Possible damage to CTs

[shockking]

Our field team disconnected the CT's on a live 12 kV recloser without shorting the leads first. This was a unique/one-off situation without an established procedure, and the CT leads are bundled in the control cable to an SEL-351R. We didn't realize what had happened until after. There were no issues observed other than some funky event reports from the 351R. The CT's saw about 170 amps at 12 kV for about 20 mins. My question is, how likely is it that the CTs were damaged? Everything seems to be working normally, no obvious damage or other issues. Thoughts?

 

[LarryFine]

The most likely damage would be to the insulation within the CT's windings.

 

[Elect117]

You should set aside some time to take it out of service and have the CT tested.

With an open on the secondary windings you will end up with high core saturation and higher voltages than the insulation should probably experience. It is hard to tell since the recloser could be 17kV rated and have a higher BIL or VA rating. You could have residual magnetism which will lead to errors in the recorded values.

 

[shockking]

Here's the recloser nameplate fyi. Thanks for the feedback.

 

[petersonra]

It will probably be more cost effective to replace them than to try and test them and see if they have been damaged.

 

[Elect117]

It will probably be more cost effective to replace them than to try and test them and see if they have been damaged.

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These things aren't cheap to replace. I don't think they resell parts in the device.

 

[David Castor]

Some reclosers have a shunt resistor across the CTs to prevent damage if the CTs are open-circuited. I'd check the instruction manual or ask the manufacturer. 20 minutes is a long time . The CTs can almost certainly be replaced if necessary, but it would have to be taken out of service, obviously,

 

[petersonra]

Some reclosers have a shunt resistor across the CTs to prevent damage if the CTs are open-circuited. I'd check the instruction manual or ask the manufacturer. 20 minutes is a long time . The CTs can almost certainly be replaced if necessary, but it would have to be taken out of service, obviously,

Would likely have to be taken out of service to do any real testing too.

 

[JoeStillman]

Looks like the CT's are encapsulated with the vacuum interrupter. I don't imagine they are replaceable.


What does G&W say?

 

[ggunn]

Something we found out the hard way as well is that this type of CT should be installed with shorting bypass switches.

 

[Hv&Lv]

Looks like the CT's are encapsulated with the vacuum interrupter. I don't imagine they are replaceable.
View attachment 2572651

What does G&W say?

Your right. They aren't replaceable.
We have a couple dozen of them. Dang near bulletproof. Check your amps and see if it's off any at all. 1000:1 will take quite a bit though for a 351R. It doesn’t really get accurate until the amps get high, like >100

 

[Hv&Lv]