Experience with Polarization and Depolarization Current Measurements on Contaminated Motor

Motors and generators are often installed in a location where makes them susceptible to contamination. For a long period of contaminant concentration, such contaminant can lead to motor failure. This paper presents the insulation characteristic of contaminated motor by comparing polarization and depolarization current (PDC) characteristics of the contaminated motor before and after performing overhaul maintenance. In the experiment, there are two 6.6 kV motors in which the insulation conditions of the motors before overhaul are contaminated with dust, bearing oil, and moisture. The test result indicates that the high-pressure water cleaning and drying applied for contaminated motor can only reduce the contaminants and moisture not change bulk insulation characteristics.