Reportable disturbances are contingencies that meet or exceed what percentage of the most severe single contingency?

In the context of the NERC Electric Power Sector Reform (EPSR), reportable disturbances refer to significant events in the electrical grid that may require attention and reporting due to their potential impact on the system's reliability and stability. Specifically, these disturbances are defined in relation to the most severe single contingency, which is an event that results in the largest loss of capacity or capability in a power system, such as the failure of a major transmission line or the loss of a significant generation unit.

When a disturbance meets or exceeds the threshold of 80% of the most severe single contingency, it becomes reportable. This threshold is established to ensure that only substantial disturbances are documented, focusing on events that could significantly affect system performance. By defining reportable disturbances in this manner, NERC aims to streamline reporting processes and prioritize significant incidents that may require further investigation or corrective actions in order to maintain grid reliability.

Thus, recognizing that reportable disturbances represent conditions with considerable ramifications allows the electrical power sector to implement effective measures for oversight and improvement.