Finland's electricity network consists of a main grid, high-voltage distribution networks and distribution networks. High-voltage distribution networks distribute electricity at the regional level. Distribution networks can use the main grid through the high-voltage distribution network or they can connect directly to the main grid.
Structure of the electricity networks
The main grid is used in long-distance transmission connections and high transmission voltages. In order to minimise transmission losses, the voltage of the main grid is high: 400 kilovolts, 220 kilovolts or 110 kilovolts. At its maximum, this is 2,000 times higher than the voltage available in the power socket of residential properties.
The main grid is continued by high-voltage distribution networks that distribute electricity at the regional level. The distribution networks can use the main grid through the high-voltage transmission network or they can connect directly to the main grid. The high-voltage transmission networks operate on a voltage of 110 kilovolts, the distribution networks on 20, 10, 1 or 0.4 kilovolts. The lowest voltages of up to 1 kilovolt are called low voltage, the higher voltages are medium voltage (1–70 kilovolts) or high voltage (110–400 kilovolts).
The electricity network includes numerous substations and distribution substations. Substations are junctions of the network where power lines of different voltages are connected. The substations can transform, distribute and centralise electricity transmission. Distribution substations convert the high transmission voltages into low voltage suitable for the electricity users. Distribution substations can be installed on poles, in separate distribution substation structures, and, e.g., in the basements of apartment buildings.
Homes receive their electricity from the distribution networks, whereas industry, commerce, services and agriculture receive it from either the distribution network, high-voltage transmission network or the main grid. Electricity-generating power plants can also join any of the three networks. Large wind farms are connected to the grid or to the high-voltage distribution network. More and more generation plants, especially solar power, are also being connected to the distribution networks.
Cross-border connections are also included in the Finnish electricity network. The Finnish electricity network is part of the Nordic electricity system.