Space charge controlled electric field preceding inception of electric tree in XLPE at AC voltage

Electric fields associated with dynamic space charges injected from metallic needle electrode immersed into XLPE sample are analyzed by means of computer simulations. Field distributions in the material are calculated utilizing bipolar charge transport model. It is shown that the accumulated space charge becomes significant with time and affects the electric field distribution in the sample. The obtained magnitudes and profiles of the resulting fields are discussed focusing on possible mechanisms of electric tree inception in the material.