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Current transformer size
2

Current transformer size

Current transformer size

(OP)
We are trying to use one spare feeder for energising one new Transformer(750KVA,13.8kV/480Volts,60Hz.6%(Z), using feeder 1200Amps,breaker(VCB) having 600/5, ANSI C200 class current transfomer(Bus bar mounted) for protection relaying and measuring purpose. Is there any accuracy issue with this CT ratio?

RE: Current transformer size

So what is the load expected to be?  If you will have over 600A of load, you need to verify the thermal rating of the 600/5.

Is your concern relaying or metering accuracy.  If relaying, you'll need to know the available fault current.  If metering, you will need to determine the metering accuracy rating, if any.   

"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller

RE: Current transformer size

2
C200 is a relay accuracy designation. Unless rated for metering as well, it will not be suitable for revenue accuracy metering.

RE: Current transformer size

(OP)
Connected load will be around 300KW on 480 volts bus(lighting, small power and HVAC units( maximimum motor size 20KW only. Fault rating on 13.8KV side bus is 500MVA.I am concerned about only protection relaying purpose. Metering is just for indication purpose only.

RE: Current transformer size

Assuming standard overcurrent relaying, I don't think the CT performance will be an issue.  C200 is better than the majority of CTs in metal-clad switchgear.   

"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller

RE: Current transformer size

It possibly 10% or 2.5% accuracy at 100A at secondary, for protective relaying it is ok.

RE: Current transformer size

stevenal has a good point - are you concerning about accuracy for measuring purpose or you are concerning about the CT saturation during a fault?
A star for stevenal, great calculator!

RE: Current transformer size

(OP)
AS i told before only concern is protection requirements.Thanks stevenal.

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