Estimation of Dielectric Strength in High Voltage Motors for Circulating Water Pump

초록

To assess the deterioration condition of stator insulation diagnostic and overpotential tests were performed on two high voltage(HV) motors for circulating water pump(CWP). Two HV motors were installed per unit. Following the long term rewinding program, the diagnostic test was performed on two motors during the planning maintenance period. After completing the diagnostic test, overpotential test was done on the stator windings of HV motors. During the overpotential test, the No. 1 and No. 2 of HV motors failed at 8.8 kV and 7.9 kV, respectively. The dielectric strength of two motors was much lower than that expected for good quality coils (14.2 kV). Stator windings of two HV motors had deteriorated significantly. Almost all of failures were located in a line-end coil which exists at the exit of core slot. These motors were then rewound.