International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-6, Issue-3, Mar- 2019] https://dx.doi.org/10.22161/ijaers.6.3.19 ISSN: 2349-6495(P) | 2456-1908(O) www.ijaers.com Page | 159 Dry-Type Power Transformers Thermal Analysis with Finite Element Method Lucas R. Torin, Daniel O. G. Medina, Thales Sousa Centro de Engenharia, Modelagem e Ciencias Sociais Aplicadas, CEP: 09210-580, Santo André/SP, Brazil Email: Abstract — The transformer temperature is one of the main variables of interest in its manufacture and operation, since it interferes in the useful life of the transformer. In this sense, the present work proposes a thermal simulation for the temperature estimate of a dry- type transformer. Initially a thermal analysis was performed from experimental measurements of temperatures of a dry-type power transformer of 500kVA for different conditions of load. Posteriorly, a thermal simulation was proposed using finite element theory. Thus, the heat diffusion equation was used, with the following boundary conditions: convection and radiation equations; characteristics of the materials used; the measurement data and the dimensions of the transformer. FEMM 2D software was used for the proposed simulation. Finally, in order to validate the proposed analyzes, experimental measurements were compared with the values obtained in the thermal simulation. The results of the thermal simulation showed agreement with the experimentally measured values. Keywords— Dry-type transformers, Experimental measurement, Finite elements, Thermal simulation. I. INTRODUCTION Dry-type transformers are widely used in electric power distribution systems and are recommended for smaller indoor installations that require safety and reliability, require less maintenance and less damage to the environment [1]. The design and overload capacity of transformers are strongly influenced by thermal performance and behavior. The thermal influence on the power transformers is very relevant, and one of the main interest factors in the operation of transformers is the temperature, since it interferes with the aging of the insulation of the winding and, consequently, its useful life. Therefore, the temperature monitoring is essential to evaluate, in general, the wear of the transformer [2]. Studies have shown that the temperature is one of the major causes of deterioration of insulation material of power transformers and thermal stress. This thermal stress, caused by heat, is a condition where the insulation material is affected by the temperature of the environment in which it is located, when this temperature is at extreme levels, and which has resulted in electrical faults in the distribution systems. A temperature distribution and overload or overheating is a particular interest of manufacturers and customers with the purpose of prolonging the life expectancy of transformers [3], [4]. Also, in the design stage, in order to estimate the temperature, there are several numerical methods of thermal simulation, capable of dealing with complex geometries and that become important tools for the transformer designer. In this sense the finite element method (FEM) comes being widely applied after the evolution of the computational systems [5]. Considering FEM this work presents an analysis through the simulation of the results of theoretical and experimental investigations of the thermal behavior of a dry-type power transformer, when this is subject to different load conditions. These investigations, both theoretical and experimental, take into account several elements such as: transformer specification, thermal characteristics of the materials involved, transformer construction aspects; as well as the data collected in the experimental measurement, including the temperature at several points of the transformer, applied power and ambient temperature. So, it is possible to perform of dry-type power transformer simulations to estimate its temperatures at various points and obtain thermal images of the variation and distribution of temperature that occurs internally and externally to the equipment. In this way, the data collected in the experimental measurement can be compared with the results obtained in simulations. II. BACKGROUND Some analytical and experimental studies of the temperature distribution in some types of dry-type transformers have been presented in the literature. To this end a thermal mathematical model that calculates of the hottest spot temperature and its location in dry-type transformer windings was performed by [6].