possible cause of burned switchgear

[niceyuan]

Dear all,

We have 115 kV s/s; 20MVA xformer 115kv/4160V; type tested alstom switchgear with siemens controls and protection; The controls was burned started probably from the main CB controls compartment. What seems to be the reason? The station has 2 exhaust fans on one side and three louvered windows on the other side. We are experiencing typhoons on this area. We did cover the louvered windows w/ plastics before the incident to protect from entering rain water. This was the culprit as per the builder/supplier of the s/s. But the ambient of the s/s did not even came close to 50deg (since we have people visiting the place hours before the incident).

Two months before the incident we did discovered and replaced burned terminal block on the main CB control compartment. Is there any other possible cause?

Thanks

 

[waross]

First the difference between water vapor and mist.
Water vapor is water in the gaseous state. It is the source of condensation.
Water mist is finely divided water particles suspended in the air. If the source is sea water it will be finely divided salt water. When this impinges on a surface, the water tends to evaporate and leave the salt behind.
This effect causes a lot of flash-overs on distribution insulators near the ocean. If your sub is near the ocean you may be experiencing salt contamination. It is common during strong winds. Condensation may also be a problem. It depends a lot on location and the layout of your plant.
respectfully