Transformers of reduced losses and evaluation of their repair

The purpose of this work is to determine the optimum reduction of iron and copper losses in distribution transformers. Design and life-cost calculations for transformers 20 kV/400 V of a nominal power 50-1000 kVA were performed, for estimating the final transformer price for different amounts of loss reduction, in order to find out the minimum annual operational cost of these transformers. For estimating the annual cost, the final transformer price and the power and energy cost due to the transformer losses have been used. In this way, the optimal losses (iron + copper) have been found out for the minimum annual cost. The impact of a damaged tranformer's age on the economic decision for its repair has been investigated as well.