Study Of On-Line Monitoring Technology For Capacitive Equipments Based On Wavelet Theory

Parallel capacitor and HV capacitive type equipments are widely used in power system, here we call them power capacitor in all. Power capacitor's stability and safety operate is vital for the whole power system's operation. After done lots of study about power capacitor (PC), we want to find an effective, convenient and available on-line way for monitoring power capacitor's faults in power system.According to different degree of HV impact parallel capacitor and HV capacitive type equipments, the paper deals with them in separate discussions. The analysis and simulation for parallel capacitor's on-line monitoring are based on partial discharge (PD) phenomena. And the analysis and simulation for HV capacitive type equipments' on-line monitoring are based on how to improve the accuracy of tgδ's measurement. Wavelet-transform has the special ability toexpress the signal portion characters in time region and frequency region simultaneously. And the theories of signal decompose, character summarize and signal de-noise based on Wavelet-transform have put into engineering region successfully. This paper do wavelet-transform research on sample signals from power capacitor, simulation prove successful results got.The power capacitor's on-line faults and the background of this research are summarized in the first chapter, as well as the present technology for such purpose here too.The following two chapters do analysis in details mainly on PD and dielectric loss tangent (tgδ) for on-line capacitor in both phenomena and theories.It concludes when on-line PC has faults there would be accompany with PD simultaneously or PD ahead. And the phenomena of PD should be in the initialstage of capacitor's faults. The paper also proved that ways from PD for monitoring on-line PC is available and beneficial. The measurement of on-line HV capacitive type equipments' tgd can get accurate information of insulation in time, and how to improve the accurate degree of on-line tgδ is still not solve by efficiency ways at present.In chapter4, knowledge of wavelet-transform which used in later two chapters are introduced, it includes fundamental theory, decompose theory and de-noise theory based on wavelet-transform. The simulation environment of Matlab is also introduced here.In chapters, A device designed by author for on-line power capacitor's PD monitoring is introduced. And the simulation for summarize the PD signals from strong noise background is conducted in Matlab5.3's wavelet-transform toolbox, satisfied result is gotten.In chapter6, simulation based on de-noise theory of wavelet-transform for how to improve the measurement's accuracy degree of on-line HV capacitive type equipments' tgδ is conducted, also in environment of Matlab5.3, satisfied result is gotten.Conclusion of this paper's work is presented in chapter7, and questions left for ahead work is presented here also.The hard work and creative ideas in this paper as follows: understanding on faults of PC's PD, analysis of PD inside and outside PC, design of monitoring device, recognize of how to improve accurate of tgS 's measurement, wavelet-transform introduced for signal's processing and how to write programs and do simulations of wavelet-transform in Matlab5.3 here etc.