Which term best defines the deviation of system frequency from its nominal frequency?

The term that best defines the deviation of system frequency from its nominal frequency is frequency variation. This concept refers to the fluctuations in the actual frequency of the electrical grid compared to its designated standard or nominal frequency, which is typically 50 Hz or 60 Hz depending on the region. Frequency variation can occur due to imbalances between power generation and consumption, leading to either increases or decreases in frequency.

Accurate understanding of frequency variation is crucial for maintaining grid stability, as significant deviations can impact the operation of electrical equipment and the overall performance of the power system. It directly indicates how well the system is performing in terms of balancing supply and demand. Therefore, frequency variation is a fundamental aspect of grid management and operation, emphasizing the importance of real-time monitoring and control efforts to mitigate such deviations.