Medium Voltage Cable installation into Concrete Trench 2

[veegrid]

Why cannot medium voltage power cable (5kV-35kV) run into concrete trench? I guess safety issue, de-rating of cable ampacity, .etc? What's thought , direction here?

 

[cuky2000]

There are no technical reasons to preclude the MV cables in a concrete trench. Cost need to be evaluated.


Here is a Link with an example of power cable in a concrete trench.

 

[7anoter4]

One of the problems it is indeed ampacity calculation.
First, the concrete trench may be open, covered, ventilated or not ,filled [usually sand filled] and the running cables may be single core, multicore, single layer or multi layers. NEC recognizes -for 5-35 kV-duct banks and directly buried -except in open air or in tray or conduit in air. The same IEEE 835.The same Neher and McGrath- the basic theory.
In IEC 60287-2-1 chpt. 2.2.6 Cables in buried troughs
2.2.6.1 Buried troughs filled with sand
2.2.6.2 Unfilled troughs of any type, with the top flush with the soil surface and exposed to free air
There are many other publications which present methods to calculate ventilated and non-ventilated buried trough air -for instance Power Cables and Their Application, by Lothar Heinhold [part 2 chpt.18]

 

[PSEng01]

If the cables are to be installed in earthquake prone area then the movement of the concrete during a seismic event may need to be considered - probably more applicable for cables installed in ducts directly encased within concrete.