Research On Fault Location Technology Of Medium Voltage Distribution Network Based On PMU

With the development of society,people's way of life is changing,and people's way of using electricity is slightly different from the previous way of using electricity.Promoted by the national policy,distributed energy sources such as electric vehicles resulting in a different power flow mode from the traditional one-way power flow mode of the distribution network.Under the new situation,the traditional fault protection device can not fully meet the requirements,which puts forward new requirements for fault location device and technology.Synchronized phasor measurement unit(PMU)time-scaled power information,which can well meet the requirements of distribution network fault location under the new situation and has a good application prospect.This paper presents a PMU-based fault location method for distribution network.It mainly includes fault type identification of distribution network and fault location calculation of distribution network.Firstly,the fault types of distribution network are identified,and the three-phase current,zero-sequence voltage and zero-sequence current are selected as input signals for analysis.The wavelet transform is used to extract the features of the input signal,and the extracted features are input into the improved BP neural network which has been trained to recognize the fault types.Then the fault location is calculated according to the identified fault types.Firstly,the fault section is located,and the fault section is determined by the direction of negative sequence current to narrow the fault search range.Then the fault location is determined,and the fault line in the section is identified to identify whether the fault occurs on the trunk line or on the branch line.Then according to the different branches of the trunk line,the location of the fault point is further calculated by the single-terminal impedance method.The distribution network model is built on the simulation software MATLAB/Simulink,and voltage and current collected by PMU are obtained.The fault type recognition algorithm consists of three-phase current,zero-sequence voltage and zero-sequence current,which can effectively overcome the problem that zero-sequence current is very small and interferes with the identification accuracy of some fault types.It can improve the identification accuracy of inter-phase short-circuit and indirect-phase short-circuit fault types,and the method has good adaptability to noise.In the calculation part of fault location,fault section location provides fault section,which greatly reducesthe traversal range of single-terminal impedance method.In the fault section,the main and branch lines of fault location are identified,which effectively eliminates false fault points and improves the accuracy of fault location.Experiments show that the scheme meets the requirement of positioning accuracy in distribution network and is feasible and effective.