Modelling return voltage measurements of multi-layer insulation systems

The purpose of this paper is to analyse voltage return measurements starting from a theoretical analysis of a series combination of several dielectric materials. Each material is characterised by its conductivity, permittivity and dielectric response function. Computer simulations have been performed in order to interpret results of laboratory experiments performed on a test cell consisting of transformer press board in series with oil insulation. For short (<1000 s) charging and discharging times the return voltage is mainly determined by interfacial polarisation. To obtain information about the dielectric relaxation and polarisation properties of the bulk of the pressboard insulation it is important to use long measuring times