Faulty Section Location Method And Implementation Technology For Active Distribution Network Feeder

Medium voltage distribution network is the link between the transmission grid and the load.More than 80%of faults in the power system occur on the distribution network side.So the rapid removal and recovery of faults in the distribution network have a significant impact on the reliability of the power supply to the load.Currently,distribution network automation is the main method of fault isolation and self-healing in distribution networks.Distribution network automation is gradually upgrading.However,under the complicated distribution network structure,especially when the distributed generation(DG)directly accesses the feeder,existing technologies cannot meet the requirement of rapid self-healing of faults in distribution networks.DG access distribution network changes the radial structure with single power and fault current characteristics of distribution network.As a result,the faulty section locating method of the traditional distribution network feeder is no longer applicable.This brings huge challenges to the active distribution network in the rapid removal of faults and power restoration.So it has important theoretical significance and engineering application values in improving the power supply reliability of active distribution network to research the faulty section location method adapted to active distribution network feeder actively and develop the intelligent terminal devices which can locate the faulty section.In this regard,this article carries out related researches and the main achievements are as follows:(1)Theoretical analysis of the characteristics of fault ride-through current in active distribution networks.This paper analyzes the influence of fault ride-through current on the magnitude and direction of short circuit current in feeder of active distribution network and points out the reason for the failure of the existing faulty section location methods which based on the short circuit current information for the active distribution network feeders.Theoretical analysis and simulation verify the influence of DG,transient impedance and load on the fault ride-through current in the active distribution network.(2)A new faulty section location method for feeders of active distribution network is proposed.The negative-sequence current phase differences between the two terminals of both the faulty and healthy sections are analyzed when the asymmetric fault occurs in the feeder of the active distribution network,and based on the analysis a negative sequence current phase comparison criterion for locating asymmetric faulty feeder sections is proposed.The difference of amplitude ratios of positive sequence currents between the two terminals of the faulty and healthy sections are analyzed when a symmetrical fault occurs in the feeder of the active distribution network,and based on the analysis a positive sequence current amplitude comparison criterion for locating the symmetric faulted feeder section is proposed.When different types of fault occurs in the feeder of active distribution networks,the difference between positive and negative sequence currents are analyzed,and based on the analysis,a amplitude comparison criterion of positive and negative sequence current for distinguishing fault types is proposed.Theoretical analysis and simulation results show that the faulty feeder section locating method proposed is not affected by fault ride-through current and can accurately locate the faulty feeder section when different types of faults occur in feeder of active distribution networks and faulty section locating is fast and effective.(3)A prototype of intelligent terminal for faulty section locating of active distribution network feeders is developed and tested by dynamic simulating system.Based on the proposed faulty section locating principle,the locating algorithm flow is designed and the corresponding implementation software is written.Using a terminal hardware platform,a prototype of an intelligent erminal with a faulty section locating function is developed.Active distribution network physical model is built in dynamic simulation system.The current at each switch of the bus is input into the prototype terminal.The fault recording device is used to record the operations of the terminal prototype when different types of faults occur at different sections.Theoretical analysis and dynamic simulation results show that the proposed faulty section locating method and the developed prototype terminal for feeders of active distribution network operates rapidly and has high sensitivity and reliability.And it is basically not affected by factors such as transition impedance,DG capacity and load capacity.