Transmission Operator Protection System Misoperations Report
The System Protection Working Group (SPWG) provided an update on the misoperation rates of transmission operator protection systems in the second quarter of 2019. The report includes data on misoperations by voltage, equipment type, relay system type, and more. Key topics discussed in SPWG meetings and leadership nominees are also highlighted.
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System Protection Working Group (SPWG) Update to ROS January 9, 2020 Micheal Davis, Jr, P.E.
SPWG Meeting Meeting held on November 13, 2019 Next meeting is scheduled for March 3-4, 2020 2020 SPWG Leadership Nominees: Chair: John Karlik, P.E. | Austin Energy Vice Chair: Vincent Roberts, P.E. | Texas-New Mexico Power (TNMP) Some topics discussed: NPRR953 s revised definition and comments for evaluating a process for data submittals SPWG 2020 case-building schedule and procedure Some operational activities End-to-end testing between two companies Uploading relay data into software program for studies Reviewed a bug fix to enable proper translation of uploaded dated
Transmission Operator Protection System Misoperations 2019 Q2 ERCOT Protection System Misoperations Data 138kV and 345kV Combined % Misoperation Rate Overall 345kV 138kV 4 per. Mov. Avg. (Overall) 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% 2014 Q12014 Q22014 Q32014 Q42015 Q12015 Q22015 Q32015 Q42016 Q12016 Q22016 Q32016 Q42017 Q12017 Q22017 Q32017 Q42018 Q12018 Q22018 Q32018 Q42019 Q12019 Q2 Gradual increase in rolling average misoperation rate in the last year, 6.2% to 7.9%
Protection System Misoperations 2019 Q2 Q2 2019 YTD # of Misoperations Total 69 107 345 kV 20 26 138 kV 48 78 < 100 kV 1 3 By Category Failure to Trip 5 5 Slow Trip 0 0 Unnecessary Trip during Fault 39 63 Unnecessary Trip Non Fault 25 39 SPS 0 0 By Relay System Type Electromechanical 11 15 Solid State 1 1 Microprocessor 45 72 Other/ N/A 4 19 By Equipment Protected Line 23 37 Transformer 14 21 Generator 6 8 Shunt/Series Capacitor 1 3 Shunt/Series Reactor 1 1 Dynamic VAR system 1 2 Bus 9 10 Breaker 9 20
Protection System Misoperations 2019 Q2 By Voltage 138kV 3% 0% 345kV 24% <100kV (BES) <100kV (non-BES) 73%
Protection System Misoperations 2019 Q2 Summary of Human Performance Issues noted for 2019 Q2: - 138kV bus differential overtripped due to an incorrectly wired CT polarity. - A 138kV line terminal overtripped due to an incorrectly wired CT polarity. - A 345kV auto overtripped due to an incorrectly wired CT following maintenance. - A 138kV line misoperated due to field settings not match issued settings. - A 345kV line overtripped due to a carrier cut-off switch left in the Off position. - A 138kV line overtripped due to an incorrect polarizing CT circuit polarity. - A 138kV line overtripped due to incorrect mirrored bits settings. - A 138kV line terminal over-reached and tripped for a remote bus fault due to an incorrect Zone 1 ground distance setting. - 138kV bus differential misoperated due to one source not included in the differential calculations. - Two separate misoperations for external faults due to mismatch between wired CT ratio and relay setting ratio. - 138kV line overtripped, carrier relaying was enabled inadvertently during construction project. - Three events with line overtrips due to an incorrect setting on ground instantaneous relays. - 138kV line overtripped due to CTs wired on the wrong ratio. Failure to Trip/Slow Trip Misoperations in 2019 Q2: - Circuit breaker failed to trip due to a failed diode. Breaker failure relays isolated the fault. - Bus differential relay had incorrect logic, resulting in a failure to trip for a bus fault. - Capacitor bank 50P1 element was set too low, resulting in blocking the capacitor protection for tripping. Bus differential relays cleared the fault. - Ground fault protection failed to trip for a line-ground fault. Fault was cleared by backup relays.
NPRR953 Activities Relay Loadability Rating definition discussion: - Meeting with SPWG members and various other ERCOT personnel held on Sep. 16, 2019 - Discussed various SPWG comments to the original definition in NPRR953 - SPWG members expressed concerns and a revised definition was drafted Comments to updated definition within NPRR953 - ERCOT submitted a revised relay loadability rating definition on 10/29/2019 - Comments were received on 10/30/2019 - These comments and other details were discussed at the November SPWG meeting on 11/13/2019 - Based on the discussion, the revised definition seemed to be acceptable but a separate meeting would likely be needed to discuss the update/data submittal process Relay loadability update process - Meeting between SPWG members and ERCOT personnel held on 11/21/2019 - Discussed timeline expectations for submitting updates and minimum data requirements - Evaluated possible alternatives for questions related to minimum expectations for timeline requirements and data submittals - Process will continue to be evaluated as the tools are also developed or revised SPWG members also evaluated another slightly revised relay loadability rating definition - This was submitted afterwards by ERCOT on 12/04/2019
