Which power event is characterized by high voltage lasting longer than 1 minute?

A power event characterized by high voltage lasting longer than one minute is referred to as a swell. Voltage swell refers to an increase in voltage above the normal level, typically exceeding the nominal voltage for a duration longer than one minute. This can lead to various issues, including stress on equipment and potential damage when the voltage remains elevated for an extended period.

In understanding power quality events, it is important to distinguish between phenomena like surges, transients, and undervoltage conditions. A surge, for instance, is a brief increase in voltage that typically lasts for only seconds, not minutes. Transients are short-lived spikes in voltage and can happen instantaneously, lasting a fraction of a second. Undervoltage, on the other hand, occurs when the voltage drops below the acceptable level, which does not relate to a high voltage condition. Therefore, the definition and duration associated with a swell clearly categorize it as the correct answer in this context.