Neutral grounding resistors are designed for grounding the neutral point of 6–35 kV power systems in order to limit overvoltages during single line-to-ground faults (SLG), eliminate ferroresonance phenomena, and ensure selective operation of protection relays.
They ensure a reliable power supply as well as the safety of personnel and electrical equipment under ground fault conditions.
These resistors are certified by PJSC Rosseti and recommended for use in its subsidiaries and affiliated grid facilities.
They can be supplied as part of a standard product range or custom-designed according to customer requirements specified in technical documentation or questionnaires.
| Technical parameters | NGR with short-time duty | NGR with continuous duty |
|---|---|---|
| Rated voltage | 6 - 35 kV | 6 - 35 kV |
| Rated current | 7 - 1000 A | 0.38 - 78 A |
| Rated resistance | 5 - 500 Ω | 300 - 9000 Ω |
| Load duration | 10 s | 24 h |
| Climatic version | U, UHL, HL, T | U, UHL, HL, T |
| Installation category | 1, 2, 3 | 1, 2, 3 |
| Enclosure material | stainless steel / galvanized steel / painted steel | stainless steel / galvanized steel / painted steel |
| Protection rating | IP00 - IP54 | IP00 - IP54 |
| Service life | at least 30 years | at least 30 years |
| Warranty period | 5 years | 5 years |
Resistive neutral grounding systems provide an optimal solution for fast fault detection and localization, helping to prevent overheating of cable lines.
Alternative systems, such as isolated or solidly grounded neutrals, have significant drawbacks. Isolated systems may experience dangerous transient overvoltages and difficulties in fault location, while solidly grounded systems are subject to high short-circuit currents with a risk of arc formation.
Installing a neutral grounding resistor between the transformer neutral and ground limits the ground fault current to a safe level for a sufficient duration to allow protection systems to operate, fault localization, and prevention of equipment damage.
