Research On Simulation Of Power Cable Fault Location Theory

With the development of economy and the improvement of people’s quality of life, the demand of city space and the requirement of the appearance of the city are on the increase. Because of the overhead line squanders space and affects the appearance, it is replaced by underground cable gradually for saving space and without prejudice to appearance. The rapid development of modern economic life, at present, in order to meet the requirement of power supply reliability, more cables will be used to transmit power. With the increase of the number and run-time of the cable, the rate of cable fault is more and more high. It can not locate the cable fault fast and accurately that using the traditional method of fault location, because the cable is generally buried in underground or laid in cable trench, and that will cause economic losses and bring much inconvenience to people. In order to reduce the losses and the inconvenience after the fault, it becomes crux that locating cable fault quickly and effectively. Therefore, it has important significance and practical value for further study of the cable fault location.At present, the main means of power cable fault location are the impedance method and traveling wave method, and most of the use of cable fault location method is traveling wave method, due to the limitation of the impedance method. Therefore, in this paper, after impedance method being briefly introduced, the traveling wave method is introduced emphatically, such as the propagation of traveling wave method in the cable, the principle of several commonly used kinds of traveling wave method. Then, wave forms of the traveling wave methods are discussed and compared. It is possible to conclude that the differences, range of application, advantages and disadvantages of the traveling wave methods. Wavelet analysis is used to de-noising. As the traveling wave method will produce noise in the measurement process and the wave forms are needed to de-noising. Decomposition level and threshold rule of fault feature extraction of wavelet are confirmed by introducing the basic principle of wavelet analysis, the basic steps and several common threshold rules of wavelet de-noising, and then the decomposition level and threshold rule are verified by simulation with MATLAB.Further research and analysis of traveling wave method are needed by stimulation with ATP-EMTP after the theoretical analysis. In the simulation process, firstly, a cable model dependent frequency is built and the feasibility of variable frequency cable model is verified. Secondly, the three section type arc model for simulation of high resistance fault is built by TACS in ATP-EMTP, and its feasibility is confirmed through simulation. Finally, based on determining the wave velocity and pulse width, it is simulated with ATP-EMTP respectively by using the corresponding traveling wave method that the open circuit fault, low resistance grounding fault and high resistance grounding fault of cable, and the feasibility and shortcomings of traveling wave method in cable fault location is concluded by analysing simulation results.