The electrical breakdown of insulating oil

The author attempts to reconcile the various approaches to the mechanism of breakdown in insulating liquids. The author argues that a breakdown model is necessary if sensible use is to be made of the abundance of practical data which has been accumulated. Models are proposed based on the latest information and the effects of particles, water and dissolved gas discussed in the light of these models. The partial discharge initiated at an electrode is proposed as the key mechanism in the breakdown process. This initial discharge must exceed a critical value for a local discharge to become the precursor to a breakdown. Particulate contamination is clearly important in facilitating a local discharge. Electrical breakdown is a weaklink process. Only one unusually large discharge (for example from an exceptionally large particle) is necessary to cause a breakdown of the system