Fundamentals of Power System Protection

An electric power system should ensure the availability of electrical energy without interruption to every load connected to the system. The high voltage transmission lines carrying bulk power could extend over several hundred kilometers, as these are overhead lines and are exposed to their breakdown due to natural calamities, falling of external objects, and damage due to the insulators. These are not only due to mechanical damage but also in an electric fault. One of the sources of trouble to continuous supply is the shunt fault or short circuit which produces a sudden and sometimes violent change in system operation. Protective relays are meant to mitigate the effects of faults. This text treats the entire spectrum of relays, from electromechanical to the state-of-the-art numerical relays for protection of transmission lines, turbo alternators, transformers, busbars, and motors. The protection engineer has to strike a balance between the threat perception and the security offered by the protective scheme.