When might a power system be required to deploy spinning reserves?

The deployment of spinning reserves is crucial in maintaining the reliability of a power system, especially after unforeseen disruptions. The most relevant scenario for requiring spinning reserves is following a generator outage. When one or more generators in the power grid suddenly fail or go offline, there can be a rapid loss of generation capacity that may result in an immediate imbalance between supply and demand.

Spinning reserves are resources that are online and can be increased in output on short notice to manage this imbalance. They typically consist of generating units that are already running at less than maximum output and can quickly ramp up their generation to compensate for the lost capacity. This prevents potential voltage drops, frequency instability, and blackouts from occurring in the power system.

When considering the other scenarios, although they represent situations that can affect the power system, they do not exclusively necessitate the immediate deployment of spinning reserves. For instance, during peak load periods, the base generation might already be utilized, and other types of reserves (non-spinning or standby) may be summoned rather than spinning reserves specifically. Demand falling below generation could lead to excess supply, but it doesn’t directly create a need for spinning reserves. Similarly, during scheduled maintenance, while some units are offline, the system should typically be managed