Failure Analysis of Decay-like Fracture of Composite Insulator

In recent years, a new type of composite insulator mechanical failure appeared in high voltage transmission lines, which is a type of severe accident for power system, but only few studies on it have been reported all over the world. In this paper, this type of failure was named Decay-like Fracture by summarizing and analyzing the general features, and the decay-like fracture of composite insulator was treated and studied as a new type of composite insulator mechanical failure. By analyzing some field failed composite insulators in China, main features of decay-like fracture were then summarized. The fracture spot of decay-like fractured insulator became crisp and looked like decayed wood. The mechanisms of the normal fracture and brittle fracture of composite insulator cannot explain decay-like fracture, and boron-free Fiber Reinforced Plastic (FRP) core which has been widely used to prevent brittle fracture could not prevent decay-like fracture. Decay-like fracture is not a pure mechanical failure. The discharging and surface micro current on the core surface would finally lead to mechanical fracture of composite insulator. But the process and mechanism of decay-like fracture still need further researches.