Experimental study of different approaches to the measurement of mechanical vibrations in transformers with fiber-optic interferometric intrinsic sensors

Interferometric sensing with an optical fiber as an intrinsic transducer is presented for core vibrations and windings vibrations inside two power transformers. Different approaches to in-field measurements are compared experimentally. The design of the fiber-optic probes is of enhanced sensitivity, with compensation of external influences and is shown to withstand the harsh transformer conditions. The sensors are based on detecting dynamic deformations in-contact with the magnetic laminates of the core, or dynamic displacement between two elements of a block inside the transformer. In all cases a differential scheme is used for detecting the elongation on one or more sections of a fiber, but several configurations are considered in the detection of the optical phase. Our results show direct measurements of the vibrations of the transformers at significant regions for its predictive diagnosis.