Analysis of Three Recent Blackouts

Analysis of Three Recent Blackouts San Diego Gas & Electric -09/08/2011 Indian Northern Grid 07/30/2012 Indian Northern & Eastern Grids 07/31/2012 Bharat Bhargava Advanced Power System Technologies, Inc. 359 Amberwood Drive Walnut, CA 91789 Copyright 2016 Advanced Power System Technologies, Inc. All Rights Reserved 1

Presentation Outline / Objectives Objectives: Review the three recent blackouts San Diego / Baja California September 8, 2011 Indian Northern region July 30, 2012 Indian Northern/Eastern/Northeastern regions July 31, 2012 Outline basic causes and common factors in these blackouts What can we learn from them to improve system performance and avoid/prevent blackouts What new tools and technologies are available that can help operators to avoid blackouts in future 2

FACTS Power transfer economics and system reliability are competing goals. Systems are designed considering the worst loading condition scenarios and for loss of one element. Systems are well planned and designed as they withstand outage of one element Most disturbances occur, not for loss of one element, but multiple contingencies occurring over an extended time period Very often, the line loadings and margins are not adjusted when line outages occur outside one s control area resulting in lack of wide area situational awareness. Tools are needed to monitor Wide Area stresses and for keeping an eye and awareness of other systems as well 3

New Tools can Increase Transmission Capacity and Reliability New Tools are available and can help in Monitoring wide-area system stresses Establish wide area system stress limits Increasing loading if margin is there Reducing loading if the safe limits are exceeded Comparing stress level with bench marked cases and ensuring adequate margin for dynamic loading/stresses on the system Monitoring slowly growing oscillations and their damping One of the major cause of wide spread outages Monitoring voltage levels and support at all critical locations. Voltage support is critical for safe system operations Event reconstruction, validation and analysis of mitigation alternatives 4

San Diego Gas & Electric System Blackout on September 8, 2011 5

San Diego - WECC Disturbance September 8, 2011 San Diego system was importing power on two major import paths Hassyampa N. Gila- Imperial Valley Miguel 500 kv South of SONGS Five 230 kv lines (Path 44) Power also flows thru the underlying 220/115/92 kv system from Devers bus to IID and Western Administration Lower Colorado SDG & E had established individual path ratings Hassyampa N. Gila 2200 MW Path 44 south of SONGS 1800 MW SDG & E monitors these thru the EMS / SCADA system The (N-1) criterion requires that other system components should not overload for loss of a line/component 6

San Diego - WECC Disturbance September 8, 2011 Sequence of Events - 1 Heavily loaded system and stressed system conditions with hot weather (115 degrees in IID) Safe operation and (N-1) criteria requires that loss of a path should not result in exceeding the normal rating of other paths. RTCA are generally employed to ensure that the system is operating with in safe operating region The Hassyampa N. Gila line tripped at 15:26 hrs while carrying 1394 MW load due to an operational error Loss of this line resulted in increased power flow on Path 44 from 1302 MW to 2386 MW which exceeded the path 44 rating of 2200 MW. This indicates that SDGE was operating beyond the safe operational limit 7

San Diego - WECC Disturbance September 8, 2011 Sequence of Events - 2 IID flows also increased from 90 MW to 240 MW and resulted in overloading the IID transformers which tripped and increased power flow on path 44 to 2600 MW Increased Loading on path 44 may have also resulted in low voltages in CFE area and tripping of generating units in CFE system Loss of these units increased the loading on path 44 above 3200 MW (15:32:385) Path 44 has relay settings at SCE end to isolate SDGE & CFE system if the current exceeds 8000 amps or 3186 MVA Power flows on Path 44 continued to stay above 3200 MW and resulted in relay separation at SONGS. Simulations of the disturbance showed that the angle difference across the breaker at N. Gila exceeded the sync-check relay setting and may have prevented the line re-closure 8

San Diego - WECC Disturbance September 8, 2011 - Impacts Amount of Load lost 7835 MW Areas impacted San Diego 4293 MW (1.4 million customers) CFE 2150 MW (1.1 million customers ) IID 929 MW (146,000 customers) APS 389 MW (70,000 customers) WALC 74 MW ( 5 customers + APS customers) Southern California 450 MW Total customers Impacted 2.7 million Estimated cost $ 6 Billion Time to restore power 12-18 hours 9

San Diego - WECC Disturbance - September 8, 2011 Review of the NERC/FERC report - 1 Actions that could have helped Conducting Real Time Contingency Analysis (RTCA) Monitoring angle difference across open breakers Wide Area system monitoring and Situational Awareness Monitoring / alarming on power flow on Path 44 and angle difference between SONGS and Miguel Nomogram display of Path flows two major import paths Monitoring voltage sensitivity and angle sensitivity at appropriate locations SDG&E has 6 PMUs that could have been used for wide area visibility 10

