Working principle of the product: In a neutral point non-effectively grounded system, a neutral point is led out through a grounding transformer, which is connected in series with the high-voltage thyristor and then grounded. When the system is running normally, the thyristor does not conduct. When a single-phase ground fault occurs in a branch, the neutral point voltage of the grounding transformer rises. The main controller in the device detects the grounding signal and triggers the thyristor to conduct. A pulse can flow through the zero sequence loop. The controlled zero-sequence current passes through the faulty branch. The faulty branch line selection signal acquisition unit detects the line selection signal and sends it to the main controller to determine the faulty branch, fault type and fault time. Then, according to the nature of the single-phase ground fault, different working methods are used to let the arc suppression coil and contact arc suppression cooperate with each other to eliminate arc faults and protect each other. For transient ground faults and arc ground faults, after completing the line selection, quickly start the pulse arc suppression coil and contact arc suppression, and use the contact arc suppression to bypass the transient, high-frequency ground capacitor current and pulse arc suppression coil temporarily. state inductor current, when the pulse arc suppression coil operates stably and realizes compensation, exit the contact arc suppression, and then exit the pulse arc suppression coil after the fault is eliminated.

Since there is a pulse arc suppression coil to limit the operating overvoltage caused by the opening of the vacuum contactor for contact arc suppression, this combined working method overcomes the traditional arc suppression coil or arc suppression coil for instantaneous ground faults or arc ground faults. The shortcomings of the separate application of contact arc suppression are more conducive to the elimination of faults and greatly improve the reliability of the device. For permanent single-phase ground faults, the contact arc suppression work is quickly started after line selection is completed, and the ground capacitor current is directly bypassed, thereby well protecting the safety of the faulty branch, especially the cable branch, and ensuring the safe operation of the system. The full voltage monitoring device monitors and records the entire line selection and arc suppression process, and can monitor the system’s three-phase voltage and its harmonics, voltage flicker, arc overvoltage, lightning overvoltage, and operating conditions during normal operation and when a fault occurs. Voltage and other steady-state and transient shocks are monitored in real time, recorded regularly, and alarmed for users to further analyze the working status of the power system.