Application of computational fluid dynamics to predict the temperature-rise of gas insulated switchgears
Accurate temperature-rise prediction in gas insulated switchgears (GIS) is necessary to reduce the number of heat-run tests during the product development process. An electromagnetic-thermal-fluid coupled model using computational fluid dynamics (CFD) is developed to predict the temperature-rise of a 110-kV three phase GIS in common tank type. The GIS includes the three-position isolation/ground switch and the circuit breaker insulated with SF6 gas at 5 bar. In this model, the contact resistance, eddy current, skin effect, thermal flow, and thermal radiation are considered. The ohmic losses generated in the conducting components are calculated through the harmonic electromagnetic analysis with MAXWELL 3D software. Then, the predicted losses are imported to the commercial CFD software ANSYS Fluent to fulfill the thermal simulation. Based on this model, the distributions of heat generation, gas velocity, and temperature-rise are obtained. The results show that the maximum power density and temperature-rise both occur at the contact zones of the three-position isolation/ground switch. To verify the developed model, the temperature-rise tests of the GIS are carried out at 2200 A. The simulation and measurement results are close with a maximum error of 3.99 K.
Estimate the Temperature Rise of Medium Voltage Metal Enclosed Switchgear by Simplified Heat Transfer Calculations
Electrical equipment will experience a rise in temperature during normal operation. During a development process, prototypes and laboratory tests will be required to make sure the temperature rises are within acceptable limits as defined by standards. The aim of having a tool to predict the temperature rise, is to reduce the number of prototypes and test loops needed in the laboratory during a development period. Advanced simulation tools such as CFD can give valuable results, however, they require expertise user and extensive compute and manpower allocation. This paper presents a practical design approach developed for providing a first, quick and rough estimate of the temperature rise of the most critical parts in an air insulated switchgear. The main idea behind the method is to first use the method described in IEC 60890 to estimate the temperature rise of the gas inside the switchgear. Then, simplified heat transfer calculations are used to estimate the over-temperature of critical parts relative to the surrounding gas. The accuracy of the temperature estimates will depend on how well the power input is known, especially the contact resistances. Further, it may be challenging to predict the influence of large metallic construction elements that may function as heat sinks.
Determination of heat circumstances in the motor protection switch considering air flow
This paper presents the determination of heat conditions in the motor protection switch, with consideration to the air flow inside the switch. The finite-element method (FEM) was used for the calculation of the temperature conditions. Because of the temperature-dependent material properties and the geometrical peculiarities of the model, a sequential procedure for the calculation of the heat circumstances was developed. The specificity of the model is that the inside air is separated into two domains. These two domains are physically completely separated, but they have an indirect influence on each other through the thermal conductivity of partition walls