AC withstand voltage characteristics of insulator string covered with snow

Abstract

This paper describes the results of investigation into the withstand voltage characteristics of UHV class tension insulator string covered with snow. AC withstand voltage tests were conducted in a testing room and at an exposure testing station constructed in heavy snow area. The withstand voltage of up to 10 m long tension insulator string covered with snow was almost proportional to gap length or insulator string. The relations between the withstand voltage and some nature of snow on the insulator string were investigated. And a design example of the length of the insulator string covered with snow was presented.

Modeling of AC arc inside wet snow =

“…The higher the conductivity, the higher the leakage current flowing through the snow. The leakage current also increases with the density and water content of the snow [7].…”

“…It should be noted that practically no exploratory research work is available on the mechanisms of flashover occurrence involving snow-covered insulators. However, it is well-established that several parameters, including snow type and density, snow amount and distribution and melted water conductivity are major parameters affecting the withstand voltage characteristics of snow-covered insulators [2,7]. It has also been established that the flashover performance of snowcovered insulators is affected by the height of snow and the ratio of the length of the snow cap to the insulator length [2,7].…”

“…However, it is well-established that several snow parameters, including type and density, amount, distribution and conductivity of the water melted form snow are the major parameters which affect the AC withstand voltage characteristics of an insulator assembly covered with dry snow [2,7]. The electric properties of snow which is accumulated on an energized insulator surface also depend on geometric factors and on the nature and quality of its contact with the electrodes.…”

“…In cold climates, the accumulation of glaze ice or wet snow on the outdoor insulators of power networks may considerably affect their electric performance, as well as cause structural damage. Particularly in heavy snowfall areas, wet snow and superimposed contamination can be at the origin of corona discharges and partial arc initiation, leading under certain conditions to insulator flashover and consequent power outages [2,[4][5][6][7]. Such problems generally appear on tension insulator assemblies, and rarely on suspension assemblies, since tension assemblies are more prone to large amounts of snow accumulation [2].…”

“…In contrast to ice-covered insulators, few studies have been carried out on the flashover performance of snow-covered insulators [2,[4][5][6][7]17,18].…”