Traveling Wave Fault Location Research In Transmission Lines Based On S Transform

Since the reform and opening up, the social economy has developedrapidly. So，the national demand for electricity is increasing sharply，it putforward higher requirement for the reliability and safety of power of electricpower industry. High voltage transmission line is the link between power plantsand users, which charged with the important function of power transmissionand is the core of electric power system. It makes great sense to the safety andstable operation of the power system that locating the fault of transmission linerapidly and accurately.When faults occur in the transmission line, it will produce transienttraveling wave. Fault state can be superimposed by normal component and faultcomponent, of which fault component contains a variety of information relatedto fault. After analysising the transmission characteristic of transient travelingwave signal in transmission line，decoupling the transient traveling wave signal,and phase mode transformation，the result comes the independent zero modecomponent and the line mode component. No matter which mode componentand method you choice to locate the fault，fist of all, you should determine thewave velocity, which is one of the main factors that influencing the accuracy ofthe fault location and its size is closely related to the parameters oftransformation lines. Adopting the method of external fault to determine thewave velocity for fault location, the simulation results shows that the velocityhas a higher accuracy on the condition of online mode component. Based on it,the method to locate the traveling wave fault on the basis of S transform（ST）has been proposed. The ST algorithm can help extract the fault signalcharacteristic information of line mode component. Using the position errorfrom multiple setting fault location as a error sequence Δx to analysis StandardDeviation, Std Dev and range which comes from the difference between theminimum and maximum values in data sequence indicate the stability of thealgorithm, in which the standard deviation reflect the discrete degree of the data,the range reflect the fluctuation range of the data.Gauss function in ST is fixed, which makes the accuracy of the travelingwave head exist certain errors. In view of disadvantage of ST，the modified Stransform（MST）has been proposed to adjust the window function parameter toget fit function. On contrast with STFT, the simulation results of CWT, ST and MST applied in traveling wave fault location shows that the MST has a higherstability and accuracy.Based on the travelling wave fault location of double terminaltransmission line, to further solve the determination of the fault branch andfault location of three end and over three end transmission line mode. Theproposed of fault judgement matrix is to determine the fault branch, handletraveling wave signal with MST. On the basis of this judgement, chosing theactual parameter of the Jingjintang500kv transmission line to establish themodel for a experimentation. The result indicates the method determining thefault branch is right, furthermore, in fault location, the MST has a higheraccuracy.