Guam Power Authority automatic underfrequency load shedding study

This paper describes the development of a new automatic underfrequency load shedding scheme on the Guam Power Authority's (GPA) system using a transient stability simulation program. The new scheme strives to minimize the amount of load shed by selecting frequency settings based on the severity of generation or load unbalance and the availability of spinning reserves. The fast speed of frequency decay due to loss of generation is shown to be particularly pronounced in an island system, requiring more careful design of any load shedding scheme than large interconnected systems. The use of a well-prepared transient stability study model allows the simulation of specific contingencies and the fine-tuning of load shedding strategies for optimality. The trade-off between equipment protection, customer service availability, and practical operating issues, such as, synchronization of generators to the grid, are discussed.