BHP BHP Group Limited

By Rhiannon Hoyle and Rob Taylor

SYDNEY-A statewide blackout in South Australia caused mining operations including a large copper mine run by BHP Billiton Ltd. to be suspended and reignited a nationwide debate over renewable energy, which the state relies on heavily for power supplies.

South Australia, the country's fourth-largest state by area, was continuing to experience widespread power outages on Thursday after wild storms led to blanket power outage the prior day. Australia's Bureau of Meteorology said strong-to-gale-force winds, abnormally high tides and heavy rainfall were lashing the state.

BHP Billiton said its mine and processing facilities at Olympic Dam, one of the world's biggest deposits of uranium, copper and gold, were shut down after the state lost power on Wednesday.

"Back-up generators are currently providing power to critical infrastructure and will allow a restart of operations when power is restored," a spokesman said in an emailed statement.

Oz Minerals Ltd., an Adelaide-based copper and gold miner, said its Prominent Hill mine in central South Australia, about 200 miles from Olympic Dam, had also been suspended. "The company has not yet received any definitive timeline as to when power will be restored to the site as suppliers determine the full extent of damage to their transmission networks," Oz Minerals said in a statement on Thursday.

The fallout from the storms reopened a long-running national debate about the role of renewable energy in Australia's electricity grid, currently dominated by fossil-fuel generators relying on plentiful coal and natural gas.

South Australia, governed by center-left Labor opponents of Prime Minister Malcolm Turnbull's ruling Liberal-National coalition, relies on wind and solar generation for 41.3% of its electricity needs, against a national average of 14.6% last year, according to Australia's Clean Energy Council.

Some federal lawmakers pointed to South Australia's aggressive shift toward renewable energy as a major reason for the statewide outage, saying that unlike fossil-fired generation it was inherently more intermittent and weather-dependent.

But South Australian Premier Jay Weatherill said the storm had been "a weather event, not a renewable energy event." Photographs posted on his Facebook page showed images of large power pylons bent over and flooding.

Australian Energy Market Operator, which is responsible for operating the country's largest gas and electricity markets, said initial investigations have identified the root cause of the blackouts as likely to have been the loss of multiple 275-kilovolt power lines during the severe storm. The power lines form the backbone of South Australia's power system.

The reason why there was a cascading failure of the network after that is still being looked into, it said.

Origin Energy Ltd., one of the country's largest energy suppliers, said its two gas-fired power stations in the state were helping supply power to the state and the company was working with authorities to resume supplies of electricity.

SA Power Networks, which operates a distribution network across South Australia, warned people in the state to be prepared for extended outages. As of Thursday morning, Australian Energy Market Operator said about 70,000 of 850,000 customers in South Australia remained without electricity.

--Robb M. Stewart in Melbourne contributed to this article.

Write to Rhiannon Hoyle at rhiannon.hoyle@wsj.com and Rob Taylor at rob.taylor@wsj.com

(END) Dow Jones Newswires

September 29, 2016 00:39 ET (04:39 GMT)

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