Investigation of Transformer Lockout Event Caused by Breaker Failure Protection Misoperation

Breaker Failure (BF) protection is crucial for the security and reliability of power systems. As one example, a breaker failure event at a Dominion Energy Virginia (DEV) distribution substation resulted in a transformer Lockout (LO). This was due to a fault on one of the circuits associated with the BF relay scheme. The event was investigated by using data from digital fault recorders (DFRs), control drawings, Aspen Oneliner software, and field wiring checks This paper describes the breaker failure, outlines DEV's BF protection scheme, and recommends strategies to mitigate BF misoperation in the future, especially for electromechanical relays.