Recovery voltage response of XLPE cables based on polarisation and depolarisation current measurements

Abstract

Recovery voltage measurement (RVM) is one of the common diagnostic techniques for the condition assessment of electrical insulation. The method has been used to examine the dielectric response, especially deterioration or depolymerisation of the polymeric insulation under ageing condition. In this study, a mathematical model of the RVM measurement based on the Debye equivalent circuit is elucidated. The methodology for determining the modelling parameters from the polarisation and depolarisation currents (PDCs) is described. For the experiments, two short-sections of service-aged 11-kV cross-linked polyethylene insulated (XLPE) cable are used, and the PDC of these test specimens are measured. Here, the model adapted comprises three R-C relaxation branches, where each branch represents a polarisation type. From the derived model, the peak of the RV can be predicted and are constructed over a wide range of charging time. Bode plots of the test objects are also presented with the magnitude and phase response which assist in understanding the RVM response.