The Fault Analysis And System Design Of Single Phase-to-ground Fault For Distribution Based On SVM And Wavelet Transform

The continuity, reliability, economy and safety of distribution network, which is connected with the customers directly as the final part of the power system, influence people’s lives and social productivity. The faults in the power system, where most faults occur, will result to a huge loss to social productivity and daily life. Therefore, the distribution network fault location system with higher reliability will guarantee the development of social economy and the improvement of people’s life.This thesis constructs a distribution network fault location system according to the method of fault location using the model choosing current signal at bus bar and voltage signal at load side. Besides, the theory of fault location by the traveling wave, which distinguishes the faults and turbulent motion by support vector machine and recognizes the smoothing noise and signal singularity with wavelet transform is applied in the thesis.The main contents of the thesis are as follows:Firstly, to analysis traveling wave on the distribution network for transient signal, double-end distribution network traveling wave fault location and double-end ranging principle of current signals with bus terminal load terminal voltage signal are used after comparing various positioning methods according to the characteristics of distribution network. Failures in the distribution network, a kind of single-phase ground faults of highest frequency, are difficult to located. The feasibility of the method of double-end current-voltage mode distribution network is testified through simulating10KV distribution network ground fault by SINULINK in the thesis.Secondly, this paper presents the method to apart all kinds of transient disturbances from permanent faults by supporting vector machine aiming at the transient disturbances of the power quality caused by the using of the high-power nonlinear device. In addition, six features of abnormal signals are extracted as the input vector of the support vector machine according to the signal features of the transient disturbances and faults, then a reasonable kernel function is elected and the best parameter to distinguish the fault signal and transient perturbation signals in distribution system is selected through the simulation.Thirdly, the threshold is used to smooth de-noising on the traveling wave signal according to wavelet transform and the analysis of multi-resolution wavelet, and the signal singularities by modulus maxima method is found. At last, a new distribution network fault location system is constructed based on the theories of distribution network fault location system and the practical problems to be solved, including handheld device, hardware and software components.In summary, this thesis mainly introduces the implementation of the traveling wave fault location system of the distribution network combining with the transient analysis of wave signal in distribution network, presents a new method to improve the reliability and precision of the fault location in distribution networks, and realizes the construction of fault location system of the distribution network by the theory in turn.