Powering Europe - European Wind Energy Association

Immediateopportunitiesforupgrade:optimaluseofthenetwork
rewiringwithhightemperatureconductors
Rewiring existing lines with low sag, high-temperature
wires offers the possibility to increase the overhead
line capacity by up to 50%, as electrical current carrying
capacity directly depends on the power line sag
and the line temperature. Depending on the specific
situation, rewiring may be possible without having to
obtain a permit, thus offering a fast way to significant
transmission capacity enhancement.
powerflowcontroldevices
The installation of power flow control devices in selected
places in the network can help to optimise the
utilisation of the existing grid. Flexible AC Transmission
Systems (FACTS 2 ) are widely used to enhance
stability in power systems, but some FACTS solutions
also support power flow control. Physically, in large
radial European transmission networks, there is a
lack of power flow controllability, because there is
only one way for the power to flow. The lack of controllability
can sometimes lead to congestion on a specific
transmission line while there is still capacity on
alternative lines. Since large-scale wind power changes
the pattern of generation in the grid, the growth of
wind power can increase the economic feasibility of
AC power flow control. An example of this was shown
in TradeWind simulations [TradeWind 2009], where
increased wind power generation in central Norway
would cause the corridor to Sweden to overload while
there was still free capacity on the corridor to south
Norway. One option in this case would be to reduce
the hydro generation in central Norway when the
wind speeds are high, but according to research, this
would not be the preferred market solution if there
were a possibility to control the AC flow. Consequently,
it may be economically attractive to control the
flow in certain AC lines, even if it would cost in terms
100
of investment in auxiliary equipment. Thus, power
flow control can ensure that existing transmission
lines are utilised to the maximum, which is important
given the public’s reluctance to accept additional
power lines, and the long-term project implementation
which is normally associated with reinforcement
of transmission systems.
technologiesthatcanhelpimplementnewnetwork
operationstrategies
An assessment of the online dynamic network security
by Wide Area Monitoring (WAMS) may substantially
reduce traditional conservative assumptions about
operational conditions, and thus increase the actual
transfer capability of a power system. WAMS uses advanced
GPS based surveillance tools to enable network
operators to react in close-to-real-time for trading,
fault prevention and asset management, and thus
maintain the required reliability and system performance
with increasing renewable generation. There are
some organisational and regulatory challenges for the
wide-spread introduction of WAMS, notable the need
for standardised monitoring technologies, synchronised
data acquisition and online data exchange.
Usingdistributedwindplantstoimprovetransmissionoperation
Investments in the grid also can be reduced by the
technical capabilities of the wind farms themselves,
in particular when combined with technologies that improve
the control of reactive power. This could for example
be achieved by installing wind power plants at
selected sites along the transmission grid especially
for the purpose of grid support, which has a similar effect
to installing FACTS. The advantage of wind plants
over FACTS is that they produce energy in addition to
grid support.
2 FAcTS (Flexible Ac Transmission Systems): power electronic devices locally implemented in the network, such as STATcOMs, SVc’s etc.
Powering Europe: wind energy and the electricity grid