Space charge formation and electrical breakdown at high temperature region in PVC for electrical wiring assembly

The Polyvinyl chloride (PVC), the most popular insulating material, is used as an insulating material of various electric products. When using an electrical wiring assembly code over the power capacity, PVC could melt by the joule heating and cause an electrical breakdown. Therefore, it is necessary to clarify the electrical breakdown phenomena near the melting point (170°C) in PVC. In this paper, space charge distribution and conduction current have been measured in PVC sheets up to the electrical breakdown in the range from room temperature to 200°C under DC electric field. The breakdown strength decreases with temperature in PVC. Small hetero-space charges are accumulated near both of the electrodes at room temperature region. At high temperature region above 100°C, it is observed that positive charges are injected from anode and move toward the cathode; the electric field is emphasized near the cathode due to the packet-like positive charge in PVC. It shows a thermal breakdown process of the electric fields due to positive charge behavior and conduction current increase with temperature near the melting point in PVC. © 2012 The Institute of Electrical Engineers of Japan.