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Insulation for CT circuits

Insulation for CT circuits

Insulation for CT circuits

(OP)
I have a line differential relay (SEL) between two 15kV substations approximately 300 feet apart. The construction group has pulled a 3 conducter #10 w/ground cable for the CT circuit and used the cable ground conducter for the XO. My question is: Is this allowed? I have always used a four conducter #10 for CT circuits and would like some specification for this to get it changed.I can't find one. Any help?

RE: Insulation for CT circuits

Four insulated conductors, isolated from everything else.  Always.  Without exception.

RE: Insulation for CT circuits

Single ground point for a differential CT. Other wise things happen.

RE: Insulation for CT circuits

(OP)
Thank you guys. I agree with both of you. My problem is I can't find a specification to fight my case. Any help there would be GREATLY appreciated.

RE: Insulation for CT circuits

Laws of physics.  Don't need no stinkin' specification.

RE: Insulation for CT circuits

CT neutral wire is a current carrying conductor and not a ground wire and should be an insulated wire. Standard practice, despite a single point ground for "safety" reason as per electrical code.

RE: Insulation for CT circuits

IEEE C57.12.13.3 Guide for Grounding of Instrument Transformer Secondary Circuits and
Cases

RE: Insulation for CT circuits


Steven — Shouldn't that standard be C57.13.3?
   
 

RE: Insulation for CT circuits

(OP)
Thank you Gentlemen,
I will check the above. Sometimes you have to put something in writing in front of people.
Your help is much appreciated.

RE: Insulation for CT circuits

Oops. Yes. Thanks Scott.

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