Finite element analysis of distribution transformer under harmonics condition: A review

The modern world is moving towards the smart grids and increased use of electronic loads. The realization of smart grid technology is the increased use of distributed energy resources, introducing new intelligent, communication and control systems that are mostly electronic circuits. The issues associated with this technology are bi-directional flow of power flow, increased harmonic emissions, direct current offsets and unbalances, voltage variation and switching transients. The increased usage of electronic loads at distribution level are generating harmonics, which in turn increases power losses in the transformers and cause pre-mature damage. These loads mostly inject the odd harmonics in the distribution system, resulting in the temperature rise of the transformer. It causes accelerated aging of transformer thereby called the attention of manufacturers and researchers to develop the procedures for enhancing the system reliability. In the literature, several methods have been proposed for calculating losses and derating the transformer such as experimental, IEEE recommended, analytical and Finite Element Method (FEM). This paper reviews the finite element analysis of distribution transformer under harmonics condition. The losses associated with harmonics, modeling and derating of transformer are the topics included in this paper. It is found that the main focus is paid on derating and losses calculation of the transformer for a percentage of harmonic contents.