Study Of Fault Location In Long Distance Transmission Line Using S Transform

High voltage transmission lines are the vitals of power system, which bears the importanttask to transmit electricity. With the expansion and deregulation of the power system, faultlocation algorithms on high voltage long transmission plays a significant role in safety andeconomical operation of the power network. When faults occur in the transmission line, thefault point generated traveling wave reaching two sides of the bus line. And it is the crucialproblem to accurately detect the wavefront, but the existing identification methods based onrecognizing the wavelet transform modulus maxima wave are low levels of exactness in longdistance transmission line, even when high impedance fault and small angle fault occur intransmission line, the existing methods are difficult to recognize wavefront.A wavefront recognition method based on S transform is proposed for the first time onfault location of long distance transmission line in this article. S transform can analysis thecharacteristics of signal’s amplitude change over time on each frequency componentindependently, thus determine the mutation time of traveling wave accurately, realizing thegoal of marking the wavefront accurately. There are obvious advantages when compared withwavelet transform. Firstly, different ways for fault location on transmission line are classifiedand summarized, and then a single-terminal fault locating method based on traveling waves isadopted to avoid two-terminal location algorithm affected by GPS. Secondly, for the mutualcoupling among each phase of the three-phase line, this article used phase-to-moduletransformation to eliminate the coupling factors that affect the accuracy of fault location. Byuse of EMTP and MATLAB, single-phase ground fault on transmission lines is simulatedwhen occurs in different position, through different transition fault resistance, with differentline length. Then S transform is used to analysis transient current signal, and obtainsatisfactory test results.It is a big difficulty to do fault location when small angle fault occur in transmission line,the result in this paper shows that signal processing through S transform can solve it. Compared with wavelet transform’s results it can be seen that S transform has distinctadvantages.Simulation results shows the method proposed in the article improves the accuracy offault location, and which is effective and feasible.