power and fiber-optic in same bank? 2

[Senselessticker]

Hey folks,

Does anyone know of any code or technical reasons why 13.8kV feeders and fiber-optic cable cannot be run in the same underground duct bank (assuming of course that each is in different conduits and the duct bank is installed per NEC 310)? Anyone have suggestions as to why such is scheme is a "bad idea"?

Many thanks for any reponse.

 

[dpc]

The main problem is accessing/maintaining the fibers later if there is a dig-in or other problems. There are no technical concerns. If this is an industrial facility where all maintenance is the responsibility of one entity, I wouldn't have too many concerns, but I would think about ways of limiting need to expose workers to 15 kV cable when working on fiber.

On large facilities, it is sometimes a good idea to provide separate duct bank systems, including manholes, for medium-voltage cables and keep them separated from the rest of the cables.

 

[itsmoked]

As DPC sez, if the 15kV fries or explodes somewhere, are you going to take a big revenue hit with severed fiber? It could happen during the fault or repair of the fault.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dpc]

Keith is right, but I guess my main concern is the problem of having fiber splicer going into manhole or duct bank with 15 kV circuits nearby. This may not even be allowed in some jurisdictions.

When the telco or cable company hangs fiber on a power pole, they have to stay a certain distance below the high voltage lines so that their people can do maintenance. If the fiber is within the zone of the high voltage conductors, you have to have a lineman or someone with high voltage training to do the work. There could be similar issues in a duct bank configuration.

 

[Dumbo2929]

Use common ductbank, but separate manholes for power and fiber optic.

 

[Senselessticker]

Thanks for all the post folks. Due to the fact that each will be maintained by different entities...I'm going to recommend each bank be seperate. Originally, I had planning on sharing bank with seperate manholes, but I'm afraid its going to turn into the infamous "who pays for what" issue.