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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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    Settings should really come out of the basic design - co-ordination and discrimination with downstream (and potentially upstream) devices and meeting required disconnection times being the main drivers. Zs/earth-fault current levels are a part of that - e.g. to achieve RA ≤ 50V/IA etc.but measured values should really only be used to verify the design assumptions as it were - since (especially for TT systems) they can vary considerably over time - so calculations should really be based on design worst cases rather than what they happen to be today.

       - Andy.

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  • 0

    Settings should really come out of the basic design - co-ordination and discrimination with downstream (and potentially upstream) devices and meeting required disconnection times being the main drivers. Zs/earth-fault current levels are a part of that - e.g. to achieve RA ≤ 50V/IA etc.but measured values should really only be used to verify the design assumptions as it were - since (especially for TT systems) they can vary considerably over time - so calculations should really be based on design worst cases rather than what they happen to be today.

       - Andy.

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