On August 9, 2019, energy system accident occurred in the UK, which cut off electricity supply to about one million consumers and caused major transport problems, especially in the rail industry. The weaknesses in the efficiency of the backup energy supply of certain critical infrastructure objects, such as hospitals, subway, as well as technical shortcomings in the electric traction of the locomotive passenger transportation fleet were identified.

Thus, at 4:58 pm a gas-fired power plant of Little Barford, with the capacity of 740 MWt, was disconnected from the grid. The German company RWE, owning the power plant, notified that the reason for the shutdown was a technical problem that occurred, and automatically, according to the regulation, the power plant shut off. RWE considers that the occurrence of a chain reaction to systemic problems of the energy network was the cause of the incident and called for a thorough study of its functionality. Already at 5 pm, the offshore Hornsea offshore windfarm with 1.2 GWt capacity was disconnected from the grid. Orsted (Denmark), the owning company, informed of the launch of automatic control systems that have commanded a significant reduction in generation. As a result of disconnection of these two power plants, the frequency in the network fell to 48.88 Hz (with a minimum permissible frequency of 49.5 Hz) and caused the automatic shutdown of a number of regions by the National Grid transmission system operator to prevent total system failure. Ofgem national energy regulator requires an immediate preliminary report on the reasons of blackout by 15 August and a detailed technical study by mid-September 2019.

National Grid representatives deny the likelihood of cyberattacks and also say that the accident could not have been caused by the uneven nature of wind generation. Instead, energy sector officials blame National Grid for hiding energy system problems. According to The Guardian, during several months of 2019, there have been at least three cases of a sharp fall in frequency – on May 9 to 49.55 Hz, on July 11 to 49.58 Hz, and in June to almost 49.5 Hz after a sudden shutdown of the West Burton gas-fired power plant, with the capacity of 1305 MWt, owned by the French EDF Energy. All three system-wide crashes were avoided only by promptly integrating operation of so-called “network security providers” (mini- and micro-generation facilities, storage systems, flexible power consumption facilities of manufacturing plants and supermarkets).

The blackout caused another wave of criticism of the government’s policy of decarbonization and transition to RES. In particular, proponents of fossil fuels focused attention on the fact that in case of a similar technical problem which happened in 2008, when two powerful energy sources suddenly disconnected, the use of coal, gas and nuclear power units helped to avoid mass shutdown of consumers. In turn, the opposition Labor Party called for the system operator privatized more than 30 years ago to be returned under the state control and to revise the company’s dividend payment policy (at the end of 2018, much of the profits were paid to shareholders, which reduced the share of capital investment in the development of the energy grid).

Instead, the National Grid system operator calls for the implementation of a special program of construction and connection to the grid of new high-maneuverability capacities for frequency control purposes and as a source of additional generation in case of unexpected failure of a number of large power plants or a significant change in the mode of operation of RES facilities. To do so, it needs the approval of a national regulator in the UK energy sector and probably some increase of the electricity transmission tariff.

Also, National Grid is likely to initiate an investigation into the activities of distribution system operators in the regions most affected by blackout, in order to check the functionality of their systems and ability to guarantee the energy supply of critical infrastructure. It is expected that National Grid may be held liable for the disruption of operation of a number of railway junctions, hospitals and other socially important sites. Instead, the system operator believes that the system of selective shutdown of private sector consumers did not react before the power supply to critical infrastructure was stopped.

Thus, a number of railway routes resumed operation only 4-6 hours after the power supply was restored. A major problem was the fleet of German-made locomotives purchased in 2014 as a part of upgrade program. The locomotives were unable to resume operation until a special repair service arrived to reconfigure the automatic control and management system.

A system crash in the UK’s energy system is a testament of importance of a balanced development of all elements of the energy system in any country. The probable cause of the accident is the unpredictable sharp fall in generation capacity at peak consumption in the evening of the day before the weekend, which wasn’t quickly balanced with the available reserves.

As a result of the incident, the National Grid system operator faces an additional challenge following the expected tough scenario of the UK leaving the EU in autumn 2019, linked to the need to revise the modes of interaction with continental Europe’s grids due to cancellation of acting format of economic relations with the operators of neighboring countries, in particular, France and Belgium.