Improper sizing of a power transformer may lead to shortening of its operating life or cause overloading failures. Based on ANSI/IEEE C57, IEC 60076-2 & 60726 standards, ETAP can easily determine the proper size of a power transformer. Many factors affecting the performance of transformers are considered in this module including ambient temperature, altitude, cooling stage and type (dry of fill), expected future growth of the required load and transformer short-circuit requirement (transformer impedance and the BIL insulation level).