Electrical cable Overheating

[Roshan]

I hava a 185sqmm SWA/XLPE underground cable supplying 240kW(Peak) at 400v. Ambient temp. around 28 c .

• What is considered the upper temperature limit the cable can heat upto?
  
• What is the standard (theoretical calculation) available to get the overheating limit?

 

[Wilko]

Hi - you can ask manufacturer to confirm, but max conductor temperature of 90 C may be possible, depending on the installation terminations also being rated to that temperature. Otherwise I use 70 C.
Is 28 C the ambient temperature of the air or the ground?

 

[marconi]

http://www.aeicables.co.uk/literature/CurrentRatings.pdf

See page 8/11 and Reference method D.

 

[FatAlan]

Hi Roshan. Welcome to the forum. Do you guys in Sri Lanka have to add extra armour for elephant proofing?

 

[TJ Anderson]

How much current are you pulling through that cable out of interest?


As already said, 90C for Thermosetting cable but terminations will likely only be rated for 70C. Where your terminations are will be subject to different rating factors though. E.g. you could have cable in buried ductwork in excess of 70C and termination points above ground at less than 70C which would be fine. Also, how deep is it buried and is it grouped with any other cables?

 

[Rpa07]

Sounds like a college question - not sure if he’d ask on a forum relating to a 185mm, that’s a big booger.