Research On Fault Location Technology Of Low-voltage Distribution Network Based On Reflection Measurement Method

With the development of society,electrical energy has become an indispensable part of people's life and work,and electrical energy is transmitted through power cables.Therefore,ensuring the reliability of electrical energy transmitted by power cables is vital to users.The low-voltage distribution network is the closest part of the user to the distribution network.Its complex topology,numerous branches,and changing operating environments lead to a high probability of power cable failure in the low-voltage distribution network.After the power cable fails,the specific location of the fault can be determined quickly and effectively,and the fault can be repaired to avoid the losses caused by the power grid failure.The low-voltage distribution network is different from the medium-and high-voltage distribution network in that its branch length is short and affected by time synchronization.The traveling wave method commonly used in the medium-high-voltage distribution network cannot be directly applied,and a new fault location method is needed.Firstly,analyze the commonly used cable fault detection methods and determine that the reflection measurement method based on correlation calculation is a method suitable for low-voltage distribution network cable fault detection.Based on this,the detection principles,parameter effects,signal selection,and transmission principles of the sequence time-domain reflectometry,spread spectrum time-domain reflectometry and chaos time domain reflectometry were studied.The problems encountered in fault detection in the low-voltage distribution network environment are analyzed.Secondly,based on the reflection measurement method based on correlation calculation,this paper studies the fault location of cables in low-voltage distribution network environment.Aiming at the fault location under the complex topology of the low-voltage distribution network,a fault location method based on multi-point joint detection is proposed.This method is based on the chaos reflection method,and sets multiple test points in the topology network to test the power grid.After detection,after the power grid fails,the measurement results of multiple test points are fused to determine the accurate fault line.Thirdly,a low-voltage distribution network model is established through the simulink simulation platform,and the proposed method is verified.Simulation resultsshow that the method can achieve accurate fault location in the complex topology environment of the low-voltage distribution network,and solves the complex topology.Location ambiguity at a single test point.A preliminary design of a logistic chaotic signal source based on FPGA was made through the System Generator development platform,tested in actual measurement scenarios,and the method proposed in this paper is verified.The measured results show that this method can be used in complex topological environments The accurate positioning of the cable faults further proves the effectiveness of the proposed method.Finally,aiming at the problem that the performance of the traditional generalized cross-correlation algorithm based on the second-order statistics is severely reduced in the impulsive noise environment of low-voltage distribution network,an improved cable fault location algorithm based on generalized correlation entropy is proposed.This algorithm combines the concept of correlation entropy,replaces the power spectrum in generalized cross-correlation with the correlation entropy spectrum to suppress impulse noise,and determines the time delay of the fault reflection signal through peak detection.The simulation results show that the method can accurately estimate the time delay of the fault reflection signal under impulsive noise environment,and has good performance under strong impulsive noise intensity and low generalized signal-to-noise ratio environment.