Blackouts can happen anywhere How power systems collapse

Questions are still being asked about what caused last month's outage on the Iberian peninsula. Could it happen elsewhere?

- Jillian Ambrose

Europe's biggest blackout in over 20 years on the Iberian peninsula unleashed hours of chaos for people in Spain, Portugal and parts of France late last month. But in the aftermath it has raised a question for governments across the world: could it happen here?

Europe's political leaders and energy system operators have given assurances that such blackouts are rare, and that European power grids are some of the most stable in the world. Yet energy experts have warned that no grid is infallible. Prof Jianzhong Wu, the head of the school of engineering at Cardiff University, said blackouts "can happen anywhere".

"Despite today's high standards of reliability, low-probability but highimpact blackout events can still happen. These networks are not designed to be completely blackout-free because achieving such a level of reliability would require investment far beyond what is economically feasible," he said.

Charmalee Jayamaha, a senior manager at the UK government-backed Energy Systems Catapult, said: "No system can be 100% resilient," so risks "need to be balanced with our willingness to pay to reduce them".

What are the risks that could trigger a catastrophic blackout? Here we look at the top reasons a power system might collapse.

Atmospheric conditions

Extreme weather and natural disasters present a clear risk because storms, heatwaves and earthquakes can cause devastating damage to critical infrastructure. Lightning strikes and solar flares have also been known to damage vital equipment such as substations and power lines, which are crucial to maintaining the stability of the grid.