Overfrequency

Overfrequency refers to a condition in an electrical power system where the grid frequency rises above its nominal operating value. The nominal frequency is typically 50 Hz or 60 Hz depending on the region. This rise in frequency indicates that the total generation of electricity in the system is exceeding the total demand.

The frequency of an AC power system is a critical parameter that reflects the balance between the mechanical power input to generators and the electrical power output. When demand decreases suddenly, or if there is a rapid increase in generation, the rotational speed of the generators increases, leading to an overfrequency event.

Minor overfrequency deviations are common and are usually corrected automatically by the system's control mechanisms, which adjust generator output to match demand. However, significant or sustained overfrequency can pose risks to the power system. It can lead to voltage instability, damage to sensitive equipment, and in extreme cases, cause protective relays to trip generators offline, potentially leading to cascading failures.

To prevent and mitigate overfrequency, power systems employ various control strategies. These include automatic generation control (AGC), which continuously adjusts generator output, and demand-side management programs that can reduce load when necessary. Overfrequency protection systems are also in place to automatically disconnect loads or generators if the frequency exceeds predefined safe limits.