Secondary Control

Balancing services deployed in the “minutes” time frame.

Secondary Control

Typically includes the balancing services deployed in the “minutes” time frame. Some resources, such as hydroelectric generation, can respond faster in many cases. This control is accomplished using the Balancing Authority’s control computer (terms most often associated with this are “Load-Frequency Control” or “Automatic Generation Control”) and the manual actions taken by the dispatcher to provide additional adjustments. Secondary Control also includes initial reserve deployment for disturbances.

In short, Secondary Control maintains the minute-to-minute balance throughout the day and is used to restore frequency to its scheduled value, usually 60 Hz, following a disturbance. Secondary Control is provided by both Spinning and Non-Spinning Reserves.

Typical Frequency Trend for the Loss of a Generating Resource (from ). Point A is defined as the pre-disturbance frequency; Point C or Nadir is the maximum deviation due to loss of resource; Point B is defined as the stabilizing frequency and; Point D is the time the contingent BA begins the recovery from the loss of resource.