Model for partial discharges associated with treeing breakdown: III. PD extinction and re-growth of tree

When the electrode separation is long or the applied voltage is low, the tr ee cannot directly grow to the plane electrode, and extinction of partial d ischarge (PD) with the re-growth of new channels can be observed after a lo ng time. Before PD extinction, the light emission of the PD changes from th e whole tree structure to only the region near the needle tip, and the PD p attern also changes from wing-like to turtle-like. These phenomena are cons idered to be related to the increase of channel conductivity by PDs. Assumi ng the channel conductivity is higher in the region at tree tips or in the tree channels than near the needle tip, the simulation results coincide wit h the experimental results.