Yesterday we received a call from one of our clients, that whenever they switch on its VCB Trolley of 11KV Protection Panel tripping occurs in both the Metering Panel and also the Grid End Consumer Panel.
When our team reached there site we did the following things.
When our team reached there site we did the following things.
- We checked the panels protection relay, all instantaneous tripping flags were down.
- We disconnected there INCOMING and OUTGOING cable.
- Removed the Trolley from the Panel.
- Checked The Trolley's Insulation of both the three Interrupters and also the resistance of three phases w.r.t ground, which was low as we expected.
- Then we checked the Insulation of all the panel circuit w.r.t ground, which was also low.
Note: Due to this low resistance Panel was not standing on 11KV.
The resistance level for 11KV min. 22MΩ
Reasons:
When we inspected the Panel room and its surroundings, we came across following causes of this fault
- High humidity/moisture level.
- Panel Room size less than recommended.
- No Proper Ventilation.
- 1window in the room without rain protection.
- An uncovered water trench in front of the room.
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