Nov 30 2024 Pacific Northwest Hydro Disturbance

On November 30, 2024, at 18:31 Pacific Time, the Pacificorp (PACW) Merwin-Cherry Grove 115 kV line trips due to a fault. PACW Merwin Hydro Unit #3 tripped offline immediately after.

For the next 12-13 minutes, multiple nearby units including Transalta Centralia, PACW Merwin Hydro, PACW Yale Hydro experienced oscillatory MW fluctuations until PACW operators shut down both Yale units.

The oscillations were visible throughout the Pacific Northwest and further south, where oscillatory MW flows were transmitted via the California Oregon Intertie (COI).

Source: Daigle, David T, “Utilization of Synchrophasors for Monitoring System Disturbances at CAISO”, North American SynchroPhasor Initiative, April 15, 2025, Minneapolis MN, “https://www.naspi.org/sites/default/files/2026-06/01_01_01_Daigle_CAISO_20250415.pdf”

This disturbance was particularily visible via the Vancouver, WA KGRID Waveform Measurement Unit due to its placement less than 30 miles from Merwin and Yale units. During the oscillation, a strong 1.23 Hz fundamental frequency was observed with 2nd, 3rd, and 4th harmonics of this fundamental clearly visible. KGRID is a community led project to collect power system waveform data from throughout the world for the benefit for the research community. Zoom in on the frequency waveforms in the KGRID plots (you can click items in the legend to hide them) and you can observe the Vancouver frequency oscillating against the rest of the system. An important note is that the KGRID units in this plot use NTP (internet) time, no GPS units were online at the time of this event, so the timestamp accuracy may be limited.

Download the waveform and phasor data in .csv format here: