Determining Inertia of 60 Hz Japan Power System using PMUs from Power Loss Event

System inertia is an important part of evaluating the initial frequency drop after a disturbance. Low system inertia driven by high levels of inverter interfaced renewable energy sources (RESs) results in large frequency drops, which significantly lead to violation of frequency safety thresholds. Thus, enhancing operator awareness of system inertia would preserve high-quality frequency regulation in the system with RESs. This work presents a practical study of inertia estimation of the 60 Hz Japan power system using phasor measurement units (PMUs) and the recorded disturbance (i.e., active power loss). Using phasor data provided by eight PMUs in a longitudinal transmission network, the frequency and rate of change of frequency (ROCOF) values from each significant area are analyzed to estimate accurate system inertia based on frequency spectrum and mode shape analysis. The obtained results indicate that not all PMUs can provide inertia estimation with accuracy due to the effect of interarea oscillation. Evidentially, the accurate latency of inertia estimation could be found at the PMUs installed around the center of inertia frequency.