Energy Explained: Voltage

17/06/2020
3 min

Most of us never think about voltage until we need the right batteries to power a TV remote, or a new gadget. But did you know that the right voltage levels are critical to the entire power system?

What is voltage?

Voltage is like the pressure that pushes electrons (carrying electricity) to flow through the powerlines.

In Australia, our power system mostly uses alternating current, also known as “AC” electricity. This means that the direction of voltage reverses rapidly many times a second. It looks like the waveform image we’ve illustrated below.

graph showing importance of voltage

This is what a full cycle voltage waveform looks like. In Australia’s power system, this full cycle waveform happens 50 times a second.

On a smaller scale, voltage is measured in volts (V) – from the 1.5 V battery in the TV remote, to the 230 V wires running from street poles to our houses.

But at the power system level, where a much larger pressure keeps electricity flowing, voltage is measured in kilovolts. 1,000 volts = 1 kilovolt (kV).

Why does voltage matter?

It is critical that the voltage is always at the right level.

If voltage is too high, the connected equipment can be damaged or “fried”. This is like watering your flowers outside with a high-pressure hose.
too high voltage infographic  

If voltage is too low, the connected equipment can operate poorly or does not operate at all, like turning on your hose for only a trickle to come out.

too little voltage infographic

Different voltage levels are also needed for different purposes.

·        If you need to transport large amounts of electricity over long distances (like from a power station), higher voltages are essential because it reduces the potential loss of electricity along the journey.

·        If you need to transport electricity to homes or businesses, a lower voltage is better because it’s a safer option to use in homes and works well with the voltage levels required by our appliances (like your fridge, toaster and kettle).

If a voltage in the network is not at the right level, this may mean there is another issue on the system which is leading to a voltage rise or fall.

How does AEMO manage voltage?

AEMO works with industry members to regulate voltage levels across the high voltage transmission network.

There are voltage support services available that can respond quickly if an event in the power system disrupts the voltage. These services act to regulate the pressure in the network and are provided by:

  • Network service providers turning on local sources of voltage support, like capacitor banks (this is like adding a pump to a water system).
  • Power generators controlling their local voltage levels.

Under unusual circumstances AEMO can also consider switching parts of the transmission system on or off to help control voltage.

Want to know more about the basics of our energy system? Read the rest of the series, or contact media@aemo.com.au to let us know what explainers you would like to see! 

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