Initial transformer sizing for single-phase residential load

The authors describe a method for determining the correct economic size of distribution transformers using end-use appliance load profiles and the ANSI/IEEE Standard C57.91-1981 thermal model. The method was developed to select the distribution transformer size required to serve single-phase residential loads. The goal of this method was to minimize the cost of serving residential customers with electric power while maintaining high power quality and reliability. The three steps in determining the proper transformer size are estimating the load to be served, calculating the thermal loads on candidate sizes of transformers, and calculating the present value of revenue requirements of each transformer size. The transformer selected is that transformer with the lowest present value within set limits of thermal load