The Network Code for Emergency and Restoration

The Network Code for Emergency and Restoration (NC ER) specifies the common requirements for handling emergency, blackout and restoration states in the power system. NC ER harmonises the operation of power systems throughout the EU and with Third Countries.

The Network Code for Emergency and Restoration (NC ER) is intended to prevent a blackout and, more widely, the spread of disturbances and the deterioration of the system’s state. However, if a blackout occurs, the aim is to restore power rapidly and efficiently.
The NC ER took effect on 18 December 2017, and the required measures are being implemented. The NC ER requires 24-hour operability and the implementation of an automatic under-frequency control scheme by December 2022. This autumn, work is underway on a testing plan related to the system defence plan and the restoration plan.

System defence plan and restoration plan

The NC ER obliges all European transmission system operators to prepare two plans: a system defence plan and a restoration plan. The significant parties and substations needed to implement these plans must also be designated.
The system defence plan includes manual actions and automatic schemes designed to prevent a blackout in the event of an emergency in which the normal “corrective measures” have proven inadequate.

The restoration plan includes the manual actions and automation for restoring the power system in the event of a blackout. Fingrid delivered its plans to the Energy Authority in December 2018. At the same time, Fingrid submitted separate lists of the significant parties and substations for the system defence plan and restoration plan for approval by the Energy Authority.

The terms and conditions of paid services related to the plans were also submitted to the Energy Authority for approval, as well as proposals for suspending and restoring market functions and for the imbalance settlement rules applying in the event that market functions are suspended. The Energy Authority approved Fingrid’s proposals in June 2019.

Work is now underway on the test plan required by the NC ER. This will include stakeholder consultations during the autumn. The test plan will be presented to the Energy Authority in December 2019.

The plan promotes cooperation between significant parties and providers of the black start service. The test plan defines:
• The functionality of the black start capability
• Under-frequency control scheme
• Voice communication systems
• The main and backup power supply systems for the transmission system operator’s control room and backup control room
• The functionality of other critical tools, equipment and premises, including data connections to the substations specified as significant
• Backup power supply systems for the substations specified as significant
• Transferring the transmission system operator’s control room functions to the backup control room

The automatic under-frequency control scheme is a part of the system defence plan

Fingrid has defined all of the distribution system operators and high-voltage distribution system operators (1), consumers connected directly to the grid (2) and existing and new power plants of type C (over 10 MW) and D (over 30 MW)(3) as significant network users for the purpose of the system defence plan.

The designated parties (numbered) are
obliged to:
• participate in implementing the automatic under-frequency control scheme (1,3)
• participate in the automatic disconnection of generation occurring at over-frequency (if such a scheme is implemented in the Nordic synchronous area and in Finland) (1,2,3)
• comply with the transmission system operator’s instructions regarding active power, reactive power and voltage regulation, as well as generation and load shedding (1,2,3)
• pass on the transmission system operator’s requirements and instructions to the parties designated by the transmission system operator connected to their grids (1,3)
• handle the testing requirements in relation to the functionality of automation (1,2,3)

The restoration plan demands 24-hour operability

In terms of the restoration plan, the significant network users are the distribution system operators connected directly to the grid and the operators of high-voltage distribution systems with an average consumption of more than
30 MW, as well as existing and new type D power plants (over 30 MW).
The third group consists of distribution system operators that own substations that handle routes to the grid or grid trunk lines.

Distribution system operators connected directly to the grid and high-voltage distribution system operators are obliged to:
• meet the 24-hour operability requirements for the availability of critical tools and premises, including the control room
• ensure the operating capacity of substations designated as significant
• ensure the operation control system and the other systems essential for the operation control system to function, including data communication to substations designated as significant, and
• voice communication with Fingrid.

The 24-hour operability of a power plant means that, following the loss of an external power supply, for at least 24 hours:
• the power plant is capable of carrying out actions necessary to keep the plant going for a long time on its own consumption and
• connection measures are taken so that it is possible to synchronise the power plant with the network when the electricity is restored or begin a restart as quickly as possible in order to support the restoration of the grid.

Distribution system operators and power plants must:
• implement voice communications in such a way that calls from the transmission system operator can be prioritised
• handle the testing and monitoring requirements applying to the functionality of automation and telephone connections.

Limited frequency sensitive mode at under-frequency (LFSM-U) and at over-frequency (LFSM-O) is only required for new and modernised power plants. At present, there are no new requirements for going onto or staying on the plant’s own consumption, nor for islanding and blackstart features.

Substations to take note of remote control and metering data

In total, 234 substations have been given significant status. On the grid, these substations are transformer and switching substations with remotely controlled switchgear. On distribution systems, substations are significant if they are connected to the grid and have remotely controlled switchgear.

The distribution system operator must implement 24-hour operability at the substations designated as significant. For substations, 24-hour operability means that following the loss of the external power supply:
• the distribution system operator’s essential voice communications work for at least
24 hours
• the substation’s metering and status data are available on the operation control system for at least 24 hours for restoration following a major disturbance
• the relevant switchgear can be remotely controlled for at least 24 hours (the power plant’s connection to the main grid)
• the substation’s backup power supply must be capable of covering the substation’s own consumption for at least 24 hours.

Agreements have been made to implement the assured 24-hour voice and data communication between Fingrid and the significant parties using Erillisverkot services and satellite phones. The parties will select an appropriate implementation method to ensure their own operating capacity and data communication.