Effect of PMU analog input section performance on frequency and ROCOF estimation error

Phasor measurement unit (PMU) performance depends on the performance of the PMU´s analog input section and the limitations of its DSP algorithms. For the different PMU performance requirements established in the standards, the relative importance of these two factors varies significantly. For steady-state frequency and rate-of-change-of-frequency (ROCOF) measurements, this paper shows that estimation error is primarily dependent on noise mechanisms in the input section and the effective bandwidth of the signal processing algorithms. Estimation error may be predicted based on understanding these two factors, and optimum performance may be realized by careful design choices. When the PMU function is implemented with separate data acquisition and computation functions, this interaction must be carefully considered, so that the PMU results are equivalent to those from an integrated, conformant PMU - as users expect.