Discharges and the formation of tree-shaped breakdown structures

摘要

The picture of the electrical tree process that has emerged from a stochastic model is one of a discharging skeletal structure embedded within a space-charge region of its own creation. The space-charge controls the discharging pattern (spatially end temporally) and hence indirectly the discharge induced avalanche damage. Minor variations of the trapped space-charge density will lead to preferred directions for new channel formation, and provide a physical explanation for the random choice of the stochastic model. Regarding space-charge fields as contributing a negative feedback into the non-linear damaging process, treeing can be seen to be a consequence of a near-equilibrium situation. Conversely when the space-charge effect is small under a rapidly rising driving force, runaway in the form of a single puncture ensues.