I think it's an inch per kV - 10 %. So 138kV is around 10.35 ft phase-phase. 6' phase to ground.

do you have any reference, IEEE etc.

Thanks

You can get cable spacing standards from the National Electric Safety Code. I believe the 2008 or 2007 is the latest version. It is published by IEEE.

Hello Guest,

You may already have the answer but, just in case go to this page and join the IEEE.

I copied this which was on the search page of google, as I think you may need to be a IEEE Member to look further?

http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2FielD%2F4432333%2F4432334%2F04432335.pdf%3Farnumber%3D4432335&authDecision=-203

It will tell you the correct height above ground or the top of the building if you join and or ask a question on the IEEE site above

Correction Canada Electrical Code Table 30 (rule 36-108)

Minimum air gap Bus Supports and Rigid Conductors (outdoor)

120kV - 1350 mm

161kV - 1830 mm

Not center to center but from live parts

Phase to phase.