A novel pilot protection scheme for distribution network with DGs

With the rapid interconnection of a large number of distributed generations(DGs), new challenges for protection of distribution network are posed. Three-section current protection will be no longer applied due to the change of structure of distribution network. To date, the majority of the solutions are adding directional elements or using differential protection scheme of high-voltage transmission. The former requires additional voltage transformer, the latter requires communication channel of high synchronization. However, that can not be realized in distribution network of low voltage. In allusion to the low voltage distribution network (weak communication, lacks of enough voltage transformer), this paper proposes a novel pilot protection scheme based on positive sequence current phase. Firstly, phase variation is obtained by compare the phase of sequence current before and after fault. Then, internal fault and external fault can be determined by compare phase variation of two terminals. Compared with traditional phase comparison pilot protection, this scheme only needs to transmit numerical value of phase variation, therefore communication channel of high synchronization is not required; compared with the traditional directional comparison pilot protection, this scheme only needs to collect current information, therefore there is no need for additional voltage transformer. Simulation proves the validity and superiority of proposed pilot protection scheme.