Study on the Influence of Key Structure Parameters of Conical Insulator on AC and DC Electric Field Distribution

Abstract

In AC and DC power system, the conical insulator is an important component in gas insulated switchgear (GIS) or gas insulated transmission line (GIL) equipment. The flashover phenomenon formed on the surface of the conical insulator is the key factor determining the insulation strength of GIS/GIL equipment. Studying the influence of the structural parameters of the conical insulator on the electric field distribution along the surface under the AC and DC voltage is of great significance for increasing the flashover voltage of the insulator and improving the insulation reliability of the equipment. In this paper, the key structural parameters of the conical insulator (inclination angle and fillet radius) are taken as the research object. The electrostatic equation is used to calculate the AC electric field distribution along the surface under different structural parameters. Consider the generation, migration, diffusion, recombination of free ions in gas, and the nonlinear relationship between gas current density and electric field strength. A numerical model for the charge transport and accumulation in DC GIS/GIL is established, and the DC electric field distribution along surface under different structural parameters is calculated. According to the calculation results, the influence laws of the inclination angle and fillet radius of the conical insulator on the AC and DC electric field along the surface are obtained, and the difference of the AC and DC electric field distribution along surface is compared. The results show that under the AC voltage, the electric field strength along the surface increases as the inclination angle increases, and decreases as the fillet radius increases; Under the DC voltage, the electric field strength along the surface has different distribution patterns near the high voltage conductor and the grounding shell: the electric field strength near the high voltage conductor decreases as the increase of the inclination angle, and the electric field strength near the ground shell increases as the increase of the inclination angle; Under the DC electric field, the polarity of the accumulated charge on both sides of the conical insulator is different, the concave surface accumulates a negative charge, the convex surface accumulates a positive charge, and the concave negative charge density is 1.6 times the convex positive charge density. The surface average charge density increases as the inclination angle increases and decreases as the fillet radius increases. The conclusion of this study has reference value for guiding the design optimization of GIS/GIL conical insulator structure.