XLPE Cable Ampacity 1

[SAMBOY]

1) I just want to know if an XLPE cable on a ladder type cable tray inside a plant can be considered installed in "free air"? 2) Is there any difference in ampacity of a 250 mm sq XLPE Cable rated at 15kV when installed in 4160V system (consider indoor application)?
Thank you guys in advance.

 

[gordonl]

The cable gets the free air rating as long as the spacing is 1 cable diameter or more.

You should use the 15KV ampacity rating because the insulation provides thermal insulation to the copper whether it is electrically required or not.

As an aside, you have to watch yourself with XLPE in tray because it usually doesn't have sufficient fire rating without armour at 15KV. To get an unarmoured cable with suffcient fire rating for indoor tray, EPR is often required.