Localized heat generation before dielectric breakdown of polyethylene films

The contribution of the thermal process to DC electrical breakdown of polyethylene films at room temperature was investigated along with the character and the distribution of the weak points in the films. Local Joule heating in polyethylene film was detected before DC electrical breakdown at room temperature. When a high-temperature point appeared in a film, the conduction current increased with time. An analysis of the time variation of the conduction current and the temperature rise showed that the current flows mainly around the high-temperature point. The final breakdown occurred at the point of the highest temperature. The concurrence of the breakdown point and the Joule heating point suggests that a thermal process takes part in the DC electrical breakdown of polyethylene films at room temperature and that the weak points leading to the breakdown in the film occur where the current density is higher than the average. Local electromechanical deformation also appears to contribute to the DC electrical breakdown of polyethylene.<>