Development of a Versatile Voltage Stability Index Algorithm

Power system experts have shown interest in the development of methods for predicting system status in the form of voltage stability indices. These indices performed well because they were primarily used for system planning as utilities then were either highly localized and regulated by the state or owned and operated by big electricity consumers. However, the situation changed drastically with the advent of unbundling, privatization/competition and power pooling in the last two decades. Consequently, incidents of power outages have become a common occurrence worldwide because of increasing load demand without proportionate increase in electrical power supply due to difficulties posed to the building of new generation centers and transmission lines by residents and environment. This paper, therefore, develops a versatile index algorithm that incorporates robust features so as to guarantee the optimal utilization of the various voltage collapse indices to adequately predict, monitor and detect the status of power system both online and off-line. It reviews existing voltage stability indices, and for the first time outlines index selection criteria to guide system operators and planners in their optimal usage to reduce outages and operational cost. The work, also, presents a new index computation scheme utilizing the complex pi-model of the medium and long transmission line. This new index will be used to effectively determine the status of power systems to prevent system overloading during power pooling and long distance wheeling of power, which has become a common phenomena among independent system operators (ISOs) and regional transmission organizations (RTOs) during peak and emergency periods. The simulation results show a favorable performance of this new index on both IEEE 14 and 30 bus systems with respect to existing indices.