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Lead plaintiff Carol Matthews and an estimated 10,000 members claimed energy provider SPI Electricity's faulty equipment ignited the Kilmore East/King Lake bushfire in February 2009.
SP AusNet and other parties agreed to settle the action on Tuesday morning.
The fire killed 119 people, destroyed 1200 homes and caused an estimated $1 billion worth of damage.
SP AusNet said the settlement was reached without admission of liability by the company or any other party.
The group also sued Utility Services Corporation Limited, which was contracted by SP AusNet to maintain the line, and the Department of Sustainability and Environment (DSE) for allegedly failing to reduce fuel loads.
The total payout will be about $494.7 million, paid by SP AusNet, Utility Services Corporation Ltd and Victorian State Parties.
In a statement, SP AusNet, which is registered as SPI Electricity, said it sought to conduct its defence in a manner to avoid adding to the group members' pain, while demonstrating that SP AusNet managed its network competently and efficiently.
"The conductor which broke and which initiated the fire was damaged by lightning, compromising its fail-safety design in a manner which was undetectable at that time," the company said.
This point, it said, was accepted by experts.
"It is a tragedy that the conductor eventually failed on one of the worst days imaginable."
Maurice Blackburn lawyers said the payout was more than double the previous highest Australian class action settled of $200 million in the Centro shareholder class action.
"After the state's deadliest and most devastating bushfire took 119 lives and 1242 properties, after a Royal Commission and after Australia's longest ever class action trial, the survivors of the 2009 Kilmore-East Kinglake Black Saturday bushfire get some justice today," Maurice Blackburn said in a statement.
The class action was so large the Victorian government funded a purpose built courtroom to accommodate the teams of barristers, expert witnesses and large numbers of people interested in attending the trial.
The settlement is subject to court approval.
A date for the hearing of the proposed terms is yet to be fixed.
SP AusNet said its liability insurers would pay its contribution.