The System Operation Guideline, formerly known as network codes, sets minimum requirements and joint harmonised operational codes for transmission system operators (TSO), distribution system operators (DSO) and electricity producers and consumers. Other requirements for TSOs include compiling more detailed common methods and operating methods (methodologies), regarding which stakeholders will be publicly heard before they are sent to the authorities for approval.

Will system security improve?

The new Guideline will harmonise operational planning and control activities and thus contribute to maintaining good system security. Increased information exchange and continuous cooperation in, for example, a regional system security coordination office, will also improve the situation.

Market expansion and the spread of new forms of electricity production in the industry mean that electricity grid transmissions and operational situations are in a state of constant change, which makes them difficult to forecast. Although it will still be impossible to completely avoid power system disturbances in the future, the new rules provide a good framework for keeping the system security of the electricity system at a quality level.

Monitoring becomes more complicated, quality improves

One of the basic principles of system security in the future will continue to be the so-called (N-1) principle, according to which the power system should be able to withstand any possible individual fault without experiencing any consequences in another area. Deviations may be made from the (N-1) principle during changes in connections, during the activation of reserves, or if the effects of the disturbance are concentrated in a small area.

System security will still be reviewed using network calculation software based on European grid models, so that the calculations focus more on the probabilities and impacts of the faults being examined.

Fault cases are classified as ordinary, exceptional or out-of-range. If the probability of exceptional or out-of-range faults increases significantly as a result of weather conditions, they should be included in system security reviews. Dynamic oscillations should also be examined and the operational situation of the power plants changed if necessary in order to maintain stability after the disturbances.

More information, exchange and training

Each TSO should plan and monitor the electrical system’s frequency, voltages, transmission flows and connection status in real time and exchange necessary information with the TSOs in neighbouring countries. This makes it possible to identify exceptional circumstances rapidly so that TSOs can cooperate to restore the situation to normal. The exchange of planning information and real-time data between parties connected to the grid will be improved in order to bring overall management to a better level in operational situations that are changing more than ever.

An essential component of the maintenance of system security is professional operations personnel, whose training will be developed in a more formal direction. People working in power system control room tasks must have a valid operator certificate. The planning and development of the training will also be improved by naming an experienced training coordinator for each TSO, who will be responsible for the planning and implementation of the training programme.

More accurate parameters for frequency control

With regard to frequency control and reserves, the Guideline provides more specific details concerning how TSOs should handle frequency control and the use of reserves in cooperation with other TSOs within the same frequency area. The Guideline also sets limit values for the frequency and for the reserves associated with maintaining it and for their parameters. These parameters will help to determine the system security level of the interconnected Nordic grid and also the maximum size of a power plant that can be connected to the grid.

Earlier outrage planning, more accurate calculation

In terms of operations, the Guideline specifies in detail how TSOs and other parties connected to the grid should handle cooperation and the exchange of information to achieve good system security. An important part of this work is the creation of a common European grid model for system security reviews and the calculation of transmission capacity. The model will be used to calculate transmission capacity for various periods of time: year, week, day and intraday. This minimises errors in calculation results because all of the calculation parties have access to the same, more accurate input data.

A common plan and schedule for transmission outages will be compiled in order to help ensure adequate transmission capacity during outages and preserve a good level of system security. In the future, the mapping of outage needs that cause restrictions in transmission will begin earlier than previously. A party which is connected to the grid should submit its outage needs for the next year to its transmission system operator by 1 August.

Parties connected to the network and the TSO will further specify the plans as necessary during the autumn before the final plan is completed by 1 December.

System security is also ensured by preparing for power sufficiency during summer and winter by performing the corresponding forecasts and ensuring that the adequacy of active and reactive power reserves is monitored.