An Uncertainty-based Criterion for Aggregation of Consistent ROCOF Measurements

Modern power systems are characterized by fast dynamics and require increasing resilience and short recovery times when faults occur or operating conditions change suddenly. To detect possible events promptly, Transmission Systems Operators (TSOs) often rely on the Rate of Change of Frequency (ROCOF) values collected by multiple Phasor Measurement Units (PMUs) installed at different buses. However, such data are often aggregated blindly, i.e., without taking into account neither the related measurement uncertainty, nor possible inherent differences of ROCOF values due to grid topology. This paper instead investigates the problem of ROCOF data aggregation from a double perspective. On one hand, we performed extensive Monte Carlo simulations in two case studies to get a trustworthy evaluation of grid-level ROCOF definitional and measurement uncertainty both in ordinary and transient operating conditions. On the other, a criterion is proposed to aggregate the PMU ROCOF data only when they are consistent and the associated measurement uncertainty is within given boundaries. The proposed criterion is validated using the same data sets mentioned above.