A critical review of partial-discharge models

Partial-discharge (PD) measurements in compliance with the standard IEC 60270 are based on the main quantity apparent charge. This term is deduced from a simple PD model comprising a capacitive network. However, from a physical point of view, a PD defect cannot be represented by a capacitance, as argued by Pedersen and his coworkers. As an alternative, Pedersen proposed a field theoretical approach that is based on a dipole model. This more sophisticated concept has been ignored in the past, whereas the capacitive PD model is accepted also nowadays. Apparently, the reason for that is that the charge transfer can easily be calculated for the capacitive equivalent circuit, which is not the case if the field theoretical approach based on the dipole concept is adopted. As will be reported in this article, the analysis can substantially be simplified if instead of gaseous discharges in spherical, elliptical, or cylindrical cavities, as commonly regarded in the relevant literature, the establishment of a dipole moment in a uniform field between solid dielectric layers is considered.