Partial Discharge Fault Detection of Oil-Paper Insulated Equipment Based on Optical Fiber Direct-Coupled F-P Sensing

It can detect the partial discharge of power transformer timely and effectively, which is an important guarantee for the safe operation of the new power system. Fiber optic F-P sensors can be built into oil-immersed power transformers for on-line partial discharge detection due to their anti-electromagnetic interference, small size, corrosion resistance and other advantages. Existing fiber-optic F-P ultrasonic sensors are mostly of the indirect-coupled through the diaphragm, and the fiber-optic direct-coupled F-P sensors in this paper are of the dielectric refractive index-altering type, which can broaden the detection frequency range. In this paper, a direct-coupled F-P sensor is developed based on the change of refractive index of the medium inside the F-P cavity. Because in the acoustic signal propagation process medium density is only affected by the size of the acoustic pressure, and the refractive index of the medium is only regulated by the density of the medium, so the direct-coupled F-P sensor is only regulated by the acoustic pressure, with a wide frequency response of MHz level. The frequency band response of the direct-coupled F-P sensor was found to have a flat frequency response region covering 1 kHz to 200 kHz, which can make up for the narrower response interval disadvantage of the indirect-coupled F-P sensor. The direct-coupled F-P sensor was used in oil-paper insulated equipment to measure the localized discharge signals, and the results show that the direct-coupled F-P sensor can effectively sense different types of localized discharge signals.