Development Of The On-line PD Monitoring System For The Large Generator Stator Winding

The large generator is one of the important devices in power system. Partial discharge (PD) accured in its insulation can lead to deterioration of the insulation, resulting in insulation breakdown and short circuit. Traditional off-line test can not present the real status of generators in operating station, so it can not ensure safe-operation of generators. Insulation faults are still occured. It's necessary to develop a complete and practicable on-line partial discharge monitoring system for the large generator stator winding. According to the past research and the knowledge from references, a new type the on-line PD monitoring system for the large generator stator winding is developed in this thesis.First of all, in this thesis, the causes and characteristics of three different types of PD are discussed and the propagation law of PD pulse in the large generator stator winding is analyzed. Based the theoretical analysis, a hardware of the on-line PD monitoring system for the large generator stator winding is designed, which includes the wide band sensor, the signal prepoccessing circuit and the PD signal collecting unit. Then based on the technology of serial communication, the control procedure of the on-line monitoring system is designed.Secondly, the amplitude frequency characteristics of the monitoring system has been tested with signal-generator and high-speed digital-ondoscope. The test result shows that the actual operating frequency band of the system is consistent with the designed value. This indicates that the system can be satisfied with the need of PD monitoring. Further more the PD of the high voltage generator stator winding has been tested using the system, and the result shows that the system has higher sensitivity. Then the test result is processed in wavelet analysis, so the system has certain denoising and anti-interference capability. After statistic analysis, the 2-dimensional partial discharge pattern is obtained that has established foundation that can be used for further insulation diagnosis and on-line monitoring for the large generator stator winding.