Physics of Partial Discharge

This chapter takes the physics described for electrical breakdown between conductors and focuses on the physics of partial discharge (PD), which some have called partial breakdown or a localized discharge, which does not result in an electrical short between the conductors. It also discusses the impact of PD on various insulating materials and shows how PD causes electrical aging and eventual failure of the insulation system. PDs can interact with dielectric in different ways: through electron bombardment, chemical erosion, and thermal degradation. The first interaction is based on the so-called dissociative electron attachment (DEA). DEA occurs when an electron with sufficient energy collides with a molecule breaking the chemical bonds between some atoms in the molecule. Corona PD shows striking differences between the discharges of different polarities. PD in voids (cavities) are typically the most harmful purely electrical aging phenomenon in equipment using solid and liquid organic insulating materials.