Transmission Line Fault Location Based On Electromagnetic Time Reversal

When fault occurs,if the fault cannot be eliminated in time,it may lead to a power outage of the primary load in extreme cases,which will cause social chaos and immeasurable damage to the economy.In the current transmission line fault location method,the traveling wave method has the problem of difficulty in identifying wave heads.In addition,in the fault analysis method,the ranging accuracy of the single-ended method is easily affected by the transition resistance and the operating mode of the system,while the double-ended method requires extremely high data synchronization at both ends.To solve these problems,in this paper,the electromagnetic time reversal algorithm based on spatial focus is used for fault location,and an improvement is proposed to improve its applicability.For the calculation of the voltage and current of the fault line,the fault transmission line is equivalent to a series transmission line in this paper,and the BLT super-matrix equation combined with the electromagnetic topology theory is used to calculate the voltage and current of the fault point and both ends in the frequency domain.It solves the problem of difficulty in calculating line voltage and current caused by complex refraction and reflection at the fault point,and provides necessary conditions for the use of the subsequent frequency-domain electromagnetic time reversal location algorithm.The calculation results show that the BLT super-matrix equation can well reflect the refraction and reflection of fault traveling waves.The current fault location methods based on electromagnetic time reversal algorithm exist the problems that the fault phase in the reversal process needs to be known in advance and there is a dead zone in fault location using the decoupled modulus.In order to solve the problems,this paper theoretically analyzes the propagation law of transient traveling waves on faulty and non-fault phases when fault occurs.It is proved that the coupling current of the non-fault phase has the same phase shift and propagation delay as the fault phase current,and can also transfer the fault distance information.Based on this,an improved electromagnetic time reversal algorithm based on coupling current of non-fault phase is proposed.This improved method assumes that one or several phases are the fault phases in the reversal stage.The current of each guessed fault point is calculated according to the reversed current of the assumed fault phase.The guessed fault point with the largest 2-norm of current is the real fault point.The calculation results show that the algorithm has good location accuracy under different fault points and fault types,and is not affected by the transition resistance and the phase angle difference between the two ends of the power supply.For the fault location of the hybrid cable-overhead transmission line,this paper firstly uses the phase comparison method based on Kaiser window to determine the fault section of the hybrid line.The adopted Kaiser window effectively solves the problem of spectral leakage in the phase comparison of Fourier transform and reduces the phase error.Then,it is only necessary to set several guessed fault locations in the fault section,and use the improved algorithm proposed in this paper to determine the real fault location.This method effectively solves the problems of the difficulty of wave head identification in the traveling wave method and the complex ranging function and the appearance of false roots in the fault analysis method in the fault location of hybrid lines.The localization results show that the method has good accuracy.