Pacific Southwest DisturbanceSeptember 8 2011          8,Event Analysis Overview Presented to IEEE PSRCMay 17, 2012 – Main...
September 8, 2011 Event• 11 minute cascading outage in Pacific Southwest• 2.7 million customers out in AZ, S.CA, MX, some ...
Customer Impacts          Entity         Load Lost (MW)           Customers         SDGE                  4,293           ...
Joint FERC/NERC Inquiry• Announced September 9, 2012• Teams formed comprising over 30 senior technical staff of  Teams for...
Inquiry Teams•   Data Requests/Management•   Sequence of Events    Sequence of Events•   Modeling/Simulation•   Cause Anal...
Sequence of Events6                  RELIABILITY | ACCOUNTABILITY
Simplified System Diagram    Serrano            Devers                          Palo Verde                             S-C...
Phase 1 – Pre-Disturbance             • Hot, shoulder season day; some               generation and transmission          ...
Phase 2 – Trip of H-NG 500 kV                                  • H-NG 500 kV trips at                                    1...
Initiating Event – Tripping of           Hassayampa – North Gila 500 kV Line     Series Capacitor      Bypass Switch      ...
Hass. – N. Gila 500 kV Line Trip              South of SONGS Current                        CCM Unit 1                    ...
Phase 3 – Trip of CV Transformers                                      • 15:28:16 – CV-2 and CV-1                         ...
CV Transformers Trip               South of SONGS Current      Coachella Valley         230/92 kV      transformers trip13...
Phase 4 – Ramon Xfmr Trip                                  • 15:32:10 Ramon 230/92kV                                    tr...
Ramon Transformer Trip             South of SONGS Current           Voltage collapse in              l        ll    i     ...
Voltage in Northern IID 92 kV System                                     Over‐Voltage Trip                                ...
Blythe 161 kV Voltage     Trip of Hassayampa         p          y p                          El Centro – Pilot            ...
Phase 5 – Yuma Separates                               • Yuma AZ Separates from IID                                 and WA...
Yuma Separation                South of SONGS Current                       YCA                     generating            ...
Phase 6 – High-Speed Cascade                              • El Centro – Pilot Knob 161kV                                li...
El Centro – Pilot Knob 161 kV Trips                 Early                 Phase 4                 activity                ...
Phase 6 – High-Speed Cascade                              • S-Line RAS trips IV                                generation ...
Phase 6 – High-Speed Cascade                        South of SONGS Current                                         Imperia...
Phase 6 – High-Speed Cascade                                • SONGS separation scheme                                  ope...
SONGS      separation                                SONGS Unit 3                                  electrically           ...
SONGS        SONGS     separation         SONGS Unit 2 GSU                         trip and transfer of           SONGS au...
Phase 7 – S CA Separates                             • Yuma island separates from                               SDG&E when...
UFLS Operations in the Island28                   RELIABILITY | ACCOUNTABILITY
Voltage                                                             Voltage                                               ...
Phase 7 – CFE Separates                            • Underfrequency UFLS                              SDG&E and CFE       ...
Actual vs. Simulated Frequency      31                        RELIABILITY | ACCOUNTABILITY
Phase 7 – Complete Blackout                                • IID, Yuma, SDG&E, and CFE                                  bl...
Use of PMUs in EA33                  RELIABILITY | ACCOUNTABILITY
Sammis-Star                                                                                                  Hard-Chamb   ...
PMU Data from SONGS35           RELIABILITY | ACCOUNTABILITY
7 Phases of Event                                            Trip or Gila 161/69 kV                                       ...
EA Modeling37                 RELIABILITY | ACCOUNTABILITY
Simulation vs. Actual Flows                                                South of SONGS Flows          4000          350...
Inquiry Findings39                  RELIABILITY | ACCOUNTABILITY
Key FindingsWeaknesses in two broad areas:• Operations planning  Operations planning• Real‐time situational awarenessContr...
