Havbrise array cables
Test programme for a 54-turbine offshore wind farm.
48 km
tested, no rework.
Size
54 turbines, 48 km of 66 kV cable
Location
North Sea, 30 km off western Norway
My role
Graduate engineer, cable testing
Team
5 in the cable team, 2 vessel crews
Duration
21 months, 2014 to 2016
01
The situation
Havbrise is a 54-turbine wind farm off the west coast of Norway. The turbines are linked to the offshore substation by 54 lengths of 66 kV array cable, 48 km in total, buried in the seabed. I joined the cable team straight from university in September 2014, a year before the first cable was laid.
Array cables are a common source of insurance claims in offshore wind. A fault found after burial means bringing a vessel back, at a cost of around 150,000 USD a day. The project had no single test programme. The factory, the installer and the owner each had their own plan, with gaps in between.
02
What I did
My manager gave me the test programme to run. I mapped every test each cable would see, from the factory floor to the seabed. I found two points where nobody was responsible for checking the cable at all. One was straight after loading onto the vessel. I added a test of the outer sheath at both points.
I witnessed the factory tests for all 54 lengths and spent eleven weeks offshore during installation. After each cable was pulled into a turbine and connected, we tested it before the vessel moved on. I kept one record sheet per cable, with the same fields in the same order, so a problem would show up as a number out of line.
03
What changed
All 48 km passed the final high-voltage test at the first attempt. No cable had to be reconnected, repaired or replaced, which the installer told us was a first for them. The sheath test after loading caught one damaged cable drum while it was still in port, where swapping it took a single day.
The farm exported its first power in the summer of 2016, on schedule. My record sheets went into the owner’s handover pack and were used again on Norrvind’s next project. This job taught me that testing is mostly planning. The offshore part only works if the paperwork was right six months earlier.
48 km
Array cable tested
54 lengths of 66 kV cable
0
Cables reworked after installation
Final high-voltage test results
11 weeks
Spent offshore during installation
Vessel rotations, 2015 to 2016
