A neutral ground resistor (NGR) is a device used to limit the flow of current in a power system by providing resistance between the neutral point and the ground. It is typically used in high-voltage electrical systems to protect equipment from damage caused by excessive fault currents.
What is a Neutral Ground Resistor?
A neutral ground resistor (NGR) is a device used in high-voltage electrical systems to limit the flow of current by providing resistance between the neutral point and the ground. It protects equipment from damage caused by excessive fault currents during an earth fault event. By limiting the flow of current between the neutral point and the ground, NGOs play an essential role in ensuring the reliable operation of power systems.
How does it work?
In a typical three-phase AC power system, there are three conductors – one for each phase – and a neutral conductor. The neutral conductor is grounded at the transformer, which provides an earth reference for the system.
During normal operation, the current flowing through each phase conductor should be balanced, such that the net current flowing through the neutral conductor is zero. However, in the event of an earth fault – where one of the phases comes into contact with the earth – a large amount of current can flow through the neutral conductor.
This sudden surge of current can cause significant damage to equipment, including transformers and generators. By installing an NGR between the neutral point and the ground, this excess current can be limited to a safe level.
The NGR works by providing resistance to the flow of current between the neutral point and the ground. This resistance limits the amount of current that can flow in the event of an earth fault, protecting equipment from damage.
Types of Neutral Ground Resistors
There are several types of NGRs available, including:
- High resistance earthing
- Low resistance earthing
- Reactor earthing
- Petersen coil earthing
Each type has its own advantages and disadvantages depending on the specific application.
Conclusion
In summary, a neutral ground resistor is an important component in high-voltage electrical systems that helps protect equipment from damage caused by excessive fault currents. By limiting the flow of current between the neutral point and ground during an earth fault event, NGOs play an essential role in ensuring the reliable operation of power systems.
