Partial discharge measurements in high voltage motors.
Buchan, John G.
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The work presented in this thesis is concerned with the development of an on-line technique for detecting and locating partial discharges in the stator winding of a high voltage electrical machine. This technique forms part of an on-line health monitoring strategy for the insulation of high voltage machines. Existing diagnostic techniques and partial discharge measurement systems are reviewed. The requirement for an on-line partial discharge location technique is discussed. An experimental investigation was carried out into the propagation characteristics of partial discharge pulses within a model stator winding. This allowed identification of the main propagation characteristics which were used as the basis for the development of a partial discharge location technique. In the development of a location technique, a means of on-line detection of discharge signals at the motor terminals is required. A study was therefore made on the use of the Rogowski coil for the non-invasive measurement of partial discharges. A partial discharge location system was developed based on the correlation of partial discharge pulses detected at the two ends of a motor phase winding. The performance of the location system was investigated by injecting artificially generated discharge pulses into the model stator winding. Further verification of the ability of the technique to locate the position of discharges was done by injecting high voltage discharges. The final part of the research work was to develop a theoretical model to predict the propagation behaviour of partial discharge pulses in the stator winding of an electrical machine . The effect of electromagnetic propagation through the endwinding region is incorporated in the model of two adjacent coils in a winding.