5 CONCLUSIONS
In this paper, the dynamic distribution of surface charge
was measured under variable voltage cycle. It is found that the
surface charge decay became much more serious when the
voltage cycle increased. Moreover, the decay time of surface
charge was measured. The decay rate of positive surface
charge was much faster than that of negative one, which was
attributed to the charge neutralization.
By applying the voltage with variable cycle, the effect of
surface charge decay on variation of partial discharge location
was investigated. As applied voltage cycle increased, due to
the surface charge decay, CRHEL before and after voltage
zero-crossing point decreased. Besides, because the surface
charges could accumulate at two interfaces in the usage of
VTD electrode, CRHEL under VTD electrode was larger than
that under VMD electrode. Regarding VMD electrode,
CRHEL for the case with negative discharges occurring in the
former half-cycle was larger than that with positive discharges
occurring in the former half-cycle, which was attributed to the
faster decay rate of positive surface charge than that of
negative one. However, there was almost no difference about
CRHEL for these two cases when VTD electrode was used.