Step-up Transformers

In switch yards near the power stations, the electricity produced by the generators passes through a series of transformers which produce the very high voltages required for long distance transmission from the Latrobe Valley to the major load centres. High voltages (with low current) are used to reduce energy loss, mainly in the form of heat, that occurs in the transmission lines.

Transformers can change the voltage of an alternating current.

In 1831 Faraday designed the first transformer. A transformer consists of two linked electromagnets.

The incoming current travels through the wire turns of the first coil. This passage of current in the first coil induces a current in the second coil. The voltage is altered according to the number of turns in the two coils.

A transformer that increases voltage is known as a step-up transformer. For example, if the second coil has twice as many turns as the first coil, the voltage is doubled.

The generators feed current into the first coil of a series of transformers. The voltage is increased by each of the transformers until it has been stepped up to the transmission voltage. For example, for transmission at 500kV the voltage has been increased to 25 times the generated voltage.

A transformer that decreases voltage is known as a step-down transformer. For example, if the second coil of a transformer has half as many turns as the first coil, then the voltage is halved.

Before electrical power is used in the city it passes through a series of step-down transformers so that the output voltage is lowered. The voltage is reduced in steps to a level where it can be used in industries requiring 10 000 volts and further reduced, in local substations, to 240 volts for use in our homes.