Underground cable ducts to be exposed in the air 1

[FuzzyQ]

Hi there,

There are a set of cables in PVC ducts with concrete casing running underground up to a hill. A field work is going on to dig into the soil underneath the cable ducts and move the soil out. Eventually, the cable ducts will be exposed to air but somehow supported above ground.

As I know the cables are 13kV and paper insulated.

Does any one know that in this case, to be safe and keep the cable fuctional,any considerations to be in place? the 13kV clearance will not allow people to work too close to the ducts when the cables are on line, right? - like shovelling around it? The temperature rise when the cables are exposed under the sunshine will cause possible aging/other problems?

Many thanks!!

 

[itsmoked]

How long a run are you considering being undermined?

Why would the cables be exposed to sunlight? Won't they still be enclosed under the ducts top too?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[wareagle]

Quote "Does any one know that in this case, to be safe and keep the cable fuctional,any considerations to be in place? the 13kV clearance will not allow people to work too close to the ducts when the cables are on line, right? - like shovelling around it?"
As long as the cables are in the duct bank, I would think one could work the area. They can not get to the cables can they?

 

[FuzzyQ]

Thanks for the replys.

The cables are about 40 meters long. They are going to dig into the hill and embed some pipelines underneath. During the construction time (about a year), the cable ducts will have to be left on the ground,while they were originally designed underground.

Yes.The duct bank and concrete casing will still be kept.

 

[EEJaime]

If the concrete duct bank is exposed to air instead of buried, the temperature rise might be slightly altered but not necessarily in a negative way. As long as the conduit bank is rigidly supported, there should be no problem.

One word of caution, we had a very similar installation and we specifically warned the contractor to hand excavate to expose the exact concrete duct bank dimensions and configuration, but instead he took a "shortcut" and tried to dig underneath the conduit bank with a backhoe. Well the original installation was not as specified and the conduit runs were only concrete "capped". The backhoe pulled out two conduits, ensnared the conductors, pulled them out of their terminations in a University Union building 12.47kV substation and destroyed the substation as well as darkened a large portion of the University for a week as the lines were re-routed.

Regards