Research Of Cable Grounding Fault Of Distribution Network Based On Wavelet Singular Entropy

The rapid development of the city makes the demand for electricity rising, while the planning of the city also limits the use of overhead lines, so the proportion of cable in the distribution network increased year by year. At the same time, the cable usually laying under the ground, there are several mechanical damages during laying cables , and it probably cause the phenomenon of water tree branches and then produce more serious failure. Therefore, it is possible to find a suitable method to find the point of failure within short time after the fault occurs, to restore the power supply quickly. It is of great significance to increase the reliability of the distribution network.Cable fault location generally includes three steps: identify the fault type, fault distance positioning, fault point accurate search. In this paper, a variety of grounding faults of cable failures in the distribution network are proposed. Formed a fault type identification system based on wavelet singular entropy: including fault preliminary classification module, two-phase fault classification module and ground fault classification module. Among them, the preliminary classification module is the minimum frequency band coefficient energy of the zero sequence voltage obtained by the wavelet analysis of the fault signal as the input of the preliminary classification module. The simulation results show that the method can correctly identify various ground faults and is not affected by the fault location and the transition resistance.Extract the first half of the fault current traveling wave signal , and use Kalman Boolean transform to remove the coupling effect, then the three components independent of each other in the frequency domain are obtained and the signal can be more obvious detected. Then, the wave velocity stable components which are not affected by the grounding resistance and the geodetic resistivity are decomposed by wavelet to obtain the high frequency fault information.Then, the wavelet transform is carried out to obtain the singularity of the signal, and the time between the first and the second maximum point corresponding to the traveling wave is found.According to the formula of double-ended D-type traveling wave principle, the fault distance can be obtained to achieve the purpose of positioning. The simulation results show that the method can locate all kinds of cable grounding faults to meet the engineering accuracy requirements.