Experimental Investigation of Space Charge in XLPE Cable Using Dust Figure

In order to use XLPE in dc cable insulation, it isnecessary to solve various problems about space chargein XLPE insulation. The cross-section dust figure (CDF)is introduced as a new method to study a space chargedistribution in solid insulations and new results arepresented. The XLPE insulation layer is mostly occupiedby positive and negative hetero-charges rather than byhomo-charges, and these hetero-charges cause the dcinsulation characteristics to differ from those of oilfilled cables. The space charge distribution varies ina complicated way as a function of temperature, voltageand voltage application time. We further found thatalthough charges injected from an electrode form a homocharge layer, most of them spread toward the oppositeelectrode and form a hetero-charge layer. The distributionobtained by the CDF is consistent with otherexperimental results on dc XLPE cable.