Power Transformers Short Circuit Impedance Calculation Using Energy Method Based on Leakage Flux

Short circuit impedance value is one of the most critical specifications of power transformers, which is guaranteed by the manufacturer. The manufactured transformer in the factory will be tested and the measured short circuit impedance value must be equal to the calculated value in the design stage with an allowable tolerance. One of the essential methods for calculating short circuit impedance value is the energy method. In other papers, energy method is thoroughly reviewed, but the purpose of this paper is to show a method which calculates short circuit impedance value practically through a combination of simple equation and FEM based simulations. In this paper, the energy method has not been used as steted in many references, instead, the energy value inside the transformer is used. It is notable that the presented paper goal is not to provide a new computational method for calculating short circuit impedance like other methods such as energy method. In this paper, the concept of short circuit impedance, calculation methods, and measurement methods will be expressed first. Actually, the presented method in this paper is practical for industrial factories and researchers because calculations are more straightforward and more compact and the software (ANSYS Maxwell) needed for the simulation is also available to everyone. As a result, the need for other noncommercial industrial software and heavy calculations is eliminated. Finally, a 315 MVA power transformer has been accurately simulated, and short circuit impedance is calculated using the presented method. To ensure the accuracy of the simulations and calculations, short circuit impedance value in the transformer technical data sheet and obtained value from simulations will be compared.