3D heating hazard assesment on transformer covers. Arrangment decisions
Purpose - The purpose of this paper is to apply a 3D methodology to assess the heating hazard on transformer covers and present a practical tool to design amagnetic inserts arrangement. Design/methodology/approach - A practical 3D methodology linking an electromagnetic analytical formulation with thermal finite element method is used for computation. Such methodology allows the evaluation of the temperature on metallic device elements heated by electromagnetic induction. This is a 3D problem which in the case of power transformers becomes especially difficult to apply due to the discretization requirement into the thin skin depth penetration compared to big machine dimensions. Findings - From the numerical solution of the temperature field, decisions on dimensions and different amagnetic inserts arrangements can be taken to avoid hot spots on transformer covers. Research limitations/implications - Some parameters presented in the model as heat exchange coefficients and material properties are difficult to determine from formulae or from the literature. The accuracy of the results strongly depends on the proper identification of those parameters, which the authors adjust based on measurements. Originality/value - Differing from previous works found in the literature, which focus their results in power loss computation methods, this paper evaluates losses in terms of temperature distribution, which is easier to measure and validate over transformer covers. Moreover, an experimental work is presented where the temperature distribution is measured over a steel cover plate and a cover plate with amagnetic insert.
heating hazard transformer cover transformers amagnetic insert hot spot bushings leakage flux analytical method finite element analysis poynting's vector