Operations PlanningFailure to consider in seasonal, next‐day, and real‐time studies:• Status of external generation and tr...
Operations PlanningRecommended TOP/BA Improvements in WECC:•    Obtain information on neighboring BAs and TOPs, including ...
Situational AwarenessRecommended Improvements in WECC:•    Expand entities’ external visibility in models through more    ...
System Protection IssuesRecommendations:•    IID and other TOs review transformer overload protection                     ...
Questions?45                RELIABILITY | ACCOUNTABILITY
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131 nerc pacific southwest disturbance presentation

  1. 1. Pacific Southwest DisturbanceSeptember 8 2011 8,Event Analysis Overview Presented to IEEE PSRCMay 17, 2012 – Main Committee Meeting
  2. 2. September 8, 2011 Event• 11 minute cascading outage in Pacific Southwest• 2.7 million customers out in AZ, S.CA, MX, some up to 12 2.7 million customers out in AZ, S.CA, MX, some up to 12  hours• Initiated when single 500 kV line tripped, but not sole cause• Power redistributed, increasing flows through underlying  systems, causing voltage drops and equipment overloads• Ripple effect led to tripping of lines and generators,  automatic load shedding, and operation of a Remedial  Action Scheme and an intertie separation scheme Action Scheme and an intertie separation scheme• Restoration process generally effective2 RELIABILITY | ACCOUNTABILITY
  3. 3. Customer Impacts Entity Load Lost (MW) Customers SDGE 4,293 1.4 million CFE 2,150 2 150 1.1 1 1 million IID 929 146 thousand APS 389 70 thousand WALC 74 Note Note: 64 MWs of WALC s load loss affected APS s customers  Note: 64 MWs of WALC’s load loss affected APS’s customers3 RELIABILITY | ACCOUNTABILITY
  4. 4. Joint FERC/NERC Inquiry• Announced September 9, 2012• Teams formed comprising over 30 senior technical staff of Teams formed comprising over 30 senior technical staff of  FERC and NERC, plus several NERC contractors and industry  subject matter experts• Multiple meetings and exchanges with affected entities to  gather facts• T Team products combined into final report d bi d i fi l• Outreach sessions to gain feedback on draft findings and  recommendations4 RELIABILITY | ACCOUNTABILITY
  5. 5. Inquiry Teams• Data Requests/Management• Sequence of Events Sequence of Events• Modeling/Simulation• Cause Analysis/Human Performance y /• Operations Tools/ SCADA/EMS• Frequency Analysis q y y• System Planning/Design• Equipment Performance/System Protection• Restoration5 RELIABILITY | ACCOUNTABILITY
  6. 6. Sequence of Events6 RELIABILITY | ACCOUNTABILITY
  7. 7. Simplified System Diagram Serrano Devers Palo Verde S-Corridor SONGS Path 44 Imperial WAPA Irrigation District Lower Hassayampa H 161 kV 92 kV Colorado H-NG SDG&E Corridor S-Line Miguel Imperial Valley North Gila CFE7 RELIABILITY | ACCOUNTABILITY
  8. 8. Phase 1 – Pre-Disturbance • Hot, shoulder season day; some generation and transmission outages • High loading on some key facilities: H-NG at 78% of normal rating; CV transformers at 83% • 44 minutes before loss of H-NG, IID’s RTCA results showed loss of CV 1 transformer would load CV-1 CV-2 transformer above its relay trip point • 15 27 39 APS t h i i 15:27:39: technician skipped a critical step in isolating the series capacitor bank at North Gila substation; H-NG trips ; p8 RELIABILITY | ACCOUNTABILITY
