Development and pattern identification of end-winding discharge under effect of relative humidity and temperature for HV motors

Abstract

During operation of high voltage (HV) motors, different types of discharges, e.g. surface discharge, corona discharge and bar-to-bar discharge can occur at the same time, increasing the difficulty of partial discharge (PD) sources determination and PDs pattern identification. In this study, the end-winding of a 10 kV motor coil was artificially aged and the related PD was measured. The initiation and variation of different PDs under multi-factor stresses were studied. The localised fingerprints coexisting with multiple PDs were identified and analysed. The results confirm that the end-winding discharge process was significantly influenced by the experiment relative humidity (RH) and temperature. The bar-to-bar discharge was easily recognised at a lower voltage since the identification of bar-to-bar discharge pattern would be affected by the corona discharge pattern at a higher voltage. It is shown that it is more difficult for the corona discharge to be detected when RH exceeded 80%, while the surface discharge dominated at the higher RH. In addition, the PDs were more easily identified with the rise of the temperature. This study can provide a reference in PD identification test and be useful for the PD online monitoring of HV motors.

Keywords

• partial discharges
• corona
• machine testing
• electric motors
• pattern identification
• hv motors
• high voltage motors
• surface discharge
• motor coil
• end-winding discharge process
• experiment relative humidity
• bar-to-bar discharge pattern
• corona discharge pattern
• pd identification test
• partial discharge source determination
• multifactor stresses
• voltage 10.0 kv