×
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

Dual Interrupting Ratings of 115kV Mark IV Circuit Switchers

Dual Interrupting Ratings of 115kV Mark IV Circuit Switchers

Dual Interrupting Ratings of 115kV Mark IV Circuit Switchers

(OP)
A couple questions for Substation design folks, but first some background: I am performing the P&C design for a brownfield 115/12.47kV Sub (in fact, it is a complete redesign, all existing relays are getting scrapped). The 115kV part of the station has: two busses using a S&C Mark IV as a tie; Bus 1 connects to a Utility Line (protected by a breaker), an outgoing line (protected by a breaker), and a 115/12.47kV transformer (protected on the high side by another Mark IV, and a breaker on the low side); Bus 2 connects to another Utility and another Outgoing Line (both protected by breakers). Among the P&C schemes being implemented: the transformer has a differential, and both Bus 1&2 are treated as a single bus and are protected by the same bus differential scheme.

The Mark IV's have a 3000/7000 A interrupting rating. The 7000 A interrupting rating, according to available S&C literature, is only effective when "the total connected length of all lines on the source side of the Circuit-Switcher is NOT less than 15 miles," otherwise the 3000 A rating should be used. According to some limited fault duty data we have received, the available fault current from Utility is about 1300 MVA (~6300A per phase) on a 3 phase fault and from any one line the phase current is above the 3000 A level on a 3 phase fault. Now the questions.

1.) What electrical phenomena contribute to these duel interrupting ratings on the Mark IV CI's? (My research has revealed several possible contributions, I'm hoping a knowledgeable person can pare that down)

2.) If the cumalitive source side line distance is not known, is their another method to determine which rating should be used for implementation of the Mark IV's?

Thanks!

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