Under what condition is a Geomagnetic Disturbance Action cancelled?

The correct condition for canceling a Geomagnetic Disturbance Action is when measurements are below 10 amps for 3 hours. This threshold indicates that the geomagnetic disturbance has subsided to a point where it no longer poses a significant risk to the transmission system. By monitoring the current flowing through the system, operators can effectively gauge the impact of geomagnetic disturbances. When the measurements fall below this specified level for a sustained period, it reflects a return to stable conditions, allowing for the cancellation of the disturbance action.

In contrast, other conditions focus on higher current measurements, suggesting ongoing risks that would necessitate maintaining the action taken. For instance, if measurements are above certain thresholds, it indicates that the system is still experiencing significant geomagnetic interference, which would mean that proactive measures should remain in place until the lower threshold is reached. Thus, monitoring these parameters is critical for ensuring the integrity and stability of the transmission system in the face of geomagnetic events.