The Study On Dielectric Spectroscopy Characteristics Of Transformer Oil-paper Insulation And Micro Electric Current Measurement Technology

Dielectric spectroscopy insulation diagnosis method is a non-destructive insulation diagnosis method,which can reflect the change characteristics of the various dielectric parameters of insulation on the time domain and the wide frequency range,especially significantly insulation aging effect,thus increasingly drawn the attention of researchers at home and abroad.In view of time on low frequency measurement with the frequency domain method in the dielectric spectrum tests is too long,this thesis changes from the current signal on time domain measurement to frequency domain to get low frequency characteristics of the medium,to instead of direct measurement with frequency domain method,so a lot of time is saved.The Debye model of linear insulation system is established in frequency domain analysis in the thesis.The change law of curve of PDC and FDS can be obtained with parameters transformation in the model,and has good uniformity with experimental results at home and abroad.The relationship between the parameters of Debye model and the shape of the curve under the function of all kinds of factors can be used to elucidate the measurement results in dielectric spectrum insulation diagnosis.Micro electric current measurement circuit,which is designed through the principle of I-V and high performance operational amplifier,can measure accurately current signal from uA to nA.Finally,a experimental system was set up,which was used to measure the depolarization current of insulation on different water content,and made data fitting and FFT transform.At last,the value on frequency domain were calculated,and made analysis about the curve of the real part of complex capacitance,the imaginary part of complex capacitance and dissipation factor.The analysis results show that change rule of loss factor curve on different water content is similar,but along with the increase of the content of water,loss factor increases accordingly.The experimental results show that test system can accurately measure the micro electric current in a certain range.