Arc flash hazard is a huge concern in areas where you are operating medium voltage (1kV – 34kV) and low voltage (less than 1kV) equipment. Mostly because, when you inadvertently initiate a fault, an arc flash ensuing it releases enormous amount of heat energy. The composition of this arc includes molten bits of copper or aluminium busbar or cable.
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.
The Directional Comparison Blocking (DCB) scheme is the most popular pilot relaying scheme, implemented to protect high voltage power lines. This scheme is more dependable than a permissive transfer trip scheme because it trips the breaker even when there is no carrier signal from the remote end pilot relay. Let’s dive into details.