Detection of Single-Phase to Ground Faults in Low-Resistance Grounded MV Systems

Abstract

The Conventional zero-sequence (ZS) overcurrent protection method exhibits poor performance for single-phase to ground faults (SPGFs) with high impedance in low-resistance grounded systems (LRGSs), a type of medium-voltage (MV) distribution system. Hence, in this study, a novel SPGF detection methodology, designed specifically for LRGSs, is proposed. Considering the effects of system imbalance, a crucial limitation to the method based on ZS components, the concept of the Δ-circuit is first utilized to suppress such effects, maintaining the independence of the ZS network. Based on this, the proposed method computes the ZS power factor of a line to discriminate the line state, with the assistance of single-phase instantaneous reactive power theory (SIP) and the 4th-order components of the instantaneous active power. Not only the arcing features, but also the inherent characteristics brought by the unique grounding mode are subtly involved. Multiple simulations conducted in PSCAD software verify the good performance of the proposed detection method for various SPGFs, including those with low or high impedance and those with linear fault impedance or nonlinear arcs.