Study On Evaluation Method Of The Damp Status Of Oil-immersed Bushing And Evaluation Software Design

As an important auxiliary device of large transformer,oil-immersed bushing is the weak link in transformer insulation system.In the process of operation,the main insulation damp of oil-immersed bushing will cause serious transformer fault,which will lead to severe power system accident.The article is based on frequency domain dielectric spectroscopy,research the frequency domain dielectric characteristics of damp bushing,extract frequency domain characteristic parameters which can reflect the state change of damp bushing sensitively to evaluate moisture content of bushing.Develop assessment software suitable for the conditions in the field,for oil-immersed bushing damp state diagnosis and assessment is of great significance.In this paper,the polarization mechanism of oil-paper and the principle of frequency domain dielectric spectrum are clarified.On the basis of the design and construction of the damp bushing model,the temperature characteristics and damp characteristics of oilimmersed bushing frequency domain spectra are studied in this paper by testing the frequency domain spectra of different damp states and temperatures,modified Cole-Cole double relaxation model to analyze the bushing frequency domain spectrum and explain oil-immersed bushing main insulation damp mechanism according to frequency domain characteristic.Test results show that the low frequency part of the bushing frequency spectrum is dominated by the conductance loss,which is very sensitive to the moisture state and temperature change,the polarization is dominated by the conductance loss and dipole polarization in the middle frequency band and in the high frequency band,the polarization and interfacial polarization are dominated by the dipole.In this paper,the frequency domain characteristic parameters of Cole-Cole model is studied and there is a good mapping relationship between the characteristic parameters and water content.The relationship between the damp state of bushing and the parameters of the frequency domain is established,and propose the method for evaluating the damp condition of the oil-immersed bushing.The method is verified by oil-immersed physical bushing,and it has good application effect.Based on the LABVIEW software programming design oil-immersed bushing damp condition assessment software,combined with MATLAB data processing functions and based on Access database function realizes the historical data storage,access,calls,designing the data display panels,perfect the data information,the curve shows that achieve man-machine interface interaction function.Experimental verification was carried out on the application of the running bushing of different voltage levels in the laboratory physical bushing and Yunnan Power Grid substation.The test bushing is compared and calculated.The results show that the evaluation software result of oil-immersed bushing is consistent with the calculation result and operation state,and can be applied to field test evaluation.