The Woodend area blackout was caused by a tree being blown onto a power line near Donovan's Lane, off the Calder Highway, by winds greater than 100kmh.

"Crews had a fairly onerous task to patrol and isolate the supply line," Powercor media relations manager Damien Batey said.

The first loss of power occurred at 7.06am, and the problem section was identified about 10.35am.

"The system couldn't cope with fewer supply points and at 9.38am additional customers lost power," he said.

Customers had their power reinstated progressively, the outage having affected residents and businesses from Malmsbury to North Blackwood.

All of them were reconnected by 1pm.

The State Emergency Service was kept busy with 15 tasks in and around Woodend yesterday morning.

Media unit manager Allan Briggs said most of the tasks related to fallen trees and branches.

Also yesterday, about 5000 Powercor customers in the Nhill district were without power for several hours.

A power pole that caught fire was weakened and subsequently snapped off in the wind, causing customers to lose power at 9.34am.

Half of those customers had power back by midday.

"It was a very complex reconstruction job," Mr Batey said.

"All customers were back on by 1.55pm, largely thanks to the response to our request to reduce power consumption."