(Reuters) The hunt has begun for the cause of a massive blackout across Spain, Portugal and parts of France that halted trains, bank machines and traffic lights, in one of Europe's biggest ever power system collapses.
CYBER ATTACK?
Spanish grid operator Red Electrica ruled out a cyber attack as the cause but Spain's High Court said it would open an investigation to determine the cause.
EXPLANATIONS SO FAR
Red Electrica in a statement on Monday night pointed to a "strong oscillation in the power flow which triggered "a very significant loss of generation".
Aurora Energy analysts said the frequency of the grid dropped from the nominal 50Hz to 49.85Hz, triggering automatic emergency protocols.
Jon Nazca REUTERS
SPAIN-ENERGY-OUTAGES
"The frequency decline likely began due to severe oscillations in high-voltage lines in southern France or inland Spain. Hypotheses include a physical fault (line disconnection), a sudden loss of generation within Spain or an atmospheric phenomenon," they said. This loss of generation went beyond what the electrical systems are designed to handle and the Spanish grid was disconnected from the European system. The electrical system then collapsed, affecting both the Spanish and Portuguese systems, Red Electrica said.
Spain was also exporting power to France and Portugal at the time of the outage. Exports to France were close to the available net export capacity until 10:00 a.m. local time. According to Red Electrica data, exports to France stopped at 12:35 p.m. local time from 868 MW beforehand.
"One of the problems was that there wasn’t enough firm power, like gas and nuclear and hydro storage, to handle the sudden fall of power generation," an industry source said, referring to the drop in solar generation.
WHAT CAUSES POWER OUTAGES?
The most common cause of an unplanned power cut which disables electricity on a large scale is extreme weather such as storms, lightning strikes or high winds. The weather at the time of Monday's collapse was fair.
Power outages can also happen when there are faults at power stations, power distribution lines, substations or other parts of the system.
Electricity flow between systems in Europe is maintained at 50 Hertz (Hz) to ensure stability. If that level varies, backup systems disconnect assets such as power generation sources from the grid to protect them from damage.
SPAIN'S ENERGY MIXSpain is one of Europe's biggest producers of renewable energy, relying on wind and solar for 43% of the total, well above the global average, data from think tank Ember shows.
Solar photovoltaic (PV) accounted for 59% of Spain's electricity at the time of the blackout, wind nearly 12%, nuclear almost 11% and combined cycle gas plants 5%, Red Electrica data showed.
In a span of just five minutes, between 12:30 and 12:35 p.m. local time (1030-1035 GMT) on Monday, solar PV generation plunged by more than 50% to 8 gigawatts (GW) from more than 18 GW, the data showed.
"One of the problems was that there wasn’t enough firm power, like gas and nuclear and hydro storage, to handle the sudden fall of power generation," an industry source said, referring to the drop in solar generation.
WHAT FACTORS COULD BE INVOLVED?
Another source with direct knowledge of the sector said that leading up to the outage the Spanish grid was running with very little "inertia", which is energy stored in a large rotating mass like a generator or in some industrial motors that acts as a buffer as it can quickly be used to compensate for sudden changes in demand or supply.
"In those conditions (when there is little inertia) if there’s a drop in production for whatever reason, the grid loses (more) inertia and everything fails. And in a blackout, you need to rebuild inertia before bringing things back online, which takes a few hours," the source said, requesting anonymity.
HOW IS POWER RESTORED?
A "black start" is the process of restoring power after a major cut. It involves gradually restarting power plants individually and reconnecting them to the grid.
As Spain tried to get more power back on Monday it turned more gas and hydropower plants online and increased power imports from France and Morocco.
EXCESS RENEWABLES?
Monday's collapse has sparked debate about whether the volatility of solar and wind supply made its power systems more vulnerable to such an outage.
Spain's Prime Minister Pedro Sanchez said on Tuesday there was not a problem of excess renewable energy.
Still, the rapid development of renewables in Europe has flooded grids during periods of heavy sunlight and weak demand, sometimes driving wholesale electricity prices down to zero or negative and forcing solar farms to curtail their input.
Analysts expect an increase in negative price hours in Spain and Portugal in 2025 due to further expansion of solar farms.
The situation shows the complexity of managing modern energy systems as they integrate increasing levels of intermittent renewable energy, said Victor Becerra, professor of power systems engineering at the UK's University of Portsmouth.
