Nature and operation schemes of normally closed-loop distribution systems

This paper explored the nature and operation schemes of normally closed loop distribution systems. The operation scheme of this type of system was drawn based on its specific configuration, and then the suitable ratings of its main transformer and feeder conductors were assessed. According to the assessment results, a typical normally closed loop was build, and its performance was evaluated through power flow and short circuit analyses. Based on the analyses, the nature of the typical closed ring can be recognized, such as power flows and directions in the loop, voltage profiles of the loop, and short circuit MVAs along the loop, under both normal and abnormal conditions. These results are of value to the distribution engineers to properly plan and operate this kind of electric power distribution system.