Time-resolved space charge observation in water-treed XLPE

Using an improved PEA system which is capable of measuring space charge distribution at minimum intervals of 25 /spl mu/s, the charge distribution inside water-treed polyethylene was examined. When a power-frequency ac voltage (50 Hz) was applied, charges were observed around the tip of water trees and on the electrode at the non-degraded side, but not on the electrode at the water-treed side. This means that the conductivity of water trees is high. When the frequency of applied voltage was as high as 2 kHz, charges became observable also on the electrode at the water-treed side. This implies that the conductivity of water trees is slightly low at this frequency.