Voltage rating of CT’s??

[adamscb]

Do CT’s have voltage ratings? We deal with a lot of 480v motors in my plant, and we use 0-5A CT’s for amp indication on our DCS system. Could I take a CT I would normally use on 480V and use it on say 2300V? 4160v? Or even 13.8kV or 69kV?

 

[junkhound]

Yes, the insulation rating of the CT.
Voltage rating has no effect on CT operation, but ya don't want the line arcing to YOU or your test equipment.
IF, ah say IF, you can put enough insulation on a megavolt line and still fit it thru a 5A CT, the CT would work.

Never saw a 5 A CT with a big enough hole to take that much insulation.

 

[jim dungar]

Shielded MV conductors are allowed to lay directly on grounded surfaces, otherwise they could not be installed in metallic conduit. So it is possible it install a 600V rated CT over shielded conductors. In fact it is a common industry practice, particularly in switchgear.

Check with your CT manufacturer, most of them have some application note for this. Especially in regards to running the shield grounding conductor backwards through the CT to prevent incorrect readings due to current flowing on the ground.

You typically do not see this in open air switch yards because those conductors are usually not shielded.

 

[LarryFine]

A CT has no real voltage rating because it's always shorted by either the meter or a shorting bar.

 

[jim dungar]

A CT has no real voltage rating because it's always shorted by either the meter or a shorting bar.

No but it does have a rating for L-G voltage. Most of the windows type CTs you have seen are probably 600V, even the ones in MV switchgear.
The concern is the insulationbetween the conductor inside the window to the steel core and then from the steel core to any grounded surface.