The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

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 12 replies
  • Subscribers 31 subscribers
  • Views 4108 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

Parallel TX Tails - Neutral Arrangement

MW (aka Inrush - for those who remember me!)
So this is the new look forum... Impressive!


I have a question regarding AWA transformer tails. I'm looking at a situation where I need three parallel cables per phase.


My question is related to the neutral conductor arrangement. The neutrals need to be installed between the inter-group trefoils in order to maintain equal current sharing. Therefore, I can either have two neutral conductors of slightly larger CSA to give approx. the same CSA as the overall parallel phase conductors. Or, alternatively, three neutrals of the same CSA as the phase conductors split (oddly) between the two groups.


What convention is normally adopted in this situation?


Many thanks in advance.
Parents
  • 0
    this depends on the mechanics, but if the run is long and the desire is to avoid stray magnetic fields, and so keep the inductive volt drop down, it is common to have L1 L2 L3 in each bundle, and then however many such bundles you need can be separated, and neutrals between. This assumes neutral current is less than phase currents, but if for some reason it is not expected to be you can have 4 cables per bundle (then strictly not trefoil , more of a 4 leaf clover..).

    The key thing is the magnetic situation wants you to keep flow and return currents close, so the cancellation is good and the fields roll of with distance as fast as possible, but cable size and thermal considerations want spacing for cooling.
Reply
  • 0
    this depends on the mechanics, but if the run is long and the desire is to avoid stray magnetic fields, and so keep the inductive volt drop down, it is common to have L1 L2 L3 in each bundle, and then however many such bundles you need can be separated, and neutrals between. This assumes neutral current is less than phase currents, but if for some reason it is not expected to be you can have 4 cables per bundle (then strictly not trefoil , more of a 4 leaf clover..).

    The key thing is the magnetic situation wants you to keep flow and return currents close, so the cancellation is good and the fields roll of with distance as fast as possible, but cable size and thermal considerations want spacing for cooling.
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