Today’s LiveWire Spotlight evaluates three NERC Lessons Learned – “teachable moments” where control and Protection System failures threatened electric system reliability.  The Lessons address scenarios where (1) differential relays protecting 3 distribution transformers simultaneously Misoperated during a low voltage fault, (2) a single-phase fault on a known-bad CCVT (disconnected at the taps, but still attached to high voltage) induced ground currents causing a relay pilot system to fail, and (3) a routine update crashed the automatic generation control system at a BA’s primary and backup Control Centers – forcing manual scheduling and ACE calculation.

Control and Protection System failures continue to be a leading cause of BES service loss and is among NERC’s top reliability concerns.  Severe penalties may be levied if an outage occurs, and it is found that an Operator did not act upon these Lessons Learned.