Fault line selection method for small-current grounding system based on VMD-DTW transient energy ratio

The single phase grounding fault line selection has the following problems for small-current grounding system, including low reliability, large computational amount and complicated algorithm implementation. To solve these problems, a method based on VMD-DTW transient energy ratio is presented in this paper. Firstly, the variational mode decomposition (VMD) is used to decompose the transient zero-sequence current within 1/4 cycle after the fault and get different frequency band modes. Then, the dynamic time warping (DTW) is introduced to calculate the transient similarity measure of corresponding mode of different lines. Finally, the transient energy of each line is calculated with the similarity measure as the weight, and the line with the energy ratio of 1 is the fault line. To test the reliability of this method, a typical model of 10kV distribution network is built in MATLAB/SIMULINK. The simulation results verifies that the method has a good fault line identification rate, and is not susceptible to fault location, fault closing angle and transition resistance.