Future of Wind Energy - Wind Energy Systems for Electric Power Generation - page 167

Fig. 8.3 Principal comparison of HVAC and HVDC connection cost
Model connection designs have been investigated. Examples based on a wind
farm rating of 100 MW for both AC and DC connection are shown in Fig. 8.4
[Rei05]. The offshore grid is at 33 kV AC, star configuration; the undersea cable
is operated at 150 kV AC or 150 kV DC, respectively, and the mainland AC side is
also assumed at 150 kV [Bres07]. The cable connection may be made in one or two
parallel undersea cables. Nominal voltage of 300 kV for undersea cables is under
consideration.
In current technology the cable is using copper conductor, VPE insulation, a lead
sheath and steel wire armour. Trends for future technology are superconducting and
gas-isolated cables.
8.1.3.3 Comparison
When comparing AC and DC connection the differences affecting investment cost
and losses should be noted, see Table 8.1.
Table 8.2 lists design features of modem HVDC connections as compared with
the well-known classical concept. Consequently the advanced HVDC using active
front-end voltage-source converters is considered the preferable solution.
8.1.4 Specific Issues and Concerns
In planning offshore wind farms several issues regarding environment, acceptance
and safety have to be considered [Mus05].
- Nature conservation
Regulations exist in view of the conservation of habitat for wild-living plants
and animals. They establish natural reserve areas and define protected species of
flora and fauna. In the European Union the topic is addressed by the FFH (Fauna,