Electricity company Essential Energy's bushfire planning was "inadequate" before a Black Summer blaze sparked by powerlines burnt through 3000 hectares on the NSW mid-north coast, an inquiry has been told.
Adam Casselden SC, counsel assisting the long-running bushfires coronial inquiry, said the Failford Road fire at Darawank began in late October 2019, when two branches fell on powerlines.
"The contact between the branches and the conductors caused electricity to pass through the branches, generating embers, which led to a fire igniting in dry vegetation," Mr Casselden said, reading from an expert report at the Lidcombe Coroner's Court on Wednesday.
The fire threatened the Rainbow Flat and Hallidays Point communities for three weeks, destroying houses and structures.
Essential Energy had classified the lines as only a "moderate" bushfire risk, meaning the branches did not need to be cleared, Mr Casselden said.
"Furthermore, the area did not receive a pre-summer bushfire inspection."
Bushfire risk consultant Paul de Mar and Jason Sharples, a University of NSW professor of bushfire dynamics, both found the moderate classification was inadequate.
Professor Sharples said Essential Energy's modelling data was based on five severe days from the 2013 bushfire season, when long-term data was far more valuable.
"The longer the better ... something in the order of 30 years," Prof Sharples said.
"With five days in a particular year, there's no guarantee those conditions on those days are going to represent the conditions in every part of the state."
The company's modelling also involved a "house loss index", with the most serious risk category predicting the loss of more than 2000 homes, the inquiry was told.
Mr de Mar's written report said those figures did not reflect the history of bushfires, as no blaze in NSW has destroyed more than 500 houses.
He said that meant some regions could be wrongly considered a low risk.
Essential Energy risk strategy manager Ian Fitzpatrick said the modelling was based on research from other academics, and the policy was being updated.
"There's likely to be changes, but how significant they are and which way they go is too early to call," he said.
The inquiry has completed this year's hearings. It will resume in March to examine the deaths of three US firefighters, who were killed when their large air tanker crashed near a southern NSW fire ground in January 2020.
