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.
Development of Partial Discharge and Prediction of Short Term Development Trend of Insulators in GIS
To improve the effectiveness of ultra high frequency (UHF) method applied to partial discharge(PD) detection caused by insulators in gas insulated switchgear(GIS), and to achieve the development trend prediction, the developing process of PD is studied based on step test method. Phase resolved partial discharge (PRPD) patterns, phase resolved pulse sequence (PRPS) patterns and characteristic fingerprint information are extracted, then an information fingerprint library for the diagnosis of PD severity is built based on the effective information. Clustering algorithm and least square method are employed to build the division rule of development stages, PD's evolution mechanism is then studied considering with the experimental phenomenon. The prediction in the early stage of PD are studied based on Auto-Regressive and Moving Average (ARMA) model theory, the development trend of PD with step changed and nonlinear changed patterns are predicted.
A novel coupled magneto-thermal-flow analysis for temperature rise prediction of power apparatus
Many works on the temperature distribution of power apparatus have usually done by coupled magneto-thermal analysis. This method takes advantage over computing time. However, this method can not consider the internal gas or oil flow in the power apparatus such as gas insulated switchgear, GIS bus bar, and power transformer. Moreover it can not show the internal temperature distribution of the power apparatus exactly. This paper proposes a new coupled magneto-thermal-flow analysis considering Navier-Stokes equations. The convection heat transfer coefficient is calculated analytically by applying Nusselt number for natural convection and is applied to the boundary condition to the proposed method. Temperature distribution of the GIS bus bar model is obtained by coupled magneto-thermal-flow analysis and shows good agreement with the experimental data.