Material for Gland Plate

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Anonymous Poster	Material for Gland Plate 09/13/2010 12:29 AM
	I need to connect 3 single core 300 sq mm copper XLPE armoured cables of 33 KV (E) voltage grade to my 33KV / 1150V, 5750 KVA transformer primary. The system frequency is 50 Hz. Do I need to provide gland plates of non-magnetic material like Aluminium in the transformer primary terminal box & 33 KV switchboard ? Is the eddy current loss in mild steel gland plates due to single core cables at 50 Hz level sufficient to cause heating ?
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Material for gland plate 09/13/2010 2:32 AM
	<...the eddy current loss in mild steel gland plates due to single core cables at 50 Hz level sufficient to cause heating ?...> Yes. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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TonyS Guru Join Date: Aug 2010 Location: Resting under the Major Oak Posts: 4347 Good Answers: 181	#2 Re: Material for gland plate 09/13/2010 5:06 AM
	Ensure the glands and nuts are brass or aluminium __________________ The reports of my death are greatly exaggerated.
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Anonymous Poster	#3 In reply to #2 Re: Material for gland plate 09/13/2010 5:11 AM
	Do you mean if brass cable glands are used, mild steel gland plates are acceptable ?
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TonyS Guru Join Date: Aug 2010 Location: Resting under the Major Oak Posts: 4347 Good Answers: 181	#4 In reply to #3 Re: Material for gland plate 09/13/2010 5:23 AM
	You can use steel gland plates but a slot has to be cut between each hole to stop eddy currents. The slot is best filled with epoxy resin to stop ingress of dirt and creepy crawly things. __________________ The reports of my death are greatly exaggerated.
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electricalexpert65 Guru Join Date: Oct 2009 Posts: 2061 Good Answers: 169	#5 Re: Material for Gland Plate 09/13/2010 10:25 AM
	If you earth the armour of these cables only at one end, I do not foresee any circulating current.
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TonyS Guru Join Date: Aug 2010 Location: Resting under the Major Oak Posts: 4347 Good Answers: 181	#6 Re: Material for Gland Plate 09/13/2010 4:56 PM
	Right let's start again from the beginning. If a single core cable passes through an iron loop the loop becomes a CT. So a steel gland plate with no slots or a gland with a steel locknut become CT's carrying the full current of the conductor. Use brass or aluminium to save problems. Circulating currents through armourings deserve a chapter all of there own. __________________ The reports of my death are greatly exaggerated.
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Anonymous Poster (1); electricalexpert65 (1); PWSlack (1); TonyS (3)

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