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DannyD
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Join Date: Oct 2009
Location: kuruman NC. SOUTH AFRICA
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Earth Leakage Relay

11/21/2012 12:13 PM

Dear Engineers

how do i select the earth leakage relay( sensitive current rating) of an istallation (eg:250mA,375mA,500mA etc)? any formula/calculation for that.

i have 243kw load, 525Volts, 278A. 150mmsq(supply cable, 100m long), 300A main circuit breaker with shunt trip. so i have to select the size of my earth leakage relay.

please help.

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Joshi
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#1

Re: Earth Leakage Relay

11/21/2012 2:53 PM

Is leakage current, of the order of 250 mA, not dangerous/fatal for personnel? Should you not scale it down to a more rational, safe value?
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TonyS
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#2

Re: Earth Leakage Relay

11/21/2012 9:33 PM

Depends what you want the E/L relay for. Protection against shock or protection of equipment.

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PWSlack
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#3

Re: Earth Leakage Relay

11/22/2012 3:17 AM

One could always look up the protocol in good-old British Standard 7671.

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DannyD
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#4

Re: Earth Leakage Relay

11/23/2012 9:12 AM

i want to protect the equipment

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DannyD
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#5

Re: Earth Leakage Relay

11/23/2012 9:27 AM

in addition, the standard protection for human shock i know is 30mA max. but what i am now asking is for the supply that supplies the heater bank which is used in my plant to dry material. and i will also prefer to use the relay with time delay, but my problem is the size (milli- Ampere rating).

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PWSlack
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#6

Re: Earth Leakage Relay

11/26/2012 8:21 AM

British Standard 7671 is still widely available...

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