IEEE Power & Energy Magazine - March/April 2016 - 60

✔ Bipole 1 smoothing reactors were approaching their

end of life with more than 35 years in service. In 2014,
Manitoba Hydro replaced the existing oil-filled units
with air-core reactors to ensure reliable operation and
alleviate environmental and fire concerns.
✔ The bipole 1 bypass vacuum switches are part of the
original mercury-arc valves switching scheme and
require substantial maintenance. The new outdoor
SF6 type bypass switches have been procured and are
being installed.
✔ Bipole 1 is protected against switching and lightning
transients with gapped arresters that are over 30 years
old, and they experience more frequent breakdowns,
causing safety concerns. In 2013, Alstom Grid was
contracted to assess the technical requirements of
new gapless arresters, which are now in the process
of procurement.
✔ Bipole 1 operates with the original analogue pole and
bipole control equipment, as they were not replaced
during the pole 2 valve replacement in 2004. The
replacement evaluation has been initiated for these
controls in a time frame after the completion of the
construction of the new bipole 3.
Refurbishing the existing HVdc system has been a long,
complex, and costly process. The investment is deemed necessary, however, to achieve the required high availability
and long life required of the facility, as it is a major component not only of the infrastructure within the utility network
but also in the province's economy.

strategy of complete pole replacement allowed the operation of both poles 1 and 2 to continue while the construction
of the new pole 1 was under way. Figure 3 shows the land
requirements for the pole replacement.
The Danish terminal is owned by the utility Energinet,
and the Swedish terminal is owned by Svenska-Kraftnät. As
a result, the project scope allocated to Alstom Grid for the
two contracts was different for each converter station. At the
Swedish terminal, the scope was full turnkey, including civil
works and ac and dc switchyards, whereas at the Danish end
the project was managed by the utility themselves, including
civil works and buildings, and Alstom Grid manufactured,
installed, and commissioned the equipment.
The equipment scope of supply included the thyristor
valves (as shown in Figure 4), converter transformers, dc
reactors, ac harmonic filters, ac and dc switchgear, auxiliary power supplies, HVdc control and protection systems,
human-machine interface (HMI), ac protection, building
services, and safety interlocks. The environmental impact of
this new installation was a significant factor in the design of
the new facility, with extremely onerous audible noise limits,

Konti-Skan Pole 1 Replacement
The original Konti-Skan pole 1 link between Sweden and
Denmark was implemented using mercury-arc technology, in
1965 and was rated at 250 MW, 250 kV, 1,000 A as a single
valve group. Pole 2 was added in 1988 using thyristors, rated at
300 MW, 285 kV, 1,050 A. The dc circuit between the converter
stations is more complex than most HVdc links, with three sections of overhead line and two sections of submarine cable. One
overhead portion of the circuit passes through Laesoe Island for
a total distance of about 115 km. Over the life of the pole 1
equipment, the sections of cable have been replaced or repaired
and upgraded resulting in unused capacity in the overall dc conductor circuit. In addition, the pole 1 and pole 2 converter stations on the Swedish side were located approximately 30 km
apart, but at the Danish end the two poles are adjacent.
The drivers for refurbishment included a) removing mercury from the installations for environmental, health, and safety
reasons; b) reducing the maintenance requirements; c) increasing pole 1 capacity to make use of the unused cable and line
capacity; d) replacing obsolete control systems; and e) replacing power circuit equipment that was at or near end of life,
especially the converter transformers. The decision was made
to replace the complete pole 1 equipment with a new pole and
to also take advantage of the opportunity to colocate the two
poles on the Swedish side at the site of pole 2 at Lindome. This
march/april 2016

New Pole 1
Pole 2
Old Pole 1

figure 3. The Danish terminal of Konti-Skan at VesterHassing. (Photo courtesy of Energinet, Denmark.)

figure 4. The thyristor valve hall at the Konti-Skan converter
station. (Photo courtesy of GE.)
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2016