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ELR and EFR Settings for a existing factory.

Ishan

Could someone provide a valid reference on how to set Earth Leakage Relay (ELR) or Earth Fault Relay (EFR) settings at the distribution board when the earth fault current or loop impedance is known through testing with a loop impedance meter? Thank you.

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    Clearly if the supply impedance is so high that the EFR will not operate, then it is set too high ;-) Between that , and as alluded considerations of voltage rise during the largest non tripping fault, as an upper bound, and not wanting to trip on day to day operations (so slower and coarser than any protection down stream )lies a wide band of acceptable settings.  Between 0.1 and 1 percent of the full load current is a good place to start if you need a trial value.
    Mike.

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    Clearly if the supply impedance is so high that the EFR will not operate, then it is set too high ;-) Between that , and as alluded considerations of voltage rise during the largest non tripping fault, as an upper bound, and not wanting to trip on day to day operations (so slower and coarser than any protection down stream )lies a wide band of acceptable settings.  Between 0.1 and 1 percent of the full load current is a good place to start if you need a trial value.
    Mike.

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