IMPULSE BREAKDOWN OF INSULATORS AND AIR GAPS OF SIMILAR ELECTRODE CONFIGURATIONS - EFFECTS OF TEMPERATURE

Comparative measurements are reported on the breakdown, under lightnin g and switching impulses, of a concentric electrode arrangement in whi ch the inter-electrode space is spanned either by an insulator surface or by air. Temperature in the system has been varied in the range 10 < T < 100 degrees C. The variation of positive and negative 50% flasho ver voltage, and the times to breakdown at 100% flashover, are present ed for each temperature level tested. Flashover voltages, analyzed as a function of relative air density delta, show a variation of the form delta(m), where 0.8 < m < 1.0 for positive polarity and m > 1.0 for n egative polarity at the highly stressed electrode. Variations are the same, in the presence or absence of the insulator surface, but absolut e positive flashover voltages are lower across the surface, than in ai r, while negative flashover voltages are higher. Times to breakdown de crease with increasing temperature.