Dielectric properties of water-treed XLPE insulation

Attention has been recently been turned to different methods for measurement of dielectric response and charge storage phenomena to develop sensitive non destructive tools for XLPE cable insulation. Such measurements are usually performed as "frequency domain" measurements of the capacitance and loss factor, or as "time domain" measurements of the depolarisation current and return voltage. The aim of this work has been to investigate the effect water trees may have on the dielectric response of XLPE cable insulation. This paper describes results of the above mentioned measurements on XLPE Rogowski type test objects, which were subjected to laboratory water tree ageing.