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Failures in the field winding of synchronous generators cause degradation in performance and accelerated wear of components. A number of offline and online test methods has been developed over the years, and airgap flux monitoring has been proven to be the most effective solution for reliable detection of the fault. However, there are concerns on reduced sensitivity for cases where the number of turns per pole is large. In this letter, the fault indicators used in commercial applications for airgap flux based fault detection are analyzed for salient pole synchronous generators, and a new simplified method with improved sensitivity is proposed. Experimental testing on a 330-MW generator under controlled fault conditions is given to verify the claims. A comparative study shows that the new method can provide a simplified means of improving the sensitivity and reliability of the technology presently employed in the field.
Yun et al. (Fri,) studied this question.