Book excerpt: Voltage Stability is a relatively recent and challenging problem in Power Systems Engineering. It is gaining in importance as the trend of operating power systems closer to their limits continues to increase. Voltage Stability of Electric Power Systems presents a clear description of voltage instability and collapse phenomena. It proposes a uniform and coherent theoretical framework for analysis and covers state-of-the-art methods. The book describes practical methods that can be used for voltage security assessment and offers a variety of examples.