Approaches for Numerical Simulation of Partial Discharges

Insulation degradation is the primary reason for aging and eventual failure of electrical equipment. Any measurement that forewarns an impending breakdown of the equipment can be a boon to asset managers. Partial discharge (PD) is one such phenomenon that can be monitored for assessing the quality of insulation. However, the phenomenon of PD is quite intricate and requires an understanding of various concurrent processes. In this paper, some of the methods used to simulate this complex event have been reviewed. At the fundamental level, PD is a localized breakdown that occurs without complete bridging of the insulation. These are feeble and extremely fast, nanosecond discharges. They can be thought of as motion of charges under the influence of an external electric field, which has exceeded the breakdown strength in a small region of the insulation. When such discharges occur in voids in solid insulation, they generate signals in the electrical, chemical and acoustic domains. Also, PD causes physical damage due to bombardment of these charged particles on the walls of the void. The charges are generated by ionization of the gas filled in the void. Once ionized, the motion of these particles is governed not only by the external field, but also by the space charge so created. There are various methods that can be used to simulate the motion of these charges.