Multichannel ultrasound instrumentation for on-line monitoring of power transformers with internal fiber optic sensors

In this paper a multichannel instrumentation system for acoustic monitoring of power transformers using internal fiber optic sensors is presented. The system is designed to drive four sensor heads, which gives the ability to locate faults by measuring the time of flight of the acoustic emissions. Moreover, it can be extended to drive up to eight channels in order to expand the capabilities of this system. An acoustic test bench in water is used to reproduce acoustic emissions with similar characteristics to those produced by faults in power transformers. Experimental tests with a sensor immersed in water are presented. These show a resolution better than 10 Pa. Results of location using three internal sensors and a trigger reference show that the system is accurate to 1 cm.