UK span than that of a one-phase network.

UK National Grid
Distribution System

Task 8

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Summarise the reasons for a three-phase supply

A three-phase network is a commonly
used method to alternate current electric power into generation, transmission
and distribution. Worldwide Power Grids use the system to transfer power. The
main reasons the three-phase network was put in place is due to the fact that it
has a longer life span than that of a one-phase network. A three-phase network
will produce 3x the power of that of a single-phase network. Also with the
three-phase you get 3 wires instead of the usual 2 wires. Another reason three-phase
networks are used is the fact they can withstand more pressure and force. For
example, if a turbine has a single one-phase generator the probability of it
being shaken to the point of disconnection due to the vibrations and torque
varieties is quite high. However, a single three-phase generator could handle
this without any stress or problems.

Constant power is one of the three-phase network’s key
features. The power is constantly delivered all while the amount of conductor material
is less than a one-phase network. If a test was conducted for both a one-phase
and three-phase network, both networks running the same amount of power and
voltage. The results would show the three-phase come out on top of the two. In
the long run the three-phase network is the best option as it is more economical
than a 2 wire one-phase network.


Use diagrams to show the voltages at all
significant parts of the system, from generation through to end user, and
briefly explain the reason for the voltages used







Consumers get electricity through
power stations. Wires and cables within the National Grid are used to transfer
electricity from power stations. Energy is lost as heat when electricity is transferred
through wires and cables. The National Grid try to/must keep a low flowing
current to avoid losing more heat. The more heat is lost, the higher the
current gets. A high voltage is
needed to be able to transfer such a low current through cables and wires and
to keep the amount of energy from escaping as heat to a minimum. For example, “Power
stations produce electricity at 25,000V. Electricity is sent through the
National Grid cables at 400,000V, 275,000V and 132,000V.” (,
2018) Power stations use step-up
transformers as they can create the extremely high voltages that are needed to
transmit electricity through power lines. Another transformer is used to
dramatically reduce the voltage before it enters an average household. This is
done through a step-down transformer, which is the last process before a safe voltage
of 230V is distributed into each household.



In-text: (, 2018)

Your Bibliography: (2018). BBC – GCSE
Bitesize: The National Grid. online Available at:
Accessed 19 Jan. 2018.

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