Spain and Portugal’s Five Seconds of Instability: A Moment for Reflection on Power System Resilience

Exploring what past and present events—from South Australia to Spain—can teach us about designing, operating, and supporting resilient power systems in a changing energy landscape.

On April 28, Spain and Portugal experienced a rapid and widespread blackout. Within seconds, the grid lost over 15 GW of generation, significantly inverter-based, and the entire Iberian Peninsula was plunged into darkness. A disturbance in the Aragón–Catalonia corridor led to cascading failures: frequency dropped, France interconnectors tripped, and all forms of generation disconnected. What followed was one of Europe’s largest recorded blackouts.

Tram Overhead Lines - Lisbon, Portugal (Fri 15 Aug 2013)

Australia's Wake-Up Call Came in 2016

South Australia's system blacked out during extreme storms across multiple, geographically dispersed areas, which triggered a series of related transmission contingencies—but the critical factor wasn't just weather. It was the response to it:

• Some wind farms disconnected due to protection settings that were either incorrectly designed or not implemented as specified—whether from configuration errors, commissioning issues, or unauthorised changes.

• The Heywood interconnector tripped, triggering system collapse.

• There was no grid-scale storage or adequate system strength online at the time.

What Followed?

Australia didn’t just rebuild—it rethought how a grid should operate with high renewables:

• AEMO strengthened operational resilience with enhanced weather forecasting, modelling transmission tripping scenarios in real time.

• Contingency analysis has always been central to system operations, but post-2016, more stringent operating envelopes were introduced to increase resilience to a broader range of disturbances.

• Synchronous condensers were installed, and system strength services became part of TNSP obligations or developer arrangements.

• New mechanisms like Mandatory Primary Frequency Response (PFR) and Very Fast FCAS were introduced, along with grid-forming battery trials.

In the last 12 months, South Australia has reached just over 70% annual share of Forecastable Variable Renewable Energy (FVRE)—defined here as utility-scale wind, utility-scale solar, and rooftop PV.

In that period:

• There were 272 days where instantaneous FVRE share reached 100% or more during at least one trading interval

• And 37 full days where FVRE met or exceeded 100% of operational demand across the entire day

These figures highlight both the pace of change—and the operational complexity being successfully managed—in a system built around high levels of variable generation, supported by firming capacity, system strength, and strong operational discipline.

Grid resilience relies on more than just generation mix

Events like the recent Spanish blackout—or the Callide C4 incident in Queensland on 25 May 2021—remind us that major disturbances can occur in any grid, including those with a high proportion of synchronous machines. In many cases, the underlying issues relate not to the technology type but to incorrect protection settings, control system interactions, or inadequate coordination.

At Callide, a significant explosion and unit trip triggered a rapid loss of generation, leading to large frequency deviations. But unlike South Australia’s 2016 event, the broader NEM held together. The incident reinforced the value of a well-operated system—with coordinated frequency response, adequate reserves, and appropriately configured controls. Notably, many inverter-based resources successfully rode through the disturbance, further challenging the notion that low short circuit ratio (SCR) environments inherently compromise stability.

All these events also reinforce the importance of accurate and validated generator models. During the Generator Performance Standards (GPS) process, developers provide models that forecast how new plants will behave under various system conditions. But that’s only the first step. During testing and commissioning, these models must be validated to reflect real-world performance. Model fidelity is central to ensuring system security—not just for initial approval, but throughout the operational lifecycle. Without trusted models, operators and planners cannot reliably assess whether the system will land in a secure state following a credible contingency.

Beyond the technical: how blackouts are interpreted

As past events have shown—most notably the 2016 South Australia system black—large-scale blackouts will always trigger political fallout. Renewable energy is often the first target, even when detailed investigations point to deeper, system-level issues. That’s why it’s so important to focus on operational preparedness, system strength, and coordinated interconnection, rather than falling back on familiar narratives.

Recent commentary from analysts such as Pratheeksha R of Rystad Energy reinforces this view. Spain’s high renewable share highlighted the challenge of balancing intermittent supply without grid-forming capability or fast-response storage. Portugal’s reliance on imports exposed its limited flexibility and lack of domestic storage options. And even France, while more insulated, faced challenges managing sudden shifts in power flow.

As noted, this disruption is a clear signal: without stronger domestic resilience and improved regional coordination, future grid failures could be even more severe.

What Spain Might Be Revealing

Red Eléctrica has now shared initial information about the blackout, including a 44-minute public briefing. Some of the confirmed points include:

• Two generation loss events occurred in south-western Spain, in close succession.

• The French grid operator (EdF) opened breakers to prevent cascading impacts beyond Spain.

• The event resulted in a zero-voltage condition, with all generation offline.

• The restart was sequenced and measured, beginning with imports from France, and 99% of customers were reconnected by 7 a.m.

• RE is still collecting data and has explicitly asked stakeholders not to speculate on what tripped, how much, or why.

In that spirit, this post does not attempt to diagnose the Spanish event, but rather reflects more broadly on the operational themes raised by events of this scale. For grids that are undergoing—or have already undergone—rapid renewable integration, some recurring challenges continue to surface:

• The need for well-tuned control and protection systems

• The importance of system strength and fast frequency support

• The need for generator models to be both well developed and validated during commissioning—so they can be trusted in planning and operations

• The value of robust forecasting and restart procedures

These are not conclusions about Spain—but they are part of an evolving global conversation about how power systems are planned and operated amid the profound structural changes of the energy transition—where traditional, centralised generation is giving way to more variable, distributed, and inverter-based sources.