Study On Frequency Response And Denoising Of Zinc Oxide Valve Divider

Overvoltage is an important factor affecting the reliability and stability of the power system.Overvoltage measurement is of great significance in the study of overvoltage and insulation design.The current variety of voltage dividers have achieved some results,but also have their own limitations.This paper presents a voltage regulator using zinc oxide varistor,using zinc oxide arrester as the carrier,in series the divider valve at the end of the zinc oxide arrester,and the overvoltage comes from the partial divider valve.In view of the proposed zinc oxide varistor divider,this paper has done the following work:The microstructure and conduction mechanism of zinc oxide varistor are briefly introduced.A variety of zinc oxide arrester models are compared,and a model consider both microstructure and parameters of zinc oxide varistor is selected.The influence of different parameters between the divider valve and the main valve of the arrester is analyzed.The main parameters of the simulation are the thickness,contact area and grain density of the zinc oxide varistor.Conclusions are as follows:The effect of seed pitch and grain size inhomogeneity on the residual voltage waveform of the divider valve is the most obvious.The influence of various physical parameters on the residual voltage waveform of the divider valve is larger than that of the small current region in the high current region,but the influence of the residual voltage waveform is very small in both cases.Therefore,in the choice of the divider valve that connected to the end of the zinc oxide arrester,better choosing the same batch firing zinc oxide valve with arrester main valve,so that the results can be optimized.The sinusoidal sweep test of 110 kV zinc oxide arrester and 35 kV zinc oxide arrester was carried out,and the frequency response under different series pressure plate was obtained.The sine sweep test of the same kind of zinc oxide varistor was also carried out,and the frequency response of different number of the same type of valve series was obtained.The following conclusions are drawn:(1)The arrester valve is in a high-impedance state at a non-conducting voltage,mainly relying on its capacitive to divide voltage,so its amplitude response is poor in the low frequency band,and in the high frequency band,the capacitive characteristic of the arrester valve makes the frequency Response to pick up,we can see the arrester valve is fit for high-frequency signal divide in the non-conduction area.Comparing the phase characteristics of the same type of valve and different valves,it can be seen that the different series of valves will cause the phase frequency characteristics to increase sharply in the low frequency range.(2)When the arrester ends in series with different batches of the valve,due to the difference in the firing process,the valve grain size,grain boundary thickness and other parameters will make its frequency response characteristics deteriorate,which will directly lead to low frequency attenuate faster.(3)The frequency response of the same type of valve will not change with the number of the valve to produce a large change,so it should be as far as possible to use the divider valve that has the same type with the main body valve of zinc oxide arrester.The overvoltage signal collected in the field contains the noise.The wavelet threshold denoising based on wavelet transform is used to denoise the overvoltage signal.A new threshold function is used to denoise the overvoltage signal,and compared with the traditional threshold.The denoising effect of the new threshold function is better than that of the traditional threshold,and it is more suitable for denoising the overvoltage signal with plentiful frequency components.