Effect of sun radiation on the thermal behavior of distribution transformer

Performance and life of oil-immersed distribution transformers are strongly dependent on the oil temperature. Transformers, working in regions with high temperature and high solar radiation, usually suffer from excessive heat in summers which results in their early failures. In this paper, the effect of sun radiation on the transformer was investigated by using experimental and analytical methods. Transformer oil temperature was measured in two different modes, with and without sun shield. Effects of different parameters such as direct and indirect solar radiation on the thermal behavior of the transformer were mathematically modeled and the results were compared with experimental findings. Agreements between the experimental and numerical results show that the model can reasonably predict thermal behavior of the transformer. It was found that a sun shield has an important effect on the oil temperature reduction in summer which could be as high as 7 °C depending on the load ratio. The amount of temperature reduction by sun shield reduces as the load ratio of transformer increases. By installing a sun shield and reducing oil temperature, transformer life could be increased up to 24% in average.