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The electricity grid remains stable during transmission outages

Electricity transmission must be suspended or restricted when parts of the main grid and grid connections are built and renovated. Fingrid plans outages with its customers well in advance. Customers should keep their contact details up to date in the My Fingrid service to ensure effective communication of transmission outages.

This year has seen a record number of transmission outages in the main grid. Most of the interruptions are related to the investments required to support renewable energy: more and more transmission line connections and substations are needed as the number of wind turbines increases dramatically.

All electricity transmission outages require lengthy planning, as they affect the parallel and serial operations of a great many parties. For example, there was an outage lasting more than three weeks on the west coast last summer to allow several working groups to work safely on transmission lines and substations.

“All the work was completed according to the planned schedule and order of work. The transmission outage time announced beforehand was only exceeded by two hours, which is an excellent performance,” says Pasi Mantila, Expert at Fingrid.

The Leväsuo substation project and associated transmission line arrangements in Oulu this summer required electricity transmission outages due to the enormous number of customers’ regional network lines and industry connection lines connecting to the substation.

“The transmission outages in Leväsuo in Oulu were a major effort for all the parties involved, but consumers did not notice a thing.”

“The Leväsuo transmission outages were a major effort for all the parties involved, but consumers did not notice a thing – they all received electricity as normal. The work was planned in detail well in advance, and Fingrid kept us up to date,” says Kimmo Määttä, Supervisor of the Operation and Maintenance Team at Oulun Energia Sähköverkko Oy.

Pasi Mantila emphasises that the major projects would not have been completed on schedule without good foresight, planning, communication and cooperation.

“I would like to thank Fingrid’s customers, contractors and maintenance personnel for their contribution to ensuring that this year’s outages were carried out safely and without compromising system security,” Mantila says.

Congestion management maintains system security

There may be several transmission outages in the main grid simultaneously, especially in the summer, but efforts are made to schedule and arrange them so they do not jeopardise the system security of the main grid or restrict the transmission capacity. Restrictions to the transmission capacity could limit the effective functioning of the market and raise the market price of electricity.

“The process of planning transmission outages begins several years in advance to ensure it is even possible to implement the outages at the intended time,” says Mikko Piironen, Unit Manager at Fingrid.

Under certain circumstances, the electricity transmission capacity may be insufficient during an outage. In this case, Fingrid resorts to congestion management to ensure that the maximum volume of electricity transmitted in the main grid complies with the system security limits: the main grid must retain its ability to withstand the failure of an individual line or production plant.

One frequently used congestion management method is to limit Finland’s cross-border transmission capacity. In practice, this means that only a certain volume of electricity may be imported to or exported from Finland.

Occasionally, one solution is to limit the output of electricity production plants regionally. In other words, electricity producers are told the maximum power they can produce in a certain time window.

“Limiting electricity production or the transmission capacity of cross-border connections is essential to safeguard the main grid’s system security during outages,” Piironen says.

Information exchange and close contact

During transmission outages, electricity producers and distribution system operators are responsible for implementing production restrictions according to Fingrid’s instructions.

In the Oulu region, Caverion’s control centre monitors wind power, among other things, and sets the wheels in motion when Fingrid announces the exact timing of a planned outage.

“We send instructions to every power plant individually and set restrictions. We keep everyone up to date at our end of the line,” says Janne Kiiskilä, Control Centre Manager at Caverion Industria.

During an outage, the parties exchanged information about the network’s status. Kiiskilä says that working with Fingrid has been a smooth experience.

“We share metering data freely and tell them if we notice even a small deviation in the network. And if Fingrid detects a disturbance in the grid, they ask us for data about it, for example,” Kiiskilä says.

Last year´s extensive outages required thorough planning.

Transmission outages in a small section of the electricity network are everyday occurrences at the control centre. However, last year’s extensive outages affected a larger part of the grid and lasted several weeks. They required thorough planning and will also guide the development of systems and operating models in the future.

“We have gained valuable experience and the opportunity to examine our internal process and refine how we work with Fingrid,” Kiiskilä mentions.

Keeping contact details up to date in My Fingrid

Transmission outages are planned well in advance and implemented according to Fingrid’s annual schedule to ensure a high level of system security in the grid and minimise inconvenience to all parties.

According to the annual schedule, Fingrid sends an enquiry to producers and distribution system operators about the need for transmission outages, so their contact details must be up to date in the My Fingrid service. Sometimes, the customer’s designated responsible persons change suddenly, and Fingrid needs the latest contact details.

“Every party should have a contact person for operations in the My Fingrid service and provide details about the control centre that provides operational services so we can contact them if necessary and be sure our information reaches them. The party can then send the information onward to the right people,” Pasi Mantila advises.

He advises customers to provide one email address on the service so that Fingrid can send information about transmission outages and restrictions.

Customers can enter their contact details and outage needs into My Fingrid. Fingrid compiles its outage needs and those of its customers by January.

“When we know all the outage needs, we notify all the parties. If necessary, we hold outage meetings to review the arrangements in more detail,” Mantila says.

Kimmo Määttä from Oulun Energia Sähköverkko says that meetings were held back in summer 2022 to plan the transmission outages in April 2023. In other words, planning began well in advance.

“Maintaining system security is important to us, so the various options are discussed openly. This is how we identified the best solutions for everyone and could synchronise our schedules with Fingrid,” Määttä says.

He encourages every operator to enter their outage requirements in the My Fingrid service in good time so that the outages can be planned – if these things are rushed, it could jeopardise system security and, above all, occupational safety.

“On occasion, we have been asked the previous evening if we could cut off the power to a site for the duration of their work,” Määttä says.

He adds:

“Work needs to be forecast about one year ahead and communicated to Fingrid. A systematic approach also helps those who are doing the work.”

Annual transmission outage schedule

  • In November, Fingrid emails a transmission outage enquiry to all its connecting customers, asking them to respond via My Fingrid by the end of November.
  • By January, Fingrid coordinates the transmission outages it needs with those reported by customers. Fingrid notifies customers of all the known transmission outages required and their timetables by the end of January.
  • After January, the final outage times are agreed upon with customers by email, phone and, in the case of larger outages, at separate outage meetings and customer meetings.
  • No later than 21 days before the start of the outage, an outage plan is drawn up to finalise the timing, switching of electrical installations, and work taking place during the interruption. System security calculations are also made at this point.
  • No later than 9 days before the start of the outage, a switching plan is prepared, after which a switching schedule is also prepared for each electrical installation.
  • Approximately 7 days before the start of switching, Fingrid’s outage order is sent to the control centres and operational contact persons providing the outage service. The customer always prepares the switching plans and schedules related to its own electrical installations.

More details about transmission outage schedule


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