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
  • Replies 2 replies
  • Subscribers 32 subscribers
  • Views 982 views
  • Users 0 members are here
Options
You may also be interested in

Busbar system vs MCCB Panel board for LV distribution?

newbieuser

What are the pros and cons of using Bus bar chamber system vs MCCB panel board for LV distribution in a given system i.e TT? I know MCCBs are probably going to be more expensive and also easier to switch on after a fault. However, if there was a fault you would like an electrician to check out the faults and make sure that the fault doesn't appear again. Then it doesn't matter as if it was bs-88 fuses the electrician would come in check the fault and replace the bs-88 fuses after wards. I guess it also depends on the scale of the building or site.

For a given TT system, if the main incommer MCCB has earth leakage protection, will the outgoing MCCBs also need them?

Also talking about TT systems, would the fault never travel back to the main transformer or substation as who knows where the supply cables are coming from, hence needing RCDs?

Thanks.

  • 0

    Also talking about TT systems, would the fault never travel back to the main transformer or substation as who knows where the supply cables are coming from, hence needing RCDs?

    In TT the return path is via the ground = terra firma ground This is normally a relatively high resistance path compared to the copper of the live and neutral.
    In reality most of the resistance / voltage drop is in the near field of the electrodes (*)in the ground where the current is entering and leaveing - in the space between the current is spread over such a massive area that the resistance of any given slice of mud is quite modest.

    If the incoming earth protetion is set fine enough outbound submains may not need closer earth protection, but to avoid a one-out all-out problem, there are usually tiered levels of both trip current and time delay.

    Mike.

    (*) wiithin a volume of soil of dimensions comparable to the  electrode dimensions

  • 0

    Hi, When comparing a standard MCCB panel board with a busbar-switched fused arrangement, I have previously found the former to be less expensive when using fixed MCCBs (thermal and magnetic) However, the cost difference becomes significant when the client requires form 4 separation instead of form 1 separation.

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