Seven tornadoes on day of SA blackout

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Seven tornadoes on day of SA blackout

Seven tornadoes tore though South Australia on the day of the statewide blackout in September.

At least seven tornadoes ripped through South Australia on the day of the statewide blackout in September, a new report by the Bureau of Meteorology says.

The 54-page report comes after severe storms tore down three major transmission lines in the SA's mid-north, overloading the main interconnector with Victoria and causing a power outage across all of SA.

"Multiple supercell thunderstorms produced damaging to destructive wind gusts, including at least seven tornadoes, very large hailstones and locally intense rainfall," the report, released on Monday, said.

"These supercell thunderstorms and tornadoes impacted the South Australian power network, contributing to a state-wide power outage."

The bureau found that one tornado at Wilmington cut across several transmission lines and destroyed five transmission towers, and also collapsed a farm shed, overturned a caravan and tore down gum trees.

Another tornado at Wild Dog Creek packed winds up to 260km/h and cut a 23km path of destruction, including hurling a one-tonne field bin about 300m.

The bureau described the weather event as "one of the most significant severe thunderstorm outbreaks in recent decades".

SA Treasurer Tom Koutsantonis said the report should put to rest the debate over who or what was to blame for the blackout.

"Prime Minister Malcolm Turnbull and Deputy Prime Minister Barnaby Joyce have both used the blackout to attack renewable energy policies in other states," he said.

"This report clearly and definitively states that tornadoes destroyed transmission lines in the north of South Australia, triggering the blackout.

"It's time opponents of renewable energy accept that fact."

An earlier report by the Australian Energy Marker Operator found that nine of 13 wind farms switched off during severe storms and this played a role in the shutdown.

AEMO said in October that safety settings on these wind farms forced them to disconnect or reduce turbine output when transmission lines were brought down.

But it said the intermittent nature of wind energy was "not a material factor" in the blackout.