The control systems of an electrical power station must cope with the normal changes in demand for power and with fault transients that arise locally or in the grid network. To achieve design-life and to restrict damage-progression, the individual control loops must be co-ordinated so as to prevent the violation of operational constraints during these induced manoeuvres. Due to the complex non-linear interactive dynamics, proposed control schemes can be vindicated in general only by detailed simulations of several major plant items. This book describes the underlying "physics" and simulation of the principal components of an electrical power plant with particular reference to certain types of nuclear steam generators. As well as the basic equations and their numerical solution, emphasis is given to the role of operational constraints and fault transients in determining the salient features of both the simulation and the control strategies for the plant.