MRD-BJ Neutral Grounding Resistor (NGR)
In a power distribution network, the neutral grounding system is usually classified into ungrounded, resistance grounded as well as arc suppression coil grounded. Our MRD-BJ neutral grounding resistor (NGR), sometimes called neutral earthing resistor (NER), is especially developed for resistance grounding.
Benefit
If our neutral grounding resistor is installed, the ground fault current will be reduced significantly when compared to ungrounded system. At the same time, the voltage increase of un-faulted phase is also lowered obviously, and the zero sequence voltage is only half the value of ungrounded system when single phase ground fault occurs.
In this regard, our neutral grounding resistor could reduce transient overvoltage and eliminate resonance overvoltage when a ground fault of one phase takes place, and a simple protective relay can locate and clear the fault. So, this power resistor is highly recommended to protect electrical system and corresponding equipment.
Grounding resistor| Model | System voltage (kV) | Initial current (A) | Time rating (s) | Nominal resistance (Ω, ±5%) | Withstand voltage (kV) | |
| 8/20μs lightning surge | 1 min at power frequency | |||||
| 6.3 | 100 | 10 | 36.4 | 60 | 32 | |
| 6.3 | 200 | 10 | 18.2 | 60 | 32 | |
| 6.3 | 400 | 10 | 9.09 | 60 | 32 | |
| 6.3 | 600 | 10 | 6.06 | 60 | 32 | |
| 10.5 | 400 | 10 | 15.16 | 75 | 42 | |
| 10.5 | 600 | 10 | 10.10 | 75 | 42 | |
| 10.5 | 800 | 10 | 7.57 | 75 | 42 | |
| 10.5 | 1000 | 10 | 6.06 | 75 | 42 | |
| 35 | 1000 | 10 | 20.20 | 185 | 95 | |
| 35 | 2000 | 10 | 10.10 | 185 | 95 | |
Vaious resistor, with nominal resistance ranging from 1Ωto 2000Ω, can be designed as per customers’ requirements. The allowed rated currrent should be from 1A~2000A, and the time rating should be 10s, 15s, 30s, 60s or 2h.
Operating Condition
1. Indoor and outdoor application
2. System frequency: 50Hz or 60Hz
3. Altitude: Not over 3500m (Please specify when ordering because high elevation leads to poor heat dissipation)
4. Ambient condition: -20℃~ 70℃, 95%RH at the most
5. Wind pressure: Not over 700MPa (equals to wind speed of 34m/s)
6. Seismic intensity: Lower than Class VIII as demonstrated by the China Seismic Intensity Scale
7. Environmental pollution level: Class IV or lower
8. Surroundings: No flammable or explosive objects, no corrosive gas or conductive dust
9. Our neutral grounding resistor will generate heat during work, thus leading to a big temperature rise. So, there should be certain space around this electrical device during installation and operation.
Ordering Instruction
The following information is required when ordering our neutral grounding resistors.
1. System voltage (kV)
2. Rated current in short time
3. Rated resistance (Ω)
4. Current transformer (if required): Capacity, current ratio and precision
5. Disconnect switch (if required): Electrically or manually controlled
6. Wiring method: Top in down out, bottom in down out, side in side out, side in down out
7. Maximum time on
8. Enclosure: Material, IP rating, color code and installation site
