Modelling of dielectric processes in oil-paper insulation for replacement of Return Voltage Measurement

In Hungary, the main diagnostic method for power transformers has been the Return Voltage Measurement (RVM) for decades, however, the measurement time is quite long. In order to get information about the condition (moistening, ageing) of the oil-paper insulation, the changes of the RVM curves have to be compared. In this study, the authors introduce a method, wherewith the faster voltage response (VR) measurement can provide the curves of the RVM, with acceptable error. The newly developed method bases on an iteration method that describes an equivalent circuit of the transformer insulation containing only five Debye elements. The method has been tested on a transformer insulation model and also on a model insulation R-C circuit. The results show, from the results of VR measurement the elements of the equivalent circuit can be determined and the Return Voltage Measurement can be simulated in an appropriate software.