Power flow on path 44 after Hassyampa N. Gila line (from FERC/NERC Report) 11

San Diego Path Ratings and Loading before the - WECC Disturbance on September 8, 2011 Major Paths into the Blackout Area Path Ratings Path Loadings in MW Percent loading 500 kv H-NG (Part of Corridor 1 into blackout area) 1,800 MW(31) 1,397 MW 78% Path 44 (Corridor 2 into blackout area) 2,200 MW (32 ) 1,302 MW 59% 230 kv S Line (Part of Corridor 3 into blackout area) 239 MW 90 MW 38% SDG&E Import SOL 2,850 MW 2,539 MW 89% SDG&E to CFE Path 45 800 MW S-N; 241 MW N-S 60% 408 MW N-S Note: 1. Normal system rating 2200 MW 2. Emergency (30 minute ) ratings - not known 3. Trip setting at 8000 Amps (3200 MW) at 145 % 12

Power flows to SDG&E, CFE and IID before the N.Gila-Hassyampa line trip SCE 1302 MW Path 44 (2200 MW) Relay operation set at 3186 MW SONGS SDGE CFE IID 1800 MW (30 deg.) Devers busses 90 MW (239 MW) N.Gila 1397 MW (20 deg. ) (1800 MW) APS/SRP 13

San Diego Path Ratings and Loading after the N.Gila- Hassyampa line trip Major Paths into the Blackout Area Path Ratings Path Loadings in MW and % rating 500 kv H-NG (Part of Corridor 1 into blackout area) 1,800 MW 0 MW 0 % Path 44 (Corridor 2 into blackout area) 2,200 MW 2362 MW 107 % 230 kv S Line (Part of Corridor 3 into blackout area) 239 MW 189 MW 38% SDG&E Import SOL 2,850 MW 2,539 MW 89% SDG&E to CFE Path 45 800 MW S-N; 241 MW N-S 60% 408 MW N-S Note: 1. Normal system rating - 2200 MW 2. Emergency (30 minute ) ratings - not known 3. Trip setting at 8000 Amps (3200 MW) at 145 % 14

Power flows to SDG&E, CFE and IID after the N.Gila-Hassyampa line trip SCE 2000 MW (30 deg.) 2386 MW Path 44 (2200 MW) Relay operation set at 3186 MW SONGS SDGE CFE IID Devers busses 184 MW (239 MW) N.Gila - 400 MW (20 deg. ) (1800 MW) APS/SRP 15

Power flows /Current on Path 44 5 4 Trip level setting 3 After line trip Path 44 Current 2 Normal Rating 1 Before line trip 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Reference: FERC / NERC Report 16

PV Curve for North Gila Bus (Source: NERC/FERC Arizona Outage Report 17

Indian Grid Blackouts on July 30/31, 2012 Reference : REPORT OF THE ENQUIRY COMMITTEE ON GRID DISTURBANCE IN NORTHERN REGION ON 30th July 2012 AND IN NORTHERN, EASTERN & NORTH-EASTERN REGION ON 31st JULY 2012 Issued on 16th AUGUST 2012 NEW DELHI 18

North Indian Blackout July 30, 2012 Disturbance occurred at 02:33:00 on July 30, 2012 High loading in Northern Region load of 38226 MW Generation of 32640 MW Imports of 5836 MW mostly from the Western Region Several 400 kv lines out of service because of Planned outages (10) Unscheduled outages (5) Voltage control (6) Western Northern grid connected on Bina-Gwalior-Agra 400 kv line line loaded to 1355 MW (2.2 SIL) Three 230 kv lines 19

North Indian Blackout July 30, 2012 Amount of Load lost 38,200 MW (Estimated) Areas impacted Northern region People Impacted 300 + million Estimated cost $ 6 Billion Time to restore power 12-18 hours Ties lost A & B NR separated from WR and ER Separation initiated by tripping of Bina-Agra circuit on Zone 3 20

Generation, Imports/Exports in Indian Regional Grids before Blackout Northern Region 32636 MW +5686 MW A Western Region 33024 MW - 6229 MW C B 535 MW Eastern Region 12452 MW - 239 MW North Eastern Region 1367 MW - 53 MW Total Load : 79479 NW 21

Northern India Grid and Regional Interconnections Effected Area Northern Region July 30, 2012 Source: Indian Blackout Investigation Report dated August 16, 2012 22

