In the 6-35KV AC power grid of the power system, the neutral point of the grid can be grounded through methods such as ungrounded, arc suppression coil grounded, high resistance grounded, and low resistance grounded. In the power system (especially in urban power supply systems where cables are the main transmission lines), the high ground capacitive current may create specific "critical" conditions for the occurrence of "intermittent" arc grounding overvoltage, leading to the generation of arc grounding overvoltage. The application of neutral point resistance grounding method forms a discharge channel for energy (charge) in the grounding capacitance of the power grid, and injects resistive current into the fault point, making the grounding fault current have resistive capacitive properties, reducing the phase angle difference with voltage, lowering the reignition rate of the fault point current after zero crossing and arc extinguishing, breaking the "critical" condition for arc overvoltage generation, and limiting the overvoltage to within 2.6 times the phase voltage. At the same time, it ensures the accurate determination and removal of primary and secondary faults in the feeder line of high-sensitivity grounding fault protection equipment, thereby effectively protecting the normal operation of the system.
After the system is grounded through a resistor, it can limit the fault current to achieve the following protective effects:
1. Reduce combustion and melting accidents of faulty electrical equipment.
2. Reduce mechanical power when fault current passes through lines and equipment.
3. Reduce electrical vibrations and injuries to personnel caused by stray currents in the grounding return path.
4. Reduce the impact and flashover damage to personnel when someone happens to be at the fault point.
5. Reduce and eliminate the instantaneous line voltage drop caused by grounding faults.
6. Ensure control over instantaneous overvoltage.
The BNR transformer neutral point grounding resistor cabinet is used on the neutral point of transformers in 6-35kV AC power grids to achieve the use of neutral point grounding through resistance in these power grids.
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