Practical issues on negative sequence current monitoring for condition monitoring in induction motors

Negative sequence current monitoring is a well-known application that capable of identifying stator faults in induction motor using a simple measurement technique. However, the technique is sensitive to other asymmetrical sources of negative sequence, faults or disturbances. This paper addresses the issues on negative sequence condition monitoring based on such sources. The paper provides a comprehensive investigation of various negative sequence contributors such as sensor calibration, inherent asymmetry, voltage unbalance, shorted turn faults, eccentricity as well as broken rotor bar under load variations, and presents practical results.