1. Knowledge of main transformer neutral point discharge gap
1. The discharge gap is mainly used to protect the arrester. When the lightning voltage exceeds the value that the arrester can protect, in order to prevent the arrester from being damaged by breakdown, a discharge gap is installed. When there is a high lightning voltage, the gap is broken down and discharged, thus protecting the arrester. As for how to cooperate between them , depends on the lightning protection voltage of the arrester.
2. Prevent dangerous overvoltage from occurring at the faulty neutral point on the high voltage side after the ground fault trips.
The gap protection of the neutral point of 3.110KV and above systems is mainly to prevent overvoltage! Because equipment at this voltage level uses graded insulation due to insulation investment issues, the insulation level is relatively low near the neutral point. If overvoltage occurs, the equipment will be damaged. Gap protection can play a role. However, due to the selection of neutral point grounding, a system should not have too many neutral points grounded, so some transformers have neutral point grounding switches. Not closed (due to configuration of protection). At this time, if an overvoltage occurs in the transformer itself, the transformer will be protected by gap protection. The principle is voltage breakdown. Under a certain voltage, the gap will break down and lead the voltage to the earth.
Gap protection can play the role of transformer winding insulation. When overvoltage occurs in the system (atmospheric overvoltage, operating overvoltage, resonance overvoltage, lightning overvoltage, etc.), when the gap is broken down, the zero sequence protection will act and the gap will not be damaged. In case of breakdown, overvoltage protection will operate to cut off the transformer.
4. Meet the sensitivity requirements of protection.
5. Prevent overvoltage and insulation damage caused by different closing phases.
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