Research On Application Of Fault Location Technique For Multi-terminal Transmission Lines Using Date Acquired By Fault Recorders

Multi-terminal transmission line(MTL)is the most common type of power line in high-voltage transmission networks.Different from a single transmission line,MTL has many branches,which makes the fault location more complicated.In the bus substation of each terminal of the MTL,fault recorder devices are equipped.However,most of the fault recorders in the substations can only display the fault information,and much of them has not been fully excavated,which leads to a waste of the recorded fault information.By using the fault data of fault recorders to realize accurate fault location of MTLs,the practical value of the fault recorders can be improved,which has great significance to fast detection of faults,efficient repair work,reduction of losses caused by outage and improvement intelligent fault perception.This paper firstly investigates the current fault location techniques of transmission lines at home and abroad,and summarizes the advantages and disadvantages of these methods.Aiming at the structure of the MTL,the transmission equations of the line is analyzed.Based on the distributed parameter model,the distribution features of the steady-state sequence voltages and currents in normal operation and single-phase-to-earth fault are analyzed.Then,by analyzing the time-domain characteristics of the zero-sequence currents measured by fault recorders mounted at both terminals in each line section of the MTL,the faulty section identification criterion considering the Pearson correlation degree of the zero-sequence currents is constructed.In the faulty section,introducing the synchronous measurement errors of the phases of the fault data recorded at both terminals,the voltage amplitude difference function including the fault distance based on distributed parameter model is established.Searching the minimum value of the function by gold-search algorithm,accurate fault location can be estimated.In the proposed method,the noise-interference in the actual field is considered.Mathematical morphology is employed to de-noise the raw signals and wavelet transform is utilized to determine the data window.Finally,a MTL simulation model is constructed by PSCAD/EMTDC and various fault simulations are constructed.The calculation results demonstrate that the proposed fault location method is not affected by fault distances,fault resistances,fault inception angles,noises and synchronous measurement error of phases.Strict synchronization is not required in the method.In addition,the fault data of the fault recorders in actual field is adopted to test the performance of the proposed method.Accurate fault location results are obtained,which shows the high practicability value of the method.