current division - 3 sets of conductors

[magoo2]

I saw an earlier post on this topic, but it involved 2 sets of conductors. This one involves 3 sets and comes from an application at one of our power stations.

An installation is planned for a single circuit with 3 sets of 8 kV shielded cable on non-magnetic cable trays. How can we arrange the 9 conductors such that the current division is reasonably equal?

The conductors have a diameter of about 2 inches and will be installed flat with no stacking. The cable tray is 36 inches wide. Each circuit carries 3000 A so each conductor will have approximately 1000 A.

I read that we should avoid A A A B B B C C C. It seems like A B C A B C A B C would be better, but what is the best arrangement?

 

[mgtrp]

ABC-CBA-ABC if they have to be laid flat, but trefoil would be better again.

 

[dpc]

How long is the circuit? The shorter the run, the more problems you will have.

Some type of ABC ABC ABC or ABC CBA ABC grouping should be used, but you also want to try to keep the cable lengths as equal as possible.

This might be a good application for metal-clad (MC) cable such as Okonite C-L-X.