Today’s LiveWire Spotlight examines three “teachable moments” recently posted by NERC where transient-induced Protection System Misoperations threatened electric system reliability.

  1. A close-in Fault at a 230 kV substation lasting for less than a cycle tripped both connections to an upstream high voltage transmission station.
  2. A lightning strike in 2020 near the same substation tripped the connections again, but this time the data confirmed AC coupling on the supply forced a false signal.
  3. A 345 kV pylon was hit by a massive lightning bolt, Faulting Phase B. Neither the primary nor the backup relay reacted, forcing 14 remote relays to clear the Fault.

Protection System Misoperations continue to be a leading cause of BES service loss and are 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.