Partial discharge is an electrical discharge that does not bridge the space between two conducting electrodes, typically as a result of a localised breakdown in cable insulation in high-voltage systems. Due to the discharge not spanning the entirety of the insulation, thus not being electrode to electrode, the discharge is referred to as ‘partial’ in nature.
Partial discharge can be classified according to three primary types: internal partial discharge, occurring inside insulation; surface partial discharge, tracking across insulation; and corona partial discharge, from a sharp electrode into gas. Each kind of partial discharge is likely to manifest itself differently, however the effects are always harmful if left unchecked, degrading insulation’s protection over time. In most cases, insulation will eventually become unable to withstand the high voltage load, resulting in failure and the possibility of dangerous arc flashes. It has been observed that up to 80%