Assessment of upgrading existing primary feeders from radial to normally closed loop arrangement

The problems that we may face while upgrading primary feeders from radial to normally closed loop arrangement have been explored in this paper. Four existent distribution feeders with original radial arrangement fed by two distribution substations of Taiwan Power Company were utilized as sample feeders to form a normally closed loop with three different types of connection between any two of these radial feeders. The two radial feeders were normally tied together at their ends to form a closed ring. The three different arrangements are the two feeders fed by the same transformer, by distinct transformers in a substation and by distinct transformers located in different substations, respectively. The power flows, voltage profiles and short-circuit capacities of the sample distribution feeders with originally radial arrangement and normally closed loop arrangement were evaluated, and the impacts of the arrangement upgrading were assessed. The outcomes are of value to the distribution engineers to upgrade an existing distribution network with unqualified performance and unable to meet the requirements of its customers in the present day or in the near future.