The objective of the present study is to propose a practical laboratory method to simulate wet atmospheric ice accretion on H.V. insulators. The method developed is based on first accumulating a low density soft rime on energized insulators and then to heat the produced deposits. The liquid water fraction of the ice accretion is then determined using a centrifuge. This approach makes it possible to determine the performance of insulators under wet-snow-like conditions with relatively simple, low cost equipment.
Over the last few years, several electrical power failures due to ice and wet snow accretion occurred on Hydro-Quebec overhead power lines (Drapeau. 1991: Hydro-Quebec, 1995). These power outages were due, in part, to the occurrence of flashovers on ice and snow covered insulators. In order to gain a consistent understanding of the roles of ice and snow in insulator flashover, a research program was established at the University of Quebec in Chicoutimi, in collaboration with Hydro-Quebec. The first stage of the research work involved ice accumulation on insulators. A part of the study, concerning the determination of atmospheric conditions favoring the accretion of the most severe type of ice, i.e. the type of ice associated with the highest probability of flashover, was reported in previous papers (Farzaneh et al, 1995; Farzaneh and Drapeau, 1995). The second stage of the research, which is the subject of the present paper, deals with a practical laboratory simulation of wet icing accretion on H.V. insulators. The best example of such accretions is wet snow. This form of atmospheric wet icing is said to form when snow flakes, 1 to 5 mm in diameter, coalesce partially before touching the ground, if they come into contact with a positive temperature up to + 4°C.