Power line sag/tension calcs 2

[sabrepoint]

Hello All

From time to time I have done calcs to determine the changes in conductor tension under differing wind loads and temperatures. But for a new job I'm starting, I need to consider the effects on sag and tension when lines are subjected to radial ice, of which I have no experience (I live in a warm area). I've performed manually calcs using an old (1940s) British text as basis ... answers seem to be reasonable, but ideally I'd like them checked.

Might be a bit cheeky here, but would it be possible for someone to run the required calcs (including ice) through a line design program to check my results if I provide all the details for a base set of conditions?

Thanks for any response.
Graeme

 

[jbartos]

Comment: Often, power lines are down due to the larger accumulation of ice in form of icicles.
Visit

http://www.timesfreepress.com/2000/JAN/24JAN00/NEWS0424JAN.html

for:
In Georgia, more than 10,000 residents in Catoosa County and more than 1,000 in Walker County awoke to cold and dark homes due to power outages, as iced-over trees fell onto already-sagging power lines drooping with icicles.

http://www.americanlifelinesalliance.org/pdf/IceStormSummaries.pdf

for: Storm on 1/1/1952 when:
Ice on wires 2" in diameter with 6" long icicles in MO

 

[alehman]

You are most correct jbartos. ANSI C2 (NESC) most certainly does not account for the worst cases.

Another consideration: I live in the midwestern U.S. where I have personally experienced several extended outages due to ice storms. The last one was in December of 2001, when electicity at my home was off for six days. The vast majority of the damage is normally caused by trees and limbs burdened with ice which break and fall on lines (and houses and cars). The fireworks from arcing lines and damage in general was quite amazing and took several months to clean up. Thousands of trees were destroyed. One utiltiy pole in my back yard was broken in two when a large tree limb fell on a line it supported.

As a side note, my company recently completed a study for several communities in my area on the costs and possible benefits of relocating overhead lines underground. Needless to say the costs would be rather substantial.