Analysis on Heating Causes of Composite Insulators in Online Operation

In recent years, composite insulators have frequently been heated during online operation. Since the cause and mechanism of the heating are unclear, massive trouble had been caused to the relevant department. This paper has conducted a withstand voltage temperature rise test on the heating composite insulator and found that after the composite insulator shed absorbs water, its high-voltage end will generate obvious heating under the action of the operating voltage. Through the dissection test, it is speculated that due to defects in the core rod-sheath interface of the composite insulator, local discharge occurs at the interface on the high-voltage end side, causing the composite insulator to heat up, and finally causing serious damage to the core rod. During the alternating current (AC) field exposure of silicone rubber, it has been observed that the AC field enhances the solution’s permeation through the silicone rubber. This phenomenon could potentially be linked to the recurrent thermal issues experienced by composite insulators in proximity to the grading ring at the high-voltage end.