Abstract:
This research studies the characteristics of breakdown voltages under AC voltage. The study was
carried out into three parts. The first part was the investigation of the influence of conducting
floating object on the affected breakdown voltage in rod-plane gap. From experimental results, it can
be seen that the main factors affecting the breakdown voltage were the shape of floating object, the
size of floating object and the object position. The second part was to study the effect ofhumidity on
breakdown voltage of 12.5 em diameter standard sphere gaps. From experimental results, when
humidity was increased, the breakdown voltage increased. Using the humidity correction factor, as
given in IEC 60052 standard for testing with AC voltage at humidity range not exceeding 16 glm3
was still valid. The final part was to study the wave shape of breakdown voltage of a sphere-sphere
gap and a rod-plane gap by investigating phase angle and polarity of breakdown voltage wave shape.
From experimental results, when gap distance was increased, phase angle increased. In spheresphere
gap, the breakdown occurred on both positive and negative cycles but it occurred on positive
cycle only in rod-plane gap.