Sheringham Shoal

Project Overview

The Sheringham Shoal offshore wind farm is 35km², located 17 to 23 km offshore from the coastal town of Sheringham, North Norfolk. Water depth at the wind farm site varies between 15 and 22 metres (LAT), with a maximum tidal range of about 4m. The farm is owned equally by Statoil and Statkraft through joint-venture company Scira Offshore Energy Limited. The project utilised Statoil’s longstanding offshore activities and Statkraft’s expertise in renewable energy.

The wind farm has 88 wind turbine generators, each with a unit rating of 3.6MW. The turbines are connected via the inter array cables and fed back to two offshore substations. The 33kV array cable circuits interconnecting the WTGs and the substations are rated up to 36MVA where the voltage is stepped up to 132kV before being transmitted ashore. The total installed power capacity of the wind farm is 315 MW, which is electrically divided in two halves due to restrictions in the onshore grid connection capacity.

From the offshore transformer stations, power is exported through two submarine export cables coming onshore near Weybourne, where they are connected to the underground export cables. All offshore cables are buried with a depth of 1.0m to top of cable.

  • 1m burial (to top of cable) for soil strengths of up to 80kPa
  • 0.5m burial (to top of cable) for soil strengths of up to 150kPa

Project Schematic

Project Award to Offshore Energy

VSMC was awarded the cable installation scope of work by Statoil. VSMC chose Offshore Energy to provide the engineering resource and consultancy to the Sheringham Shoal project, including analysis, design and the preparation of operational and installation procedures, task plans and manuals:

 

  • Review of company documents
  • Detailed cable routing
  • Sub-station topside equipment specification, design, manufacture, testing and integration and mobilisation to the T piece
  • WTG topside equipment specification, design, manufacture, testing and mobilisation to the T piece
  • Design, testing, manufacture and installation of HDPE pipe J-tube extensions
  • Engaged in project HAZOP and safety studies
  • Interface engineering
  • Installation analysis
  • Protection design / analysis
  • Pre-lay grapnel run (PLGR) and route clearance operations
  • Collection of the submarine export cables from manufacture
  • Installation of J-tube bell-mouth structures (diver intervention)
  • Installation of infield cables between WTGs and substations
  • Pull-in and termination of infield cables to WTGs
  • Pull-in of infield cables to offshore substations
  • Protection of the submarine infield cables between WTGs and offshore substations
  • Testing of FO and conductors insulation test
  • As trenched survey of cable route to determine burial
  • Preparation of as built documentation for the project handover

These were delivered to the satisfaction of both VSMC and Statoil.