Rotor temperature monitoring using fiber Bragg gratings

Rotor temperatures of field windings are seldom measured, as permanent installation of sensors on the rotor is often difficult and can present undesired risks. However, new possibilities exist with the use of fiber Bragg gratings (FBGs). Up to 20 sensors can be mounted in series in a single fiber. Moreover, several fibers can be used in parallel, and the signal passed from the rotor to the stator through a multichannel optical rotating joint. A demonstration of such a use of FBGs has been undertaken in a Hydro-Quebec power plant, where 32 pole-to-pole connections and 28 poles were instrumented. Measurements were carried out during a heat run test and FBG results are compared with average temperature calculated from voltage and current.