| The condition monitoring and fault diagnosis of excitation system will not only evidently enhance the reliability of excitation system but also provides the technique foundation of condition based maintenance in power plants.In this thesis , the condition monitoring and fault diagnosis of excitation system are studyed; the monitoring content and methods are selected; condition monitoring system of it is improved. The software and hardware of this system are designed, hardware scheme and software platforms are determined, signal conditioning circuit board is designed and produced, The application programme has also been developed in use of LABVIEW8.2 .In the developed system, a new AC sampling method based on virtual instrument is realized. In this method, the reactive power measurements are accomplished by Hilbert translation, and frequency tracking technology is completed by software synchronization of varying sampling points. Tests show that this method is easy to be realized and the measuring accuracy is high. An approach to track and evaluate the performance of excitation system has also been proposed, which is realized as follows: performance indexes can be acquired through automatically capturing and analyzing the transition process and querying the relevant data from database, thus the corresponding function of excitation system can be judged and the trend of performance indexes can be concluded. Then the criterions of the transition process has been gained through theory and experiments, by which transition process can be timely captured.Aimed at the fault diagnosis of generator excitation power unit, various faults have been simulated in laboratory, excitation voltage waveforms in fault have been recorded, fault data have been noted and FFT of them has been done, the fault classes have been distinguished.A series of experiments have been done in the excitation system of a pin-sized test generator. These tests indicate that this system is stable and has realized the main functions as follows: condition monitoring and testing of excitation system, performance tracking and evaluating, database , data query and report automatically building etc. |
