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A triple junction, joining place of a conductor, insulator, and gas substance, is a critical place with low dielectric strength in a high voltage apparatus. Around this triple junction, the electric field intensity is abruptly increased and the breakdown phenomena can be easily observed. To predict the breakdown characteristics of the triple junction, it is essential to estimate the distributions of electric field intensity with very high accuracy. In this work, to more accurately evaluate the electric field around the triple junction, we propose an advanced FEM (A-FEM) adopting a singularity function combined with the conventional FEM augmented with only one unknown variable. Index Terms--Finite-element method (FEM), singularity function, stress intensity factor, triple junction.

Optimal design of the direct-driven PM wind generator, coupled with finite element analysis and genetic algorithm, has been performed to maximize the annual energy production over the whole wind speed characterized by the statistical model of wind speed distribution. Particularly, the parallel computing via internet web service has been applied to loose excessive computing times for optimization. Index Terms--Annual energy production (AEP), genetic algorithm (GA), parallel computing, permanent magnet (PM) wind generator.

This paper presents a new magnetothermal finite element analysis for predicting the temperature rise of the extra-high voltage gas insulated switchgear bus bar. The power losses of a bus bar calculated by the magnetic field analysis are used as the input data to predict the temperature rise for the thermal analysis. The heat-transfer coefficients on the boundaries are analytically calculated by applying the Nusselt number considering material constant and model geometry for the natural convection. The temperature distribution in a bus bar by coupled magnetothermal finite element analysis shows good agreement with the experimental data. Index Terms--Coupled magnetothermal analysis, current-carrying capacity, EHV GIS bus bar, heat-transfer coefficient.

Transient electromagnetic forces in radial and axial directions induce critical mechanical stress on windings and transformers. In this paper, short-circuit electromagnetic forces that are exerted on transformer windings are investigated. A 3-D transformer model is considered to calculate the transient electromagnetic forces. The magnetic vector potential, magnetic flux density, and electromagnetic forces due to the short-circuit transient currents applied to the power transformer are analyzed by a coupled electromechanical finite-element method. The results obtained are compared with the analytical results and show good agreement. The numerical modeling technique dealt with in this paper is expected to be useful in the design of power transformers. [ABSTRACT FROM AUTHOR]