Research On Distribution Network Relay Protection And Fault Section Detection

Distribution network is a significant part of power system and redistribute the power energy.The voltage of distribution network is low;however,it has numerous branches and electric components,making fault more easily to happen.Precisely locating and isolating the fault will reduce the loss and protect the grid.Nowadays more types of load and distribution generation such as wind and solar photovoltaic power are connected to distribution network with complex structure.Impact has been brought to distribution network protection and fault location by these new factors,and changes should be made to the old schemes.First of all,a new distribution line protection scheme is proposed considering the influence of electric vehicles charging power.The charger of EV is simulated,and its load characteristic is analyzed.The driving pattern model of EV consumer is built and daily load curve of 1500 EVs is described.The impact on traditional distribution line protection scheme by charging load is analyzed and the new over-current protection scheme based on reactive power fault component is introduced.The scheme is verified by the PSCAD simulation.Then,two improved inverse-time over-current(ITOC)protection schemes are proposed considering the impact of DG penetration.The operation characteristic and setting of ITOC protection is introduced.The impact of DG fault current on ITOC protection operation time is analyzed,and the modified ITOC protection based on telecommunication is proposed.Another scheme brings in the low-voltage acceleration factor and modified the ITOC protection operation equation,which can accelerate the operation time and guarantee the selectivity at the same time.The PSCAD simulation verified the effectiveness of two proposed schemes.At last,a new type of fault location algorithm aimed at distribution network with complex topological structure is proposed.The principle of artificial fish swarm algorithm(AFSA)is introduced,and AFSA-PSO,a new kind of hybrid optimization algorithm,is proposed.The optimization of example verified the fast convergence of the proposed hybrid algorithm compared to AFSA and PSO.The AFSA-PSO is applied to distribution network fault location problem,and it is tested on IEEE standard 33 nodes distribution network.The calculation result verified the effectiveness of the proposed AFSA-PSO algorithm.