LONG TERM BEHAVIOUR OF OUTDOOR TERMINATIONS MADE OF SIR

More and more cable accessories for medium voltage are made of SiR (Silicone rubber) and in special of LSR (liquid silicone rubber). The terminations show some great advantages - like wide range application, excellent ozone and UV-resistance and retention of hydrophobicity – compared to heat shrink terminations. Medium voltage terminations made of liquid silicone rubber with integrated refractive stress control element were tested in the outdoor test field at the University of Applied Science Zittau/Gorlitz for 5,5 years. The terminations had a rated voltage of 12/20(24) kV. During the whole test a voltage of 18 kV was applied to the terminations and also the condition of the terminations was checked visually and flashover or breakdowns were recorded. After this long term test the overall condition of the terminations was checked and compared to the ratings given by new terminations to know if aging occurred during the tests. These condition tests after 5,5 years consists of measurement of the contamination of the pollution layers, measurement of the hydrophobic class along the termination. Furthermore voltage test – AC-withstand voltage, lightning impulse tests and partial discharge test were made. After all these tests the terminations and the stress control element were dismantled and the edge of the outer semi conductive layer of the cable was visually checked if some electrical aging traces would have occurred during the tests. From these results some recommendations for maintenance and design requirements for the creepage distance can be given.