1. CHARLES ISIADINSO
SUBSTATION & SUBSTATION
A switchyard is a substation without step-up or step-down
transformers. It located just outside the power station and operates
only at a single voltage level. Its primary use is to deliver power
generated to the grid. The 3-phase electric current leaves the
generator via isolated-phase buses, which are connected to a
generator busbar (a metal bar used to transfer electricity to the
switchyard), each isolated-phase bus is connected to a separate
generator busbar as a preventive measure, so if there is a problem
in one busbar, the other two phases aren’t affected and the plant
can still supply electricity. This is especially useful during
maintenance and repairs as one busbar can be taken offline, but
the plant can still supply the grid, even if it is two-third power.
Substations, however, use a generator step-up transformer to step-
up (or down) the voltage of electricity flowing through
transmission lines. Substations exists along the transmission
network to step-up (or down) the voltage of electricity to an
appropriate level to comply with consumer needs.
The grid works such that electricity leaving the plant is stepped-up
for efficient transmission; the voltage is too high to be consumed

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directly so as the transmission network approaches consumers (e.g.
homes and businesses), it passes through a substation, which steps
the voltage down. Electricity leaving this first substation is usually
still at a very high voltage so, further along the line, electricity
passes through another substation. The number of substations is
determined by the power requirements of the consumers. For
example, if there is a large bread factory on the same line, but
ahead of, a small town, there will be a substation to step down the
voltage to one close to the requirements of the bread factory, but
still significantly higher that that of the town first then the
electricity will then flow through another substation further closer
to the factory, which will step voltage down to meet the factory’s
requirements before being supplied to the factory. After the
factory, electricity will flow through a further substation and here
the voltage will be stepped-down to one suitable for the town.
Small step-down transformers will reduce the voltage further
before electricity is supplied to homes and shops. Electricity
leaving the town passes through a substation to step-up the voltage
again so it can be efficiently transmitted to the next set of
consumers.
The substation also has provisions for bypass, so if electricity is
being transmitted to a set of towns, one small another very large,
not all electricity entering the small town substation will be
stepped-down, some will bypass the substation and carryon to the
large town substation, this is especially the case if the distance
between the two towns is large. A typical mid network substation is
shown below, with the blue line being the bypass line and the red
lines, being the step-up (or down) line(s).
Components of the substation above are:

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1. Primary and secondary power lines (1 and 12 respectively)
2. Ground wire
3. Transmission lines
4. Transformer (used to measure primary line voltage)
5. Disconnect switches
6. Circuit breakers
7. Current transformer
8. Arrester/insulators (protects against lightning)
9. Main step-up (or down) transformer
10.Control building
11.Security fence
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].
3. "Electrical Substation." Wikipedia. Wikimedia Foundation, 30
June 2014. Web. [Accesses 03 July 2014].
4. "Substations." High Voltage Substations & Substations. Beta
Engineering, n.d. Web. [Accessed03 July 2014].
5. "Busbar." Wikipedia. Wikimedia Foundation, 26 June 2014.
Web. {Accessed 03 July 2014}.