Long range transported pollutants and conductivity of atmospheric ice on insulators

Internationally comprehensive studies were performed to analyze the effect of clean or contaminated snow and ice accretions on high-voltage insulators. The authors´ experience with transmission lines in inland mountainous areas reveals a substantial contribution of pollution from anthropogenic (man-made) contaminants. One observation of a flashover case with thin rime ice layers in contrast to the many cases with thicker accretions without similar failures led to the question of the role of the ion content of the ice. Fifty-five ice samples were analyzed. The contributions to the conductivity from natural (sea salt) and man made ions (sulphur and nitrogen components) are given. It is shown that long-range transported anthropogenic ions contribute to more than 50% of the conductivity in 33 of the 55 cases. In 21 cases, the contribution was more than 80%.<>