Dielectric Breakdown Of Epoxy Resin Under Saline-fog Environments

A limited factor of electrical and electronic systems in saline-fog environment is the dielectric breakdown phenomenon of solid insulating materials, because it typically takes place at applied electric field much lower than the bulk breakdown strength. In this paper, based on the measurement of dielectric breakdown and theoretical analysis, epoxy resin has been employed to investigate the effects of material characteristics and fog parameters on the insulating properties.By utilizing the monocular-video-zoom microscopes, the sample surface was analyzed. Based on the surface energy theory, it can be found that the contact angle decreased with increasing the saline-fog conductance. It is considered that the chemical distortion on the surface under the saline-fog environment is responsible for dielectric breakdown under a low electric field. The printed electrodes have been developed to carry out the experiment, which is absolutely different from the conventional electrode contact. For the conventional electrode contact that the metal electrodes pressed on the insulating material directly, there is an energy gap between the electrode and insulating materials resulting from their poor contact. For the printed electrodes, the interface potential barrier is reduced due to the ideal contact.The breakdown phenomenon of sample surface was observed under dc voltages. Based on the band theory of solids, the developing process was proposed to explain the phenomenon. It is considered that the ideal electrode contact increases the dielectric breakdown voltage and decreases the decentralization. The leakage current during the breakdown process was investigated and considered to be dependent upon two related processes: discharge initiation and carbon/tracking formation. Then the further analysis was carried out to study the effects of saline-fog conductance, discharge energy and molecular construct of materials on the dielectric breakdown. Meanwhile, the dry band formation caused by the leakage current and the corresponding surface scintillation discharge were deduced theoretically to find their influences on the two opposing process: carbon formation and carbon removal.