No abstract

Internationally comprehensive studies have been performed to analyze the effect of clean or contaminated snow and ice accretions on high voltage insulators. Our 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. 55 ice samplesareanalysedandthecontributionstotheconductivity from natural (sea salt) and man made ions (sulphur and nitrogen components) are found. It is shown that long range transported anthropogenic ions contributed to more than 50% of the conductivity in 33 of the 55 cases, and in 2 1 cases the contribution was more than 80%.

No abstract

In locations exposed to freezing conditions over the station service life, additional measures for selecting adequate station insulators at distribution and transmission voltage levels should be taken. This second part of the paper describes the selection process and mitigation options, based on the environmental parameters, as discussed in Part I. These include insulator size, shape, surface material, surface quality, electric field improvement, and orientation.

No abstract