Energy Explained: Frequency

3 min

What is frequency?

Frequency is how many times voltage cycles every second. In the Australian power system, voltage cycles 50 times in one second, meaning our system’s frequency is 50 hertz (Hz). We’ve visualised this for you below:

Australian power system frequency graph

Why is frequency so important?

When our system’s frequency is at 50 Hz, generators and consumers can safely deliver or withdraw power without impacting the connected equipment.

We can get the right frequency range by matching the amount of power that goes into the grid with the amount of power that comes out. To do this, AEMO forecasts how much power Australian consumers need every five minutes, and then matches that to how much power our electricity generators need to produce.

Graph showing the balance of frequency in the power system

We do this for almost all of Australia every five minutes!

Maintaining this balance can be challenging as our power system cannot generally store electricity. As electricity travels almost at the speed of light, we must manage this balance in real-time.

(We can attach storage devices to the grid like batteries, or pumped hydro plants, but ultimately what goes into the power lines must always equals what goes out.)

What happens if the frequency deviates from 50 Hz?

If the frequency goes too far away from this 50 Hz mark, the system can become unsafe, and generators and consumer might have to disconnect to protect themselves from any damage.

There are natural deviations in supply and demand that can cause frequency to go slightly above or below 50 Hz, which can be managed but there are also large disturbances in the system, such as a large power plant tripping off, which can severely affect the supply-demand balance and throw off the frequency of the system.

To keep frequency close to 50 Hz, there are different lines of defence in our frequency control. We’ll be releasing an article on frequency control next week, so stay tuned!

Want to know more about the basics of our energy system? Check out last week’s explainer on Voltage, or contact to suggest an energy topic of your own!  

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