Transformer neutral point gap grounding explanation

First, the knowledge of the discharge gap at the neutral point of the main variable

1. Discharge gap is mainly used to protect the lightning arrester. When the lightning voltage exceeds the value that the arrester can protect, the discharge gap is installed to prevent the arrester from being broken down and damaged. When there is a high lightning strike voltage, the gap is breakdown discharge, thus protecting the arrester. As for how to cooperate between, according to the lightning arrester lightning voltage and.

2. Prevent dangerous overvoltage at the fault neutral point on the high voltage side after grounding variable trip.

3.110KV and above system neutral gap protection is mainly: to prevent overvoltage! Because of the problem of insulation investment in equipment at this voltage level, the insulation level is lower near the neutral point. If the overvoltage will cause damage to the equipment, clearance protection can play a role, but because of the choice of neutral grounding problem a system should not have too many neutral grounding, so some of the transformer neutral grounding switch did not close (protection configuration reasons). At this time, if the transformer itself occurs over voltage, then the protection of the transformer will be realized by the gap protection, the principle is voltage breakdown, under a certain voltage his gap will breakdown, the voltage to the earth.

Gap protection can play the role of transformer winding insulation, when the system overvoltage (atmospheric overvoltage, operating overvoltage, resonant overvoltage, lightning strike overvoltage, etc.), when the gap is broken down by the zero sequence protection action, gap is not broken down when the overvoltage protection action to remove the transformer.

4. Meet the sensitivity requirements of protection.

5. Prevent over-voltage caused by different closing periods and damage to insulation.

The so-called protection gap definition:

It is a simple lightning protection device consisting of two metal electrodes. One electrode is fixed on the insulator and connected to the live wire, and the other electrode is connected to the grounding device through an auxiliary gap, and the specified gap distance is maintained between the two electrodes. Under normal circumstances, to protect the clearance of the land is, of the insulation and insulation strength under insulation level of the protection circuit, therefore, when the lines have been struck by lightning, in the first place for overvoltage protection clearance breakdown, will be a lot of lightning current into the earth, make the over voltage drop dramatically, which have the effect of protection circuits and electrical equipment.