Accurate stator fault detection insensitive to the unbalanced voltage in induction motor

This paper deals with the detection of inter turn short circuit fault based on the negative sequence current as indicator of this stator fault. This work focuses first on the development of new analytical expressions of the negative sequence current under stator fault conditions. Then, through an analytical study of these expressions, it has been shown that although the negative sequence current possess attractive features to detect the stator fault it is sensitive to the supply voltage unbalance, a drawback which strongly reduces the performance of the detection. To improve the accuracy and the reliability of the detection, authors propose a robust technique which permits to reduce significantly the effect of the voltage unbalance. A study of the impact of measurement errors of voltage and current is also discussed in this paper. The efficiency of the proposed technique is verified by simulation using a fault model then validates experimentally.