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The authors review the procedures available for the periodic testing of industrial power system components, with particular reference to the mining industry. The inherent limitations of these tests are discussed, and appropriate applications for these tests are suggested. The use of negative-sequence monitoring as an inexpensive but powerful detector of incipient failure in industrial power systems is proposed. It is emphasized that negative-sequence monitoring does not interfere with normal operations and is continuous. In laboratory experiments, it has been proven to be a sufficient indicator for detecting electrical deterioration within a squirrel-cage induction motor. It is concluded that, despite the effects of an unbalanced voltage supply on the measurement and the present uncertainty over how to compensate for these effects, negative-sequence monitoring can be a significant and powerful addition to a plant's motor testing program.>
Sottile et al. (Sun,) studied this question.