A Differential Excitation Sensor for Defects of Transmission Lines by Pulsed Eddy Current Testing

Transmission lines exposed to outdoors are susceptible to damage from environmental erosion, so regular defect inspection is required to ensure operational safety and stability for their essential role in power systems. Aiming at the problems of complex structures of stranded transmission lines that are difficult to clarify the size and position for defects, this article proposes a method using a differential excitation sensor for pulsed eddy current testing (PECT) of transmission lines, which can effectively detect and locate wear flaws down to an axial length of 1 mm and a radial depth of 0.36 mm. With the sensor, the axial position of the transmission line defects is identified by the peak and trough states of output signals, while the sensitivity differences between the two detection coils are used to determine the specific strand layer where the breakage is pinpointed. Furthermore, the defect severity is quantified based on the peak value of the signal. Consequently, this method systematically locates and quantifies defects in transmission lines, improving the accuracy and precision of the inspection and confirming the potential of the sensor for industrial testing.