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Fiber optic interferometric method for acoustic emission (AE) detection in power transformer's bushing is developed and tested in emulated AE signals. It was shown that the proposed system can detect AE from inside a bushing replica. It was also shown that system sensibility is better than traditional piezoelectric acoustic sensors usually used for AE detection originated from partial discharge (PD) on power transformers.

We propose a passive optical sensor for online magnetic field monitoring in large hydrogenerators, based on FBG (Fiber Bragg Grating) technology and a magnestostrictive material (Terfenol-D). The objective of this sensor is to detect faults in the rotor windings due to inter turn short-circuits. This device is packaged in a novel rod-shaped enclosure, allowing it to be easily installed on the ventilation ducts of the stator of the machine. This sensor was developed and tested in laboratory and it has been evaluated in a field test on a 200 MVA, 60 poles hydrogenerator.