Why outages can last longer in extreme heat

9 March 2018

If a power outage occurs on an extremely hot day it can sometimes take longer to restore compared to what it would on any other day. There are a number of reasons why this happens and it all comes down to safety.

Network protection devices

The electricity network is fitted with what we call “protection devices” designed to minimise the impact of blackouts and to prevent damage to infrastructure such as poles and wires.

These devices work differently on extremely hot days then what they do on days with lower temperatures. Here’s how.

On an average summer day

On an average day, if a branch falls onto a wire, a protection device immediately cuts the power and then automatically reconnects it. If the fault (in this case the branch) is no longer detected, the power remains on.

If the fault is still touching the wire, the protection device will cut the power again and crews will be able to find where the branch has fallen based on its proximity to the protection device that cut power. Crews then go to the site and repair the fault.

On an extremely hot summer day

Should the same branch fall on the same wire on a day of extreme heat, power will be cut along the entire line and there will be no automatic reconnection. This is to make sure sparks don’t potentially start a fire.

The only way for crews to find the fault is to manually patrol the entire line by truck or even on foot which means it will take longer to reconnect power supply.

Extra restrictions on Total Fireban Days

On extremely hot days the CFA declares fire danger ratings or issues a total fireban. This means extra restrictions are in place for safety reasons which can make it harder for our crews to access areas to find faults.

In these conditions, trucks cannot be driven onto grassy areas in case the vehicle exhaust starts a fire so paved or gravelled roads need to be found which can slow the crews down.

If crews are entering an actual bushfire affected zone, a CFA escort may be needed which again means it can take longer to find and fix a fault.