Dynamic Behaviour and Instability During the 2025 Chilean Blackout: Causes, Controls, and Systemic Impact

System (Sistema Eléctrico Nacional, SEN) during the February 2025 large-scale blackout using

RMS‑type simulations calibrated against SCADA and PMU recordings and post‑event analyses.

On February 25, 2025, the SEN experienced a total blackout triggered by an undesired trip of a 500 kV double-circuit backbone line. The trip occurred after the line’s communication channel was reconnected, causing unintended operation of its line differential protection (ANSI 87L). This event occurred during operation with low system inertia, high power transfers through the 500 kV backbone, and high participation of inverter-based resources (IBR), including more than 2.2 GW of distributed photovoltaic (PV) generation embedded in distribution networks.

Two simulation scenarios were considered: (i) Event recreation, replicating the actual disturbance sequence, including uncoordinated tripping of synchronous units, IBRs, and distributed PV, and assessing the observed performance of the conventional Under‑Frequency

Load Shedding (UFLS) scheme, the Defense-Plan UFLS (DP-UFLS) scheme, and Automatic

Generator Shedding (AGS) schemes; and (ii) Full compliance scenario, assuming full grid-code compliance of generation protection schemes and correct operation of UFLS, DP-UFLS, AGS, and IBR ride‑through functions.

The results show that, although the initiating contingency was severe (system split into two islands), a system-wide collapse could likely have been avoided if generation and remedial schemes had operated in accordance with existing and mandatory requirements.

Finally, ongoing EMT-type studies and further improvements in IBR and load modelling are outlined, together with conclusions and lessons learned.