Impact of short-circuit impedance and tap changing method selection on the key-design parameters of core-form power transformers

Making a competitive transformer design is a nonlinear mathematical optimization task which should be solved in the tendering design stage. Due to the complexity of the power transformer design, a wide range of optimization algorithms are been proposed in the literature. Despite the large number of design optimization methods, most of them neglect the effect of tapping arrangement from their transformer model in the tendering design stage. In this paper, the effect of these different regulation types is examined by a power transformer design methodology which applies geometric programming-based meta-heuristic algorithm. The impact of the selection between a two-winding built-in, a reversed and a coarse-fine regulated tapping arrangement is examined focusing on the total ownership cost and the key-design parameters. A design example on a 63-MVA, three-phase core-type power transformer with the three types of tapping arrangements is presented, and their effect on the parameters is analyzed.