Research On Fault Location Method For Cable-Overhead Hybrid Transmission Lines

With the advancement of urbanization construction,cable lines are widely used.Transmission lines begin to develop from single-type overhead lines to cable-overhead hybrid transmission lines,with relatively small footprint and more stable transmission performance.Because the wave impedance of the cable line and the overhead line is discontinuous,the traveling wave propagation point except the fault point exists in the traveling wave propagation process,that is,the connection point between the cable line and the overhead line.Therefore,compared with the single overhead line,the mixed transmission line The faulty wavefront reflection process becomes complex and variable,resulting in the cable-overhead hybrid transmission line not being able to directly use the existing fault location method to achieve accurate calculation of the fault location.In view of the above problems,this paper firstly performs the phase-mode transformation of the single-ended fault current to extract the'fault line mode current,and uses the db4 wavelet to perform the wavelet transform multi-resolution analysis on the extracted fault line mode current,which will be obtained under the sixth scale.The wavelet coefficient is used as the feature quantity to express the fault traveling wave waveform.Then the clustering analysis method is used to express the similarity and difference of the fault current waveform feature quantities at different fault locations,and the fault waveform database is established.Finally,the fault distance calculation is realized by combining the regression analysis equation based on the coefficient of determination.In the ATP-EMTP simulation software,a cable-overhead hybrid transmission line simulation model is built to simulate the fault conditions of different fault locations and different transition resistances in the hybrid line,and the fault waveform feature quantity is extracted at the single end of the line and used as a sample.The fault waveform database is built,and the clustering analysis method and the regression analysis based on the coefficient of determination are used to realize the establishment of the fault location system.Because the regression analysis has high requirements on data quality,the K-Means algorithm is used to optimize the fault location system established in this paper to achieve higher accuracy cable-overhead hybrid transmission line fault location.The cable-overhead hybrid transmission line fault location method proposed in this paper is based on the fault waveform feature similarity principle and the clustering and regression algorithm for fault location.It is not necessary to calibrate the fault initial traveling wave and the fault point reflected wave without detecting the line.Wave speed,high precision and low error.The simulation results show that the method can achieve accurate ranging under different fault locations and different transition resistance faults.