Fault Analysis and Pilot Protection Scheme for Various Single-Phase Line Breaks in Resonant Grounding Systems

Due to small fault currents and different fault characteristics under various grounding types on both sides of the fault point, the existing methods are facing challenges in the analysis and protection principle for single-phase break faults (SPBFs) in resonant grounding systems (RGSs), including inaccurate fault identification, low sensitivity, and insufficient reliability under high-impedance grounding and intermittent arc faults. In this paper, fault characteristics of zero-sequence voltages upstream and downstream of the break point with different grounding modes are analyzed. The SPBFs with grounding at single-side and without grounding only exhibit the amplitude or phase characteristic, while SPBFs with grounding at both sides incorporate the two features. On this basis, a pilot protection scheme is developed for various SPBFs in RGSs, where internal and external SPBFs are determined by combining the features of the amplitude and phase of dual-terminal zero-sequence voltages. The effectiveness of the proposed methodology is validated through a closed-loop hardware test by applying a real-time digital simulator (RTDS) and the developed protective devices. Experimental results prove that the protection scheme performs well under different fault types, fault locations, fault resistances, and the presence of inverter-interfaced distributed generators.