Research On GIS Mechanical Fault Diagnosis Method And Its Application Based On Acoustic Imaging Technology

Gas Insulated Switchgear is the key equipment of power system.Its normal operation is one of the important guarantees for the safe and reliable operation of power system.According to statistics,mechanical failures are one of the major failures types of GIS,accounting for 39.3%of all failures.Therefore,the diagnosis of GIS mechanical failures has always been a hot topic for researchers.Vibration and noise signals of GIS are closely related to its mechanical state,containing rich mechanical state of GIS and failure information.Due to the fact that there is no directly electrical connection between the acoustic imaging device and the power system,the device is not susceptible to electromagnetic interference.The acoustic imaging characteristics includes overall vibration of GIS which can avoid the variability of vibration in different locations of GIS.Therefore,it is of great significance to study the vibration and noise characteristics of GIS and the mechanical failure diagnosis technology of GIS based on acoustic imaging system.Firstly,this thesis established a GIS power frequency current loading system,developed an acoustic imaging test device based on sound intensity,analyze the source and propagation path of the vibration noise.Secondly,study the acoustic characteristic GIS in different current and different measure point through experiments.What's more,established the finite element simulation model according to the actual size of GIS and calculate the modal parameters by COMSOL Multiphysics.Obtained modal frequency,vibration mode,damping ratio through experimental modal analysis and compared with the results of simulation.This thesis mainly introduces three imaging methods of acoustic imaging technology,among which beamforming imaging adopts remote field measurement,resulting in poor sound resolution and weak description of slight changes in sound field.Near-field acoustic holography,on the other hand,can retain evanescent wave components because its measuring surface is close to the sound source surface,so that the reconstruction accuracy of sound field is not limited by wavelength,and thus can describe the slight change of sound source,which is more suitable for multi-fault fine diagnosis of near-field equipment.The advantages of the acoustic intensity scanning imaging method are that the measurement accuracy can be improved with the increase of the grid density,and the acoustic intensity has directional characteristics.Background noise in other directions can be shielded,and the sound size and distribution of the measured object can be accurately measured in a complex acoustic environment.This thesis also studied the acoustic characteristics of GIS under different mechanical failures by power frequency current loading system and acoustic imaging device,including looseness of anchor bolts,looseness of spacer bolts and poor contact of disconnecting switch.Extracted the eigenvalues from the cloud image and summarized the regulation under different failures.Finally,proposed a diagnostic method based on entropy,energy,contrast and correlation.The results show that the standard deviation of correlation,the mean of contrast and the standard deviation of contrast can be used to distinguish the looseness of insulation basin bolts and anchor bolts for the faults at the busbar cylinder.For the fault at the isolation switch,the standard deviation of the contrast and the mean of the contrast can be used to diagnose whether there is poor contact of the isolation switch.