Deterioration of Corona Armor Tape by Partial Discharge and its Lifetime Evaluation for Form-wound Rotating Machine

It has been reported that low resistive-corona armor tape (CAT) used in the stator coils of a rotating machine is deteriorated by partial discharge within void or delamination in the main insulation of the stator coil, resulting in an unacceptable high resistivity of the material. Hence, the lifetime evaluation of the CAT is an important issue for the reliable operation of the machine. In this study, the determinant of the lifetime of the CAT is experimentally investigated. As a result, it was clarified that the lifetime of the CAT was determined by ozone concentration produced by partial discharges and the duration of exposure time to ozone. Furthermore, the lifetime of CAT can be well organized by the discharge energy of partial discharge, which enables the lifetime estimation of the CAT under the given operating conditions of the machine.