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
  • Emergency and Restoration, ER


Transmission System Operation, SO

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.

Emergency and Restoration, ER

With regard to emergency and restoration, the network code focuses on improving coordination between TSOs in situations of disturbance. The objective is to prevent the spread of situations of disturbance, to stop the state of the system from developing into a major disturbance and to ensure that the system returns to a normal state as quickly as possible.

The network code obliges TSOs to appoint significant parties from a system perspective, who will implement the requirements presented in the network code in their own plants, systems and guidelines.