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A single line-to-ground (SLG) fault may lead to a more severe line-to-line fault and power supply interruption if the ground-fault current exceeds a certain value. Arc suppression device (ASD) is a good solution to eliminate the ground-fault current. A novel hybrid ASD is proposed in this paper, which consists of a passive device and an active one. The passive device utilizes multi-terminal breakers and an isolation transformer to couple a secondary voltage of a Zig-Zag grounding transformer to the neutral point to compensate the majority of the ground-fault current. The active device uses a single-phase voltage source inverter to eliminate the residual fault current due to the leakage inductance of the Zig-Zag grounding transformer in the passive device. A dual-loop voltage and current control method for the active device is designed for the accurate residual current compensation. Results of simulation and prototype experiment validate the effectiveness of the proposed hybrid ASD. The proposed hybrid ASD does not need to detect distributed line-to-ground parameters, and it has lower cost, less control complexity, higher reliability, and better performance, compared to other ASDs.

Accurate faulty phase detection under single-line-toground (SLG) fault is the basis of the emerging voltage-based fault arc suppression technology. Most conventional faulty phase recognition criteria assume the distributed line-to-ground parameters are symmetrical, therefore suffering invalidity in actual distribution networks especially under high-resistance ground-fault conditions. This paper firstly analyzes the magnitude and phase angle variation models of the phase-to-ground voltages before and after the SLG fault. Considering the asymmetrical distributed parameters and the line impedance, the specific phaseto-ground voltage variation rules corresponding to SLG fault on each phase are then discussed. Based on the voltage variation rules, a robust and practical method for faulty phase identification is proposed ， which does not need the distributed parameters. Finally, the correctness of the variation rules and the availability of the proposed method is verified by simulation. Comparative study shows the proposed method has better accuracy and applicability with the conventional methods when the asymmetry and ground-fault resistance are high.