Defining Power System Frequency

The definition, measurement, and interpretation of the frequency of a power system is a challenging problem without (so far) a satisfying solution. Power engineers may be drawn to a definition that does not require a particular procedure to be followed in order to obtain interoperable results. However, this may not be achievable, as at least some measure of filtering of the signal may be needed. Further, because of the short window of observation required to meet real-time constraints, the interpretation of the result is difficult. The usual meanings, both mathematically and linguistically, do not apply. Disturbances in the power system cause further problems for interpretation. The goal of the paper is to provide a firm foundation for understanding the matter.