12/06/2026
Three days at AEW. One conversation kept repeating.
The conversation was not about Class A as a credential. It was about what conventional instrumentation actually shows you when something goes wrong — and what it does not.
The reference point most often raised was the Iberian event on 28 April 2025. ENTSO-E documented two pre-event oscillation periods leading into the cascade: a 0.63 Hz local oscillation between 12:03 and 12:08, classified by ENTSO-E as converter-driven instability primarily affecting the Spanish and Portuguese power systems, and a 0.2 Hz inter-area oscillation between 12:19 and 12:22 on the East-Centre-West continental mode.
Both sat within the conventional PMU detection envelope. ENTSO-E investigated using PMU phasor data at 100 ms sampling, ten samples per second. The phasor swings were visible. The macro-level symptom was visible. The technology did its job.
What the phasor data does not resolve is the inverter-control sub-cycle dynamics that ENTSO-E identified as underlying the converter-driven instability. The interactions between IBR control loops, harmonic injections, and the sub-synchronous response of the network — a layer of evidence beneath the phasor swing — sits at a different time resolution entirely.
This is the territory point-on-wave measurement was built for. VECTO's small signal stability algorithm concurrently identifies three ranges of dominant oscillation phasors between 0.1 Hz and 43 Hz: inter-area, local-area, and the 10 to 43 Hz IBR control-loop band. Underneath, 50 kHz GPS-synchronised synchrophasor waveform data with absolute time accuracy under 100 ns provides the raw signal a converter-driven event leaves behind before it reaches the phasor.
The conversations at AEW landed on the same place: phasor-grade visibility is necessary, and not sufficient.
Reference: ENTSO-E, Final Report on the Grid Incident in Spain and Portugal on 28 April 2025, published 20 March 2026.
See entsoe.eu/publications/blackout/28-april-2025-Iberian-blackout/.