What is the need of power system security assessment? How contingency analysis help in it? Well prevention is better than cure, so failure of electrical supply or blackout is the disease and security assessment is the diagnosis in first stage of the disease and contingency analysis is a method of diagnosis. So, it tells us about the disease in early stages and the way to prevent it from becoming a dangerous one. In this book everything has been explained in details about Power system security assessment and contingency analysis method and how these can be used to prevent blackouts effectively.