WRAPUP 1-Chile sees power unstable, refinery, mines back up

* Chile power supply seen unstable for next seven days

* Aconcagua oil refinery restarts diesel output

* Most copper mines in south-central Chile back up

* Anglo spokesman says does not know if blackout hit mines

SANTIAGO, March 15 (Reuters) - Chile's power supply will remain unstable this week, President Sebastian Pinera said on Monday, after mines and a refinery resumed operations after an outage left most of the world's top copper producer in the dark.

Millions of Chileans had no power on Sunday evening after a transformer failed in the central electricity grid, two weeks after a 8.8-magnitude earthquake killed hundreds and destroyed roads and wiped out coastal villages.

Most copper mines in south-central Chile had resumed operations on Monday after the blackout temporarily halted output.

The key Aconcagua oil refinery restarted producing diesel and is seen returning to normal operations by late next week, Mining Minister Laurence Golborne told reporters on Monday. He added gasoline output could resume this week.

"We aim for normalcy by the end of next week," Golborne said, adding that authorities would have a better idea by late March on when the Bio Bio refinery would reopen after it was damaged by the Feb. 27 quake.

A prolonged stoppage at the 116,000 barrels per day Bio Bio refinery will further increase fuel imports.

A spokeswoman with state oil company ENAP said earlier on Monday authorities were evaluating if Sunday's outage caused any damage to the Aconcagua refinery.

Pinera said on Monday the country's main power grid will be unstable for the next seven days and work was underway to fix the faulty transformer that caused the blackout.

MINES RESUME OUTPUT

State-run Codelco, the world's top copper miner, said its El Teniente and Andina mines were operating normally after the blackout hit output. Smelter Ventanas was also back online.

The two mines produced 614,000 tonnes of copper last year, or 9 percent of the country's annual output.

Antofagasta Minerals' (ANTO.L) 312,000-tonne-per-year Los Pelambres copper mine was also returning to normal. Its smallest Salvador division resumed output after having energy supply problems after the outage.

Shaky energy supply following the Feb. 27 quake could afflict medium-size mines in Chile and lift copper prices on concerns of supply disruptions in a country that produces around a third of the world's mined copper.

An Anglo American (AAL.L) spokesman in Chile said Monday he didn't know the status of operations at Los Bronces and El Soldado mines.

The strong quake late last month briefly halted Anglo American operations and that of other mines in the south-central region.

Most of Chile's copper is extracted in the northern region, which is powered by a grid that was not affected by the quake and continued to function normally despite the power cut.

Codelco's largest mines in the north were not impacted by the blackout and had normal energy supply.

Freeport-McMoRan Copper & Gold Inc (FCX.N) said Monday its Candelaria mine in Chile was affected by the blackout, but that the impact to production was expected to be minimal.

A company spokesman said the mine was without power for about three hours on Sunday, but production had begun to ramp up again as power supply was being restored. [ID:nN15184913] (Reporting by Antonio de la Jara; Fabian Cambero, Euan Rocha and Alonso Soto; Writing by Eduardo Garcia; Editing by Walter Bagley)