The Research About Wavelet Analysis On Fault Location Applications In Small Current Grounding System

Our country used small current grounding system for6kv-35kv system. When this system occurred single-phase ground fault, fault current is small. Especially we use the neutral point grounded by arc-suppression coil, the fault current reduce much further, this makes small current grounding system fault location is very difficult to achieve. With the reliability requirements and automation of distribution network increased, the study about small current grounding system single-phase fault location has become very urgent.This paper elaborates how to select the line fault lines and measure fault distance, and these two aspects are both based on wavelet analysis. Because wavelet has strong processing ability for weak signals and transient signals, we propose a small current grounding system single-phase fault location method based on wavelet transform theory. This method has strong anti-interference effects, is not affected by the ground resistance, high reliability and accuracy, etc.The line selection method in this article use zero-sequence current after the ground fault occurs, we use Db10wavelet to make four-layer wavelet decomposition on fault zero-sequence voltage and the zero-sequence current of all lines, so we can find fault time and fault line. And, we do a lot of fault simulation on different grounding resistance and different fault time, these simulation verify the validity and accuracy of the method. Among them, we also made a detailed simulation when occurs Intermittent are grounding fault, this is a very important part of the whole article. After the select lines, we propose a new positioning method based on modulus maximum and backward travelling wave. MATLAB simulation shows that this method is very high accuracy. In practice, due to the sampling frequency can not be too high and the impact of electromagnetic interference, the method in practice remains to be tested.