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Anonymous Poster

What to Do With Opened Out Put of Live CTs?

01/15/2011 6:28 AM

I have an Energy Meter at main DB and 3 CTs 400/5A are connected with it. I want to remove the Meter for repairing but what to do with CTs, should I short their points or leave them open after disconnecting the Energy meter?

What possible happen if i leave their out put points open?
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Anonymous Poster
#1

Re: What to do with opened out put of live CTs?

01/15/2011 6:40 AM

Smells that you want to test our knowledge, about which you know something already.
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5
pravinba@yahoo.com
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#2

Re: What to do with opened out put of live CTs?

01/15/2011 6:44 AM

Before you remove the energy meter, you must short the CT secondary terminals in the Terminal block. CT shorting link arrangements must be available in the terminal block. Never open CT secondary when the CT primary is carrying current. If it occurs, the voltage across the secondary rises to a huge value. Due to the absence of back emf the working flux increases and the core gets saturated. This leads to overheating and the CT finally will fail or a flash-over can occur.
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Tornado
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#3
In reply to #2

Re: What to do with opened out put of live CTs?

01/15/2011 7:01 AM

What total stinking idiot voted this as off-topic? It is exactly and importantly correct.

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kvsridhar
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#4
In reply to #3

Re: What to do with opened out put of live CTs?

01/15/2011 7:35 AM

i agree, so my GA to take it further after you have negated that OT vote.

Maybe the first button being OT and the second one being GA, people inadvertently vote wrong ? i think Admin should make the GA button more prominent than the OT button.

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Tornado
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#5
In reply to #4

Re: What to do with opened out put of live CTs?

01/15/2011 8:00 AM

Excellent. Pravinba is now honored. It is probably too much to hope that his/her critic will acknowledge this.

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msamad
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#7
In reply to #2

Re: What to do with opened out put of live CTs?

01/15/2011 9:32 AM

I also agree this is exactly the right answer (one more GA). But there is the possibility of some non-standard wiring without the shorting link terminal available. In this case, either (1) short it from CT secondary terminal or (2) do the replacement work at de-energized condition. But option 2 is preferred for safety consideration.

- MS

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TonyS
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#6

Re: What to do with opened out put of live CTs?

01/15/2011 8:26 AM

I'll add to the score.

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Anonymous Poster
#8

Re: What to do with opened out put of live CTs?

01/15/2011 10:19 AM

Pravinba is the real OP.
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thccontrols
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#9

Re: What to Do With Opened Out Put of Live CTs?

01/16/2011 2:12 AM

simple... you short them out

Next question please!!
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Anonymous Poster
#10
In reply to #9

Re: What to Do With Opened Out Put of Live CTs?

01/16/2011 5:49 AM

Is italian prime minister silvio berlusconi guilty??
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Anonymous Poster
#13
In reply to #10

Re: What to Do With Opened Out Put of Live CTs?

01/18/2011 12:43 AM

This made me laugh...

Yes, he is.... mostly of being Italian and breathing!!

NEXT!!
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rhkramer
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#11
In reply to #9

Re: What to Do With Opened Out Put of Live CTs?

01/17/2011 9:04 AM

Yes, but you short them out before disconnecting the load (the meter or whatever).
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Anonymous Poster
#12
In reply to #11

Re: What to Do With Opened Out Put of Live CTs?

01/18/2011 12:41 AM

I personally would have the supply/power/load isolated, disconnect the DEAD CT's, short them out and THEN continue. Nearly 40 years in the electrical game and I AVOID working in live panels as MUCH as possilble.
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kvsridhar
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#14
In reply to #12

Re: What to Do With Opened Out Put of Live CTs?

01/18/2011 1:03 AM

Sensible i know. But rather disappointing for a design engineer. i spent considerable time perfecting the shorting-link system for many withdrawable equipment - MCCBs, ACBs, Relays ... believe me, some of them were tested to ridiculous levels for establishing reliability.

Still, your advise is very much valid. Unless there is extreme difficulty in interrupting main power.

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spradhan
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#15
In reply to #14

Re: What to Do With Opened Out Put of Live CTs?

01/18/2011 7:49 AM

I agree with you (GA from me)since,it is not desirable to switch off the feeder just for replacing a defective meter ,particularly in production shops/industries.Further,special terminal blocks with sliding type shorting links for CT wring are available in the market which are easy & safe to use.

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Anonymous Poster (5); kvsridhar (2); msamad (1); pravinba@yahoo.com (1); rhkramer (1); spradhan (1); thccontrols (1); TonyS (1); Tornado (2)

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