The topside of the substation has been moved from Heerema Fabrication Group's (HFG) yard to Schiedam for the last fabrication activities.
This transportation of the substation, which will be the world's largest offshore transformer platform once installed, marks the start of its journey to the Helgoland area in the North Sea.
It is to be installed on an already installed jacket in August.
With a capacity of 690MW, the offshore substation is the most powerful ever built and will initially serve the 288MW Amrumbank West wind farm.
The project will be connected with alternating current (AC) cables to the converter platform, where the power will be converted to high-voltage direct-current (HVDC) for transmission through 85 kilometres of sub-sea cable and 45 kilometres of land cable to an onshore station at the grid connection point at Büttel.
HFG started work on the 10,200-tonne topside in October 2012, after being handed the construction contract by Siemens.
The connection will be operated by Tennet and is due to be up and running in 2015.