Study On The Online Monitoring Of Generator Stator Winding Partial Discharge Based On The Ultrasonic Method

The security and stability of the power grid are growing importance, with the rapid development of the national economy. As one of the important devices in power system, the reliability of large-scale power generator's operation is solidarity with the security and stability of power grid. The generator stator winding failure frequency accounted for more than 25% of the generator failure rate, so in recent years, the online partial discharge monitoring technique of generator has been widely developed. Because the electrical measuring method which commonly used in partial discharge monitoring of generator can not determine the specific location of the discharge point, researches have proposed the electrical-sound joint detection method, which uses ultrasonic signals generated by partial discharge to location PD points. However, the process of ultrasonic propagation delay will have a greater impact to the accuracy of the location in actual testing. In the context of the study, the main content and the conclusion of this article completed as follows:①The characteristics of partial discharge (PD) of large generator, and the mechanism of ultrasonic generated by partial discharge was learn. By reading the corresponding acoustic data, master the basic acoustic theory and the general properties of ultrasonic was mastered.②The noise of normal operation generator was tested for the spectrum analysis of the noise signal.; After detecting the partial discharge ultrasonic signals, the spectrum of the ultrasonic signals was analyzed and the spectrums of two signals was compared to build the foundation for the next step study.③Using corresponding acoustic theory as a foundation, the distribution of the ultrasonic sound field was simulated by the finite element simulation software of COMSOL Multiphysics. For analyzing the distribution of the ultrasonic sound field in the space, the single stator bar model was constructed. Then generator stator model was built to analyze the distribution of the ultrasonic sound field in the stator model.④Using the two-dimensional stator model as a foundation, the propagation path of the ultrasonic in the stator was simulated.⑤By learning the ultrasonic positioning method, understanding the key factor in impact of accuracy of ultrasonic positioning is delay estimation error. The reasonable ultrasonic sensor distribution method proposed to reduce the alignment of delay estimation error by using the simulation results and theoretical as a foundation.⑥Using the spectrum analysis of noise signal and ultrasonic signal as the basic, design corresponding model circuit was designed, to verify the sensor distribution method in scene environment. The results show that the sensor distribution proposed by this paper has a certain extent feasible. However, many conclusions of this paper are is obtained based on simulation and experiment. It is necessary to verify in a real location system.