Hello Gents,

I work in a project where an emergency diesel generator set is used to supply critical loads in case of normal source failure. As this generator set is located outside the building where the cable route shall cross a main road and as per the client request, the cables shall be laid inside a concrete encased duct bank along the whole route. My question is, Is there an installation method in IEC/BS for such installation ( concrete encased duct bank buried in ground) because I have found is ducts buried in ground directly without concrete or cables laid in in floor concrete trough or in building void. I also thought about calculating the total derating factor with conventional ways but I was a litte bit stuck with how to calculate the soil thermal resistivity factor. Also the grouping factor, as the cables will be laid in 2 or three layers.

Thanks in advance for your help