How to Test a Capacitor Bank

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Genaro Active Contributor Join Date: Jan 2007 Location: Morelia, Mich. Mexico. Posts: 11	How to Test a Capacitor Bank 05/02/2007 1:40 PM
	I have a double capacitor bank, in a subestation 13.2 KV-440 volts, with three transformers, 750, 500 and 112.5 KVA. The capacitors are for f.p. compensation. Each one of the capacitors bank is for 50 KVAR, 480 volts, plate data. There was a failure that provoked the outage of the whole subestation, causing the surge arrester of the main entrance of the subestation to fail. None of the transformers suffered any harm. It seems the origin of the problem was a loose conection in the capacitor bank's switch. Having no lab equipment for testing capacitance, how can I test whether or not the capacitors are damaged ? The capacitor banks are delta connected. Of course I do have means for applying variable a.c. voltage, multimeter, and apparatus like that. Thank you for any comment __________________ Genaro
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Anonymous Poster	#1 Re: How to test a capacitor bank 05/02/2007 4:44 PM
	In that confined of an environment; I guess that I would take an ohm meter and check it for shorts and if that went well I would charge the capacitor with a small voltage (100V or so) then come back in a couple of hours and see how much has leaked off. If you have acess to an insulation resistance tester it might make the same tests a little easier. Other than that I am not sure you have the capability to test more than that .
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Langdom Commentator Join Date: Sep 2006 Location: Argentina Posts: 59	#2 In reply to #1 Re: How to test a capacitor bank 05/03/2007 12:20 AM
	If capacitors past these test sucesfully can be connected to the net. After this use an clamp meter to read current across each capacitor. If the currents are very similar (+/- 20%) all are ok. Discard capacitor with very high or very low current and replace with new.
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vermin Guru Join Date: Jul 2006 Location: Silicon Valley Posts: 5356 Good Answers: 50	#3 Re: How to Test a Capacitor Bank 05/03/2007 2:35 AM
	Put your tongue across the capacitor poles to find the bad one. Works every time, as long as you have enough people. __________________ "Perplexity is the beginning of dementia" - Professor Coriolus
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aurizon Guru Join Date: Jun 2006 Location: Toronto Posts: 3968 Good Answers: 120	#4 In reply to #3 Re: How to Test a Capacitor Bank 05/03/2007 7:19 AM
	Excellent suggestiom. To make sure you get all the credit for it, we will use your tongue... __________________ Per Ardua Ad Astra
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vermin Guru Join Date: Jul 2006 Location: Silicon Valley Posts: 5356 Good Answers: 50	#6 In reply to #4 Re: How to Test a Capacitor Bank 05/03/2007 11:32 PM
	What tongue?! __________________ "Perplexity is the beginning of dementia" - Professor Coriolus
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capacitorbob Active Contributor Join Date: Oct 2006 Posts: 14 Good Answers: 2	#5 Re: How to Test a Capacitor Bank 05/03/2007 9:07 AM
	After the capacitors are back on line, amp probe them. If the capacitors have a 480V nameplate, you will get 1.2amps per KVAR at 480V and 1 amp per KVAR at 440V. You don't have to take the low ones off line unless they are part of an LC type filter bank, but you should eventually replace them.
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Anonymous Poster (1); aurizon (1); capacitorbob (1); Langdom (1); vermin (2)

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