Ultrasonic Guided Wave Techniques And The Application To NDT In Transmission Cable

The overhead transmission cable is used in traditional ACSR. The aluminium wire are twisted together around galvanized steel wire. The currents to flow only in the surface of the aluminium wire because of skin effect. The galvanized steel wire Is to bear the ultimate tensile. Any break in the aluminium wire to lead to increase the local resistance,and enhance the local temperature. Accelerated the place of damage ageing. The ultimate tensile are weakened when damage is occurred in the steel core. When the damage is more serious,it is to lead to the transmission cable collapsed. Ice covering and broken-cables are two common faults and damaged forms of The overhead transmission cable. With paying more and more attention to that the integrity of in-service structures, Structural Health Monitoring (SHM) has attracted more attention. SHM is an effective way to get the condition of the structures in-situ and real-time. In this paper, the piezoelectric ceramic is used as actuator and sensor. Elastic wave generated by the actuator propagates in transmission cable. The propagation characteristic of elastic wave in transmission cable is studied, and the active monitoring technology of elastic wave is utilized in damage, ice detection of transmission cable.Firstly, introduces the basic theory of ultrasonic and propagation characteristics of elastic waves in rod and theoretically investigate the propagation of elastic waves in helical waveguides. The dispersion curves for helical geometry.Secondly, the characteristic of piezoelectric component and the piezoelectric formula which describes the piezoelectric effect were introduced in detail. As the structure of transmission cable is rather special, a set of fixture is designed. The sensor and actuator are clamped in the transmission cable tightly, and the sensor and actuator can move along the transmission cable easily. Propagation characteristics of elastic waves in transmission cable is researched by the designed experiments. The attenuation of elastic wave in transmission cable is studied.Finally, an effective experiment is established, and the active monitoring technology of elastic wave is utilized in damage, ice detection of transmission cable. Ice or breaking is located by analyzing the signal delay time of peak arrival by wavelet transform. The different types of damage or defects can be identified well using the extracting characteristic of signal efficiently by analyzing power spectral density.