thumb|Track of the overhead line section of Baltic Cable in Sweden

The Baltic Cable is a monopolar HVDC

From the landing point at the southern coast of Sweden, the powerline transitions to an overhead line a few kilometres inland. It runs to a termination tower in Kruseberg which is attached to a 400 kV/130 kV substation of the Swedish power grid.

thumb|Kruseberg [[converter station on the Swedish side of the Baltic Cable HVDC interconnection]]

The anode, which is situated in the Baltic Sea, consists of 40 titanium nets each with a surface of 20&nbsp;m<sup>2</sup>, which are laid on the sea bottom under plastic tubes and stones. It is connected to Kruseberg converter station with a 23-kilometre-long underground and submarine power line, which consists of two parallel-connected cables with 630&nbsp;mm<sup>2</sup> cross section.

The cathode is situated in the Baltic Sea north of Elmenhorst. It consists of a bare copper ring with a 2-kilometre diameter. It is connected to the static inverter plant in Lübeck-Herrenwyk with a 32-kilometre-long cable. The first 20&nbsp;kilometres of this cable have a cross section of 1400&nbsp;mm<sup>2</sup> and the last of 800&nbsp;mm<sup>2</sup>. This cable is laid in the tunnel under Trave River at a distance of 2.5&nbsp;metres from the high voltage cable. The separation reduces the magnetic field, which may affect compasses of vessels in this highly frequented area. As the cable is a monopolar line, it produces much higher magnetic fields than bipolar cables with the same ratings.

Operation

Because this overhead line can generate radio interference, there is a highly effective active filter system installed at the Kruseberg converter station. In the Lübeck-Herrenwyk converter station, there is no requirement for such a system, because there is no overhead powerline section on the German side.

The cable cannot be operated at the maximum transmission rating of 600&nbsp;megawatts, because the 380&nbsp;kV line which begins at the converter station of Lübeck-Herrenwyk ends at the Lübeck-Siems substation. This is the only 380&nbsp;kV powerline in Germany which has no direct connection to the Central European 380&nbsp;kV grid, which caused the Baltic Cable to have a 372&nbsp;megawatt (MW) capacity instead of 600&nbsp;MW. This bottleneck was solved in 2004 when an additional 220 kV line was built. However power flows on 220&nbsp;kV and 110&nbsp;kV lines face increased losses of the transmission.

In the area of the converter station there is also a 110&nbsp;kV/220&nbsp;kV sub-station, fed by two 110&nbsp;kV circuits from the Lübeck-Siems sub-station. There is no transformer for coupling the 380&nbsp;kV- and the 110&nbsp;kV-grid in the area of the Lübeck-Herrenwyk converter station.

In 2016, the owner Statkraft started a court case against Swedish authorities in disagreements over profits from electricity trade in the cable.

In the night from April 16, 2017 to April 17, 2017 on the electrode cable on Priwall peninsula a fault occurred, which resulted in the generation of hydrogen at the fault location as it acted as cathode. The hydrogen got ignited by the generated heat and a 3 metres high flame shot off the ground. As there is no device monitoring the state of the electrode cable, no alert was made to the operators. Fire brigades were first not able to extinguish the fire, but the flame went out when the current was switched off.

Expansion schemes

Of the two originally planned 380&nbsp;kV lines to Lübeck (from Krümmel Nuclear Power Plant to Lübeck-Siems and from Schwerin substation to Lübeck-Herrenwyk), the 380&nbsp;kV line between Krümmel and Lübeck-Siems was canceled according to speakers from E.ON AG.

There is still the option to build a 380&nbsp;kV line from Lübeck to another 380&nbsp;kV substation in Schleswig-Holstein, Hamburg or Lower Saxony. The construction of the 380&nbsp;kV link between Lübeck-Herrenwyk and Schwerin is not progressing due to opposition from ecologists.

See also

  • Electricity sector in Sweden
  • List of high-voltage transmission links in Sweden
  • Estlink, cable between Estonia and Finland
  • LitPol Link, cable between Lithuania and Poland

References

Specifications

  • Baltic Cable AB website
  • ABB: Baltic Cable - An HVDC cable links Sweden with Germany
  • THE BALTIC CABLE HVDC LINK (www.transmission.bpa.gov)
  • THE BALTIC CABLE - Pictures (www.transmission.bpa.gov)