220KV EHV XLPE Underground Cable suitability for High Altitude (>1000m) ?

[Rejeckted]

Dear friends,

Is there any relevant IEC or other standards clause that discusses the suitability of EHV Cables for high altitude?

Laying Conditions: Underground
Altitude: > 1000 m
Cable: XLPE Insulated 220 KV, 1200 sq.mm - Unarmored Cu Cable (2XLyC2Y)- which is Copper Conductor, XLPE Insulated, Lead Sheathed, Copper Screen and HDPE O/SH.

Kindly share any relevant clause or current de-rating to be considered for the same. My research tells me that air gets less dense and hence thermal conductivity takes a hit. Moreover the dielectric breakdown strength of air reduces. But, due to the altitude the temperature is sort of less at hill stations.

Thanks
Chris

 

[cuky2000]

Unlike other electrical components that depend on the air as insulating media, XLPE cable clearance only depends on the solid dielectric insulation characteristics. HV XPLE cable can be physically in contact with the earth and even touching the cables. Therefore, the altitude will have a negligible effect on the dielectric properties of the XLPE insulation.

On the other hand, depending on the installation environment of the cable, ampacity ratings may need to be adjusted or derated to control heat flow. The enclose link shows a typical derating factor. Notice that for practical power system, the cable ampacity derating will be reduced around 5% for 10,000 ft (~3,000 m) altitude. Also for final ampacity, check the temperature at at the site.