What impact would lower rH and quite high altitudes have on hazard distances and arc flash hazards in general? We are working on a 23 kV transmission system at 5000 meters in the Andes Mountains.

At higher altitudes the voltage stress will definetly cause the air to electrically break down sooner at a lower voltage level(approx.2-10%).(google for these actual correction values/formula)

Thanks for the info. I have been Googling around but an having trouble finding definitive info as to how much impact it might have. Will keep looking.

Try this link:


http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F6616%2F17682%2F00816711.pdf%3Farnumber%3D816711&authDecision=-203


Study of the breakdown voltage of the air in high altitudes, applying lightning impulses (1.2/50 μs) under conditions of controlled humidity and temperature


Note:You will need to be a I.E.E.E. member

I will try to get the sphere gap graphs for you.

Here is a link to these spark gap correction factors for humidity and altitude(it is the 4th one down on this list).Enjoy )


http://www.google.ca/search?sourceid=navclient&ie=UTF-8&rlz=1T4RNWE_enCA309CA309&q=sphere+gaps+correction+factors