What does the transformer neutral point gap grounding protection include?

Transformer is one of the essential electrical equipment in the power system, mainly used to convert voltage or current. When the transformer is running, a large amount of electromagnetic interference will be generated, one of which is the floating of the neutral point potential, which will pose a threat to equipment and personal safety. In order to ensure the normal operation of the transformer and personal safety, neutral point gap grounding protection measures came into being.

Neutral point gap grounding protection refers to the grounding protection of the neutral point of the transformer to avoid high voltage caused by voltage loops or coupling capacitors, which may cause electric shock to equipment or personnel. risk. The structure of neutral point gap grounding protection mainly consists of tap changer, insulated isolation switch, neutral point gap, gap oscillator, DC bus, grounding knife switch, etc. The grounding knife switch is a switch that controls the grounding of the transformer and is a key part of the neutral point gap grounding protection system.

There are several types of neutral point gap grounding protection:

1. Inductor neutral point grounding protection

Inductor neutral point grounding protection It means that in a transformer or reactor, the neutral point is connected to the ground through an inductance of a certain value, so that the current passing through the neutral point is impeded, effectively limiting the size of the ground fault current. In practical applications, inductor neutral point grounding protection has the advantages of short response time, reliable action, and little interference to the system.

2. Contact neutral point ground protection

Contact neutral point ground protection means that the contact is connected to the ground. When the contact is closed, the protector is spaced The capacitor inside is charged. When the ground potential rises to a certain level, the contacts will automatically act to protect the transformer. This kind of grounding protection has the characteristics of simple structure, low cost and high reliability.

3. Gap neutral point grounding protection

Gap neutral point grounding protection refers to the use of electrical signals generated by gaps affected by the ground, through oscillators and detection devices, etc. Receive and analyze signals to determine the occurrence of a neutral point ground fault and automatically cut off the fault. Gap neutral point grounding protection has the advantages of short response time, strong adaptability, and high reliability, and is widely used in neutral point grounding protection of substations.

In the neutral point gap grounding protection, the gap oscillator is an important device that plays a key role. The gap oscillator uses the gas discharge in the gap as the signal source, detects the instantaneous changes in the neutral point gap voltage and converts it into an electrical signal with a certain frequency, so as to detect and protect the transformer when it is grounded. Gap oscillators can be divided into two types: capacitive gap oscillators and inductive gap oscillators.

The capacitive gap oscillator has a relatively simple structure, can detect small neutral point potential changes, and has a short response time. However, it is not sensitive enough and is easily affected by the environment, and is close to a short circuit at both ends. Easy to over-response and high malfunction rate.

The inductive gap oscillator has the advantages of high sensitivity, long continuous and reliable working time, the ability to adapt to a variety of voltage changes, short response time, and low malfunction rate. However, the manufacturing cost of inductive gap oscillators is high, the cost is high, and the maintenance and repair are also complicated.

Neutral point gap grounding protection plays a very important role in the power system, ensuring the safe and stable operation of the entire power grid. By analyzing the neutral point gap grounding protection in different application environments, especially the research on gap oscillators, the reliability and accuracy of the neutral point gap grounding protection can be continuously improved and provide more effective solutions for the development of power systems. protection.