Principle and Application of System Protection Scheme to Distribution Network

A new system protection scheme to distribution network using optical communication is proposed. The fault zone can be located quickly through the protection devices next to each other exchanging fault signal with direction information. The protection device has a bi-direction reclosing function. Isolating the fault and restructuring the network can be realized using the protection action information such as the first action and post-acceleration action. The fault information that every protection device gets is divided into two groups according to its direction. This way effectively solves the problem of multi branches in distribution network. The feeder relay in substation acts as backup when any protection devices or primary devices malfunction, or communication is interrupted. Based on the multiplexing technique, a novel type of optical MODEM can rapidly deliver Boolean variable besides the normal communication function (less 20 us). This proposed scheme is successful through physical simulation experiment and this scheme has been put in practice in a real distribution network for about two years