Study on the electrical field and the potential distribution of composite insulator with a partial micro-gap in interface

In composite insulator surface, a partial micro-gap may appear because of a long running, a workmanship defect or some micro impurities, etc. The micro-gap may make partial electrical field strength seriously distorted, and ionize the air in micro-gap easily. Even more, it could probably a stable partial discharge, which will directly corrode central rod, age umbrella skirt, and sheath and decrease the mechanical character of the central rod. Then a composite insulator with a partial micro-gap is analyzed with Finite Element Analysis Software in this paper. By changing the size of the micro-gap from 0.5mm to 3mm, and the site of the micro-gap, the field strength at the junction of composite insulator hardware and sheath, the umbrella skirt inside axis of field strength near the micro-gap, the micro-gap internal field strength, the whole surface field intensity and potential distribution along composite insulator umbrella skirt are calculated. The conclusion shows that the existence of a partial micro-gap makes field strength seriously distorted in the micro-gap, where a high distortion field will generate even up to 161.76% and 181.65% than normal within the micro-gap. The serious distortion will further affect the insulation performance of composite insulator, and finally it would cause a potential hazard to serving power grid.