LOAD SHEDDING ON AN ISOLATED SYSTEM

Underfrequency load shedding (UFLS), in previous generations shunned by the industry as an admission of poor planning and operation, has become a generally accepted practice. There is by now a considerable body of literature on the subject, dating back to midcentury. That literature, however, deals with the subject in the context of large interconnected systems. Smaller, isolated systems, which are more vulnerable to serious disturbances, have operating characteristics that require somewhat different guidelines, due to their lower inertia, limited reserves, and lack of access to off-system assistance. This paper reviews the objectives and principles of UFLS, and reports their application, to a small island power system.