Economic Comparison of Secondary Voltages; Single- and Three-Phase Distribution for Residential Areas [includes discussion]

Abstract

The semiburied system with distribution transformers in partially buried housings and with direct-buried primary and secondary cables has been used to a limited extent with varying degrees of success. One of the difficulties of this basic type of distribution system is that continual reinforcements are required as load grows in exactly the same manner as for the overhead systems. In the case of the overhead system, however, these reinforcements are relatively easily made by the addition of pole-mounted transformers or changing of secondaries or secondary runs. It is the authors' opinion that the area coverage higher secondary voltage system described in this paper circumvents these difficulties. Relatively large areas of the system can be reinforced for load growth by simply changing out one transformer, and running a few trunks from the transformer station to predetermined feed points in the basic secondary main system. ConclusionsThe nature of this paper is such that some of the conclusions take the form of the authors' opinions. are conventional 120/240-volt singlephase and 120/208-volt 3-phase systems; and single-phase and 3-phase higher secondary voltage systems. The 3-phase systems are considered because they can provide savings to both utility and consumers when the consumers have large motors. The studies have been made for average peak diversified demands up R. A. ZIMMERMAN ASSOCIATE MEMBER AIEE THE HIGH COST of serving heavy residential loads with the conventional 120/240-volt radial system indicates that other system possibilities and voltages should be explored. The use of higher secondary voltages in commercial areas suggests that the potentialities H. E. LOKAY ASSOCIATE MEMBER AIEE of higher voltage systems be studied for residential areas. The purpose of this paper is to present and compare the results of such studies with the results of studies of the conventional 120/240-volt radial system.