Distance Between Cables

Which country code is to be followed?

Ambient conditions?

We are in India .The ambient temprature is from 45 to 48 deg cent.

Sriram

Refer to IS-1255

You may choose any spacing (greater than minimum required as specified in IS) & accordingly your derating factor changes. You may get lesser no. of runs requirement for higher spacing (if you are looking from ampacity perspective only). There are other aspects like voltage drop during normal running, during highest motor starting..

go to any cable manufacturer's website, you will get derating table.

Current rating furnished by manufacturers assumes "1 D" (D= Diameter of the cable) between two runs of cable, an ambient of 30 deg.C. You have consider derating due to both. For India, better consider ambient as 50 deg.C. If you decrease the distance between the cable, separate derating applicable. Consult with Cable catalogue / vendor.

It is better if you consider single core cable in tre-foil formation instead of three core cable. This saves cable cost as well as helps in better layout. Usually 3C cable is good upto 240 sq.mm. for easy laying. You may need 6 runs of 1C-630 sq.mm. / Ph only.

For bending radius, if you have single core cable then the radius= 20D and for three phas cable, radius=15D

Where D= overall diameter of the cable(including insulation and everything).

Ur free to lay Ur XLPE cable side by side with a slit gap of of 5mm or more to allow for air circulation or one suspended on top of another. The important thing is to allow for free air circulation that enhances heat dissipation.

For the bend, take any bend of appropriate internal radius that will not be injurious to the cable.

Dickson.

As per Clause 5.3 of IS 1255, the minimum bending radius of 11kV Multi core XLPE Cables is 15 D, where 'D' is the over all diameter of the cable.

Though the IS does not specify any spacing between cables laid horizontally on a cable tray, cable manufacturers do give appropriate de-rating factors, for carious cable spacings right from touching to many clearance distnaces. This is given both for horizontal spacing as well as vertical spacing. This has to be referred to and the cable to be de-rated accordingly.