1. Transmission Operator Protection System Misoperations 2014 ERCOT Transmission Protections System Misoperations Data – 138kV and 345kV Combined (Not including Failure to Reclose) NOTE: Includes only transmission system protection system misoperations from 1/1/2011 thru 6/30/2014 reported by Transmission Operators

2. Value # of MisoperationsTotal48 345 kV17 138 kV29 < 100 kV2 By CategoryFailure to Trip1 Slow Trip0 Unnecessary Trip during Fault25 Unnecessary Trip – Non Fault22 SPS0 By Relay System Type Electromechanical41 Solid State1 Microprocessor4 Other/ N/A2 By Equipment Protected Line33 Transformer2 Generator3 Shunt/Series Capacitor1 Shunt/Series Reactor4 Dynamic VAR system0 Bus3 Breaker2 Protection System Misoperations 2014 Q2

3. Summary of Human Performance Issues noted for 2014 Q2: -138 kV line overtrip during substation re-configuration project. New relay settings were installed on the line terminal but the carrier frequency was not changed to reflect the new substation configuration. -138 kV line overtrip occurred with MDAR relay set to zero polarization on one terminal and SEL321 with negative sequence polarization on the other terminal. -Multiple 345 kV lines overtripped due to a failed CT on a short line between a substation and a generation plant. Remote line terminals tripped due to miscoordination between the backup ground relays and the remote bus ground backup directional overcurrent relays. -Misoperation of 345 kV auto due to wind blowing the cabinet door, causing the SPR auxiliary relay to vibrate and trip. -138 kV line overtrip due to incorrect line length in Aspen model. -138 kV bus differential failed to trip for a fault due to incorrect wiring from the CTs to the relay. Protection System Misoperations 2014 Q2

4. Protection System “Human Performance” Trends “Human” performance misoperations defined as the percentage of misoperation each quarter caused by incorrect settings, incorrect design, logic errors, and as-left personnel errors.

5. Protection System Corrective Action Trends