  9. 9. Phase 2 – Trip of H-NG 500 kV • H-NG 500 kV trips at 15:27:39 15:27:39 15:28:16 15 27 39 – 15 28 16 • APS tells WECC RC line expected to be restored quickly • H-NG flow redistributes: 77% Gf % to SCE-SDGE (Path 44); remainder to IID, and WALC • CV transformers immediately overloaded above relay settings • Path 44 at 5,900 amps; 8,000 amp limit on SONGS separation scheme p9 RELIABILITY | ACCOUNTABILITY
  10. 10. Initiating Event – Tripping of Hassayampa – North Gila 500 kV Line Series Capacitor Bypass Switch Arcs Over10 RELIABILITY | ACCOUNTABILITY
  11. 11. Hass. – N. Gila 500 kV Line Trip South of SONGS Current CCM Unit 1  generator trip Hassyampa – N. Gila 500 kV  line trip11 RELIABILITY | ACCOUNTABILITY
  12. 12. Phase 3 – Trip of CV Transformers • 15:28:16 – CV-2 and CV-1 230/92kV transformers trip on overload relays 15:28:16 15:32:10 15 28 16 – 15 32 10 • Severe low voltage in WALC 161 kV system • Loading on Path 44 increases to 6,700 amps12 RELIABILITY | ACCOUNTABILITY
  13. 13. CV Transformers Trip South of SONGS Current Coachella Valley  230/92 kV  transformers trip13 RELIABILITY | ACCOUNTABILITY
  14. 14. Phase 4 – Ramon Xfmr Trip • 15:32:10 Ramon 230/92kV transformer trips on overload relay 15:32:10 15:35:40 15 32 10 – 15 35 40 • 15:32:13 Blythe-Niland 161kV line trips • 15:32:15 Niland – CV 161kV line trips • IID undervoltage load shedding; loss of generation and 92 kV transmission lines • Severe low voltage in WALC 161 kV system t • Loading on Path 44 increases to 7,800 amps; , p ; settles at 7,200 amps14 RELIABILITY | ACCOUNTABILITY
  15. 15. Ramon Transformer Trip South of SONGS Current Voltage collapse in  l ll i pocket, followed  by load tripping Multiple line, generator  and load trips Ramon 230/92 kV  transformer  trip15 RELIABILITY | ACCOUNTABILITY
  16. 16. Voltage in Northern IID 92 kV System Over‐Voltage Trip  of 92 kV System  Capacitors Trip of Over 400  Ramon 230/92 kV  MW in Northern  Transformer Trip Transformer Trip IID 92 kV Load  IID 92 kV Load Pocket16 RELIABILITY | ACCOUNTABILITY
  17. 17. Blythe 161 kV Voltage Trip of Hassayampa  p y p El Centro – Pilot  El Centro Pilot – North Gila 500 kV  Knob 161 kV Line  Line Trip  Trip of Coachella  Valley 230/92 kV  Transformers  Yucca 161/69 kV  Transformers 1 and  2 Trip 2 Trip Trip of Over 400  Trip of Over 400 Ramon 230/92 kV  MW in Northern  Transformer Trip IID 92 kV Load  Pocket17 RELIABILITY | ACCOUNTABILITY
  18. 18. Phase 5 – Yuma Separates • Yuma AZ Separates from IID and WALC when Gila and Yucca transformers trip 15:35:40 15:37:55 15 35 40 – 15 37 55 • Yuma load pocket isolated on single tie to SDG&E • Loading on Path 44 increases to 7,400 amps after Gila transformer trip; to 7,800 amps after Yucca ft Y transformers and generator trip18 RELIABILITY | ACCOUNTABILITY
  19. 19. Yuma Separation South of SONGS Current YCA  generating  g g units trip Yucca 161/69 kV  Pilot Knob  transformers  trip 161/92 kV  transformers  trip Gila 161/69 kV  transformers  trip19 RELIABILITY | ACCOUNTABILITY
  20. 20. Phase 6 – High-Speed Cascade • El Centro – Pilot Knob 161kV line trips; all IID 92 kV system radial from SDG&E via S-Line 15:37:55 15 37 55 • WALC 161 kV system voltage returns to normal • Path 44 exceeds 8,000 amp setting and timer starts20 RELIABILITY | ACCOUNTABILITY
