Improvement of the Voltage Difference Method to Detect Arcing Faults Within Unfused Grounded-Wye 22.9-kV Shunt Capacitor Bank

This paper presents an effective algorithm to protect unfused 22.9-kV shunt capacitor banks in grounded-wye connection by improving an existing voltage difference method-based algorithm. It has often been reported that it is difficult to detect ground faults with arc near the input points within the bank using existing algorithms that use only the magnitude of the differential voltage. In this paper, it is shown that ground faults with arc near the input point can be detected by fast Fourier transform (FFT) analysis of the differential voltage and that the proposed algorithm is not impacted by harmonics generated by nonlinear loads which have quantitative influence on the capacitor banks. Consequently, the proposed method using harmonics analysis can be applied as an extended version of the existing detection method. The proposed method is applied to a simplified 22.9-kV real-life Korea Electric Power Corporation system and it is verified that the proposed algorithm can clearly detect faults that are not easily detected by the existing method