IEEE Power & Energy Magazine - September/October 2020 - 29

imports, and exports from year to year can clearly be seen.
The pump storage consumption in the country was 1,650,
1,031, and 1,262 GWh, respectively, in 2017, 2018, and 2019.
The majority of the Norwegian hydropower stations is a
reservoir type, with some run-of-river facilities. There are
multiyear reservoirs that can store the normal inflow for
more than one year. The largest reservoir is Lake Blåsjø,
which has a capacity of 7,800 GWh. There is a limited number of pumped-storage power stations in Norway. The pumping capacity is roughly 1.5 GW. The existing pumping stations were built for seasonal operation (i.e., storage when the
snow is melting as well as during spring floods and heavy
raining periods, with production during peak load situations
and the winter). It became clear that it would be beneficial to
connect the Norwegian hydropower system to neighboring
networks to compensate for the large variation in the inflow
to the reservoirs between wet and dry years (60,000 GWh).
Electricity supply cooperation between the Nordic countries of Denmark, Finland, Norway, and Sweden has long
been a tradition. Cooperation sped up after the installation of
new interconnections during the early 1960s. In this way, all
four countries were joined to a common synchronous area.
Western Denmark was the only region synchronously interconnected to the continental European system. The Nordic
synchronous area typically had hydropower in Norway,
northern Sweden, and northern Finland and thermal power
in the south of Finland, Sweden, and eastern Denmark.
Transmission systems were developed within the countries
at the same time as the construction of new interconnectors
to utilize the flexibility of the hydropower system.
In 1976 and 1977, Norway and western Denmark (Jutland) were interconnected with two HVdc submarine cables
called the Skagerrak Interconnector. The total capacity was
500 MW. Since Jutland was synchronous with the continental European system, Norway now had a link to central
western Europe for the first time. Later, in 1993, Skagerrak 3
was added, with an additional capacity of 500 MW. In 2014,
Skagerrak 4 was commissioned, with a capacity of 700 MW,
making up a total interconnector capacity of 1,700 MW. In
all four countries, the electricity sector used to be dominated by one or a few integrated utilities whose responsibilities were production, transmission, holding a monopoly
on exports/imports, and, to different degrees, distribution
and wholesale operations. With liberalization during the
1990s, these dominant utilities were unbundled, and the
transmission and production parts were organized in separate companies.
In all Nordic countries, the transmission system operator
(TSO) model, where the system operator is also the owner
of the transmission assets, was chosen. This contrasted
with the independent system operator model commonly
used in North America. There, the transmission assets are
held by separate transmission owners. An important part of
the development of the common Nordic electricity market
is the power exchange, Nord Pool. The basis of Nord Pool
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was arranged at the end of 1992 when the Norwegian power
exchange, Statnett Marked, was created. When Sweden
opened its electricity market in 1996, Statnett Marked was
changed to Nord Pool and established as the first international power exchange in the world. Finland joined Nord
Pool and the common Nordic electricity market in 1998.
The western area of Denmark was included in 1999, and the
eastern area of that country was added in 2000.
In a system with approximately 50% hydro, the energy
production capability is as important as the capacity margin.
Even if there is sufficient capacity to cover peak load periods, an energy deficit may occur during dry years. During
normal years, the thermal generation capacity in Denmark,
Finland, and Sweden can cover the variations in energy production in Sweden and Norway. During dry years, however,
the need to import power may be so large that this capacity will not be sufficient. Plans for the construction of new
HVdc interconnections to Germany, The Netherlands, and
Great Britain started in Norway during the 1990s to mitigate
the supply impact. This has resulted in one new interconnector, NorNed, from Norway to The Netherlands, which was
commissioned in 2008. Furthermore, two other interconnectors from Norway are under construction, one to Germany
and the other to England.

Connection of Hydropower
to Continental Europe
The Nordic power system connects to the continental European power system for the benefit of both networks, as their
basic characteristics complement each other. Connecting the
systems strengthens the supply security on both sides and is
socioeconomically beneficial for the interconnected countries. Figure 1 shows the HVdc links connecting the Nordic
countries to other areas. The first interconnector linking the
Nordic and central western European synchronous areas was
Kontiskan 1, joining Sweden and western Denmark in 1965
with a capacity of 250 MW. This capacity was increased in
1988 with Kontiskan 2, at 300 MW. In 2006, Kontiskan 1 was
replaced by a new interconnector of 350 MW. In 1994, the
Baltic cable running beneath the Baltic Sea interconnected
the Swedish and German power systems. The capacity of the
Baltic cable is 600 MW. In 1995, the Kontek interconnector
was commissioned, linking the eastern Danish and German
power systems. The capacity of Kontek interconnector is
600 MW. The SwePol link between Sweden and Poland was
inaugurated in 2000 and has a capacity of 600 MW.
Skagerrak 1 and 2 linked Norway to western Denmark in
1976 and 1977, as mentioned previously. The positive experience and the economic results of the utilization of Skagerrak
1 and 2 triggered the decision to build Skagerrak 3, commissioned in 1993. This fact, together with the liberalization of
the electricity supply industry in Norway during the early
1990s, led to the start of several new interconnector projects
to link Germany and The Netherlands. The main partners in
these projects were large electricity production companies
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IEEE Power & Energy Magazine - September/October 2020

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