Restricted Earth Fault Relays

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TonyS Guru Join Date: Aug 2010 Location: Resting under the Major Oak Posts: 4347 Good Answers: 181	Restricted Earth Fault Relays 08/02/2013 11:01 PM
	I seem to have got my knickers in a twist over this. The resistor in the standard REF circuit? Is it a bleed resistor across the four CT's or a series resistor in line with the common (earthed) leg of the CT's? I've not worked on these for many years. The standard relay we used had five inputs. One common and four inputs from the three lines and one from the neutral. There was also the resistor and various trip connections. The more I look, the more I confuse myself. My age is getting to me! __________________ The reports of my death are greatly exaggerated.
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electricalexpert65 Guru Join Date: Oct 2009 Posts: 2061 Good Answers: 169	#1 Re: Restricted earth fault relays 08/03/2013 1:51 AM
	The resistor you see in an REF Relay circuit is called the stabilising resistor. It is provided to avoid spurious tripping of the REF relay for an external fault, in the event of one of the CTs involved in the fault saturates. It is connected in parallel to the four CTs, in series with the relay coil circuit. There are precise calculations to be made for sizing this resistor.
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TonyS Guru Join Date: Aug 2010 Location: Resting under the Major Oak Posts: 4347 Good Answers: 181	#2 In reply to #1 Re: Restricted earth fault relays 08/03/2013 9:00 AM
	Cheers for that EE. I was having a bit of a brain fart. __________________ The reports of my death are greatly exaggerated.
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