Detection of electrical tree propagation by partial discharge measurements

The partial discharge activity during propagation of electrical treeing in epoxy resin is described. The electrical trees grew in needle-plane samples without and with an internal barrier up to the final breakdown. The simultaneous taken tree growth and discharge activity show a correlation between the propagation state of the tree and the thereby measured PD. Especially the changes in the tree structure can clearly be detected. Based on these characteristics a new model describing tree growth will be presented. It appears that measurements from machine insulation can be interpreted in terms of the PD pattern.