| With the development of cities,a single cable line and overhead line can no longer meet the needs of urban construction,and the mixed use of the two can not only reduce the floor space,but also have more stable transmission performance.Since the two lines are different,the wave impedance in the hybrid line is discontinuous,so the traveling wave reflection phenomenon other than the fault point will occur at the connection point between the cable line and the overhead line.Therefore,the hybrid transmission line has a more complex fault traveling wave refraction and reflection process,which makes it impossible to directly use the existing fault location method to accurately calculate the fault location of the cable-overhead line hybrid transmission line.This paper firstly builds a hybrid line model,analyzes and compares the current waveforms generated by different fault points,and obtains the problems existing in the ranging.Then,according to the existing problems,a method of using generalized S-transform energy relative entropy to determine the fault section is proposed.On the basis of determining the fault section,a fault location method based on electromagnetic time reversal is adopted.After using the phase mode matrix to decouple the currents on both sides of the fault section,wavelet transform is used to filter the line mode currents extracted after decoupling,and the processed signal components are used as the feature quantities to express the ranging waveform;Assume the fault point and calculate the rms value of the current at each assumed fault point.When the rms value is the maximum value,the point is the fault point.Finally,through the simulation model,the data after the failure is obtained,and MATLAB is used to process the data.The effects of different fault types,transition resistance,phase angle difference of double-ended power supply,and sampling frequency on the ranging results are analyzed and verified.The simulation results show that the time-domain current method based on the electromagnetic time reversal(EMTR)theory can be applied to various faults.type,and the results are not affected by transition resistance,different phase angles of the double-ended power supplies,and sampling frequency.The feasibility of the time-domain current method based on electromagnetic time reversal in the hybrid cable-overhead line transmission line is demonstrated.In addition,in view of the problem that the fault type and transition resistance are unknown when the actual fault is found in the EMTR algorithm,an improved EMTR timedomain algorithm is proposed.The improved EMTR algorithm can realize the phase selection function of the EMTR algorithm fault location through simulation verification.It is applied under unknown conditions and has good robustness in terms of line parameters. |
