From the editors´ desk

The first article in this issue is "A Critical Review of Partial-Discharge Models" by Eberhard Lemke of Doble Lemke GmbH, Germany. The article contrasts the classical capacitive equivalent circuit model, commonly used to describe partial-discharge (PD) phenomenon, to a dipole model that was first introduced by A. Pedersen in the mid 80s. The article argues that the capacitive equivalent circuit is not capable of reflecting the physics of discharges in gaseous cavities embedded in bulk dielectrics. A better approach is to model the discharge phenomenon by a dipole moment in a uniform field between solid dielectric layers. Consequently, the electromagnetic transients detectable at the electrodes are not caused by discharging of an imaginary cavity capacitance but rather by a dipole moment established in the cavity as a consequence of gas discharges. The article reveals that the apparent charge detectable at the terminals of the test object is well correlated with the dipole moment established at the PD site.