Fiber-reinforced plastic (FRP) rods have been widely used in power equipment as insulating materials for their advantages of low-cost, mechanical and electrical performance. However, various defects may appear in FRP rods during manufacturing and operation, which pose a great threat to safe operation of power system. Despite the urgent need in power industry, a nondestructive detection method on FRP rods defects with convenience and effectiveness has not been fully developed yet. In this work, the vibration detection of FRP rods for composite insulators is applied on two different types of defect. The modal parameters of damaged and intact rods are obtained, and the natural frequency drop rate is used as the eigenvalue parameter for structural damage assessment. It has been shown that the crack defect can be quickly and sensitively detected by vibration detection. Mechanical damage is also found to cause a minor decrease in natural frequency values of FRP rods. The observations can be well explained by modal analysis theory, verifying that existence of defects results in decreased structural stiffness and reduced natural frequency. As a nondestructive method with fast operation and easy data processing procedures, vibration detection on defects of FRP rods has been proved feasible and promising, which provides potential strategies for damage diagnosis for composite materials used in power equipment.

Composite insulator,damage diagnosis,FRP rod,modal analysis,vibration detection