Neutral Grounding Resistor is an essential protective device deployed in medium‑ and low‑voltage distribution networks, self‑owned power stations, and substations for industrial and mining enterprises. It is primarily applied to 10 kV and 35 kV low‑current grounding systems. Its core functions cover fault‑current limitation, overvoltage suppression, potential stabilization, and protection optimization to guarantee safe and stable power‑system operation and resolve inherent operating hazards of low‑current grounding systems. First of all, its primary function is limiting single‑phase‑to‑ground fault current. Single‑phase‑to‑ground failures account for more than 80 % of all distribution‑grid faults. Without a Neutral Grounding Resistor, free‑flowing capacitive grounding current may reach hundreds of amperes, directly burning out cable terminals, switchgears, and instrument transformers and even triggering line fires. After the Neutral Grounding Resistor is put into service, fault current can be precisely restricted within preset safe ranges, so that impact damage to primary equipment from fault current is greatly mitigated.
Secondly, the device suppresses various abnormal overvoltages. When single‑phase‑to‑ground faults occur in low‑current grounding systems, intermittent arcing ground faults may take place. Repeated extinction and reignition of electric arcs produce arc overvoltage several times higher than the rated voltage. Long‑term exposure breaks down weak insulation of lines and equipment and further results in multi‑point grounding faults. In addition, resonant overvoltage will be excited when system inductance and capacitance are mismatched, continuously damaging insulators and surge arresters. The Neutral Grounding Resistor rapidly dissipates energy generated by overvoltage, dampens voltage oscillation, and confines system overvoltage below 2.5 times the rated voltage. It avoids insulation aging and breakdown and extends the service life of power equipment.
Thirdly, it stabilizes system potential and optimizes protection performance. Under normal operating conditions, the Neutral Grounding Resistor fixes neutral‑point potential and prevents neutral‑point shift caused by unbalanced three‑phase loads and asymmetric line parameters. It prevents excessive deviation of three‑phase voltages and maintains stable supply voltage for end‑users. When faults happen, the resistor generates stable fault‑current signals to solve the problem of weak fault signals that hinder identification by protection relays in low‑current grounding systems. Zero‑sequence protection and fault‑line‑selection devices can act quickly and accurately to isolate faulty lines and locate fault points, significantly shortening troubleshooting time and power‑outage duration.
Besides, the device eliminates potential resonance risks and improves personal and equipment safety. During no‑load or light‑load operation of power grids, ferromagnetic resonance may occur between voltage transformers and line capacitances and bring abnormal voltage fluctuations. The Neutral Grounding Resistor alters parameter conditions for resonance and eliminates ferromagnetic resonance. Furthermore, it rapidly discharges residual system charges under fault conditions, reduces risks of energized equipment enclosures and lines, and mitigates hazards of electric shock and leakage. It suits industrial plants, residential complexes, and industrial parks demanding high power‑supply reliability and safety and serves as key protective equipment for safe distribution‑grid operation.