Tens of thousands of Victorians have spent a second night without power after destructive storms wreaked havoc on the energy grid.

About 77,000 homes and businesses remain disconnected from the electricity network as of 5.30am on Thursday, down from 125,000 on Wednesday evening and 530,000 at its peak.

Crews worked through the night to clear debris and repair powerlines to reconnect properties, following damage from storms, strong winds and lightning.

But given the extent of the damage, it could take days or more than a week to restore electricity to those impacted, the Australian Energy Market Operator has warned.

AusNet executive general manager Steven Neave said that as of early Thursday morning around 75,000 of its customers were still waiting for their power to be restored.

The main areas affected are Yarra Ranges, south Gippsland and the Bass Coast.

“We’ll have 400 crews on the ground again today, we’ve been working through the night,” Mr Neave told Nine’s Today show on Thursday.

“It’s really clearing that vegetation out of the way, getting safe access to all the streets and suburbs where this storm has gone through and progressively … restoring supply as safely as we can.”

However, some customers may not get their power back until next week.

“We are hoping to have somewhere around 30,000 or more back on today, and then the bulk of them back on by Saturday,” Mr Neave said.

“Unfortunately, there could be some customers that are still off supply into next week, but we are hoping to have … the vast majority back on by Saturday.”

The disaster was one of the largest power outages in Victorian history and could take weeks to fully fix.

Victoria’s State Emergency Service has received about 4250 calls for assistance since Tuesday, with roughly 3300 for downed trees and close to 600 for building damage.

About 750 call-out requests were still active on Thursday morning.

A dairy farmer was killed when he was struck by debris while herding cows on a quad bike in Darlimurla in South Gippsland on Tuesday evening.

Five regional hospitals could remain on generator power for at least three days as authorities rush to prioritise fuel and restore energy to those sites.

Families were in the dark on whether they could send their children to school on Thursday after 80 schools and early learning centres were closed due to power outages or other issues on Wednesday.

Almost 500 phone towers and 450 NBN sites were down on Wednesday, leaving a quarter of a million customers without internet access.

Collapsed transmission lines also caused the Loy Yang A coal-fired power station in the Latrobe Valley to shut down, along with several wind farms.

– AAP