Tornadoes and Power Lines

Twenty-five years ago today, July 31, 1987, one of the deadliest tornadoes ever to hit Canada ripped through Edmonton on “Black Friday”. The tornado cut a swath of damage 40km long and up to 1km wide, with winds up to 330km/hr, rendering it an F4 tornado on the Fujita scale (which goes up to F5). The tornado killed 27 people, injured about 300 people, destroyed more than 300 homes and caused more than $332 million (close to $600 million in 2012 dollars) in property damages. There were also millions of dollars in lost productivity due to power outages.

The tornado traveled right along multiple overhead TransAlta high voltage transmission lines for many kilometres. Transmission towers and lines were ripped down by the strong winds. The tornado caused between $6 million and $8 million (close to twice this amount in 2012 dollars) damage to TransAlta’s transmission infrastructure. A substation was destroyed as well as 49 240kV steel towers, 17 138kV steel towers and 134 138kV wooden structures.

A lawyer representing Gleniffer Lake landowners at the recent Alberta Utilities Commission hearing on the Western Alberta Transmission Line (WATL) pointed out the increased risk of tornadoes affecting overhead high voltage lines when the lines are twinned, as would be the case for about 211km along AltaLink’s preferred route for the WATL, and along several kilometres of AltaLink’s and EPCOR’s 500kV Heartland Transmission Line in the Edmonton Greenbelt.

Some data show that tornadoes are attracted to above ground high voltage transmission lines. This was discussed extensively in 1987, where the Edmonton tornado followed multiple overhead TransAlta high voltage transmission lines for many kilometres. The touchdown path of this deadly tornado includes some of the greenbelt where the Heartland line is currently being built in Edmonton.

As numerous tornadoes, twisters and funnel clouds have hit Alberta in recent weeks, the risk of future tornadoes, including their relationship with and impacts on overhead high voltage power lines, is very real. The more overhead transmission lines that are built, especially as massive as the 500kV lines currently proposed, the greater the risk.

See this link for more details on the negative impacts of tornadoes, ice storms and other inclement weather conditions on overhead high voltage transmission lines. Human deaths and injuries and major power outages could be averted if power lines were buried.

~ by RETA on July 31, 2012.

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