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CT Thermal Rating Factor and CT Class

CT Thermal Rating Factor and CT Class

CT Thermal Rating Factor and CT Class

(OP)
If I can't find the CT Thermal Rating Factor TRF (or Rating Factor RF) on the nameplate, is there a way to find that knowing the CT class? In other words, how can I come up with a TRF if I do have the CT nameplate data and saturation curves.
Station that I am doing settings for has this 1960s breaker which doesn't have this data listed on whatever documentation I can find. And assuming a conservative TRF of 1.0 is not helping me since the max continuous current expected on the CT will be higher than it can take. Now if TRF is 1.5 or 2.0, then I am good.
Attaching the CT curves that has data, incase there is a way I can assume the TRF from it.

RE: CT Thermal Rating Factor and CT Class

You won't be able to get any information on the rating factor from the class, or excitation curves.

These seem to be bushing CTs on breaker, so the rating factor of the CT is based on the secondary winding and specifically the size conductor used on the secondary winding.

The curve does give you the secondary resistance, but one would need to know the size of the core to be able to guess on the wire size used on the secondary.

From an engineering perspective, if you don't know the RF of a CT, you should assume it is 1.0.

I'm surprised the ratings of the CT, including RF, aren't on the breaker nameplate.

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