CP design and modelling of Hywind Tampen wind farm
Oftentimes, a standard cathodic protection (CP) design will not sufficiently consider all factors that may affect a CP system over time. Therefore, we use CP modelling together with design codes.
The manual CP design verification of Hywind Tampen, using DNV standard DNVGL-RP-B401, showed that all structural parts are satisfactory in terms of cathodic protection. However, this does not sufficiently take into account shadow effects, uneven anode distribution, and thereby uneven anode consumption, as well as anode interference, to name a few.
Securing the cathodic protection of the Hywind Tampen wind farm
As the standard CP design calculations were not found sufficient in terms of evaluating issues as mentioned above, we ran five different static CP simulations to identify individual anode consumption and potential distribution issues using parameters from DNVGL design codes. This simulation confirmed that all structural parts are protected so long as all anodes are active for the operational life. This, however, might not be the case.
Timestep simulations showed us that some of the anodes might be 100 % consumed before the end of the design life of the structures. This would lead to under-protected areas surrounding the protection objects, which are critical areas for the structural integrity. The structure will, however, still be protected if one applies a slightly less conservative coating breakdown factor for the 0-30 m water depths.
Conclusively, the integrity of the cathodic protection can be considered adequate given that the most utilised anodes are regularly inspected towards the end of their design life.