What is the function of Earth Fault Indicator (EFI)?

[tipu_sultan]

On which principle does the EFI works?
How it detect the fault and on which basis?

 

[barry]

Not sure what you've got there in Rawalpindi, but in the US there three terminals on our wall sockets-Hot, Neutral and Ground. Normally, whatever current flows out of the HOT side should flow back into the NEUTRAL side. If there is a difference in current in those two legs, that means that current is flowing through some other path, (possibly a human). This is a ground fault. Ground-fault interrupters measure the difference in current between the two legs, and open a relay if the difference exceeds some value.

 

[chuckey]

As Barry said plus in the States, they actually inject a high frequency into the live and check that it all comes back down the neutral, if any is missing it must have gone to earth! This type is called a GLFI. The sort that Barry described, in the UK they are called RCDs (residual current detectors).
Frank

 

[tipu_sultan]

ha ha!
In Rawalpindi I am little sure that we called it GFCI. Anyway I am satisfied with you good logic in which you convey me a concept.
But now I understand that the Earth may interchangeably be used with Ground.

Thanks a lot Barry.

 

[FvM]

Earth fault indicator is a protection device used with medium voltage distribution networks. It's operation is similar to RCD.

 

[schmitt trigger]

Indeed...earthing/grounding; valves/vacuum tubes; aerial/antenna.....