Investigation of Volcanic Ash on Transmission Facilities in the Pacific Northwest

The recent volcanic activities of Mt. St. Helens starting with a minor eruption on March 27, 1980, followed by major eruptions on May 18 and 25 and June 12, 1980, precipitated investigations of possible effects of volcanic ash fallout on the Pacific Northwest power system. This report discusses the pattern and impact of the fallout, characterizes the physical and chemical properties of the ash, presents results of laboratory flashover tests on ash contaminated insulators, and summarizes effects on power system performance so far.