Impedance analyses of heavy load node in voltage stability studies

According to the contributing factors the load impedance variations are classified into external cause mode and self specific property mode. On the basis of the demonstration with regard to principal properties of the node impedance variations, it is suitable to play the role of the node impedance modules among the physical quantities characterizing heavy load node while the operating points lie on the lower half or the steep segment belong to upper half of the P-V curves. When the dynamic load flow or middle-term stability software are applied to research voltage stability for actual complicate power systems, the heavy load pilot nodes with minimum stability margin during crises should be treated specially by embedding the impedance analyses and taking close-up to express the critical situation concretely.