Internal to each Scenario, there is a *ShedLoadOnScenario-type Discrete Measurement. The LoadShedding Source of this Measurement is an algorithm output that indicates whether that Breaker must or must not be preset for the Scenario. The Scada Source, on the other hand, must be configured to receive the field variable that indicates the preset status of this Scenario in the IED.

The difference between this value and the Scada Source value triggers the preset command automatically.