1. CHARLES ISIADINSO
TRANSMISSION LINES
Due to current technological limitations, large amounts of
electricity cannot be stored effectively therefore; it must be
produced when needed. A complicated control system is used to
manage the supply of electricity, keeping it at close to demand as
possible. Poor handling of the supply-demand gap could lead to
blackout (when demand exceeds supply).
Electricity is transferred from the plant to high voltage substations,
through a complex network of power lines, called a grid (UK
national grid). Energy is lost, due to electrical resistance, which
varies with material, when transmitting electricity over long
distances. To reduce this, electricity is transmitted at voltages of
120kV or higher (the voltage is stepped up from the plant output,

2. CHARLES ISIADINSO
which is usually between 2.3kV and 30kV). The actual lines are
usually transfer the stepped-up three-phase generator AC current,
however, DC current looses much less energy over long distances
than AC so high-voltage direct current (HVDC) lines are used for
greater distances (usually hundreds of miles).
Transmission lines are bundles of air-cooled individual conductors,
usually reinforced with steel strands for strength. Aluminum is the
material of choice for the conductors as it is lighter and cheaper
than copper and yields only marginally reduced performance. The
conductors are bundled to correct for skin effect. When current
flows in a cable, it tends to flow very close to the surface. The effect
is negligible for small cable radii, but at large radii most of the
radius of the wire is wasted thus multiple small radii conductors
(12mm2
to 750mm2
) arranged parallel to each other, resulting in a
significant increase in the current carrying capacity of the
transmission line.

3. CHARLES ISIADINSO
There are different transmission lines with different operating
voltages (i.e. the voltage at which electricity is transmitted along
that line). The voltage given with a particular transmission line is
its operating voltage, e.g. 330kV.
REFERENCE:
1. "Transformer."Wikipedia. Wikimedia Foundation, 16 June
2014. Web. [Accessed16 June 2014].
2. "Electric Power Transmission."Wikipedia. Wikimedia
Foundation, 15 June 2014. Web. [Accessed 16 June 2014].