Critical Analysis of Inter-Turn Fault Related Harmonics in the Line Current

Inter-Turn faults (ITFs) rapidly evolve into catastrophic failures of induction motors, thereby needing continuous monitoring. In this regard, methods based on localizing ITF-related harmonics in the line current are an attractive option, since they only need a current sensor in the motor cabinet. This paper presents for the first time a critical analysis of these harmonics, comparing their aptitudes as ITF indicators under different conditions, to determine which are the best. Comparison is performed considering not only the principal harmonic of each type, but the whole set of main harmonics. To this end, 52 laboratory tests are generated with different fault severities, loads, voltage unbalances and supply conditions. In each test, the amplitude of up to 19 harmonics is extracted, first to determine the most sensitive indicators in each group and then to compare them with each other. Finally, a critical discussion is provided, clarifying the best approach to take.