Prob 101

[BamaBino]

Shouldn't the answer be that the Isecondary = 400A ?

Thanks

 

[Flyer_PE]

Although assigning the terms primary and secondary is somewhat arbitrary, the convention is that the system side of the CT is referred to as the primary and the relay/meter side of the CT is the secondary.

 

[BamaBino]

Although assigning the terms primary and secondary is somewhat arbitrary, the convention is that the system side of the CT is referred to as the primary and the relay/meter side of the CT is the secondary.

Thanks for the reply.

If the transducer is on the secondary, doesn't that make the turns ratio 5:400 (Np:Ns) ?

 

[cableguy]

Don't confuse going across a power transformer (example, 138kV primary -> 69kV secondary) with going across a Current Transformer (primary->secondary).

When talking about a CT, you talk about "400 amps primary current" yields "5 amps secondary current". This gives you a CT Ratio of 400:5. The CT can be attached to a breaker (that does not have a "primary" and "secondary" side), or it can be attached to a power transformer (say a 138kV/69kV, that does have a "secondary" side). But don't let them confuse you with the term "secondary" - they can word the question very confusingly (and I bet they will ). Just remember, the secondary side of a CT is the "low current" side, typically 5 amps.