Cable with Low IR Value

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electrotech Member Join Date: Nov 2012 Location: Trinidad and Tobago WI Posts: 5	Cable with Low IR Value 06/16/2013 8:58 PM
	I have a cable on my plant that has a low Ir value 3.3MΩ I think it is moisture has anyone had this problem before and can help __________________ electrotech
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#1 Re: Cable with Low IR Value 06/16/2013 9:43 PM
	Determine any sources of moisture entry to the cable insulation, and block them if possible. This could mean cables in buried or other moist locations, or with cracks in the insulation that would admit moisture. What voltage is the cable? This would govern the amount of current leakage, which might or might not be acceptable for a short time, until the cable can be dried out. While 3.3MΩ is not desirable, it isn't necessarily catastrophic, either. Continue to monitor the IR readings closely. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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pnaban Guru Join Date: Jun 2010 Location: srilanka Posts: 2725 Good Answers: 5	#2 Re: Cable with Low IR Value 06/16/2013 11:12 PM
	Is it new cable,if old 3.3Mohm not low if voltage is 400. __________________ pnaban
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Pattabhiraman Commentator Join Date: May 2013 Posts: 86 Good Answers: 2	#3 Re: Cable with Low IR Value 06/17/2013 5:28 AM
	In the first instance why did you do the IR measurement. Is there already some problem with the cable during live operation. If yes, then you will have to trace the problem physically. It could probably be due to some physical damage in the cable. If not, is the cable isolated from connections at both ends before measurement? If no, please disconnect cable and carry out measurement. Low IR values, like reading above, is practically seen in low voltage cables up to 660/1100 Volts rating and generally should not pose any problem.
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Lek Member Join Date: Jun 2013 Posts: 5	#4 Re: Cable with Low IR Value 06/17/2013 11:14 PM
	Base on my explerience, under 3.3M ohms is already consider ok in my country. As sometime when the cables were being laid, it was not been protected properly at the open end. If you worried when it come to Power Turn On, try to conduct another Hi-Pot Test. This could help to burn off the moisture inside the cables and during the process you will heard some Crack Crack sound. Maybe this could help to resolve your issue.
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Lek (1); Pattabhiraman (1); pnaban (1); Tornado (1)

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