scope:

This publication presents in a step-by-step, simplified, yet comprehensive, form the principles of system protection and the proper application and coordination of those components that may be required to protect industrial and commercial power systems against any abnormalities that could reasonably be expected to occur in the course of system operation.

Coverage is limited to system protection and coordination as it pertains to system design treated in ANSI/IEEE Std 141-1986 [1]1 and ANSI/IEEE Std 241-1983 [3]. No attempt is made to cover utility systems or residential systems, though much of the material presented is applicable to these systems.

The designer of electric power systems has available several techniques to minimize the effects of abnormalities occurring on the system itself or on the utilization equipment that it supplies. One can design into the electric system features that will:

Quickly isolate the affected portion of the system and in this manner maintain normal service for as much of the system as possible and minimize damage to the affected portion of the system

Minimize the magnitude of the available short-circuit current and in this manner minimize potential damage to the system, its components, and the utilization equipment it supplies

Provide alternate circuits, automatic throwovers or automatic reclosing devices, or both, where applicable, and in this manner minimize the duration or the extent, or both, of supply and utilization equipment outages.