Electric Cable Duct

[GIMAC]

Hi,
New member her. Hello to everyone, looking forward to receiving and giving hlepful tips.

Does anyone have any experience or information on the effects of cable duct made from different materials, or of diferent type, on the derating of the cable. Normally it's PVC duct, or solid wall PE duct, but I have now come across a twinwall (Corrugated) duct, which has air within its walls. Was wondering if the this extra oayer of air will increase the insulation and derate the cable.

/GIMAC

 

[7anoter4]

The corrugated polyethylene pipe usually it is employed for directly buried cable conduit and not for concrete embedded ducts.
However, I don't think the conduit shape or size here does it matter.For instance:
from IEC 60287-2-1 Part 2-1:Thermal resistance –Calculation of thermal resistance
ch.2.2.7.1 Thermal resistance between cable and duct (or pipe) T4′:
T4'=U/(1+ 0,1(V+ Y*Θ)*De)
Where U,V,Y are factors depending on the duct material and De it is the cable diameter. It is not any reference to inner conduit diameter.
The outside part is filled entirely with concrete.

 

[GIMAC]

Hi
It has to have an effect surely. The twinwall has trapped air within it's corrugations, and we know that this will prevent the heat from disapating, more so than if it was a solid wall pipe. I'd say that equation was not designed for twinwall pipe.
G

 

[GIMAC]

PS Not all cable duct is surrounded by concrete, it could be sand / dirt, or as dug material.
G