Reserve power and the “Styrel” system

There are several reserve power plants in Sweden, but they are far from sufficient to meet the full normal demand for electricity. Styrel means “steering electricity to prioritised power consumers” and offers municipalities, county administrative boards and electricity network operators a means of rationing electricity if a shortage occurs.
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Foto: Thomas Henrikson/MSB

Reserve power

Reserve power plants generate electricity independently of the public grid. They are usually used in parallel with the public grid in the event of a power cut.

Many key societal functions are equipped with reserve power, so that they can function even in the event of a prolonged outage. These include the Government Offices of Sweden, the Swedish Parliament, the police, SOS Alarm and major hospitals.

Teracom, which distributes radio and TV broadcasts, has reserve power for its transmitters, as well as some major newsrooms, in the ether-based media, the Internet and printed media.

Some electricity network operators also have larger reserve power plants that run on oil. These power plants can be started when there is a shortage of electricity, which can occur in extremely cold conditions. This happened, for example, in the winter of 2010, when part of Vattenfall’s reserve power plant in Stenungsund was started due to the severe cold.

The Styrel system and disconnection

If the demand for electricity is greater than supply, there is a risk of an electricity shortage. This can happen, for example, if electricity generation is disrupted during cold winters, as large amounts of electricity are used to heat homes and premises. If an electricity shortage arises, there is a risk that the electricity supply will collapse in all or large parts of Sweden. To avoid this, Svenska kraftnät may issue an instruction for parts of the electricity grid to be disconnected. Thanks to Styrel, electricity can be directed to the places where it benefits society the most. In the past, a disconnection would affect all electricity users in large areas. Styrel is an element of emergency preparedness for the electricity supply.

The electricity users prioritised at local and regional level are those of importance for life, health and for society to function. These include hospitals, retirement homes, rescue and alarm services, water supplies and telecommunications.

The Styrel system means that you might be without electricity while your next-door neighbours retain theirs. If this happens, it is because the neighbour’s house happens to be on an electricity line that has been prioritised, as there are electricity users of importance to society on that particular line.

Sources: The Swedish Energy Agency (Energimyndigheten), Swedenergy (Energiföretagen Sverige), Svenska Kraftnät (The Swedish national power grid), Risknet/FOI, The Stockholm administrative council (Länsstyrelsen Stockholm), Crismart/Försvarshögskolan (The Swedish Defense University), EON, Vattenfall, Fortum and the Swedish Civil Contingencies Agency ( Myndigheten för samhällsskydd och beredskap or MSB).