Transformer Impedance Calculation Using the Finite Element Method

The design and construction of power transformers are complex tasks because they are high-capacity machines and must provide high reliability during their operation within the power system. Inaccuracy in calculating its parameters can cause unexpected failures in the machine and put the rest of the electrical system at risk. For this reason, it is of great importance that the design parameters of the equipment satisfactorily comply with the particular specifications and applicable national and international standards. In this paper, the calculation of the transformer impedance is conducted using the finite element method (FEM) in three types of transformers: A single-phase core-type power transformer, a three-phase shell-type distribution transformer, and a single-phase self-service transformer. The results obtained with the FEM are compared against those obtained through traditional analytical formulas; which give imprecise results in the case of special designs and complex geometries. Finally, the calculated values are validated with the results of experimental measurements carried out in the laboratory. It is concluded that the Finite Element Method is suitable for accurately calculating the impedance of distinct types of transformers, especially when their internal geometries are complex.