Thermal behavior investigation of installation orientation and color effect on distribution transformers using E-TRM method and its effect on loading

Abstract

The importance of the distribution network is not overlooked by anyone. The transformer is one of the key equipment in this network. Therefore, great care and attention are needed in its design, maintenance and operation. Most of the oil-immersed distribution transformers are operated under solar radiation conditions. However, increasing the oil temperature due to solar radiation is not considered in their design. This increases the oil temperature above the design temperature value and thus reduces the life of the transformer. In this paper, due to the lack of specified equations for solar energy absorption by the fins and tank of the transformer, a novel method and equation are proposed for the calculation of the transformer solar radiation absorption amount. As well as, the effect of orientation on the corrugated tank distribution transformers oil temperature is investigated using the Electro-Thermal Resistance Model (E-TRM). For this purpose, two identical transformers with different orientations are tested experimentally and the results are compared and verified with the numerical results. The transformer tank color is one of the effective factors of solar radiation absorption. Depending on the absorption and emission rates, the effect of the different colors of the transformer tank on the oil temperature in different loading is investigated in this paper. The results show that the use of bright colors in comparison with dark colors can lower the oil temperature by about 3 °C on the rated loading of the transformer. In order to consider the effect of solar radiation on the transformer, the modified ambient temperature is introduced for the design of the transformer. Finally, the effect of transformer operation under solar radiation and with different colors is investigated and transformer loading de-rating is proposed by a novel equation.