Case Study
Hook-Up & Commissioning of an HVDC substation
BorWin3 grid connection is a 900MW high-voltage direct current (HVDC) offshore interconnection substation located in the North Sea, approximately 130km off the coast of Borkum, Germany.
It is the third HVDC grid connection project by the German-Dutch transmission network operator TenneT to bring onshore the clean electricity from wind farms offshore Borkum, after BorWin1 and BorWin2.
Installed on jacket foundation, the topside of the BorWin gamma offshore platform weighs approximately 18,500 tonnes (t) and houses a 900MW HVDC converter supplied by Siemens.
The topside of the platform was constructed and fabricated by Drydocks World in Dubai and was transported to the installation site in the North Sea by the heavy lift vessel in September 2018.
Our client required construction and specialist access support to assist with the hook up of the topside to the jacket foundation and with the hook-up and commissioning of various systems and services within the topside module.
The project required turnkey construction services including: rigging and lifting, electrical and instrumentation installation and commissioning, fabric maintenance and temporary access solutions.
The project presented a number of challenges including:
- No laydown area or underdeck access to support critical path workscopes
- Multiple simultaneous scopes of work imposed significant schduling constraints
- Complex rigging and lfting required to hook up caissons and J-tubes and remove boat landing platform
- Limited bed space onboard the platform
- An evolving scope of work throughout the project
- Onshore engineering support
- Workpack and LOLER lift plans development
- Design and supply of suitable underdeck access solution
- Supply of 12 person multi-discipline construction team
- Underdeck cross haul and installation of caissons and J-tubes
- Insulation, coatings and HVAC repairs
- Installation and fault identification of electrical systems
- Removal of transportation steel and temporary boat landing platform
- Installation of CCTV cameras
- Field welding repairs and ad-hoc fabrication activities
AquaTerra designed, supplied and installed QuikDeck as an underdeck access platform to enable easy access to support critical path work scopes and deliver cost savings.
The system was installed in Dubai and the topside lifting into position with the access pre-installed. This reduced the overall project duration.
The transfer of equipment was facilitated through the construction of a temporary cantilevered lay-down area.
Small, independent teams of competent, multi-disciplined personnel provided flexibility to work around scheduling constraints with alternative scopes to fall back on.
Smart project scheduling was used to prioritise critical path tasks and minimise equipment mobilisation.
The access platform was fabricated onshore to reduce offshore time and costs
Specialist rigging teams were used to transfer spool pieces to underdeck and remove the requirement of a boat landing platform.