Diagnostic techniques in rotating machine insulation: A diagnostic technique for model stator bars based on the maximum partial discharge magnitude

This work proposes a method to diagnose the aging of rotating machine insulation. Experiments have been performed in model stator bars, which are close to real stator bars of high voltage rotating machines, and the maximum partial discharge has been recorded as the applied voltage increases and then decreases. The resulting "hysteresis" curve shows whether the stator bar is in a "good" or "bad" condition. It is shown that the aging of the model bar influences the hysteresis curve, i.e., the latter presents a greater surface area with an aged bar than when the stator bar is not aged. The proposed method may give information not only on a yes or no basis (i.e., aged or non-aged bar), but it can also distinguish between a stator bar with a more and a stator bar with a less serious aging problem. A discussion on the merits of the proposed method follows. It is suggested that the proposed method can be used as a diagnostic tool for assessing the quality of a stator bar and for studying its aging.