Impulse breakdown of Perspex by treeing

The spatial and temporal growth of discharge channels about a point electrode in Perspex has been investigated using impulse voltages. The channels develop substantially at random. Evidence is produced showing that they consist of hollow nonconducting tubes in which a discharge must be struck before extension can occur. The discharge within a channel acts as a conducting extension of the point electrode, and further development occurs by intrinsic breakdown of the material at the end of the channel. The process is believed to be caused by avalanche formation, and material is evaporated until the rise in pressure of the gas within the ignited channel causes the discharge to be extinguished.