Victoria's power supply is back to normal after tapping into emergency reserves to meet elevated electricity demand while sweltering heat disrupted transmission lines.
The state faced its highest demand for electricity in more than five years on Friday, the Australian Energy Market Operator said.
AEMO declared an "actual lack of reserve" condition in Victoria on Friday due to outages in transmission lines from Moorabool to Mortlake and Moorabool to Tarrone.
It also activated a lack of reserve condition in NSW with emergency reserves activated in both states.
Victorians were urged to switch off non-essential appliances until 9pm to prevent a blackout.
Damage to transmission towers in western Victoria had resulted in the loss of electricity supply to the Portland aluminium smelter, AEMO said.
The transmission outage also affected supply from generators in Victoria and imports from South Australia.
AEMO managed to get energy back to normal across the states on Friday evening with sufficient generation to meet usage demand, a spokesman told AAP.
Emergency Management Commissioner Andrew Crisp said earlier in the day that transmission lines between Victoria and South Australia had tripped in the hot weather.
"That hot weather, what it tends to do on days like this, it can have an impact on our energy systems and our power supply," he told reporters on Friday.
Some 28,000 homes were without electricity across Victoria about 9.30pm on Friday, with power companies working to fix the outages.
While Emergency Services Minister Lisa Neville said high temperatures can affect the Basslink interconnector between Victoria and Tasmania, this wasn't the case on Friday.
"There was no impact to our operations at all. We have operated as designed and at full capacity today," a Basslink spokesman confirmed.
A unit of the Loy Yang power station had a failure on Thursday night but AEMO was able to draw on reserve supplies.
The heat worsened bushfire conditions, with severe danger forecast for Friday in western and central parts of the state, with emergency warnings issued for fires in the state's east.
Australian Associated Press