Offshore Electricity Infrastructure in Europe - European Wind Energy ...

factors combined with the voltage and ampacity dictate
the power carrying capabilities of a cable and
ultimately its cross sectional area. The choice of
which type of cable to use is very much project specific
and depends on a whole host of economic and
environmental factors, such as capital cost, losses,
and the thermal resistivity of the medium in which the
cable will be laid. Within the OffshoreGrid project the
following offshore AC cable maximum size building
blocks are regarded (Table 10.1). The infrastructure
cost model selects cable sizes up to the cross sectional
area shown below [27].
High voltage direct current (HVDC) solutions
In a HVDC system, electric power is taken from one
point in a three-phase AC network, converted into DC
OffshoreGrid – Final Report
by a converter station, transmitted to the receiving
point by an overhead line or underground / subsea
cable and then converted back into AC by another
converter station and injected into the receiving AC
network (Figure 10.1).
Traditionally, HVDC transmission systems are used
for transmission of bulk power over long distances.
The technology becomes economically attractive
compared with conventional AC lines as the relatively
high fixed costs of the HVDC converter stations are
outweighed by the reduced losses and reduced cable
requirements.
The following HVDC converter capacities (Table 10.2)
will be used within the OffshoreGrid design.
FiGuRe 10.1: OveRview OF vsc hvdc tRansmissiOn FOR OFFshORe wind FaRms; imaGe cOuRtesy OF abb
table 10.1 OFFshORe and OFFshORe ac cable desiGn ‘laRGest buildinG blOcks’
nominal
Voltage
(kV)
cores conductor insulation Available Pre 2020 c.s.a (mm 2)
Power rating
(MVA)
Offshore Onshore Offshore Onshore Offshore Onshore
33 3 Copper XLPE Yes Yes 1,200 2,000 52 65
132 3 Copper XLPE Yes Yes 1,200 2,000 208 259
150 3 Copper XLPE Yes Yes 1,200 2,000 237 294
220 3 Copper XLPE Yes Yes 1,200 2,000 347.5 431
400 3 Copper XLPE Yes No 800 2,000 491.7 739
table 10.2 hvdc cOnveRteR desiGn ‘buildinG blOcks’
type Voltage (kV) configuration Available Pre 2020 Power range (MW)
VSC +/-150 Symmetrical monopole YES Up to 500
VSC +/-320 Symmetrical monopole YES Up to 1,200
VSC +/-500 Symmetrical monopole /Bipole NO Up to 2,000
CSC +/-250 Bipole YES Up to 1,000
CSC +/-500 Bipole YES Up to 2,000
VSC +/-150 Symmetrical monopole YES Up to 500
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