Avalanche risk along a 420 kv transmission line in Iceland.

Abstract

Two transmission lines between Fljótsdalur and Reyðarfjörður in northeast Iceland have been investigated concerning snow avalanche hazard. Given a specific level of probability of failure for both the lines less than approximately 6.5x10-4 per year, a total sum of 82 masts might be hit by avalanches. In addition some other masts might be influenced by avalanches passing under the lines between masts. For the 82 exposed masts, the avalanche impact forces are calculated due to the accepted risk level for the transmission lines and the forces are also calculated for the cables exposed to avalanches. For each mast, the risk level must be considerable lower than for the transmission lines, and this question has been treated statistically in this paper. In order to achieve the best possible basis for the calculations of the return periods of the avalanches, weather and snow analyses are performed for the surrounding weather observational stations. A model analysis is performed for some weather situations with a high avalanche risk in order to calculate the snow drift in the mountainous areas around the transmission lines.