Switchgear| Neutral Point Grounding Complete Sets of Equipment

The neutral point in an electrical power network refers to the neutral point of a star connected transformer or generator. The grounding methods of the neutral point can be classified into two major categories: Direct grounding of the neutral point and Non-grounding or grounding through an arc suppression coil of the neutral point.

Two grounding methods of the neutral point can be adjusted by the opening and closing of the grounding switch of the complete set of devices. During normal operation, the neutral point voltage is close to 0V. However, due to asymmetric faults or three phase imbalance of the system and other reasons, the neutral point voltage has a certain value. Therefore, a lightning arrester is installed to prevent over-voltage.

Two metal rods are placed together to form an air gap, which is designed to prevent lightning. When lightning strikes or the voltage at the neutral point is too high, the air gap between the two metal rods will discharge. Once it discharges, it’s equivalent to grounding that point.

The single-phase current transformer is used to measure the current flowing from the neutral point to the ground.