First Quarter, 1991
interties connect faraway areas
have become aware of the benefits that international
power exchanges offer, the number of transmission
interties between countries has increased. Taking
the trend a step further, proposals are being considered
to transmit power over very long distances, with interties
that eventually could connect both hemispheres.
Traditionally, a utility generated all of the electricity
that its customers needed. Customers typically received
their electricity from the nearest generating plant,
which often was not very far away. Indeed, the maximum
economical transmission distance 30 years ago was
only about 500 km. This method of operation was the
norm for many years.
However, evolving technology has made transmission
over longer distances possible without significant
losses or threat of voltage collapse; escalating fuel
costs have made it desirable. Power exchanges within
a country first began to occur, and currently, power
sales also take place across national borders. There
are 50 nations that actively exchange power with one
or more countries. Three regions have formed large
interconnected power systems. Continental Western
Europe has the Union for the Coordination of the Production
and Transport of Electric Power (Ucpte). Eastern European
countries have the Comecon interconnection, and Scandinavia
has the Nordel system.
Such interties save money for all involved. The most
efficient power generation usually comes from base
load units. Often, excess base load capacity from
one utility helps meet demand peaks of another one
utility gains revenue for electricity from a unit
that would be operating anyway, the other buys electricity
at a lower cost than its own peaking units could generate
Magnified cost benefits
However, whether within a country or between nations,
power exchanges generally occur across relatively short
distances. Utilities could realize additional economic
benefits by transferring power longer distances.
Figure 1. Projection summarizes the major Interties
that eventually could connect the world's power Systems
The reason: Electric demand usually relates to the time
of day. Thus, while there might be slight differences
in customer demand between adjacent utilities, those
in different time zones would experience more dramatic
load variations. Power transfers between areas that
are in day and night could allow utilities to use their
generating resources even more effectively than they
now do. In addition, long-distance interconnections
between north and south regions could help utilities
address seasonal load variations.
Some countries anticipate great economic benefit
from long-distance transmission. To illustrate: Many
developing countries-particularly in Africa and Latin
America have vast untapped generating potential. If
there were a means of transmitting this power, they
could sell it to gain much-needed revenue. Developed
countries without ample power reserves could buy this
electricity economically. An added benefit is that
much of the untapped generating capacity comes from
clean renewable sources-such as hydroelectric and
A long-distance transfer scheme could benefit the
environment as well Fuel is saved and emissions are
cut when utilities level out their load curves. Also
besides being relatively inefficient, some types of
peak generating units burn fossil fuels. Relying more
heavily on renewables can reduce pollution. Additional
savings come from eliminating losses involved with
starting and stopping units.
Technology is available
Long-distance power transfers are technologically feasible.
The Soviet Union a pioneer of ultra-high-voltage technology
currently operates 1150-kV ac lines and l50O-kV dc lines.
With higher voltages come longer economic transfer ranges
maximum possible distances currently are up to 6400
km for dc lines and 4800 km for ac lines.
Another significant technological advance is the
multi-terminal high-voltage dc line. Major ones include
a five-terminal link between the northeastern US and
Canada and an intertie that interconnects the separate
power systems of Corsica, Sardinia and mainland Italy
(see companion article). Similarly, thyristor technology
- used to convert power between ac and dc - also has
improved and become less expensive.
It is less clear how to establish the various control
and communications systems necessary to regulate power
flows, meter, and supply data to Scada and energy-management
systems among multiple parties. Although a global
communications grid has existed for several decades
it would be complicated and costly to relay power
system data to several utilities in several countries.
In addition, since power system operators would need
to confer when problems arise, even spoken language
is a barrier. Many countries are addressing these
communications issues internally so there should be
solutions available by the time long-distance interties
are ready for construction.
It also is significant that various types of energy
storage--pumped water, compressed-air, battery, and
magnetic-field are either being refined or made commercially
viable. Some would argue that this area of technology
could help utilities use power more effectively without
the need for long-distance interties. Considering
all of the available technology, companies and governments
must evaluate each project on a case-by-case basis.
No matter how attractive the economics of long-distance
international interties are, the political aspects
of such projects remain a hurdle. Many wonder if countries
can afford to become too dependent on buying power
from other nations. While the emphasis in many nations
is on becoming energy-independent, international interconnections
mean a move toward interdependence. "The barriers
to long-distance interties definitely are political
and bureaucratic rather than technical." Says Peter
Meisen, director of Global Energy Network Institute
(GENI), San Diego, Calif, USA, a proponent of the
development an international power network. "Countries
have to decide whether this idea will complement their
US/Soviet transmission link
One of the major proposed long-distance links is between
the Soviet Union and the US. While most people think
that these countries are geographically distant, technically
their mainlands are only about 85 km apart. However,
the areas where they are closest are Siberia and Alaska,
both sparsely populated and with relatively light electric
demand. The US/Soviet line has received much attention
because it represents the most feasible point of creating
an intertie between hemispheres.
Prevalent trends in the Soviet Union support the
possibility of constructing the line. Besides opting
for higher transmission voltages, approximately 95%
of the country's generating capacity now is interconnected.
Indeed, the USSR already is able to derive benefits
from long-distance transmission because the country
spans 11 time zones.
However, such a line would be very expensive. The
cost of a UHV overhead line over relatively uncomplicated
geography is about $US 620 000/km. The estimated cost
for an underwater link under the Bering Strait is
$5-billion. Nevertheless, estimates say that potential
savings could make the project cost-effective.
GENI is promoting this intertie heavily because it
feels that it will serve as an example to other countries.
The organization foresees the development of a global
energy grid that would have far-reaching world benefits.
Several organizations within both the USSR and the
US are considering the line seriously, with other
interested groups from around the world also participating.
The American Society of Mechanical Engineers, Manitoba
HVDC Research Center, and the USSR Academy of Sciences,
for example, all are conducting feasibility studies.
Various other organizations are sponsoring meetings
for concerned parties to discuss the issue. Again,
politics and bureaucracy remain significant considerations;
as relations between the two countries seesaw, it
remains unclear whether the project will be pursued
None of the proposed long-distance interties have
gone beyond the discussion phase. Besides the US/Soviet
link, others being considered include ones between:
- Europe and Africa. The distance between the Morocco
and Spain across the Strait of Gibraltar is relatively
short. While there currently is no impetus for power
exchange, there might be in the future. There is
34000 MW of undeveloped hydroelectric power in central
Africa along the Congo River. Selling this power
to western Europe would help provide Europe with
clean power and provide needed income to African
- Iceland and UK. Iceland's renewable geothermal
and hydroelectric resources could provide economical
power for the UK. The distance between the two countries
is about 640km.
- North America and Europe. This link is the other
way of connecting hemispheres but it certainly is
the least practical. It represents very long underwater
transmission distances and thus the most technical
problems and cost. If the previously mentioned link
between Iceland the UK is built, the line becomes
more feasible because completing the link would
only involve constructing a line from Canada across
Greenland to Iceland.