Accumulation du verglas sur les nouveaux types d´isolateurs sous haute tension

Four synthetic rod insulators and two classical cap stem insulators were subjected to the simultaneous effects of freezing rain and high tension. The thickness of ice on the insulators and the type of formation is measured at regular intervals. The leakage current is shown as a function of the time elapsed before the radial thickness of ice accumulated on a pilot conductor reaches 1 3/4″. This is the limit of ice load proposed for Hydro-Quebec´s future 735 kV lines. With a view to cutting down on accumulation time in this first section of research programme on ice-covered insulators, the tests were performed at a temperature of − 10°C. The results show that the weight and thickness of accumulated ice are related to the geometry of the insulator. The leakage current increases with the thickness of ice accumulated. Because of the small distances between their skirts, the synthetic insulators favour the formation of lumps of ice which create considerable peaking in the discharge current, liable to cause flashover when the accumulation becomes considerable.