Online voltage stability monitoring using VAr reserves

For many years, system operators have noticed that the VAr reserves of key generators can indicate the degree of controllability of key bus voltages in a system. This observation has led to the development of a few VAr reserve monitoring systems. In this paper, a rigorous investigation on the subject is conducted. Using the correlative relationship between generator VAr reserves and system voltage stability margins, a practical and systematic method for online voltage stability monitoring is proposed. The method has been thoroughly tested on two real-life power systems with promising results.