  21. 21. El Centro – Pilot Knob 161 kV Trips Early  Phase 4  activity Gila  transformers  trip Pilot Knob  transformers  trip Zone 3  pickup Yucca  transformers  trip21 RELIABILITY | ACCOUNTABILITY
  22. 22. Phase 6 – High-Speed Cascade • S-Line RAS trips IV generation and S-Line, isolating IID from SDG&E 15:37:58 15:38:02.4 15 37 58 – 15 38 02 4 • Path 44 loading increases to as high as 9,500 amps and reduces to 8,700 amps after isolating IID22 RELIABILITY | ACCOUNTABILITY
  23. 23. Phase 6 – High-Speed Cascade South of SONGS Current Imperial Valley  El  Imperial Valley – El Centro 230 kV  CLR  “S” line trip generating  units trip SONGS  separation i El Centro  – Pilot  Knob 161 kV line  trip23 RELIABILITY | ACCOUNTABILITY
  24. 24. Phase 6 – High-Speed Cascade • SONGS separation scheme operates; forms SDG&E, CFE, Yuma combined island 15:38:21.2 15 38 21 2 • Combined island frequency begins to collapse24 RELIABILITY | ACCOUNTABILITY
  25. 25. SONGS  separation SONGS Unit 3  electrically  disconnects SONGS Unit 2  electrically  disconnects SONGS  SONGS generators  ring down25 RELIABILITY | ACCOUNTABILITY
  26. 26. SONGS  SONGS separation SONGS Unit 2 GSU  trip and transfer of  SONGS aux load  aux load on startup  transformers SONGS  generators  ring down ring down SONGS Unit 3 GSU  trip and transfer of  aux load26 RELIABILITY | ACCOUNTABILITY
  27. 27. Phase 7 – S CA Separates • Yuma island separates from SDG&E when IV-NG 500 kV trips on underfrequency 15:38:23.12 15 38 23 12 • APS UFLS operates, but insufficient to stabilize load pocket • Yuma load pocket collapses27 RELIABILITY | ACCOUNTABILITY
  28. 28. UFLS Operations in the Island28 RELIABILITY | ACCOUNTABILITY
  29. 29. Voltage  Voltage peaks as tie  lines open SONGS  separation SDGE UFLS begins  SDGE ties to CFE and Yuma  shedding load open on underfrequency29 RELIABILITY | ACCOUNTABILITY
  30. 30. Phase 7 – CFE Separates • Underfrequency UFLS SDG&E and CFE continues 15:38:23.13 15 38 23 13 • CFE separates from SDG&E30 RELIABILITY | ACCOUNTABILITY
  31. 31. Actual vs. Simulated Frequency  31 RELIABILITY | ACCOUNTABILITY
  32. 32. Phase 7 – Complete Blackout • IID, Yuma, SDG&E, and CFE blacked out By 15:38:38 B 15 38 3832 RELIABILITY | ACCOUNTABILITY
  33. 33. Use of PMUs in EA33 RELIABILITY | ACCOUNTABILITY
  34. 34. Sammis-Star Hard-Chamb Hard Chamb Star-S.Cant CantC-Tidd Hanna-Jun2003 Blackout Simulations RELIABILITY | ACCOUNTABILITY 345 kV 345 kV 345 kV 345 kV 345 kV Dale-W.Can 138 kV W.Ak 138 kV Bkr Failure Cham-W.Ak 138 kV E.Lima-N.Fin 138 kV CantC Xfmr W.Ak-PV Q21 W 138 1 kV Outages Babb-W.Ak 138 kV E.Lima-N.Lib E 138 kV Clov-Torrey 138 kV Star-S.Cant 345 kV Hanna-Jun 345 kV Hard-Chamb 345 kV 34 140 120 100 80 60 40 20 0 Amps) % of Norma Ratings (A al
  35. 35. PMU Data from SONGS35 RELIABILITY | ACCOUNTABILITY
  36. 36. 7 Phases of Event Trip or Gila 161/69 kV  Trip or Gila 161/69 kV Trip of Coachella  Transformers &  Valley 230/92 kV  Yuma Cogen Transformers Trip of Pilot Knob  161/92 kV & Yucca  161/69 kV  Trip of  Pilot  Transformers Knob – El  Trip of Hassayampa  Centro 161 kV  – North Gila 500 kV North Gila 500 kV  Line Line Trip of Ramon  South of SONGS  230/92 kV  / Separation Transformer 1 2 3 4 5 6 7 Disturbance Phases36 RELIABILITY | ACCOUNTABILITY
