Ice on transmission lines.
Ice on transmission lines.
(OP)
They are airing a "perfect disaster" show on the boob-tube that is based on an ice storm in the Montreal area. They are discussing the results of a major ice storm. They are focusing on the power transmission lines, 8? that serve the city. As they each get too much ice on the lines, eventually a line will snap. The sudden shock causes the towers to all fail. :(
My question is if a transmission line design has to take into consideration the I^2R losses to prevent over temperature lines from over sagging why don't they just crank up the current to keep the lines above freezing? Even if Montreal can't use the power can't they import then export it out the other side or play some other game?
My question is if a transmission line design has to take into consideration the I^2R losses to prevent over temperature lines from over sagging why don't they just crank up the current to keep the lines above freezing? Even if Montreal can't use the power can't they import then export it out the other side or play some other game?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com






RE: Ice on transmission lines.
In the Antarctic I have seen ice build up on wire radio antennas as thick as a man's arm. That becomes extremely heavy over a long span, and it certainly does tend to break things.
RE: Ice on transmission lines.
I remember an ice storm bringing down a major transmission line in western Canada years ago. The line was 800 or 900 miles long. The area affected by the storm was a valley about 90 miles long and the hardest hit section was the eastern half of the valley. The capacity of the line was 2000 amps at 500,000 volts. I don't think that heating was an option.
respectfully
RE: Ice on transmission lines.
Thanks for the thoughts.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Ice on transmission lines.
High winds are not usually a problem with ice loading because high winds blow the water off the conductors and prevent ice from building up.
RE: Ice on transmission lines.
http://www
There has also been talk about installing power electronics to circulate DC currents.
RE: Ice on transmission lines.
Thanks for the link. Very imformative.
respectfully
RE: Ice on transmission lines.
Ice-laden trees falling on lines causes the vast majority of the damage in these storms. It's hard to design for that.
RE: Ice on transmission lines.
rmw
RE: Ice on transmission lines.
RE: Ice on transmission lines.
Then, the upper air was warmed up to above freezing, while the air near the ground was below freezing. The low-pressure rain-bearing clouds were stalled for a week by neighboring high-pressure zones, and a LOT of rain fell in a short period. As the rain passed down through the cold air, it was chilled, and some experts say that is was even supercooled (ie. below 0°C yet still in liquid phase).
So this 'rain' made contact with cold objects, and stuck, freezing instantly. There was enough 'cold' in the ground to provide for lots of freezing. The accumulation rate was very high ( as much as 100mm+ of ice in 3-4 days).
It would have taken a lot of heat to stay ahead of the problem. Even if you do, a 100mm 'shell' on the structures weighs a lot more than the designers allowed for. The minimum 'standard' was to allow for 12mm (0.5inches) of ice accumulation, and most structures were designed for 25mm ( a fourfold weight safety factor). In my area, the ice built up to over 75mm, which is 36 times more ice than the minimum standard. Even without the ice on the lines, some structures were toast.
RE: Ice on transmission lines.
I live near Montreal and I once visited the IREQ (an institute
where Hydro-Quebec does some research) and they work really hard on the subject. Although de-icing the lines with helicopters does the job, it is somewhat dicey...
They (H-Q) finished a new line 2 years ago. It seems the only solution they come up with is puting a bigger, beaffer tower
between a series of 4-5 normal ones to stop the cascading
mouvment...
RE: Ice on transmission lines.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com