Research On The Correlation Characteristics Between Dielectric Loss And Partial Discharge Of Oil-pressboard Insulation

Dielectric loss and partial discharge(PD)are important indices of insulation properties for oil-pressboard insulation.The research about correlation characteristics between dielectric loss and PD for oil-pressboard insulation has theoretical significance for promoting the condition monitoring level as well as realizing the multiple fusion fault diagnosis objective for oil-pressboard insulation.The experimental platform is set up to measure dielectric loss and PD for oil-pressboard insulation in this thesis.Besides,dielectric loss and statistical parameters of PD are accurately calculated.What's more,this thesis analysis the correlation characteristics between dielectric loss,dielectric loss tip-up and PD statistical parameters.The main contents of this thesis are as follows:The surface discharge model for oil-pressboard insulation is designed,and the pressboard samples with different moisture content are obtained.The experimental platform is set up to measure dielectric loss and PD for oil-pressboard insulation,which can satisfy the requirement of dielectric loss and PD data collection.A dielectric loss value calculating method based on iterative matching pursuit(MP)algorithm is proposed.The simulation results show that the presented method can achieve a accurate as well as stable calculation result for dielectric loss.By step-stress test,dielectric loss and PD statistical parameters change laws are obtained.According to these laws,the total discharge quantity,the maximum discharge quantity and the average discharge quantity increase gradually with PD development.The total discharge number and the length of average discharge pulse firstly increase and then decrease.The regularities of the skewness of typical spectrums,the kurtosis and weibull distribution ? coefficient of Hn(q)spectrum are strong.The total discharge quantity,the maximum discharge quantity,the average discharge quantity and ? coefficient are affected by pressboard moisture content.With the increase of voltage,the dielectric loss value of the different samples increase firstly and then decreased or remain stable.When the the applied voltage is high,the dielectric loss value increasing trend is obviously slowing down,and there is even a decreasing trend.Besides,a dielectric loss variation mathematical model for insulation with local defect is established,which can explain dielectric loss change rule under the influence of PD based on step-stress test.The relationship between the dielectric loss and the PD statistical parameters is analyzed,and the correlation properties dielectric loss tip-up with PD 50 Hz fundamental component is researched as well.The results show the change law of overall dielectric loss is impacted by the increase of dielectric loss in local defect as well as PD development,and the correlation relationship of dielectric loss value with the total discharge quantity,average discharge quantity,total discharge number,regularities of the skewness of typical spectrums,the kurtosis and weibull distribution ? coefficient of Hn(q)spectrum are strong.However,these correlation relationship are not simply one to one linear relation and they are afftected by moisture content as well.It is difficult to establish a simple correlation between the dielectric loss value and a single statistical parameter.Dielectric loss tip-up is impacted by PD 50 Hz fundamental component,and these two parameters are basically monotonically related.Besides,PD 50 Hz fundamental component is impacted by the average discharge quantity.Under the combined effect of the above PD statistical parameters,the change law of dielectric loss tip-up of each sample is specific.