Fault line selection method for coal mine power grid based on RCMDE and KFCM

It is difficult to accurately select the fault line when the single-phase ground fault occurs in the coal mine power grid with the widely used resonant grounding system. In order to solve the above problem, a fault line selection method of the coal mine power grid based on the refined composite multiscale dispersion entropy (RCMDE) and the kernel fuzzy C-means clustering (KFCM) is proposed. The limitations of using amplitude, polarity and waveform similarity as line selection characteristic quantities: the applicability of the line selection method based on amplitude and polarity difference is limited. If the polarity of the zero sequence current transformer in the line is reversed, the method based on polarity will directly fail. When the sampling is not synchronized, the line selection method based on waveform similarity is difficult to obtain correct results. In order to overcome the above limitations, RCMDE is introduced to measure the complexity and irregularity of the transient zero sequence current signal of each line. RCMDE is used as the characteristic quantity of line selection. The KFCM algorithm is used to cluster the RCMDE to realize the automatic identification of fault lines. The bus fault and feeder fault are distinguished by judging whether the contour coefficient exceeds the threshold value. Finally, the feeder line with the fault point is judged through the membership degree matrix obtained by clustering. The simulation results show the following points. ① The RCMDE curve of the fault line is different from that of the non-fault line, and the curves can be divided into two types. RCMDE can be used as the fault characteristic index of fault line. ② When the bus fault occurs, there are clusters with an average contour coefficient less than the threshold value in the clustering results. However, when feeder fault occurs, the contour coefficients of the clustering results are all greater than the threshold value. Under various fault scenarios, the coal mine power grid fault line selection method based on RCMDE and KFCM can realize correct line selection. The results show that its accuracy is not affected by factors such as fault line, fault location, fault closing angle and grounding resistance. ③ Under the conditions of noise disturbance, the fault line selection method based on RCMDE and KFCM can realize correct line selection in the case of low resistance grounding or high resistance grounding. And the method has a strong anti-interference capability. ④ Under the conditions of asynchronous sampling and reverse polarity of zero-sequence current transformer in the fault line, the method based on RCMDE and KFCM can still realize correct line selection. And the line selection result has high robustness.