Indian Regional Blackout July 30, 2012 Frequency Profile in Northern Region 23

North Indian Blackout July 30, 2012 Increased loading on Bina-Gwalior-Agra caused tripping of this line on Zone 3 Tripping of Bina-Gwalior-Agra line resulted in tripping all 230 kv WR-NR lines separating WR and NR Separation of WR-NR resulted in tripping of all Ties between ER and NR NR left with a deficit of 5686 MW ( 18 % generation deficiency in NR Resulted in rapid frequency decline and NR blackout Power restored in 18-24 hours 24

Power Flows in Indian Regional Grids at the time of Blackout 5686 MW Northern Region 32636 MW + 5686 MW A Western Region C B Eastern Region 12452 MW 53 MW North Eastern Region 1367 MW 33024 MW 535 MW Total Load :79,479 MW Load Lost: 38,000 MW Ties Lost: A and B 25

North/ Eastern Indian Blackout July 31, 2012 Occurred in after-noon about 1:20 Hours, shortly after the first one, while the system was still being put together Amount of Load lost 48600 MW Areas impacted Northern region Eastern Region North Eastern region People Impacted 680 + million Estimated cost $ 10 Billion (Estimated) Time to restore power 12-18 hours (Estimated) Ties lost A & C separating NR, ER and NER regions from WR 26

North/ Eastern Indian Blackout July 31, 2012 Increased loading on Bina-Gwalior-Agra again caused tripping of this line on Zone 3, the other line was out of service Tripping of Bina-Gwalior-Agra line resulted in tripping all 230 kv WR-NR lines separating WR and NR Separation of WR-NR resulted in tripping of all Ties between ER and NR NR left with a deficit of 5686 MW ( 18 % generation deficiency in NR Resulted in rapid frequency decline and NR blackout Power restored in 18-24 hours 27

Northern India Blackout Effected Areas July 31, 2012 28

Generation, Imports/Exports in Indian Regional Grids before Blackout Northern Region 29884 MW +4016MW A Western Region 32612 MW - 6240 MW C B Eastern Region 13524 MW - 345 MW 212 MW North Eastern Region 1014 MW +212 Total Load : 76934 NW 29

Generation, Imports/Exports in Indian Regional Grids before Blackout Northern Region 29884 MW +4016MW A Western Region 32612 MW - 6240 MW C B Eastern Region 13524 MW - 345 MW 212 MW North Eastern Region 1014 MW +212 Total Load : 76934 NW Load Lost : 48000 MW 30

Indian Regional Blackout July 31, 2012 Frequency Profile in Northern Region 31

Indian Blackout Investigation Report Very comprehensive Investigation report details all sequence of events, system configurations All facts and figures are provided making it easy to review and comment Suggests steps that may be taken to improve situation and prevent future blackouts Original reports blamed the states of withdrawing too much power, but indicates that the system had several lines out resulting in reduced inter-region transfer capability Simulations may be improved for better analysis 32

Requirements for the Stability of the Grid Grid should be able to Withstand loss of ties and maintain frequency within the acceptable band Not more than 5 % imports and/or adequate UFLS Grid should be able to maintain acceptable voltages at all locations adequate voltage support and control capability Grids operate across wide area and often with angle separation of greater than 90 degrees WECC (US) operates with angle separation of 100 + degrees Eastern Interconnection operates with angle separation of greater than 200 degrees Appropriate voltage support at intermediate (every 30 degrees of angle separation) locations is very important 33

Steps Suggested to avoid Blackouts Better Wide Area Visualization Internal External at least adjoining areas Grid should be able to ES and EMS in operation Establishing Limits on power flows Use of RTCA Use of Synchronized Phasor Measurement technology Angle measurements and other metrics Withstand loss of ties and maintain frequency within the acceptable band 34

Common causes between the SDG&E and Indian Blackouts - 1 Both Systems have two major inter-connections Hassyampa-NG & SCE SONGS Path 44 WR and ER Safe operation requires that loss of one interconnection should not result in exceeding the rating of the other path Readjustment necessary after loss of one tie Both systems were clearly operating beyond safe limits No SOL established or being monitored based on the system conditions No adjustments of loading for line outages Excessive imports compared to local area generation Load 4400 MW, imports of 2698 MW (No possibility of survival when both ties are lost ) Load of 38322 imports of 5686 loss of tie-line would result in a frequency decline of about 16 % No frequency control by UFLS 35

Common causes between the SDG&E and Indian Blackouts - 2 No Situational Awareness, EMS or RTCA in operation Relay setting resulting in system separation Zone 3 relay settings in India Path 44 setting at SONGS No system stress monitoring (Angle separation) No previous analysis to define safe operating regions Power flows (Path 44 ) Angle differences (Bina-Gwalior) No use of advanced technologies for real time dynamics monitoring 36

Thanks, for questions, please email to :Bharat@advancedpstinc.com 37