Measurement of space charge distribution in epoxy resin after water absorption treatment

Internal space charge behavior of an insulating material has been widely discussed recently, and many experiments were carried out by using the materials for dc cables, such as XLPE, LDPE and HDPE. Since epoxy resin is used for an insulation of high voltage apparatus and of electronic devices, we investigated the space charge behavior in it by the pulsed electroacoustic (PEA) method. When dc electric fields were applied to the craft resins treated by immersing them in water for 1 hr and 8 hrs at room temperature, positive and negative charges accumulated near the anode and cathode, respectively, and the charge distributions changed with the immersion time. In the case of the insulation-type epoxy resin, the charge distributions did not change after the treatment. At 100/spl deg/C, on the other hand, positive charges accumulated near the cathode and negative charges accumulated near the anode in a craft resin and in an insulation resin with filler. The internal space charge in the insulation-type epoxy resin without filler did not appear in any of the treatments.