(Adds detail on steelmaker, industry fallout)
By Tom Westbrook
SYDNEY, Sept 29 (Reuters) - An unprecedented power outage across South Australia state has stopped production at major miners BHP Billiton (LON:BLT) BHP.AX and OZ Minerals OZL.AX and left one steelmaker struggling to prevent molten steel from hardening and damaging its factory.
The statewide outage sparked political calls on Thursday for an inquiry into the power sector and questions over the state's reliance on renewable energy. Prime Minister Malcolm Turnbull said it was a "wake-up call" to ensure energy security.
Although power has been restored to 90 percent of the state after Wednesday's statewide blackout, caused by severe storms, industrial areas north and west of the state capital Adelaide and the steel city of Whyalla are still without power.
Whyalla steelmaker Arrium Ltd ARI.AX said it had a blast furnace and four ladles full of molten steel and desperately needed to restore power.
"The situation is quite serious and a lot will depend on what happens in the next hour or two," said a company spokesman.
The outage has halted more than 300,000 tonnes of annual copper production capacity and knocked out the state's only lead smelter. the city of Port Pirie, the 185,000-tonnes-per-year lead smelter run by Nyrstar NV NYR.BR will be out of action for up to two weeks, the company said on Thursday.
The blackout of the country's fifth most populous state, with 1.7 million people, not only disrupted miners and steelmakers but closed ports and halted public transport.
"Let's focus now and take this incident as a real wake-up call...lower emissions is very important but it must be consistent with energy security," said Australian Prime Minister Malcolm Turnbull.
Coal-fired power plants dominate the country's power sector resulting in Australia being one of the world's biggest carbon emitters on a per capita basis. Renewable energy has struggled to increase its footprint in recent years due to scepticism over climate change amongst some the country's leading politicians.
South Australia, a major wine producer and traditional manufacturing hub, is one of the few states with a heavy reliance on renewable energy. Wind power provides roughly 40 percent of the state's electricity supply.
RENEWABLE ENERGY QUESTIONED
"Questions have to be asked: Is their over-reliance on renewable energy exacerbating their problems and the capacity to have a secure power supply," Australia's Deputy Prime Minister Barnaby Joyce, a climate change sceptic, told Australian Broadcasting Corp radio on Thursday.
South Australian independent Senator Nick Xenophon said an inquiry should examine whether the power failure could have been avoided if more gas-burning power plants had been on standby.
Power experts said the blackout was unavoidable regardless of South Australia's energy supply
The blackout happened after strong winds destroyed major powerlines, causing a surge across the grid. The network and links to neighbouring Victoria, from which South Australia can access power, shut down to prevent damage to infrastructure.
"For the Prime Minister to use the storm as an opportunity to slowdown the uptake of renewables is reprehensible," Greens politician Adam Bandt told Reuters.
Australia's renewables have been under political pressure in recent years. The government had planned to cut funding to its renewable energy agency by a A$1.3 billion, in an effort to plug a major budget shortfall, but was forced to reduce the cut to A$500 million in September to gain parliamentary support.
Australia wants to double its large-scale renewable energy generation to 33,000 gigawatt hours by 2020, which means solar, wind and hydro-electricity would have to make up nearly a quarter of power generation by then.