A fault section location method based on the slope similarity of zero-sequence current waveform for the non-effectively grounding system

Abstract

When a single-phase ground (SPG) fault occurs in a non-effectively grounding system (NUGS), it is crucial to locate the fault section quickly. However, existing detection methods for high-resistance grounding faults suffer from low locating accuracy, and their reliability needs urgent improvement. To address this issue, this paper analyzes the slope of the zero-sequence current at the upstream and downstream of the fault spot during a single-phase ground fault occurred in the NUGS. According to the differences in the slope curves between the upstream and downstream of the fault spot, this paper proposes a fault section location method that utilizes the similarity of the slope of the zero-sequence current waveform. First, the locally weighted linear regression (LWLR) is employed to fit the discrete zero-sequence current data collected at each detection point, obtaining the LWLR curve of the zero-sequence current, and accordingly, the corresponding slope curve is derived. Then, the Pearson product-moment correlation coefficient (PPMCC) of the two slope curves between adjacent detection spots is calculated. Finally, the fault section is determined by utilizing the principle that the similarity of the slope curves upstream and downstream of the fault spot is very low, that is, the section with the minimum PPMCC is judged as the fault section. Notably, this method does not require filtering out the power frequency component of the zero-sequence current, enabling excellent sensitivity in locating the high-resistance grounding fault sections. The locating results based on MATLAB/Simulink demonstrate the effectiveness of the proposed method in accurately pinpointing the fault section under various fault conditions.