A hybrid fiber-optic sensor system for multi-stress monitoring of high-voltage power transformer

For condition monitoring of high-voltage power transformers, a fiber-optic multi-stress sensing system is suggested by combining fiber grating sensors and mandrel sensors embedded in a fiber-optic Sagnac interferometer. The gratings and the mandrel sensors measure the temperature and the vibrations at multi-locations in a power transformer. To separate and demodulate the sensor outputs, we used a wavelength-sweeping laser source and placed a fiber-optic attenuator in the Sagnac loop, which enabled to separate the Bragg wavelengths from the transmission spectrum. The temperature and vibrations multi-locations could be measured at the same time by using single optical circuit and single signal processing unit.