a charge spot and a
corresponding one with higher density at the same area were
Figure 1. Experimental setup.
2242 C. Pan et al.: The Effect of Surface Charge Decay on the Variation of Partial Discharge Location
respectively observed at t=1400 ms and t=1500 ms, which
were indicated by red circles in Figure 4b. The other group
observed at t =1500 ms and t=1600 ms was also indicated. As
for the negative discharges, it is inferred that the subsequent
ones may occur at the sites where the homo-discharges had
taken place. But this phenomenon was not observed for the
positive discharges. There were no residual charges after the
first and second voltage reversal, which showed that the
surface charge decay became much obvious with the increase
of voltage cycle.