1. Introduction
In the electrical railway system, catenary is the dominant device to transmit the power from the grid side to the running locomotive. The catenary support devices are orderly arranged along the railway line and adopted to maintain a proper position of the contact wire, via a complex structure (see Fig. 1). Due to the long-term running, the impulse and vibration will easily cause the components on the catenary support device in defective states, such as the missing and loosening of the various fasteners, the flashover and broken of the insulators and the crack of the joint ears.