Models of the long-term mechanical strength of long rod composite insulators

Different mathematical models of long-term fatigue strength of long-rod insulators were evaluated by studying the effects of superimposed cyclic and constant loads. It has been shown that the strength of composite insulators can well be represented by the power type behavior of the fatigue characteristics and that the time to fatigue failure of a composite insulator strongly depends of the cyclic load amplitude and the maximum level of the total load. It has also been shown that the diameter of the core of composite insulator with crimp-mounted end fittings is the major factor determining the insulator´s fatigue and static strength.