Non-linear Impact of the Short Circuit Impedance Selection on the Cost Optimized Power Transformer Design

Since the electrical machine design is a complex task it can be divided into sub-problems, e.g. preliminary and final design processes and checking of the final design. This paper deals with the preliminary design process, which provides the key-design parameters of the electrical machine. Traditionally, these electrical machine models in preliminary design phase neglect or use oversimplified insulation system models and the tap changing selection is not involved during the calculation of key-design parameters. The aim of this study is to assess the effect of the insulation distance minimization and tap-changing on the key design parameters of a cost-optimized large power transformer. For this purpose, the paper shows some examples, where the cost optimal design — in contrast to the classical insulation design rule — contains larger insulation distances than the possible minimum values. The effect of tap-changing methods are also investigated. These cost optimization made by a verified, metaheuristic method-based transformer optimization algorithm. The results show involving the insulation design and tap-changing selection into the preliminary design process can provide more economical designs