Electricity transmission system
The national electricity transmission system consists of 5,198 km of electricity overhead lines, 284 km cable lines and 158 substations.
The backbone of the transmission system is made up of powerful 330 kV overhead lines designed to transmit large amounts of electricity, but the system is mostly made up of 110 kV overhead lines that ensure electricity reaches the regions.
The domestic electricity network is connected to cross-border alternating current connections with Latvia and direct current connections with Finland.
Overhead lines
- 1,851 kilometres of 330 kV lines;
- 3,342 kilometres of 110 kV lines;
- 5 kilometres of 6–35 kV lines.
Towers provide primary information about the voltage class of an overhead line. The higher the voltage, the bigger and taller the towers.
The voltage class of a line can be easily determined by visual inspection based on the number of insulators in the insulator chain.
The more insulators, the higher the voltage.
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Line voltage: Insulator chain length: Number of insulators in the chain: |
110 kV 1m 7-8 |
The following figure provides an overview of the elements of a high-voltage line and tower.
Cable lines
There are AC cable lines in the transmission system:
- 122 kilometers of 110 kV cables;
- 23 kilometers of 6 to 35 kV cables.
AC underground cable lines are located in the transmission system primarily in densely populated areas, such as Tallinn.
In addition, Elering operates the direct current connections EstLink 1 and EstLink 2 between Estonia and Finland. Both connections consist of both onshore and offshore cables. The lengths of EstLinks are:
- EstLink 1 – 54 km;
- EstLink 2 – 85 km.