Electrofracture mechanics of dielectric ageing

A dielectric submitted to a prolonged electrical stress will fail at nominal field levels often one or two orders of magnitude below the short term breakdown field. The damage typically consists of multiply branched hollow channels of ∼ µm diameter (electrical trees) which originate at a point of local field enhancement. Another family of damage structures consists of channels much finer in diameter and filled with water, electrolytes etc. (water trees, electrochemical trees).