Characteristics of on-line and off-line partial discharge on hydrogenerator stator windings using acoustic emission detection techniques

The on-line insulation diagnosis technology can diagnose the hydrogenerators with thermal, electric, ambient and mechanical stresses received. The condition based maintenance to which the maintenance management is done by house keeping the hydrogenerators become very important for observing the insulation of hydrogenerator stator windings. In this paper, the AE signals measured by the many AE sensors for a hydrogenerator in 11 kV class were investigated as well as the load current, temperature of stator windings and humidity in on-line measurement. Also, the AE signals were investigated the non-destructive test at off-line measurement. Additionally, the correlation of AE signals and off-line diagnosis was be obtained by doing simultaneous measurement with off-line diagnosis for a 3 kV high voltage motor as a model test. As a result, it was found that the relationship between Δ tan δ , maximum discharge charge magnitude and intensity of AE signals was recognized for no-destructive test of a hydrogenerator and a high voltage motor. Also, it was found that characteristics for intensity of AE signals at starting operation period was depended on the humidity effect, but they at normal operation period was depended on the coil temperature at on-line measurement.