Flashovers of insulators under natural pollution and HVDC

In the Dossenwald test station, near Mannheim, an insulator testfield for more than 30 test objects was constructed, fed by a stiff d.c. voltage source and controlled by an automatic test program installation. The tested types, 7 post insulators (porcelain) and 3 suspension insulators (porcelain, glass, silicone rubber), two specimen of each type in parallel, were continuously under 400 kV d.c. voltage, positive polarity, for more than 8000 h. Flashovers during that time were analysed.