Space charge measurements in power cables using a modified PEA system

This paper briefly describes the signal processing to determine the space charge and electric stress distributions using the newly developed pulsed electro-acoustic (PEA) system for use on power cables. Due to the coaxial geometry and the thick walled insulation, factors such as divergence, attenuation and dispersion of the propagated acoustic pressure wave can strongly influence the resultant measurements. This paper describes the development of a data processing technique, which allows for the factors previously mentioned, ensuring accurate measurements to be made. Most importantly, a method is presented to determine the electric stress profile across the insulation due to both the divergent applied field and consequence of trapped charge in the material. Some preliminary results of space charge measurements and the corresponding derived electric stress distributions in XLPE cables are also given