  37. 37. EA Modeling37 RELIABILITY | ACCOUNTABILITY
  38. 38. Simulation vs. Actual Flows South of SONGS Flows 4000 3500 3000 2500 MW 2000 1500 1000 500 0 15:27:30.240 15:28:56.640 15:30:23.040 15:31:49.440 15:33:15.840 15:34:42.240 15:36:08.640 15:37:35.040 Local Time (PDT) L l Ti (PDT) Simulated Actual (PMU)38 RELIABILITY | ACCOUNTABILITY
  39. 39. Inquiry Findings39 RELIABILITY | ACCOUNTABILITY
  40. 40. Key FindingsWeaknesses in two broad areas:• Operations planning Operations planning• Real‐time situational awarenessContributing factors:Contributing factors:• Not studying impact of sub 100 kV facilities parallel to EHV• Failure to recognize IROLs Failure to recognize IROLs• Not studying/coordinating effects of protection systems and  RASs during contingency scenarios RASs during contingency scenarios• Not providing effective operator tools and instructions for  reclosing lines with large phase angle differences40 RELIABILITY | ACCOUNTABILITY
  41. 41. Operations PlanningFailure to consider in seasonal, next‐day, and real‐time studies:• Status of external generation and transmission facilities Status of external generation and transmission facilities• Impact of external contingencies• Impacts on external systems p y• Impact on BPS of reliability of sub‐100 kV facilities parallel to  EHV system41 RELIABILITY | ACCOUNTABILITY
  42. 42. Operations PlanningRecommended TOP/BA Improvements in WECC:• Obtain information on neighboring BAs and TOPs, including  g g , g transmission outages, generation outages and schedules, load  forecasts, and scheduled interchanges • Identify and plan for external contingencies that could impact  Id tif d l f t l ti i th t ld i t their systems and internal contingencies that could impact  neighbors’ systems• Consider facilities operated at less than 100 kV parallel to EHV  system that could impact BPS reliability• Coordinated review of planning studies to ensure operation of  C di d i f l i di i f affected Rated Paths will not result in reliability problems42 RELIABILITY | ACCOUNTABILITY
  43. 43. Situational AwarenessRecommended Improvements in WECC:• Expand entities’ external visibility in models through more  p y g complete data sharing• Improve use of real‐time tools to ensure constant monitoring of  potential internal or external contingencies t ti l i t l t l ti i• Improve communications among entities to help maintain  situational awareness situational awareness• TOPs should review their real‐time monitoring tools (State  Estimator and RTCA) to ensure critical facilities are represented43 RELIABILITY | ACCOUNTABILITY
  44. 44. System Protection IssuesRecommendations:• IID and other TOs review transformer overload protection p relay settings• TOPs plan to take proper pre-contingency mitigation measures considering emergency ratings and overload id i ti d l d protection systems• All protection systems and separation schemes (Safety Nets, RAS, and SPS) studied and coordinated periodically to understand their impact on BPS reliability to ensure no unintended or undesirable effects44 RELIABILITY | ACCOUNTABILITY
  45. 45. Questions?45 RELIABILITY | ACCOUNTABILITY

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