The BorWin2 project has a power rating of 800 MW with a DC transmission voltage of +/-300kV. It will interconnect the two windfarms Global Tech 1 and Veja Mate which are located approximately 125 km offshore – northwest of the island of Borkum. The wind power will be transported via submarine and land cable to Diele near Papenburg, through a 75 km land cable route, where an onshore substation will reconvert it from DC to AC for further transmission and distribution within the 400-kV AC grid.
The HelWin1 power rating of 576 MW is realized at a DC transmission voltage of +/-250 kV. Two windfarms NordseeOst and Meerwind which are located about 85 km offshore are foreseen to be connected to the HelWin1 transmission system. The onshore point of interconnection with the onshore substation is in Büttel, which is approximately 45 km distant from the submarine cable landing point.
Operations performed included post-laying inspection and burial (PLIB) operations in the course of both BorWin2 and HelWin1 Grid Connection projects. The PLIB method was employed at particular locations along the cable routes in both porjects where cables where not able to be buried using simultaneous laying and burial (SLB) methodology.
In those areas the vehicle that was used for the PLIB works was the 'Venom 3K-600T' underwater jetting vehicle operated from the DP special purpose ship ‘Astrea’. Proper jetting swords (stingers) were attached to the vehicle to enable the achievement of the required burial depths (1.5m, 1.55m, 1.7m, 3.0m) at different sections.