600V Cable Spacing

[Flapjack]

I'm doing a project at a minesite for a contractor trailer complex. I'm tapping the 13.8kV line and routing via direct burial 4-1/C #2 (one of which is a ground) around the property to terminate on 13.8kv-120/240v single phase transformers, swapping phases at each transformer to balance the load. My question has to do with the spacing between the the two trenches with the 600V rated cables. I read in another thread on the forum that the engineer used 12" spacing, but I couldn't find anywhere in the code where it addressed cable spacing for low voltage.

I have the spacing at 24" currently, but didn't know if I could reduce it.

Any suggestions?

 

[petersonra]

I'm doing a project at a minesite for a contractor trailer complex. I'm tapping the 13.8kV line and routing via direct burial 4-1/C #2 (one of which is a ground) around the property to terminate on 13.8kv-120/240v single phase transformers, swapping phases at each transformer to balance the load. My question has to do with the spacing between the the two trenches with the 600V rated cables. I read in another thread on the forum that the engineer used 12" spacing, but I couldn't find anywhere in the code where it addressed cable spacing for low voltage.

I have the spacing at 24" currently, but didn't know if I could reduce it.

Any suggestions?

is any spacing at all actually required by the code? this might well be a design decision.

 

[Flapjack]

I was looking at Figure 310.60 for conductors rated between 2001 and 35000V. I guess it doesn't say that 24" spacing is required, but rather that it corresponds with the ampacity in the tables. 310.60(C)(2) addresses burial depth derating, but not width. If I spaced the trenches 12" apart I'm not sure how I could calculate the cable ampacity. Even if I did, I just realized it might not be the best idea now that I think about it. If I give a 5" cushion on the sides of the cables that leaves 2" between the trenches.

 

[dicklaxt]

I have had occasion over the years to be confronted with this .If I recall correctly the code,,,,,,,310.60 and subsequent references to which Detail to be used is in Tables 310.77 thru 310.82 which only covers much higher voltages.The spot that always got me in trouble was either client General Electrical Specification and if it had IEEE publications listed.IEEE does have some pretty stringent requirements on cable spacing or did.We often were given relief from IEEE usage,,,,,,by a client official notification in writing.



dick