedures OCN 5 days ahead Advisory 3 days ahead Watch 1 day ahead Emergency Notice Coordinate with Outage Coordination Planned and existing outages Rejected, withdrawn, restored outages Coordinate with Operations Support Study for outage impacts Continue reviewing system conditions Implement procedures as needed 7 PUBLIC

600 MW Gas Unit 1 slack Base Case SUB-F TSP 2 Load 5 Load 4 A 32% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 3 Line 2 A A 600 MW 57% MVA 57% MVA Load 6 SUB-C SUB-B A 12% MVA A Condition: RTS: Line 11 32% MVA A 59% MVA Line 4 Line 7 Ln:11 OOS for Insulator Replacement 5 hrs Line 8 Line 1 Line 12 Line 9 A A 59% MVA 12% MVA A 36% MVA Ln: 2 Planned outage: Relay Maint. in 9 d N/A Line 13 Line 10 Gas Unit 3 SUB-A A A A 38% MVA 9% MVA 48% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 1200 MW 0 MW Load 2 Nuclear Unit Load 3 Tie Line 2 Coal Unit 125 MW 125 MW Wind Units TSP 3 8 PUBLIC

Operating Condition Notice for Extreme Cold Weather This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT operator John Smith. At [xx:xx], ERCOT is issuing an OCN for an extreme cold weather system approaching [time frame] with temperatures anticipated to remain 32 F or below. TOs are instructed to: Review Planned outages and existing outages for the possibility of canceling or restoring equipment, Review and implement winterization procedures. Notify ERCOT of any changes or conditions that could affect system reliability. [TO] please repeat this back to me. This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT Operator John Smith. At [xx:xx], ERCOT is issuing an OCN for an extreme cold weather system approaching [time frame] with temperatures anticipated to remain 32 F or below. QSEs are instructed to: Review fuel supplies, prepare to preserve fuel to best serve peak load, and notify ERCOT of any known or anticipated fuel restrictions, Review Planned Resource outages and consider delaying maintenance or returning from outage early, Review and implement winterization procedures. Notify ERCOT of any changes or conditions that could affect system reliability. [QSE] please repeat this back to me. 9 PUBLIC

Advisory for Extreme Cold Weather This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT operator John Smith. At [xx:xx], ERCOT is issuing an Advisory for the extreme cold weather system approaching [time frame] with temperatures anticipated to remain 32 F or below. TOs are instructed to: Review Planned outages and existing outages for the possibility of canceling or restoring equipment, Review and implement winterization procedures. Notify ERCOT of any changes or conditions that could affect system reliability. [TO] please repeat this back to me. This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT operator John Smith. At [xx:xx], ERCOT is issuing an Advisory for the extreme cold weather system approaching [time frame] with temperatures anticipated to remain 32 F or below. QSEs are instructed to: Review fuel supplies, preserve fuel to best serve peak load, and notify ERCOT of any known or anticipated fuel restrictions, Review Planned Resource outages and consider delaying maintenance or returning from outage early, Review and implement winterization procedures. Notify ERCOT of any changes or conditions that could affect system reliability. [QSE] please repeat this back to me. 10 PUBLIC

Watch for Extreme Cold Weather This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT operator John Smith. At [xx:xx], ERCOT is issuing a Watch for the extreme cold weather system approaching [time frame]. Temperatures are expected to remain 32 F or below. TOs are instructed to: Review Planned outages and existing outages for the possibility of canceling or restoring equipment, Prepare for higher than usual loads, Review and implement winterization and emergency operating procedures. Notify ERCOT of any changes or conditions that could affect system reliability. [TO] please repeat this back to me. This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT operator John Smith. At [xx:xx], ERCOT is issuing a Watch for the extreme cold weather system approaching [time frame]. Temperatures are expected to remain 32 F or below. QSEs are instructed to: Make available, any Resources that can be returned to service and keep COPs and HSLs updated, Review fuel supplies, preserve fuel to best serve peak load, and notify ERCOT of any known or anticipated fuel restrictions, Prepare for higher than usual loads and the possible need for additional Ancillary Services, Review and implement winterization and emergency operating procedures, including utilization of Resource pre-warming techniques. Notify ERCOT of any changes or conditions that could affect system reliability. [QSE] please repeat this back to me. 11 PUBLIC

Emergency Notice for Extreme Cold Weather This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT operator John Smith. At [xx:xx], ERCOT is issuing an Emergency Notice, the extreme cold weather system is beginning to have an adverse impact on the system such as [state what the adverse impacts are]. Prepare for higher than usual loads and the possibility of load shedding. ERCOT will continue to monitor the extreme cold weather system and will convey information and instructions as conditions warrant. [TO] please repeat this back to me. This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT Operator John Smith. At [xx:xx], ERCOT is issuing an Emergency Notice, the extreme cold weather system is beginning to have an adverse impact on the system such as [state what the adverse impacts are]. QSEs are instructed to: Make Resources available that can be returned to service and keep COPs and HSLs updated, Keep ERCOT informed of known or anticipated fuel restrictions, Notify ERCOT of any changes or conditions that could affect system reliability. ERCOT will continue to monitor the extreme cold weather system. [QSE] please repeat this back to me. 12 PUBLIC

