Introduction of Neutral Grounding Method of Generator
The choice of the neutral point grounding method of the generator is the driving force of the power system. It must have the ability to respond to sudden faults during operation. The neutral point grounding method of the generator is closely related to this.
The neutral point of the generator is grounded as follows: the neutral point is directly grounded, the neutral point is grounded through a low impedance, the neutral point is not grounded, the neutral point is grounded through the arc suppression coil, and the neutral point is grounded through a high impedance. When a single-phase grounding occurs in the generator circuit of a power plant and the fault current reaches a certain value, the occurrence of "intermittent" arc grounding overvoltage may have a specific "critical" condition, resulting in the generation of arc grounding overvoltage; The withstand voltage level of the machine is weak, and its insulation is easily damaged. If the ground fault current occurs, it will cause burns to the iron core of the generator, and accompanied by a higher than normal mechanical pressure acting on the generator and its circuits. Therefore, high-resistance grounding is usually used at the neutral point of the generator. When a single-phase grounding occurs in its circuit, it can limit the arc grounding overvoltage, reduce the burn to the iron core, and reduce the mechanical pressure on the generator and its circuit.
The NS-FZ series generator neutral grounding resistance cabinet produced by Baoding Newstar Electric Technology Co., Ltd. is a complete set of equipment dedicated to the high-resistance grounding of the neutral point of the generator in the power plant. Equipment principle: Since the generator is a usable star point, a single-phase transformer associated with the load resistance can be used to form a high-resistance grounding method.
The primary side of the transformer is connected to the neutral point of the system and the earth, and the load resistance is connected in parallel to the secondary side of the transformer. When a single-phase ground fault occurs, the load resistance limits the current passing through the secondary side of the single-phase transformer, and in turn, limits the ground fault current returning to the system through the primary side of the ground transformer. Generally speaking, the resistance unit is usually designed according to a fault current of 2-12A at this time, and the rated time is 10 seconds or 1 minute. The transformer size is designed according to the same situation. The voltage rating of the transformer primary side is the same as the system line voltage, and its nominal voltage is the system line voltage divided by the secondary side voltage, which is usually 220V or 110V. In view of the internal fault of the transformer, an overcurrent relay can be used to protect it. Transformers, resistance units, and connected terminal blocks, and other components are installed in an independent cabinet.