Spain rules out cyber attack - but what could have caused power cut?

The Spanish grid relation has ruled retired a cyber onslaught arsenic the origin of a monolithic powerfulness chopped that crippled Spain, Portugal and parts of France connected Monday.

Red Eléctrica's operations manager Eduardo Prieto said preliminary findings suggest "there was nary benignant of interference successful the power systems" to connote an attack, echoing Portuguese Prime Minister Luís Montenegro the time before.

But the nonstop crushed down the chopped is inactive unclear.

The grid relation said connected Tuesday they "cannot gully conclusions" until they get factual data. Spain's Prime Minister Pedro Sánchez said investigators were trying to pinpoint the cause, and past would instrumentality each indispensable measures "to guarantee that this does not hap again."

Information is trickling retired astir what happened astatine the clip of the cut, starring to theories astir what could person caused it. Experts told the BBC it was apt caused by respective failures.

Here is what we cognize and what questions stay unanswered.

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Sánchez connected Monday evening said 15GW of powerfulness - the equivalent to 60% of request astatine that clip - was "suddenly mislaid from the system... successful conscionable 5 seconds".

Mr Prieto said during a quality league connected Tuesday that determination were 2 "disconnection events" hardly a 2nd isolated successful the south-west of Spain, wherever determination is important star powerfulness generation.

One contented that the Spanish grid relation whitethorn person been referring to was erstwhile powerfulness companies place a mismatch of proviso and request for energy that could pb to instability, and disconnect temporarily successful bid to support their systems.

However, Sánchez aboriginal said the powerfulness chopped was "not a occupation of excessive renewables". He said determination was not a nonaccomplishment of sum - meaning proviso - and determination was a comparatively debased request for energy that was rather mean successful the days moving up to the crisis.

So what precisely happened? It is unclear, particularly arsenic galore systems neglect successful energy proviso rather frequently, not lone renewables, and outages connected this standard hap determination successful the satellite astir erstwhile a twelvemonth connected average.

The mismatch betwixt proviso and request of energy tin alteration the frequence of the energy grid, which is 50Hz successful Europe and the UK.

If that frequence changes retired of a constrictive range, it could pb to harm to equipment.

"When a large institution detects that the frequence is moving retired of their tolerance, they tin spell offline to support their equipment," said Prof Hannah Christensen astatine the University of Oxford.

If tons of companies bash that successful speedy succession, it tin person "cascading effects" and pb to a black-out, she added.

But erstwhile it comes to renewables, operators person precise close short-term upwind forecasts to foretell erstwhile determination volition beryllium a surplus of upwind of star power, truthful they set powerfulness proviso accordingly, Prof Christensen said.

Renewable powerfulness has antithetic challenges to fossil substance vigor "because of its intermittency", she said, but it is simply a well-known contented that is planned for.

"It is simply a small perplexing that this wouldn't person been predicted," she said.

Prof Keith Bell, astatine the University of Strathclyde, added that "if a strategy is relying connected star and wind, they plan a strategy to bespeak that," suggesting that the further proviso of vigor from renewables volition not person been a astonishment to the grid.

"Spain has a batch of acquisition of upwind and solar, and a long-standing strategy of forecasting upwind and its impacts," helium said.

"All sorts of systems fail," helium added. "Things tin and bash spell wrong, whether that is from renewables, fossil fuels oregon atomic power. This could beryllium the Swiss food model, wherever the holes successful the strategy person happened to align."

Red Eléctrica besides suggested that the driblet of powerfulness caused a grid interconnection betwixt Spain and France to trip.

Two basal technologies are utilized to interconnect parts of a grid oregon countries - a modular transmission enactment that carries alternating currents, and increasingly, precocious voltage nonstop existent lines.

Spain has a precocious voltage enactment that came into work 7 years ago, meaning it is well-tested, Prof Bell said.

The Iberian peninsula is often referred to arsenic an "electricity island" due to the fact that it relies connected conscionable a fewer connections done the Pyrenees to France, meaning it tin beryllium susceptible to failures.

Sánchez said powerfulness was brought backmost online acknowledgment to connections with France and Morocco arsenic good arsenic state and hydropower sources.

Portugal's grid relation REN refuted archetypal reports, attributed to the bureau connected Monday, which said the blackout was caused by a uncommon atmospheric event.

The connection successful Portuguese said that "due to utmost somesthesia variations successful the interior oregon Spain, determination were anomalous oscillations successful the precise precocious voltage lines (400 KV), a improvement known arsenic 'induced atmospheric vibration'".

"These oscillations caused synchronisation failures betwixt the electrical systems, starring to successive disturbances crossed the interconnected European network."

However, REN spokesperson Bruno Silva told AFP connected Tuesday that the grid relation "did not enactment retired this statement," without giving further details.