Information on the application of underfrequency load shedding and restoration to ac power systems is compiled in this guide. Various system conditions that may require the use of underfrequency load shedding and the application of protective relays to various methods of performing underfrequency load shedding are described in this guide. Some practical examples of underfrequency load shedding applications are also provided.

This document serves as a guide for the application of protective relays used for load shedding and restoration during electric power system abnormal frequency conditions. It presents background information, a bibliography, and recommendations. It discusses abnormal frequency power system behavior, existing load shedding and restoration practices, the abnormal frequency function of typical protective relays, and possible new methods for improved load shedding and restoration. This guide is limited to electric power system applications and does not include abnormal frequency protection for power generating plants.

There is currently no IEEE guide for the application of protective relays used for load shedding and restoration during electric power system abnormal frequency conditions. This guide complements IEEE Std C37.106-2003 [B35].1 It provides information to assist in the application of load shedding and restoration schemes. Methods and examples are provided.