600 MW Gas Unit 1 slack T-24 SUB-F TSP 2 Load 5 Load 4 A 31% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 2 Line 3 A A 600 MW 58% MVA 64% MVA Load 6 SUB-C SUB-B Condition: RTS: Ln: 11 RTS N/A A Line 11 31% MVA A 59% MVA Ln: 12 OOS for Hot Spot Repair Unk Line 4 Line 7 Line 8 A Line 1 Line 12 12% MVA Line 9 A A 59% MVA 26% MVA A Nuke De-rate due to MFP failure Unk 36% MVA Coal Unit Commencing Start-Up 24 hrs Line 13 Line 10 Gas Unit 3 SUB-A A A A 38% MVA 12% MVA 41% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 1200 MW 0 MW Load 2 Nuclear Unit Tie Line 2 Load 3 Coal Unit 125 MW 125 MW Wind Units TSP 3 13 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 2 Supervisor Summary 14 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 3 Transmission event: Senior Operator @ each group will Supervise Evaluate your system Review applicable procedures Identify system threats and determine response 15 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 3 Review planned Transmission outages Evaluate Transmission capacity: Real Time Contingency Analysis (RTCA) System Operating Limits (SOL) Voltage Stability Limits (VSL) Generic Transmission Constraints (GTC) RAS, AMP, RAP, PCAP, MP, and TOAP Manage Transmission constraints: Capacity available to Security Constrained Economic Dispatch (SCED) Manual dispatch of Resources Diminishing Reserves Review TO Load Shed Obligation 16 PUBLIC

600 MW Gas Unit 1 slack T-0 SUB-F TSP 2 Load 5 Load 4 A 60% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 2 Line 3 A A 600 MW 71% MVA 64% MVA Load 6 SUB-C SUB-B Condition: RTS: A Line 11 23% MVA A 34% MVA Nuke Unit At half Output Unk Line 4 Line 7 Line 8 A Line 1 Line 12 11% MVA Line 9 A A 34% MVA 26% MVA A Coal Unit On-Line: Starting ramp from 0MW N/A 35% MVA Line 13 Line 10 Gas Unit 3 SUB-A A A A 30% MVA 11% MVA 41% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 600 MW 0 MW Load 2 Nuclear Unit Tie Line 2 Load 3 Coal Unit 125 MW 125 MW Wind Units TSP 3 17 PUBLIC

600 MW Gas Unit 1 slack T+2 SUB-F TSP 2 Load 5 Load 4 A 60% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 3 A Line 2 A 105% MVA 81% MVA 600 MW SUB-C Load 6 SUB-B Condition: RTS: A Line 11 9% MVA A 48% MVA Coal Unit At dispatch N/A Line 4 Line 7 A Line 8 83% MVA Line 1 Line 12 Line 9 A A 48% MVA 37% MVA A 9% MVA Ln: 13 Trip on galloping Unk Line 13 Line 10 Gas Unit 3 SUB-A A A 1% MVA 13% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 400 MW 200 MW Load 2 Nuclear Unit Tie Line 2 Load 3 Coal Unit 125 MW 125 MW Wind Units TSP 3 18 PUBLIC

680 MW Gas Unit 1 slack T+2 SUB-F TSP 2 Load 5 Load 4 A 78% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 3 Line 2 A A 81% MVA 90% MVA 520 MW SUB-C Load 6 SUB-B Condition: RTS: A Line 11 9% MVA A 48% MVA Coal Unit At dispatch N/A Line 4 Line 7 A Line 8 83% MVA Line 1 Line 12 Line 9 A A 48% MVA 37% MVA A 9% MVA Ln: 13 Trip on galloping Unk SCED Re-dispatch implemented N/A Line 13 Line 10 Gas Unit 3 SUB-A A A 1% MVA 13% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 400 MW 200 MW Load 2 Nuclear Unit Tie Line 2 Load 3 Coal Unit 125 MW 125 MW Wind Units TSP 3 19 PUBLIC

Gas Unit 1 680 MW slack T+4 SUB-F TSP 2 Load 5 Load 4 A 78% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 3 Line 2 A A 520 MW 76% MVA 90% MVA Load 6 SUB-C A SUB-B 0% MVA Condition: RTS: A Line 11 10% MVA A 37% MVA Line 7 Line 4 Nuke Unit Continue Ramp Down Unk Line 8 A Line 1 Line 12 83% MVA A Line 9 A 37% MVA 37% MVA A 1% MVA Coal Unit Continue Ramp Up N/A Line 13 Line 10 Gas Unit 3 SUB-A A A 17% MVA 13% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 200 MW 400 MW Load 2 Nuclear Unit Tie Line 2 Load 3 A Coal Unit 125 MW 125 MW 0% MVA Wind Units TSP 3 20 PUBLIC

