New method for in live-line detection of small defects in composite insulator based on electro-optic E-field sensor

Preliminary results based on experimental tests in laboratory and numerical investigation concerning the live-line detection of a conductive defect in HV composite insulator are depicted. The proposed method is based on E-field sensing using a non-invasive and compact pigtailed electro-optic (EO) single-ended probe. Measurements and numerical FEM modeling were done on a clean dead-end 28 kV composite insulator on which conductive defects of different size and position were simulated. Based on these simulations, the optimal location and orientation of the EO probe were determined regarding the conductive defect length and position. Laboratory tests were performed to validate these results and demonstrate the efficiency of the new detection method. The experimental results have demonstrated that using the optimal EO probe orientation, the E-field sensor was able to detect and locate conductive defect as short as 15 mm × 1 mm in contact with the HV electrode and of 26 mm × 2 mm between sheds. Moreover, the experimental tests have demonstrated the ability of the EO sensor to detect the presence of corona discharges induced by the conductive defects.