Short time decay of space charge in epoxy resin

Epoxy resin is a material that is widely used as insulation for power transformers and printed circuit boards. In this paper, the short time interval decay measurement of space charge in an epoxy resin is described. Most of the charge was positive space charge that was formed near the anode and measured just after an applied voltage in the range 8-13 kV was removed. Most of this charge disappeared within a few tens of seconds after short-circuiting. It was found that there were two regions in the decay of the space charge magnitude following short-circuiting: a fast decay region occurring during the first ten seconds, followed by a much slower decay that was followed up to 120 seconds. It was found that the rate of space charge decay in the fast region increased with the magnitude of the voltage applied to generate the space charge. It was found that the decay current obeyed the Schottky mechanism in the fast decay regions, with a relative permittivity that was near the known value for the material. It was concluded that the decay of space charge in the fast decay region was governed by charge neutralisation caused by Schottky injection