Heuristic Approach to Ring Main Unit Placement within a Self-Healing Distribution Network

Active management and protection of distribution networks are beginning to take a foothold in utilities within Africa. In this regard, Fault Location, Isolation, and Service Restoration (FLISR) scheme is a prevalent smart grid functionality for enhancing the reliability performance of a distribution system. At the high level, FLISR facilitates faster sectionalization of a distribution feeder during a failure event and reliability improvement is achieved by limiting the exposure to or duration of outage experienced by customers connected to the feeder i.e., Self-Healing. This paper introduces a Heuristic Method suitable for FLISR scheme implementation: select manually operated medium voltage isolation switches are upgraded to automated and/or tele-controllable Ring Main Units (RMU). The method assigns a Reliability Value that can be readily calculated for any manual switches under consideration. A ranking system is then introduced to rank the manual switches where ones with the highest Reliability Values are prime candidates for automation. A case study will be presented based on an actual distribution network in a utility in North Africa, using a predictive reliability model developed in CYMDIST software to compute and compare the reliability performance (SAIDI) of selected feeders with RMUs. The result shows that the reliability performance with RMU is most sensitive to feeders with longest length attributes and least sensitive to the feeders with lowest capacity attributes in the network.