Point-line Distance Characteristics Based Grounding Fault Protection for High-voltage Capacitor of DC Filter

In HVDC transmission systems, DC filters play a vital role in mitigating characteristic harmonics generated by line-commutated converters. However, existing protection schemes for these filters suffer from some drawbacks, particularly in terms of limited selectivity and insufficient sensitivity. This paper introduces a new ground fault protection method for high-voltage capacitors in DC filters, utilizing point-line distance characteristics. By analyzing currents from both the high-voltage and low-voltage sides under various fault conditions, point-line distance characteristics were introduced. Based on these characteristics, a protection scheme is designed for detecting ground faults in DC filters. The proposed method was validated through comprehensive simulations on a ± 800 kV UHVDC system modeled in PSCAD/EMTDC, with results confirming high reliability and enhanced sensitivity.