Research On Application Of Adaptive Protection In Distribution Network Containing Distributed Generation

The number of DG(Distributed Generation)connected to distribution network is increasing day by day.However,the access of DG may cause the original protection to refuse or malfunction.Therefore,it is of great significance to study the influence of distributed generation access on the relay protection of distribution network and the new protection scheme.Firstly,this paper introduces distributed generation technology and its development,and lists the impact of domestic and foreign scholars on distributed power access distribution network and its solutions.Secondly,the equivalent circuit diagrams of short-circuit at different locations are used to analyze the impact of access to distributed power supply on the original stage current protection.Simple 10kV distribution network model is built by PSACD and verified by simulation.The simulation proves that after DG access,the upstream protection sensitivity of DG may be reduced,the protection scope may be reduced,and the protection sensitivity of downstream DG and adjacent feeders may be increased,and the protection scope may be increased,in serious cases the protection may extend to the next line leading to maloperation.Finally,this paper proposes improved protection scheme for distribution network with DG.The first scheme improves the adaptive current quick-break protection to make it more adaptable in DG access.By analyzing the equivalent complex sequence network diagram of DG in different position short circuit,the positive sequence current of short circuit is worth the setting value of each protection.The simulation results show that the scheme can better adapt to the distribution network after DG is connected.The protection range of three-phase short circuit is 83.33%,but the range of two-phase short circuit is less than 80%.In the second scheme,adaptive distance protection is introduced.The branch coefficient of the ? section is expressed by DG,so that the second section of the protection is not affected by the fault current output by DG in the distribution network with DG.In order to eliminate the influence of transition resistance on distance protection,positive sequence reactance component is extracted by sequence algorithm.The PSCAD simulation results show that the protection scheme has a larger protection range and better resistance to transition resistance than the adaptive current quick-break protection.