Abstract
Capacitance C and dielectric dissipation factor tan δ of a water-treed XLPE sheet sample have been measured under the application of 100 V or 1 kV at 60 Hz. The values of C and tan δ at 1 kV are much larger than those at 100 V. The value of tan δ gradually decreases with the exposure time to the voltage of 1 kV. On the other hand, C is almost constant for the exposure time. The results have been discussed based on a model where filling of water into channels interconnecting voids is taken into account. It has been found that the increase of C and tan δ is caused by the growth of water-filled channel region by the application of voltage. The gradual decrease in tan δ with the exposure time is explained by an increase in the conductivity of water-filled channel region through which the relaxation time shifts to higher frequencies.
