The current situation of diagnosis for insulation deterioration of high voltage induction motors in nuclear power plants

Abstract

In order to evaluate aging effect on motor correctly, several data of high voltage induction motors in 17 nuclear power plants of Tokyo Electric Power Co. (TEPCO) have been collected since 1984. Collected data are nondestructive insulationdiagnosis test data including insulation resistance, static capacitance and the results of insulation destructive test after replacement of motors.
Evaluation based on the data shows that breakdown voltage (BDV) of motor coil has relationship with the motor parameters such as current increase ratio, maximum discharge magnitude, difference of dielectric dissipation factor, etc. From this viewpoint, BDV estimation formula for 6.6kV motors is established by using multiple linearregression analysis method, considering parameter used in D-map evaluation. However the measured parameters may vary due to the factors besides insulation deterioration, not only the estimated BDV but also visual inspection data are took into account for overall diagnosis. Further collection of data and evaluation willbe done continuously in order to enhance accuracy of the insulation diagnosis.
The current situation of diagnosis for insulation deterioration of 6.6kV class induction motors in nuclear power plants is described in this technical note. Alsocurrent situation of investigation on 3.3kV class motors is described.