Effect of Limiting Resistance on Distribution of Breakdown Positions under Lightning Impulse Voltage between Sphere-Plane Electrodes in Vacuum

The objective of this paper is to determine the effect of limiting resistance on the distribution of breakdown positions under lightning impulse voltage between sphere-plane electrodes in vacuum. In the experiments, a pair of sphere-plane electrodes was selected, with the material of Cu. The diameter of sphere electrode was 14 mm and the diameter of plane electrode was 40 mm. The plane electrode was grounded, and the sphere electrode was applied with a negative standard lightning impulse voltage or a positive standard lightning impulse voltage. Moreover, the breakdown position was determined by the illumination spots between the electrodes observed by a high-speed charge-coupled device video camera. The experimental results indicated that when the limiting resistance was
$0\ \Omega,\ 100\ \Omega$
and
$238\ \Omega$
, the probability of breakdown positions occurring in the “effective area” was 74%, 80% and 49% under negative lightning impulse voltage, while it was 78%, 88% and 51% under positive lightning impulse voltage. The effective area was the area covers 90% and above of the maximum electric field strength on cathode.