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.
Application of Computational Fluid Dynamics to Reduce the New Product Development Cycle Time of the ${\rm SF}_{6}$ Gas Circuit Breaker
This paper describes thermal modeling, using computational fluid dynamics (CFD), to predict the temperature rise of a high-voltage SF6 gas circuit breaker during a heat-run test. In electrical equipment, maximum temperature rise in various components is limited by their material properties and, hence, the heat-run test forms part of type test. A methodology to predict the temperature rise at the design stage is developed using ANSYS-CFX and found to be beneficial to reduce the number of heat-run tests during the product development process. The developed methodology has been implemented on a 72.5-kV SF6 gas circuit breaker and validated with the experimental temperature rise results of the existing design at two current ratings: 1000 A and 2000 A. The methodology was further used to predict thermal performance of the breaker at a higher current rating of 3150 A. The prediction helped to understand temperature rise in various components and hot-spot locations. Various design modifications were then tested virtually to evaluate the temperature rise. Thereafter, the final modified design where the temperature rise of all the components was within the permissible limits and which also satisfied other constraints of manufacturing feasibility and cost was fabricated and physically tested. Good agreement is found between the CFD and experimental results.
Flocculation tests with electrophoretically separated serum proteins.
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