Application of overhead distribution transformers through a formal loading program

This paper describes the method of applying overhead distribution transformers (167 kVA and smaller) which is employed by Southern California Edison Company. The method is based upon a program which involves a thorough and extensive investigation into the thermal and economic limits of distribution transformer loading. This application method is factored into (1) the bid analysis, including cost of losses, (2) the selection of transformer sizes for initial installation, and (3) maximum allowable loads for removal of transformers from service. The paper describes in detail the results of these investigations and on what basis the program was formulated.