Operating codes

The aim of the operating network code is the high system security of interconnected electrical systems, and to create frameworks for the efficient sharing of reserve power resources across national borders.

​The operating codes are

  • Transmission System Operation, SO
  • Network Code for Emergency and Restoration, ER

Transmission System Operation, SO GL

The network operating codes concern all transmission system operators (TSOs) in the EU area. The only things remaining outside the area of application are islands, which are not synchronously connected to the mainland. The codes set requirements for all existing and all new parties connected to the grid, HVDC systems, and for consumption facilities, closed distribution networks and parties that offer consumption flexibility or reserve services to TSOs.

Because of the operating codes, TSOs will be able to engage in more coordinated cooperation, when deciding on different remedial measures to preserve electricity system balance. Cooperation will also be done with distribution network owners and other parties connected to the network.

The operating codes give parties connected to the network the right to receive more extensive information than before about their connections. On the other hand, parties connected to the network are also obliged to provide network operatorswith more precise information than before about their plants.

In Finland, many obligations arising from the operating codes have been built into existing and present operating practices. From a point of view of the electricity market, one of the most significant new things is the change in scheduling of transmission outages that affect the electricity market and are significant in terms of system security. Furthermore, for the calculation of transmission capacity and system security, a common European grid model is being made.

The operating codes change the requirements set for reserves. In future, units that maintain reserves must, for example, be able to react to increasingly small changes in frequency. Acceptance tests for units maintaining reserves must be done at intervals of no greater than five years, whereas the present interval between testing is 10 years. In dimensioning reserves, in future TSOs will also have to prepare for over-frequency situations, which will increase the need for reserves.

In order to safeguard the quality of frequency and system security, TSOs have the right to set maximum permissible rates of power change, both for production and consumption. For technical reasons, a distribution network company, on the other hand, has the opportunity to restrict the balancing possibilities of a reserve-producing unit connected to its network.

Network Code at EUR Lex site

Network Code for Emergency and Restoration, ER

The goal of the Network Code for Emergency and Restoration (NC ER) is to to prevent the escalation of an emergency situation into a blackout and to enable efficient and fast restoration of the electricity system back to normal state.

The network code focuses on the co-operation between the transmission system operators (TSO), but it also obliges several other parties in the electricity system and in the electricity market. The network code especially brings obligations to the companies, power plants and substations named by the TSO as significant for the system defence plan or the restoration plan.

In Finland, the parties that are able to help to avoid blackout when the electricity system is in emergency state have been named as significant grid users for the system defence plan:

  • all distribution system owners and owners of high voltage distribution systems perators (DSOs),
  • electricity consumers directly connected to the main grid and
  • power plants of type C and D (> 10 MW or connection point in the main grid).

The most significant new obligation in NC ER is the implementation of the automatic low frequency demand disconnection system (LFDD). The purpose of the LFDD is to be the last line of defence before a blackout. The LFDD will stepwise disconnect 5…30 % of the Finnish electricity consumption when the frequency of the electricity system falls below 48.8 Hz.

All DSOs and electricity consumers connected directly to the main grid will participate in the implementation of the LFDD.

The partis with who Fingrid will co-ordinate the restoration after a blackout, are named as significant grid users for the restoration plan:

  • DSO connected directly to the main grid with an average consumption of more than 30 MW,
  • power plants of type D (> 30 MW or connection point in the main grid) and
  • a number of substations in the main grid and in the distribution grids.

The most significant new obligation in NC ER is the implementation of the 24 hour capability during a blackout. The named parties are obliged to ensure that their control centres and the named power plants and substations remain operational for at least 24 hours during a blackout.

Both the LFDD and the 24 h capability shall be implemented by December 18, 2022.

More information

NC ER implementation and implementation of the 24 h capability
Jari Siltala, jari.siltala(at)fingrid.fi

implementation of the under frequency load shedding system
Harri Kuisti, harri.kuisti(at)fingrid.fi

KoVa services
Pekka Tynkkynen, Suomen Erillisverkot Oy, pekka.tynkkynen(at)erillisverkot.fi



Timo Kaukonen

Planning Manager
Tel. +358 30 395 4228

Jari Siltala
Senior Specialist
tel. +358 30 395 4244