Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 17 replies
  • Subscribers 32 subscribers
  • Views 3272 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Main switch short circuit capacity.

wessex
Some guidance please.

Three phase TN-S supply from a private 800 kVA transformer. Distribution via a 240mm2 4 core SWA approx 20m in length from a transformer mounted feed pillar and protected by 315A fuses. At the intake position 100A BS 1361 type II fuses are fitted. I was looking to install a REC 4 main switch down stream from which would be three phase distribution by 10kA rated MCB's. My question is about the suitability of the main switch and its short circuit capacity at it's point of installation with regard to prospective fault current at this point which will be greater than 16kA or do the BS 1361 afford adequate protection for the switch ? Your thoughts please.
Parents
  • 0
    Thanks Mike for a very informative description for what is a complex subject. My values are simply calculated using the IET Electrical Installation design guide to give me a general idea as to what I'm dealing with. I think as you stated, it falls with manufacturer being able to confirm one way or the other.

    As a matter of interest and looking BS7671 Characteristics for the fuse, that for a 0.1 disconnection time that the fault clears at 1450 A which I take it is true up to 33kA. It's just the switch being able to with stand the energy let through during this period.


    Many thanks again.
Reply
  • 0
    Thanks Mike for a very informative description for what is a complex subject. My values are simply calculated using the IET Electrical Installation design guide to give me a general idea as to what I'm dealing with. I think as you stated, it falls with manufacturer being able to confirm one way or the other.

    As a matter of interest and looking BS7671 Characteristics for the fuse, that for a 0.1 disconnection time that the fault clears at 1450 A which I take it is true up to 33kA. It's just the switch being able to with stand the energy let through during this period.


    Many thanks again.
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines