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nagarajansuha
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Join Date: Mar 2009
Posts: 4

Ct Burden-Electrical Engineering

08/27/2009 5:40 AM

dear all,

i have one doubt regarding ct burden. one current transformer is having the specifications as 100/1A,5P15,10VA. and is used in 25 years old switchgear. now i want to replace that switchgear with new one. will it affect the existng protection philosophy when we change the ct specifications as 100/1A, 5p15,5VA. now we are going to use new micom p139 relay.
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C.S.PANT
Active Contributor

Join Date: Jan 2008
Posts: 18
#1

Re: ct burden-electrical engineering

08/27/2009 7:04 AM

You need to have 10 VA , how you can use 5 VA , protection class is o.k but burden will depend on your VA ratings i.e primary current. So 10 VA will be required.
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jack of all trades
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New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
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Good Answers: 376
#2

Re: Ct Burden-Electrical Engineering

08/27/2009 4:18 PM

This information is stated in the P139 data sheet (a little un-clearly I might add compared to previous models).

http://www.areva-td.com/solutions/US_411_US%3A%3ASolutions%3A%3AAutomation%3A%3AMiCOM+P139+.html

Check the data sheet and technical documents to ensure the suitability of your CT.

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 jack of all trades
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msamad
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Join Date: Feb 2009
Location: Houston, USA
Posts: 946
Good Answers: 244
#3
In reply to #2

Re: Ct Burden-Electrical Engineering

08/27/2009 9:20 PM

Nagarajansuha,

Look into the page 21 of Technical Data Sheet of P139 relay from this link:

(ftp://ftp.areva-td.com/brochures_web/P139%20TechnicalDataSheet%20EN%2030B.pdf).

If this link doesn't work, go to the link of 'jack of all trades' and click English below the 'Technical Datasheets'.

---------------------------------------------------------------------

Current

Conventional inputs:

Nominal current Inom: 1 and 5 A (settable)

Nominal consumption per phase: < 0.1 VA at Inom

---------------------------------------------------------------------

This means, the maximum load to the CT for this relay is 0.1 VA. So, the 5 VA CT should be good enough. However, if the CT is connected to other instruments in series (such as Ammeter, Wattmeter, KW meter, Transducer etc.), then find their VA's from the data sheet and the sum of all should not exceed 5VA (better to keep it not more than 50% of CT VA, 2.5 VA in your case).

- MS

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nagarajansuha
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Join Date: Mar 2009
Posts: 4
#4
In reply to #3

Re: Ct Burden-Electrical Engineering

08/28/2009 3:53 AM

thanks for ur suggestion.
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mohsinhamid
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Join Date: May 2011
Posts: 91
#5
In reply to #3

Re: Ct Burden-Electrical Engineering

08/02/2011 12:13 AM

salam sir,

1. why we are calculating BURDEN of CT IN VA..???

2. why the secondary load shld not be more than the burden VA..??? if more than the burden va what will happen....????
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C.S.PANT (1); jack of all trades (1); mohsinhamid (1); msamad (1); nagarajansuha (1)

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