Design of Underground Distribution for Electric Light and Power Systems

In a previous paper presented at the 10th Annual Convention of the Association of Iron and Steel Electrical Engineers the author made some suggestions, based on many years experience in designing underground distribution systems, for the guidance of engineers interested in this class of work. The previous article treated the subject only in a general manner; the object of this article is to show each step necessary in the design of an underground distribution system, such as is usually required in a medium size city. No two systems are entirely alike. The operating conditions and municipal requirements are different in every locality, it is impossible, therefore, to make any definite rules that will apply under all conditions. By assuming the average conditions met with in the smaller cities it is possible to show the fundamental principles of handling this work in a systematic manner. While systems may, and do, differ, still it is possible to design a system for any type of distribution if these principles are followed. Where costs are given they are based on normal conditions and should not be taken as being the present costs, they are used simply for comparison however and will be of value in that manner only, and if treated as percentage difference will apply under any reasonable conditions. Owing to lack of space no tables have been printed in this article as they can be found in electrical handbooks.