Due to the high salt content

high humidity and strong sunshine radiation environment

the aging state of island composite insulators has attracted more attention. It is very important to evaluate the aging characteristics of composite insulator sheds for ascertaining the aging state of silicone rubber. In this paper

39 samples with different voltage levels

service life and manufacturers were selected. The mechanical properties of insulator sheds were measured by electronic universal testing machine

and the aging characteristics and change of insulator sheds were analyzed. The results show that the tensile strength and breaking elongation of sheds at different parts of insulator are relatively consistent

which does not affect the judgment to insulator properties. There is an obvious boundary between the mechanical properties of broken and unbroken insulators

which is called the broken threshold. The tensile strength threshold of broken insulator sheds is 4.4 MPa

and the breaking elongation threshold of broken insulator sheds is 1.1. Breakage occurs when the mechanical properties of sheds are lower than the broken threshold. With the prolongation of service life

the proportion of broken insulators will increase. In the aging process of composite insulator

with the decrease of breaking elongation

the tensile strength negligibly changes at first

then presents a linear decline trend with breaking elongation

and insulator sheds are likely to be broken in the descending stage.