Minimum separation Power and Control Cable

[cuky2000]

Does any one know the minimum distance from 138 kV power cables and control cable?
a)In the same ductbank
b) Cable tray

Any reference publication or case study could be helpful.

Thanks

 

[dpc]

138 kV or 13.8 kV??

Minimum in terms of code requirements or concerns about interference or ????

Not sure there are any code restrictions regarding duct bank, but we generally give something at 138 kV its own duct bank, manholes, etc.

If you're talking 13.8 kV, I've put them in the same duct bank with low voltage, but the problem occurs at the manholes and handholes because the high voltage cable must be isolated. If I ever do it again, I'll use separate manholes.

I would never put a 138 kV (or 13.8 kV) cable in the same cable tray as low voltage circuits, but if the 13.8 kV cable is in a metal conduit or CLX, then I don't think it's a Code violation.

 

[cheleng]

1. Rule 320B2 NESC ?
2. 392.6 (F) NEC ?

 

[peebee]

The BICSI OSP design manual states that NESC includes separation requirements for "safety and protection of telecommunications equipoment" are as follows:

Power:
3" concrete foreign conduit
4" masonry
12" well-tamped earth

I do not have a copy of NESC.

EIA/TIA just says that separation from power installation should be considered. So you've apparently already already met all applicable EIA/TIA requirements if that makes you feel any better.

Induction is dependant on both length and separation, so if you're trying to avoid electrical interference, then the longer the run the more separation that will be required. Shielding, metal conduit, balanced signals, twisted wires, fiber optics, etc., all all ways to reduce or eliminate interference and therefore reduce separation requirements.

Most engineering firms seem to spec a minimum 12" separation. For medium voltage, I will generally increase that to 24 or 26". No science or codes involved in any of those numbers so far as I know, nothing more than "that oughta do it" .....

NEC will not let you mix voltages unless it's all insulated the same or if the control is directly related to the power. I will often piggyback a small handhole for control next to each power manhole, and split a common power/ctrl ductbank into the hand/man hole pair.

Hope this helps.