Insulation deterioration detection system using zero-sequence current analysis for induction motors

Generally, the insulation breakdown of motors, the main fault associated with motors, is caused by the compound factor of thermal, electrical, mechanical, and environment deterioration. For preventive maintenance for insulation breakdown, the insulation test of a stator coil is performed for motors in the power and industry plant once in several years, periodically. Insulation failure expensively deteriorates the plant operation. Therefore, for the maintenance of these motors, various tests such as an insulation test and research and development of insulation deterioration diagnosis, on-line PD (partial discharge) monitoring, etc. have been actively carried out. On the other hand, the maintenance of LV (low voltage) motors have stayed in BDM (Break Down Maintenance) because many and many LV motors are running in plant and the maintenance of LV motors should consider cost-effectiveness from HV (High Voltage) motors. This paper shows that the method of insulation deterioration detection, using analysis of the deference wave of zerosequence current between the normal condition and the fault condition, can realize life management with an on-line diagnosis system and CBM (condition-based maintenance) for induction motors.