Gas Unit 1 500 MW slack T+6 SUB-F TSP 2 Load 5 Load 4 A 37% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 3 A Line 2 103% MVA A 590 MW 64% MVA Load 6 SUB-C SUB-B Condition: RTS: A Line 11 16% MVA A 36% MVA Nuke Unit Stable Output Unk Line 7 Line 4 A Line 8 83% MVA Line 1 Line 12 A Line 9 A 36% MVA 36% MVA A Coal Unit Output @ max due to frozen coal Unk 5% MVA Gas Unit 1 Gas curtailed: Low line packing Unk Line 13 Line 10 Gas Unit 3 SUB-A A A 20% MVA 15% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 200 MW 500 MW Load 2 Nuclear Unit Tie Line 2 Load 3 Coal Unit 125 MW 125 MW Wind Units TSP 3 21 PUBLIC

Gas Unit 1 500 MW slack T+8 SUB-F TSP 2 Load 5 Load 4 A 36% MVA Line 6 Gas Unit 2 Tie Line 1 Load 1 SUB-D Line 3 Line 2 A A 590 MW 63% MVA 75% MVA Load 6 SUB-C SUB-B Condition: RTS: Nuke Unit Stable Output Unk A Line 11 20% MVA A 42% MVA Line 4 Line 7 Coal Unit Output @ max due to frozen coal Unk Line 8 A Line 1 Line 12 0% MVA A Line 9 A 42% MVA 27% MVA A 12% MVA Gas Unit 1 Gas curtailed: Low line packing Unk Wind Units Trip on Over-Speed Unk Line 13 Gas Unit 3 Line 10 SUB-A A A 15% MVA 14% MVA 600 MW SUB-E SUB-G Line 5 SUB-H 0 MW 500 MW Load 2 Nuclear Unit Tie Line 2 Load 3 Coal Unit 0 MW 0 MW Wind Units TSP 3 22 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 3 Supervisor Summary 23 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 4 EEA event: Senior Operator @ each group will Supervise Evaluate your system Review applicable procedures Identify system threats and determine response 24 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 4 See ERCOT Nodal Operating Guides: Section 4 Advisory: PRC < 3000MW Watch: PRC < 2500MW EEA Level 1: PRC < 2300MW and Not projected to recover within 30 minutes EEA Level 2: PRC < 1750MW or Unable to maintain frequency at a minimum of 59.91 Hz and Not projected to recover within 30 minutes EEA Level 3: PRC < 1375MW or Unable to maintain frequency at a minimum of 59.8 Hz and Not projected to recover within 30 minutes Frequency < 59.5 Hz, immediately implement EEA3 25 PUBLIC

PRC: 3000MW 26 PUBLIC

PRC: 2000MW 27 PUBLIC

This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT Operator John Smith; at [xx:xx], ERCOT is declaring EEA 1. [TO] please repeat this back to me. That is correct, thank you This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT Operator John Smith. At [xx:xx], ERCOT is declaring EEA 1, QSEs are to perform their necessary steps for EEA 1. [QSE] please repeat this back to me. 28 PUBLIC

PRC: 1500MW 29 PUBLIC

This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT Operator John Smith, at [xx:xx], ERCOT is declaring EEA 2 and is issuing an appeal through the public news media for voluntary energy conservation. Reduce customer loads by using distribution voltage reduction measures, if deemed beneficial and any available capacity from Load Management Programs, [Load Resources and / or ERS have been deployed]. This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT Operator John Smith, at [xx:xx], ERCOT is declaring EEA 2 and is issuing an appeal through the public news media for voluntary energy conservation. [Group 1 / Group 1 and 2] Load Resources have been deployed. Implement all measures associated with EEA 1, if not already implemented. [QSE] please repeat this back to me. 30 PUBLIC

Frequency: 59.48 31 PUBLIC

This call requires everyone to remain on the line until it is complete. [TO] I will be asking you for the repeat back. This is ERCOT Operator John Smith, at [xx:xx], ERCOT is declaring EEA 3. ERCOT is issuing an Operating Instruction for all Transmission Operators to shed their share of [amount] MW. Transmission Operators are to report to ERCOT when this is complete. Implement all measures associated with EEA 1 and 2, if not already implemented. [TO] please repeat this back to me. This call requires everyone to remain on the line until it is complete. [QSE] I will be asking you for the repeat back. This is ERCOT Operator John Smith, at [xx:xx], ERCOT is declaring EEA 3, [MW Amount] of firm load is being shed. Implement all measures associated with EEA 1 and 2, if not already implemented. [QSE] please repeat this back to me. 32 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 BLOCK 4 Supervisor Summary 33 PUBLIC

OPERATIONS LESSONS LEARNED: 2011 WRAPUP Given a winter storm event: Identified precursors Determined actions necessary to maintain system reliability 34 PUBLIC