Research On MV Distribution Power Ground Fault Selection Based On Transient Signal

East of Fushun (Liaoning province) has the heavy rain to rainstorm at11am to11pmin August16,2013. The heavy rain caused serious damage to the power supply system inFushun. And the eastern district of Fushun is at an elevation of400-500mountainlandform. Because MV distribution line wide distributed widely, with low insulationlevel, it is easy to ground fault occurs. In order to improve the speed of MV line repair,and increase the stability of power supply, it is very important and practical significant toresearch MV fault line selection with the single-phase grounding fault.In depth study of the middle voltage power line in neutral non effective groundingsystem conditions, especially in neutral non-grounded and Petersen coil groundedconditions when the single-phase grounding fault happens. It must study that from thepoint of fault generated transient zero sequence current and zero sequence transientvoltage characteristics, and the main character of the magnitude and direction ofthemselves. And the transient current signal model is established according to that. Andthe neutral non grounded and Petersen coil grounded the two cases of transient currentsignal is simulated by using ATP-EMTP software.According to the transient current signal model of fault point, and the current signalmodel for the phase mode transformation by using Karenbauer transform, modulus ofinformation was extract. Then use db4wavelet to process the information. For thenon-ground neutral system is mainly the use of the fundamental component, while thePetersen coil grounded system mainly used the fifth harmonic component, extract thefirst half cycle phase information of zero sequence current of the fault line and thenormal, and according to the information of fault line selection. The simulation resultsdemonstrate the effectiveness of the algorithm.Because we can roughly estimate the transient signal frequency, using Mallatalgorithm of the fast wavelet transform can be decomposed in a fixed level, improves thespeed of operation, can be realized.