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Participant

Join Date: Sep 2014
Posts: 2

CAG14

09/26/2014 9:12 AM

Dear Engineers,

Incase of CAG14 (REF PROTECTION) how can we connect the 3 phase CT's to the relay through rheostat.

Please clarify me.

Gupta ji can you clarify me the same.

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Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 76
#1

Re: CAG14

09/26/2014 10:34 AM

Did you read the instructions that came with the equipment? If it didn't, then did you ring the manufacturer for advice?

Tell me what you HAVE done to find out.

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Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2745
Good Answers: 163
#2

Re: CAG14

09/26/2014 11:16 AM

Welcome to CR4.

i hope the experts of CR4 will enrich your knowledge.

One humble suggestion - if you want only Mr Gupta to answer, you can send a PM (personal message) through CR4. In fact the other experts are unlikely to answer you here since you have specifically asked for Mr Gupta (there are many Guptas on CR4 i think, i hope the one you want will answer)

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Guru

Join Date: Dec 2010
Posts: 1618
Good Answers: 111
#3

Re: CAG14

05/18/2021 7:18 AM

The simple answer is you use insulated copper wire!!

If you are doing REF = Restricted Earth Fault protection, then you must also connect a Current Transformer on the earth/ground lead of the transfo winding to the relay as well as the 3 CTs in the HV connections of the same winding.

All the CTs are connected in parallel with each other and the relay. It is essential polarities are such that the sum of the 3 HV CT secondary currents is balanced by the earth CT current with normal load [see fig.3 of brochure at www ref. below] - fault is when some current goes to earth inside transfo, so not going through phase CTs. It is usual to have an external fixed resistor in series with the relay coil - not a rheostat or variable resistor, although it could be a bare coil on a ceramic former with a clamp terminal.

This may help, all I did was make web search for "CAG14 relay" to find this...

https://www.gegridsolutions.com/products/brochures/r6136d-epslanguage=en-gb.pdf

It has a MCAG catalog with connection diagram and setting calculations.

While it may not be exactly an old GEC UK CAG14 [maker became Alsthom & then Areva: CAG14 modified to MCAG14 in process] it seems identical in all relevant respects - might have different terminal numbers, but the only connections would be two for coil and two for normally-open contact plus safety earth, so easy to identify.

67model

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67model (1); Crabtree (1); kvsridhar (1)

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