POWER June 2022 - 19

TRANSMISSION & DISTRIBUTION
link is today the longest subsea connector
in the world.
4. Cable systems manufacturer Prysmian Group in December said it produced the first 20
kilometers (km) of underground cable for the SuedOstLink. This image shows the first lots of
cables-a total of 9 drums, each with 1,750 meters of underground cable. Prysmian will produce
a total of about 550 km of underground cable for grid operator TenneT for an approximately
270 km long section of the SuedOstLink (starting at the Southern Germany connection point at
Isar, close to Landshut in Bavaria). For this project two HVDC underground cables will be laid in
one trench. Courtesy: Prysmian
eral lengthy lines have been built in recent
years. A much-cited example is the
2018-completed Changji-Guquan Link, a
CSC-HVDC project that can transfer 12
GW at 1,100 kV over 3,324 kilometers
(km)-stretching from China's far northwest
to the heavily populated east. According
to Hitachi Energy, the link offers
a 50% increase in transmission capacity
compared to the 800-kV ultra-high direct
current (UHDC) links in operation.
State Grid of China, the line's operator,
reported the project has strengthened
the outbound delivery capacity
of the Xinjiang Power Grid, as well as
promoted development of the Xinjiang
Uygur autonomous region, which is rich
in coal, wind power, and solar power.
The project remains the world's record
holder in terms of voltage level, transmission
capacity, and distance. A similar
project in Germany, SuedOstLink, is
poised to transport wind power from
the north to consumers in the southern
regions (Figure 4).
But HVDC is also well-suited to submarine
cable transmission at distances
beyond 50 km, because HVDC submarine
cables do not have the physical restrictions
AC cables have, owing to the
reactive power component. This allows
underwater lines to link to asynchronous
networks, connect offshore wind power,
or supply remote islands. The October
2021-commissioned 720-km North Sea
Link, for example, harnesses Norway's
hydropower and the UK's wind energy
resources, providing a new measure of
flexibility for the two countries' power
grids. The 1,400-MW VSC (HVDC Light)
Another application that is quickly
gaining traction is HVDC's ability to interconnect
networks that operate asynchronously.
According to Rosenqvist, that
feature might be especially beneficial in
North America, where many asynchronous
interconnections exist, such as between
the Eastern Interconnection and
Western Interconnection systems, and
between the Electric Reliability Council
of Texas (ERCOT) and the neighboring
grids of Mexico and the Southwest
Power Pool (SPP). One project that could
highlight this HVDC benefit is New York's
newly approved $4.5 billion Champlain
Hudson Power Express, an underwater
and underground power cable project
linking Quebec to New York City. That
546-km line is expected to be completed
in 2025.
Finally, the burgeoning landscape of
offshore wind power has begun an effort
to harness VSC's independent control capabilities
of both active and reactive power
flow, the ability of " black-start, " as well
as its low-ground footprint. Several projects
in the North Sea have chosen HVDC
connections. That trend will carry over to
the U.S., owing mainly to its deeper water
installations, said Rosenqvist.
" There's interest in HVDC for offshore
wind integration in the Northeast,
whereas, the very first wave was typically
with AC connection because the wind
resource lease areas were a little closer
to the coast, " he said. America's first
offshore HVDC project, a 320-kV, 161km
line, could be deployed by Siemens
Energy and Aker Solutions for Ørsted
and Eversource's 924-MW Sunrise Wind
project in New York by 2025 (Figure 5).
According to Rosenqvist, more use
5. A consortium of Siemens Energy and Aker Solutions in October 2021 won a contract to
supply the HVDC system that will bring offshore wind power from Ørsted and Eversource's 924MW
Sunrise Wind farm, one of New York's first utility-scale offshore wind projects. Courtesy:
Siemens Energy
June 2022 | POWER
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cases for HVDC will likely emerge as
the energy transition reshapes power
systems everywhere and highlights its
role to preserve reliability and resiliency.
Over the near-term, HVDC's primary
role will be to provide balance and flexibility.
" You'll see tremendous interest
in HVDC around the world for the recent
efforts to integrate renewable resources
that are typically in remote areas and
bringing [that power] to the large load
centers, " he predicted. " That is true for
North America. It's true for Europe. It's
true for the large systems in in Asia. So,
you'll see a global interest for HVDC
now that you have never seen in past
history, " he said. ■
-Sonal Patel is a POWER
senior associate editor.
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POWER June 2022

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