The impact of parasitic capacitances on the accuracy of scale transformation of high-voltage dividers

Purpose. The aim of this work is the determination of the parasitic capacitance’s influence on the accuracy of scale transformation of high-voltage dividers. Analyzing the possibilities of reducing such influence is a pressing problem for high voltage measurement, especially at high frequency range of input voltage. Methodology. Mathematical modeling of the voltage divider equivalent circuit, considering parasitic capacitances and inductances has been performed in the QUCS circuit simulator software under sinusoidal alternating current conditions in the range from 100 Hz to 1 MHz. Using the FEMM software, the finite element method was used to simulate the density distribution of capacitive currents in the module with capacitance graded insulation of the high-voltage arm of the voltage divider. Results. The results of the calculations show that the percentage of parasitic capacitive currents decreases exponentially depending on the ratio of the outer radii of the shielding disks to the distance between them. However, even with the outer radii of the shielding disks of about 3 m, capacitive currents still make up about 1 % of the total current flowing in the measuring circuit of the voltage divider. Instead of increasing outer radii, it is proposed to use high-voltage capacitance graded insulation between the shielding disks. As a result, a stable error of large-scale voltage transformation was obtained when the values of parasitic capacitances change, and it is proposed to manufacture the high-voltage arm of the voltage divider from the same type of high-voltage modules. Originality. The results of modeling the dependence of the accuracy of the voltage divider scale transformation on the ratio of the structural elements geometric parameters of its high-voltage arm were obtained. The solution has been proposed that involves changing the design of the high-voltage arm of the voltage divider, which significantly reduces the dependence of its scale transformation error on significant changes in the parasitic capacitances of the structure components on grounded surfaces. Practical value. The results of mathematical modeling of the characteristics of the voltage divider high-voltage arm make it possible to design, for the purpose of serial production, the same type of high-voltage modules for assembling on-site broadband voltage dividers for any nominal voltage, which will have the possibility of integration into Smart Grid systems. References 23, tables 1, figur