Abstract: “The paper presents voltage stability margin (VSM) of radial distribution network by considering a unique reactive loading index without and with distributed generator (DG). It is shown that the branch, at which the value of reactive loading index is minimum, is considered to be the weakest branch of the system. Then, the voltage stability margin (VSM) of the feeder is selected heuristically. It is the product of reactive loading indices of all branches of the feeder. The VSM of all feeders can be evaluated. The feeder which has the smallest value of VSM can be considered as the weakest feeder of the system and is at the proximity of voltage collapse. So, for multiple feeders, the voltage stability margin of a system may be considered as the VSM of the feeder which has the smallest value. The effectiveness of the proposed VSM without and with considering DG has been successfully tested on a 12.66 kV radial distribution network consisting of 33 nodes and the results are found to be in ve”

Keywords: Distributed generators; Reactive loading index; radial distribution network; voltage collapse; voltage stability margin; weakest branch