A fire at a privately owned power station sparked an outage which left about 100,000 homes and businesses across Perth, Kalgoorlie and Geraldton in the dark for several hours last night.

Key points: Western Power said it had restored power to around 80,000 homes by 10:30pm

Western Power said it had restored power to around 80,000 homes by 10:30pm The first reports of power losses started at about 8:00pm

The first reports of power losses started at about 8:00pm The event was reportedly triggered by a generator in Kwinana failing to generate

Suburbs across inner and greater metropolitan Perth were affected.

Firefighters were called to a power station on Leath Road in Kwinana at 8:48pm following reports a bearing in a turbine was smouldering.

Almost 30 firefighters attended the power station and extinguished the fire with guidance from power station staff.

The Australian Energy Market Operator (AEMO) has confirmed the initial generator failure occurred in a turbine at the privately owned NewGen power station.

An AEMO spokesman said the effect of that failure on the network then led to two further failures at other power stations.

Those were the Badgingarra Wind Farm, 190 kilometres north of Perth in the Wheatbelt, and at a power station in Worsely, near Collie in the South West.

The power outages stretched across inner city Perth. ( Supplied: Western Power )

The spokesman said there was no forecast shortage of energy supply from the incident, but AEMO would conduct a full investigation.

Blackouts initiated to prevent network damage

When the incident occurred, Western Power began "load shedding" (rolling blackouts) to prevent damage to the electricity network.

Western Power spokesman Paul Entwistle described the loss of generation as an unusual event.

"Last night the Western Power network detected a sudden loss of generation from one of the sources that regularly supplies us," he said.

"It is extremely rare to have such a sudden drop in generation that triggers that sort of response.

"We wouldn't expect one tomorrow, we wouldn't expect one next year, but if it does happen, I guess the positive out of this is we know how to deal with it, we're prepared to deal with it, and we do."

Mr Entwistle said the automatic and deliberate responses of Western Power and its systems had performed well to restore a safe network "frequency".

"It is one of the most vital numbers we look at at Western Power. When it fluctuates too violently, like it did last night, not only do our network operation controllers swing into action but within the system itself it's got a lot of protections in place," he said.

"With a sudden loss of generation, it's like losing pressure in a water pipe, our network automatically detects the most appropriate areas to load shed."

"Unfortunately for customers that means that they go off supply until that all-important frequency is met again."

Mr Entwistle said Western Power worked with AEMO to quickly find extra sources of generation and once that supply was sourced it began restoring power to customers.

"I guess the irritating thing for customers would have been the fact that we can't just turn the whole valve on and flood the system because that would cause problems," he said.

"We had to systematically go through and open up the lines of power to match the demand, so that took a little bit of time, but everybody was back on last night by shortly after 11:00pm."

What is load shedding?

"Load shedding" occurs when an energy provider induces rolling blackouts to parts of the electricity grid for short periods to prevent widescale blackouts, when there is not enough electricity to meet demand.

It is done when energy demand outstrips supply and puts the rest of the grid at risk of being overloaded.

A number of factors can result in load shedding, including extreme weather and infrastructure outages.

In Western Australia, state-owned corporation Synergy is the largest electricity provider.

NewGen's runs its power station next door to Synergy's generator in Kwinana

A fire was reported near Synergy's Kwinana power station at 8:48pm Friday night. ( Supplied: Google Maps )

Both power stations feed the South West Interconnected System (SWIS) Network, which powers homes and businesses up to Kalbarri, 500 kilometres north of Perth, and down to Albany, 400 kilometres south.

The SWIS network also powers the town of Kalgoorlie, 550 kilometres to the east of Perth.

NewGen's Kwinana power station is jointly owned by Energy Infrastructure Trust — which is managed by Infrastructure Capital Group (ICG) — and Sumitomo Corporation.

According to NewGen's website, the power station is capable of supplying approximately 10 per cent of the state's electricity demand, and contributes to the stability of the SWIS network.

The ABC has contacted NewGen for comment.