What is a common characteristic of events that usually lead to major blackouts?

Major blackouts typically occur as a result of multiple significant events that are interconnected within the same area. This characteristic highlights the complexity and interrelated nature of power systems, where a failure in one part can cascade through the network, impacting other areas. For instance, a transmission line failure can lead to overloading and instability in adjacent lines or substations, which can compromise the overall reliability of the power grid.

Events that lead to blackouts often include a combination of equipment failures, weather-related incidents, human errors, and operational decisions that collectively contribute to the power system's inability to sustain the load. By understanding that these incidents usually involve multiple factors working in conjunction, operators can better assess risks, design more resilient systems, and develop strategies to mitigate such failures.

In contrast, events occurring during off-peak times, isolated occurrences, or those that are predictable typically do not align with the nature of major blackouts, as these scenarios might not contribute to the systemic failures that lead to widespread outages.