Month: April 2011

Pilot Relaying

Wave Trap with Corona Fittings

Pilot relaying refers to the communication network implemented on the high voltage transmission line (T-line) to transmit “trip or don’t trip” signal to and fro between two or more substations. The intent here is to trip the circuit breakers as fast as possible when a fault strikes the T-line, therefore, protecting it.

Directional Comparison Blocking Scheme

Fault Zones

The Directional Comparison Blocking (DCB) scheme is the most popular pilot relaying scheme, implemented to protect extra high voltage power lines. This scheme is more dependable than permissive transfer trip schemes because it trips the breaker even if there is no carrier signal from the remote end pilot relay. Ofcourse, the protective relays need to see the fault first.