EstLink 2 uses a traditional high-voltage DC converter which centres around the two converter stations on both sides of the Gulf of Finland. One of the converter stations connects the cable to the Anttila substation in Porvoo on the Finnish side, while the second connects the cable to the Püssi substation in Lüganuse, Estonia. The basic principle behind the converter stations is that alternating current is first converted into direct current, and at the other end of the transmission line it is converted back into alternating current. EstLink 2 will allow electricity to flow in both directions, from Estonia to Finland and vice versa, so the conversion from alternating current to direct current and back again will be possible in both the Püssi and Anttila converter stations.
Using direct current has several advantages over using alternating current:
- Firstly, the transmission losses are lower with direct current, and the transmission cable itself can be smaller
- Secondly, direct current can react more quickly to changes in the electricity grid, and this can help to reduce outages
- Thirdly, direct current capacity can be regulated faster