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anandchy
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Join Date: Dec 2010
Posts: 15

Please Help in Determining the Secondary Terminal of CT

11/03/2012 9:15 PM

We have found a old 450/1 Current Transformer in our plant store.It is a very old CT and no name plate is available.450/1 is written on CT body by a permanent marker.

There are 4 secondary terminals but these too are not marked.As there are 4 secondary terminal we guess its a dual core CT.But how can we dertmine which of these core are for protection or which is for metering or both may be for protection or both for metering.Also how can we mark these 4 terminals in 1s1-1s2 or 2s1-2s2 and assume it as metering or protection.
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Anonymous Poster #1
#1

Re: Please help in determining the secondary terminal of CT

11/03/2012 10:04 PM

And do you just happen to have a 450:1 meter to go with this?
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pnaban
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Join Date: Jun 2010
Location: srilanka
Posts: 2725
Good Answers: 5
#2

Re: Please Help in Determining the Secondary Terminal of CT

11/04/2012 1:09 AM

Do a primary injection test with two similar ammeters connected in secondary windings and compare the readings.Did they give the burden/accuracy class for each winding?.

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Joshi
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Join Date: Oct 2007
Location: India
Posts: 1246
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#3

Re: Please Help in Determining the Secondary Terminal of CT

11/04/2012 7:05 AM

Please start your search here:

NGTS326 Issue 1 - National Grid

Current transformers: how to specify them - Schneider Electric

TTR 4x. xx Indoor Bushing Current Transformer
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electricalexpert65
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Join Date: Oct 2009
Posts: 2061
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#4

Re: Please Help in Determining the Secondary Terminal of CT

11/04/2012 8:49 AM

i) With the help of a simple continuity tester you can soirt out the two pairs of windings.

ii) By doing a polarity test, you can decide s1 & s2 on these two secondary windings.

iii) By doing a ratio test, you can ascertain the CT ratio.

iv) By doing an excitation test, you can ensure whether the cores are for metering or for protection and which core is for what.
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CoronaCameraMan
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Join Date: Sep 2007
Location: Sheboygan, WI USA
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#5

Re: Please Help in Determining the Secondary Terminal of CT

11/04/2012 11:06 PM

Are you sure it's two cores and not a multi-tap ?

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