On-line monitoring of maximum permissible loading of a power system within voltage stability limits

On-line determination of the maximum permissible loading of a power system is essential for operating the system with an adequate security margin. A very simple and straightforward method of determining the maximum permissible loading and voltage stability margin of a power system using information about the current operating point is proposed. The method simply requires some locally measurable quantities, such as bus voltage magnitude, and active and reactive components of load power. The measured data are carefully processed to estimate the maximum permissible loading and voltage stability margin of a system. The proposed method was vigorously tested on the IEEE 14- and 30-bus systems and the simulation results indicated that the method can correctly estimate the maximum permissible loading of the systems at the verge of voltage collapse.