Ultrasonic localization method based on Chan-WLS algorithm for detecting power transformer partial discharge faults by fibre optic F-P sensing array

Fibre optic F-P sensor has become one of the mainstream detection methods for partial discharge faults due to their advantages of good insulation, high sensitivity, resistance to electromagnetic interference, simple structure and inexpensive pricing. The first-order resonant frequency of the acoustically sensitive diaphragm of the F-P sensor is given based on the theory of plate and shell vibration, and the fibre optic F-P sensing array is designed based on the Fabry-Perot interference principle. A sensor installation method is also proposed for introducing a fibre optic F-P probe into the power transformer interior using a fibre optic penetrator through flange at the power transformer oil change valve. A system of non-linear equations is developed by utilising the time difference of arrival (TDOA) of the partial discharge ultrasound signal propagation to the F-P sensing array. The Chan-WLS algorithm is used to convert the non-linear equations in the TDOA localisation method into a non-linear optimisation problem to be solved and experimentally verified on the 220 kV real power transformer. The experimental results show that the error in the partial discharge fault localisation is solved based on the Chan-WLS algorithm and the actual location is 20.27 cm, which is within the acceptable error.