The Theory Improvement Of The Earth Fault Detectors In Non-Effectively Grounding Neutral System

Non-effectively grounding neutral system in the power networks includes isolated neutral distribution network, neutral point grounded by arc-suppression coil, and resistance grounding system in power system . It is counted that almost 80% of the fault in grounding system network are single-phase grounding fault. When it happens, the non-effectively grounding neutral system is still symmetric. But the voltage to phase rises to 3 of the non-fault phase in the whole system. As while the arc-grounding will cause over-voltage in the whole system, and damage the facility. Therefore when the fault happens, the fault line must be found in time and broken out from the system.In this paper, according to the actual running situation of the earth fault detectors in substations recently, compared detection method, the author point out that the data analysis should changed according to the running model of the system. It is possible to use wavelet analysis to accurate analyze the singnal, especially the mutated singal and weak singal. In this paper, the author find out fault detection method based on the analysis of the fault transition state, and use MATLAB on the bases of the analysis of simulation results. Finally, the transition state of all kinds grounding faults is analyzed in detail.