Double fault flashover

TWO separate system failures led to the ‘flashover’ in Morwell last month that cut electricity to 80,000 homes across Gippsland, an interim report has revealed.

Conducted by Energy Safe Victoria, the report suggested a “common” fault, most likely caused by animal or bird contact or equipment failure, escalated because the primary protection system did not operate due to an incorrect relay setting.

“What might be a common fault has turned into a very significant event because protection, which is designed to disconnect the power rapidly and protect the system, has failed,” ESV energy safety director Paul Fearon said.

Mr Fearon told The Express an unusual cascade of powerlines dropping onto other lines, and terminal station infrastructure led to the widespread loss of supply.

“In terms of damage, one 66-volt line essentially melted; it’s a far more dramatic event than just some slow melt,” Mr Fearon said.

The report ruled out any residue or smoke from the Hazelwood mine fire as the cause of the power failure.

“The evidence of all the intact insulators in the area showed they were essentially clean, which was consistent with the washing that SP AusNet had undertaken and because of the recent rains,” Mr Fearon said.

“It’s also worth noting ESV officers attended a number of houses in Morwell’s south during the fire to check out a number of domestic electricity and gas appliances, and there was no evidence then that the smoke and, or particulates were compromising those domestic appliances.”

Although most Gippsland homes and businesses regained power within three hours, Mr Fearon said one powerline feeding the Australian Paper Mill was damaged.

While Morwell residents and passers by witnessed what looked like an explosion, labelled a ‘flashover’ by SP AusNet, Mr Fearon said the flash was the initial fault and the subsequent explosion-like visual was the power network collapsing; likening the picture to that of a welding arc flash.

SP AusNet spokesman Jonathon Geddes welcomed the interim report and its results ruling out ash or smoke as the cause.

“We can confirm that maintenance was up-to-date on the powerlines and protection systems malfunctioned, and that identical protection systems across our network were maintained and are operating correctly,” Mr Geddes said.

“Any lessons from the ESV report and our own extensive investigations will be acted upon to make sure this does not happen again.”

Mr Fearon said the report would conclude in August with an internal report on the event soon to be submitted by SP AusNet.