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arunelectone
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Join Date: Jan 2011
Posts: 2

Leg Ground Fault

01/28/2011 4:41 AM

I have commissioned 3.3kv submersible oil pump motors. It has some protection like leg ground fault. When I go to charge the breaker before , the relay shows leg grould fault. This fault would not allow to energize the breaker. We check everything but finally we removed voltage transformer star point neutral earthing then afterwards it energized the breaker. My question is what is the leg ground fault, why neutral earthing has removed for this fault, what is this reason for this.
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PWSlack
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Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
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#1

Re: leg ground fault

01/28/2011 5:51 AM

The relay is a circuit protection device. The reason for the relay showing a grounded leg fault is that there is a grounded leg fault. Removing the neutral point earthing has removed the opportunity for the relay to detect the grounded leg fault, which means that:

  1. the other two legs are root three times their original voltage to earth should the breaker be energised, and
  2. there is no protection in the event of a grounded leg fault.

This is potentially a very hazardous situation.

Somewhere, downstream of the breaker, the grounded leg fault must be isolated and removed before continuing. Once that is done, re-connect the neutral earthing and the breaker will operate correctly with all protection in place.

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Anonymous Poster
#2

Re: Leg Ground Fault

02/01/2011 4:01 AM

You need to do some tests upstream and down stream for the source of this earth fault and clear it to save your pump motors from failure later . Check all circuits associated with your power supply.

Otherwise your power cable armour is carrying it from another installation

DOES THE MANUFACTURE OF PUMP INDICATES WHAT KIND OF EARTHING SYSTEM IS REQUIRED?

JS
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