×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

CT Location on Outgoing MV Feeder Breaker

CT Location on Outgoing MV Feeder Breaker

CT Location on Outgoing MV Feeder Breaker

(OP)
ponder In MV metal-clad switchgear, are the CT's for a 50/51 relay on an outgoing feeder breaker usually located on the line side or load side of the feeder breaker? What is the most common practice and why?

RE: CT Location on Outgoing MV Feeder Breaker

CTs should be located, if at all possible, such that the circuit breaker is in the zone of protection.  So, for a feeder position you would always want your CTs on the bus side of the breaker.

RE: CT Location on Outgoing MV Feeder Breaker

Hi.
David, I think it was some missunderstanding.
As fa5r, as I know, CT location in MV metal-clad SWG is always bottom section, line side, after ES.
Best Regards.
Slava

RE: CT Location on Outgoing MV Feeder Breaker

At least in ANSI MV metal-clad gear there is room for two CTs per bushing of the breaker, so two sets on the bus side and two sets on the line side.  Usually not all are provided.

RE: CT Location on Outgoing MV Feeder Breaker

Thanks David.
Good to know,
Best Regards.
Slava

RE: CT Location on Outgoing MV Feeder Breaker

Meant to say "... metal-clad gear there is usually room for two CTs..."  There are always exceptions to everything.

RE: CT Location on Outgoing MV Feeder Breaker

As to why on the bus side; Two main reasons:

1. Because it is very convenient to install CTs around the insulating bushings which are already there to accept breaker stabs. This even allows low voltage (600V)CTs to be used as the insulation to the bus is provided by the bushings.

2. Usually the load sides will be cables and it is very inconvenient to install CTs around them, plus you end up with a portion of the cable and breaker load terminals outside the protection zone. That is not desirable.

 

RE: CT Location on Outgoing MV Feeder Breaker

From a protections point of view, we put the CT's on the bus side so we can overlap protection zones.  If the CT's protecting the line were on the line side, and the CT's protecting the bus were on the bus side, than a fault in the breaker wouldn't be detected.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources