Voltage collapse proximity indicators for radial distribution networks

Based on the single-line equivalent system of a radial distribution network, two simple methods to evaluate two efficient voltage collapse proximity indicators are presented and discussed. The two methods differ on the determination of the parameters which define the equivalent system from which the indicators are derived. Both methods can be conveniently used jointly for on-line applications to assess the state of a distribution system from the viewpoint of voltage stability; the first to monitoring the stability margin of the whole system loading, the second to sharpen the stability analysis at the critical node when the system operating point is in the vicinity of the Readability limit. The effectiveness of the proposed methods is tested on a 11 kV radial distribution system of 85 nodes and results are compared with those found by a repetitive load flow calculation.