Space charge measurement in water tree degraded XLPE cables

Space charge measurement was done with water tree degraded XLPE cables using the pulse electroacoustic method. A DC voltage was applied on the E-T type (inner semicon layer extruded-outer shield tape wound) XPLE cable in which vented water trees were generated from the outer shield. A space charge of the same polarity as that applied on the outer shield was accumulated in the vicinity of water tree region. This space charge remained stable after short-circuiting the sample. However, its decay was accelerated by applying an AC voltage. A good correlation was seen between the space charge intensity and the degree of water tree degradation