Direct Transfer Trips (DTT) are initiated from station relays when a serious event occurs in the substation. Some of these events are breaker failure, bus faults, transformer failure, etc. A lockout relay (86 device) is assigned to each event.
Month: April 2011
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.