Measurement of space charge distribution in XLPE cables under AC stress

In this paper we present a method for the determination of the space charge distribution, and hence the electric field distribution, in XLPE cables under an AC stress. The instrument has been developed from the well known pressure wave propagation (PWP) techniques, which have been successfully used in the study of materials under DC stress. Analysis demonstrates a high degree of confidence in the data. Data are reported, which show that statistically significant, at the 87% level, modification of the electric field due to the space charge occurs at the interfaces (in this case the semi conducting screens of the cable). The method described here will be useful for the study of high voltage AC insulation materials and structures. The technique is of particular interest for the nondestructive study of insulation ageing under AC electrification