ABSTRACT
Under normal conditions, a power system operates as a balanced three-phase ac system. A significant departure from this condition is often caused by a fault. Faults give rise to abnormal operating conditions, usually excessive currents and voltages at certain points on the system. Balanced three-phase fault calculations can be carried out on a per-phase basis, so that only single-phase equivalent circuits need be used in the analysis. The chapter considers the components required for protection, and surveys some approaches for the protection of generators, transformers, and transmission lines. It aims to consider the development of the sequence network for a solidly grounded synchronous generator having a double line-to-ground fault. The chapter shows how the method of symmetrical components may be combined with the formation of sequence networks for unbalanced fault situations such that postfault currents and voltages may be determined for situations such as single-line-to-ground, line-to-line and double-line-to-ground short circuits on a generator.
