Oil dielectric strength

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amitbasu Member Join Date: Jan 2010 Posts: 8	Oil dielectric strength 02/06/2010 5:36 AM
	What is the standard gap between electrodes in a test kit for testing dielectric strength of transformer oil? What is the standard diameter of spheres in each electrode? What is the effect of shape & size of the electrodes on the breakdown voltage ?
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electricalexpert65 Guru Join Date: Oct 2009 Posts: 2061 Good Answers: 169	#1 Re: Oil dielectric strength 02/06/2010 9:14 AM
	A new transformer oil should have at least a dielectric strength of 39 KV from a British standard. Transformer oils used are normally tested using ASTM D877-82 with the KV strength tester using 1" electrodes spaced 0.1" apart and the test voltage increased at 3,000 volts/min until it breaks down. The average Kv obtained after 8 trials is considered the Oil dielectric strength. Using this test method, dielectric strength at 30 kv and above is considered good. Dielectric strength between 23 to 29Kv is considered usable, but requires filtering. Below 23 kv, the transformer oil should be replaced.
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Dickson Power-User Join Date: Nov 2009 Location: Abuja, Nigeria. Posts: 126	#2 Re: Oil dielectric strength 02/07/2010 6:43 AM
	Oil stored in drums, does not retain its originsl dielectric strength, and should be tested and treated b/4 use in an electrical equipment. The recommended size of the glass cell is 55 x 90 x 100mm. The diameter of spheres or test electrodes has been specified at 12.7mm and air-gap b/w the spheres as 4mm.The quantity of the test sample shall not be less than 2 litres, which shall be drawn from the bottom of the drum, transformer or other aparatus. The oil in the test cell shall be at least 40mm above the electrodes and it shall be allow to stand for 20min b/4 performing the test to let air bubles escape. The test voltage should be raised to a specific value at uniform rate in 10.15 seconds and maintain for a period of one minute. A withstand voltage of 33 KV on a 3mm gap may be regarded as being reasonably equivalent to the standerd test. Dickson __________________ There is peace in silence and achievement in plans.
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StandardsGuy Guru Join Date: Dec 2006 Location: North America, Earth Posts: 4528 Good Answers: 106	#4 In reply to #2 Re: Oil dielectric strength 02/07/2010 4:36 PM
	What is the treatment to give the oil more dielectric strength? How does it affect loss tangent? __________________ “I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
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StandardsGuy Guru Join Date: Dec 2006 Location: North America, Earth Posts: 4528 Good Answers: 106	#3 Re: Oil dielectric strength 02/07/2010 4:33 PM
	Hi amitbasu, Welcome to CR4. Are you building a Tesla coil? "What is the effect of shape & size of the electrodes on the breakdown voltage ?" Sharp pointed electrodes will break down with smaller gap (longer spark distance). -S __________________ “I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
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Anonymous Poster	#5 Re: Oil dielectric strength 02/09/2010 10:24 AM
	Looks suspiciously like homework to me. ??
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Anonymous Poster (1); Dickson (1); electricalexpert65 (1); StandardsGuy (2)

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