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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. [ABSTRACT FROM AUTHOR]

Switchgear is an important power system protection equipment. Internal overheating of high-current switchgear has become the most common problem in the power system. In this paper, two different methods of simulation model are adopted to study the temperature rise issues of the 12-kV medium voltage switchgear. First, the electromagnetic field is calculated by using ANSYS APDL, then coupling with fluid dynamics software CFX to give the temperature and flow field distribution of the switchgear. Second, FLUENT and Maxwell 3-D are used to get the temperature and flow field distribution. It can be proven that CFX simulation of flow field is more suitable for the complex models. In the meantime, it has huge differences with FLUENT software when the temperature rise of the switchgear is calculated. In this paper, the influences of inlet velocity, the number of ventilation holes, and their positions are further studied, which could provide theoretical guidance for reducing temperature rise of the switchgear. [ABSTRACT FROM PUBLISHER]

Long-term heating and excessive temperature rise will significantly affect the electrical and insulation performance of electric power equipment, causing the potential security risk. In this paper, the temperature rise situation under normal operation of a 12-kV medium voltage switchgear is studied through modeling and simulation method. First, in the simulation analysis of the whole switchgear, based on the theory of eddy-current field, gas flow field, and temperature field, the temperature rise distribution of the switchgear under the condition of natural convection and forced convection is simulated and analyzed. Then, several improvement methods are taken to reduce the temperature rise that emerges in the switchgear, including using spring contact finger structure to replace flexible connection structure, and also the optimization scheme of vacuum circuit breaker (VCB) pole and current transformer (CT). Then, simulation and research of different improvement schemes are conducted based on the electromagnetic-thermal-flow field coupling method. The simulation results of whole switchgear show that the above coupling method is very useful for the calculation of temperature rise. The simulation results also show that the spring contact structure is beneficial to reduce the temperature rise of vacuum interrupter and mechanical connection part. After the modification of design, the temperature rise conditions of the VCB pole and CT are significantly improved. [ABSTRACT FROM PUBLISHER]

In this paper, the fluid–solid interaction model of the impact process of internal pressure in arc chamber on housing structure of low-voltage circuit breaker is established, including the computational fluid dynamic (CFD) module that can assess 3-D pressure distribution of internal gas flow in the arcing chamber and finite element module (FEM) to calculate the impact of high-pressure gas flow on the housing. Based on the CFD module, the internal pressure distribution under different breaking currents and venting conditions is simulated, in which the simulation results agree well with the experimental results. Then, based on the 3-D pressure distribution, through the 3-D FEM of housing impact, the dynamic stress and deformation of chamber housing are simulated and analyzed. By this method, the stress concentration region of arc chamber housing can be predicted, which can provide reference for structure optimization design of arc chamber. For the region where stress is concentrated, structural strength needs to be enhanced, which can effectively avoid rupture problems due to local excessive stress on the housing. [ABSTRACT FROM PUBLISHER]