Study On Method Of Fault Location Of Transmission Lines Based On Traveling Waves Principle

Transmission lines have important responsibilities in the transmission of electrical energy and are the lifeblood of the power system.The fast and accurate fault location of transmission lines is an important guarantee for the stable operation of the power system.With the continuous development of signal processing technology,traveling wave method has made progress in the fault location of transmission lines,however,there are still some problems in the actual fault location,affecting the accuracy of its positioning.Based on traveling wave theory,this paper studies the detection of traveling wave head and related fault location methods to improve the accuracy of traveling wave fault location.This paper introduces a new phase transformation matrix that can reflect the characteristics of different faults by single module.Based on the analysis of the main factors affecting the location of traveling wave faults,an optimization algorithm is proposed considering the actual propagation path of traveling wave.The algorithm is not affected by the traveling wave velocity and the wire drape,and just according to the time when the fault initial traveling wave reaches the measuring point on both ends of the transmission line and the given line length,the position of the fault point can be calculated to facilitate the practical application of the project.Since the hardware factors of the existing traveling wave distance measuring devices limit the improvement of the sampling frequency and affect the accuracy of the traveling wave location results,this paper proposes a traveling wave fault location method based on combination of sample rate conversion(SRC)and local mean decomposition(LMD).Firstly,the LMD method is used to decompose the aerial mode components converted by adoption rate,and the teager energy operator is used to extract the instantaneous frequency of the first PF(product function)component,then the time when the initial fault travelling wave reaches the two ends of the line is calibrated.Finally the fault distance is calculated by the double-endtraveling wave location optimization algorithm.In response to the problems existing in the traditional LMD method,this paper proposes an improved LMD method based on waveform matching method and linear interpolation method to reduce the effect of endpoint effect and excessive smoothing.The matching method is applied to the extension of the current line mode components,and the linear interpolation method is used to obtain the mean function and the envelope function.Then combine with teager energy operator to locate the fault location.In view of the large amount of calculation and end-effects of local averaging method,this paper uses the advantage of differential entropy(DE)in the detection of signal singular value,and proposes a transmission line traveling wave fault location method based on combination of variational mode decomposition(VMD)and DE.Firstly,VMD is used to decompose the aerial mode component decoupled by the phase mode transformation,and then the difference point of the first intrinsic mode function is detected by DE to record the time when the traveling wave head reaches the measuring point on both ends of the transmission line.Under the different fault conditions,the above several positioning methods were simulated.The results show that the proposed method has improved the positioning accuracy.