Modelling of Insulations by the Results of Voltage Response Measurement

Summary

The diagnostics of general condition of the insulation of high voltage equipment is mainly based on the measurement of dielectric properties of the insulation. The main idea is that from the changing of dielectric parameters the ageing process can be followed. It is well known that the dielectric relaxation processes of an insulation can be modelled by a circuit of Debye elements, however the determination of the parameters of the R - C branches is not a simple task, because most of the measurement techniques cannot separate the conductive and the polarisation processes of the insulation. The voltage response method has been developed for the separate investigation of conductive and polarisation processes and by further development of this method the polarisation spectrum of the insulation can be studied more precisely. This paper introduces a new iteration method, which determines the parameters of polarisation processes from the result of the extended voltage response measurement. After the validation of the method on a model dielectric, the polarisation processes of a PVC insulated low voltage cable have been investigated. The measurements were carried out on new and thermally aged samples. The newly developed method reveals that the blue and red coloured new PVC insulations have similar polarisation spectrum compared to the white one. Moreover, measurements show that a high intensity polarisation process in the 1000...10000 s time constant range appeared after the thermal ageing process.

Additional informations

Authors

Krämer Axel, Hopf Andreas