About 5000 homes in eastern Victoria are likely to be without power for several days after a bushfire brought down a key transmission line, plunging towns into smoky darkness just a day after forced rolling blackouts were only narrowly averted in the state by customers cutting back consumption.

Snowy Hydro chief executive Paul Broad said the company had been forced to evacuate all but skeleton staff at its several sites in the Snowy Mountains amid "vicious" winds and heightened fire risks, with embers jumping distances of 5-6 kilometres. All Snowy power plants remained available, although water levels were "tight", he said.