Recent experience has shown that early indication of the onset of shorted turn failures in a stator winding can be detected by the use of rotor-mounted scanning infrared sensors. Prior to the implementation of the infrared scanning sensors, the common belief was that preceding a turn insulation failure, while there may be some arcing within the winding and the pyrolyzing of insulation, there was no significant detectable evidence of turn insulation degradation until it is too late. Even if the minute electrical discharges or pyrolysis particles were detected, there was no way to determine the location of the impending fault using these conventional methods; so the obvious result was an unexpected failure. With this paper, the authors show that, at least on large salient pole machines, there is forewarning of an impending turn insulation failure that can be detected and located in time to allow for repair before a failure damages the coil and core.
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