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Accurate faulty phase detection under single-line-to-ground (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 phase-to-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 proposedwhich 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.

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 article, which consists of a passive device and an active one. The passive device utilizes multiterminal 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.

In the non-effectively grounding distribution system, residual current under single-line-to-ground (SLG) fault threats the safety of human being and power supply equipment. Active arc suppression device has been proved to be effective for SLG fault arc suppression when the line impedance is ignored. However, in practical, line impedance varies with the fault location and the load current flowing through the impedance brings about additional voltage drop, which increases the fault current and is not dealt with by the conventional methods. To achieve accurate SLG fault arc suppression with the existence of line impedance, the neutral voltage reference for full ground-fault current compensation is firstly derived and a detection method is then proposed. The pre-fault and post-fault line currents are used to eliminate the influence of load current on the line impedance voltage drop. A dual-loop voltage and current controller is then designed. The prototype of active arc suppression device was developed. Results of simulation and prototype experiment validate the effectiveness of the proposed method.

The power distribution system generally adopts neutral non-effective grounding. Most grid faults are single-line to ground (SLG) faults. As the SLG faults are difficult to monitor online, they severely threaten human health and lives and damage power supply equipment. The Peterson coils are widely used in the SLG fault arc suppression, but it belongs to passive arc suppression method which cannot compensate the active power and harmonic current. The ground residual current is still large. Active arc suppression method makes up for the defect of Peterson Coil. In order to improve the self-healing effect of single-phase grounding fault. This paper summarizes the research status of active full compensation technology, and further studies the traditional arc suppression strategy based on active voltage control. An improvement scheme of injection current control strategy is proposed. The ratio of the zero-sequence current and the zero-sequence voltage is applied to modify the reference value of the injection current instead of measuring the ground parameters. Results of simulation validate the effectiveness of the proposed control strategy.

Single-line-to-ground (SLG) fault arcs cause the intermittent over-voltages, leading to short circuits within large-scale area. In this paper, a flexible arc suppression device is proposed, which adopts a zigzag grounding transformer, multi-terminal breakers and an isolation transformer to regulate zero-sequence voltage. Principle of zero-sequence voltage regulation (ZVR) and arc suppression method is presented. By carefully choosing the secondary side voltages of grounding transformer as the input of isolation transformer, the zero-sequence voltage is nearly constrained to the opposite of faulty phase supply voltage, and the ground-fault current is limited to a very small value. This device has high adaptability for low-resistance ground fault as it doesn't adopt any electronic apparatus. A 10kV prototype was established and multiple fault conditions were experimented to verify the effectiveness of the proposed ZVR device and its arc suppression principle.

Faulty phase recognition under single-line-to-ground (SLG) fault condition is critical for some arc suppression methods in medium voltage (MV) distribution networks. Conventional methods tend to be invalid due to network asymmetry in high-resistance ground-fault condition and the difficulty of detecting phase-to-ground parameters in practice. In this paper, the variation of the three phase-to-ground voltages with the change of SLG fault resistance is analyzed in detail, and the magnitude and phase angle variation rules of the voltages are obtained. Then, the unique variation rules on SLG fault for each phase are separately and strictly discussed in theory and numerical analysis. Furthermore, a faulty phase recognition method is proposed based on the variation rules of three-phase voltages. Simulation results in PSIM verify the proposed variation rules and validate the effectiveness of the proposed faulty phase recognition method, which ensures accurate recognition of faulty phase in high-resistance ground fault.

Most renewable energy distribution systems operate with neutral point ineffectively earthed. Traditional arc fault suppression devices, such as Petersen Coil, compensate the single-phase grounding fault caused capacitive current with zero sequence inductive current. They cannot compensate the active and harmonic currents, thus have limited arc suppression performance for single-phase grounding faults. To solve these problems, an arc suppression device based on single-phase inverter is presented in this paper. When single-phase grounding faults occur, the device injects active, reactive and harmonic currents to the neutral point to force the faulted phase voltage to zero, the faulted current will be limited to zero and the fault arcs can thus be reliably extinguished. The proposed voltage control method uses the zero sequence voltage and faulted phase voltage as reference to generate the injection currents. It is not needed to measure the capacitive and fault residual currents of the distribution system, which are difficult to implement. The simulation results validate the effectiveness of theoretical analysis.