Simulation Analysis on the Impact of Different Filling Gases on the Temperature Rise of C-GIS

Abstract

SF6 has good insulation performance and is widely used in power equipment. But as climate change intensifies, the need for substitute gases is growing. While a lot of research focusing on the insulation performance of substitute gases has been done, little has been focused on their effects on temperature rise, though temperature rise is important for the safe operation of the power equipment. In this article, a 40.5-kV medium-voltage cubic gas-insulator switchgear (C-GIS) is modeled and simulated by the electromagnetic-fluid-temperature multiphysical coupled method. By implementing CFX Expression Language (CEL), the influence of temperature on thermal conductivity, density, viscosity, and specific heat capacity of gas is able to be coupled into the simulations, thus improving the accuracy of the simulations. The airflow and temperature distribution of the C-GIS with SF6 are obtained, and the temperature rise distribution is verified by experimental results. On this basis, simulation studies are conducted to analyze the influence of different filling gases on the temperature rise of the C-GIS. First, the influence of single filling gases including N2, CO2, and pressurized air is analyzed by the simulations. Second, the temperature rise distributions of the C-GIS when filled with a mixture of SF6 and N2 with different proportions of mole fraction are also obtained. By analyzing the changes in temperature rise distribution under different situations, it can be found that the temperature rise with N2, CO2, or pressurized air is relatively high. When the gas mixture is used, the maximum temperature tends to decrease with the increase of SF6 usage. According to the results of this article, it can provide a reference for selecting suitable substitute gas of SF6.