The most common type of fault in power systems is a single-phase-to-ground fault. Such a fault can lead to phase-to-phase short circuits, causing power outages, overvoltages throughout the entire grid, ferroresonance-induced overvoltages, signal interference, injury to persons experiencing electric shock, frequent tripping of overhead line networks, and stray currents flowing into the ground, which may trigger gas and coal dust explosions. Therefore, selecting an appropriate neutral-point grounding method has become a critical factor in reducing fault occurrences and enhancing the reliability of power supply in power systems.

According to China's national conditions, the commonly used neutral-point grounding methods in 6–66 kV distribution systems in China are mainly divided into two types: one is a system in which the neutral point is grounded via a small resistor, and the other is a system in which the neutral point is grounded via an arc-suppression coil.

Neutral-point grounding system with small resistance: Its advantage lies in its ability to release a resistive current signal to ground when a ground fault occurs on the line, thereby enhancing the protection relay’s sensitivity for the faulty line and enabling rapid isolation of the faulted line. However, its disadvantage is that, regardless of whether the fault is transient or permanent, the faulty line will be disconnected as soon as a fault occurs, thus failing to guarantee reliable power supply.

Neutral-point grounding system with arc-suppression coils: Its advantage lies in the fact that, when a ground fault occurs on a line, the inductive current generated by the system itself can compensate for and neutralize the fault current (capacitive current) flowing through the faulty line, thereby reducing the fault current and extinguishing the arc. This system allows the line to continue operating with the fault for up to two hours. However, its disadvantage is that the fault must be promptly cleared within two hours; otherwise, prolonged operation with the fault will degrade the insulation levels of both the connected electrical equipment and the power supply equipment.

In recent years, the State Grid and China Southern Power Grid have vigorously promoted the use of arc-suppression coils combined with small-resistance grounding systems. The primary purpose is to first use the arc-suppression coil for compensation when a single-phase-to-ground fault occurs in the system. This approach prevents transient ground faults from affecting the reliability of power supply and reduces the severity of fault-related damage. If, after a preset duration, the fault still persists, it is deemed a permanent ground fault, at which point the small-resistance grounding system is activated to quickly isolate the faulty line and ensure the normal operation of the power grid.

Based on market demand, we have meticulously developed and designed this “Arc-Extinguishing Coil and Small-Resistance Automatic Compensation Complete Set Device.” This device is a comprehensive system integrating functions such as ground fault compensation, arc-light management, rapid fault isolation, data analysis, and information communication.

The device consists of several components, including a complete set of core controllers, a grounding transformer, a bias-magnetism arc-suppression coil, a grounding resistor, a vacuum contactor, and current transformers.