(Updates wholesale power prices in fourth paragraph)
By Aaron Sheldrick
TOKYO, Feb 17 (Reuters) - Japan's overstretched electricity grid is likely to receive another Arctic blast in the coming days, which is already pushing up wholesale prices and may stress generators as they struggle to keep units running after a powerful quake.
While the world's third-biggest economy is unlikely to see millions plunged into blackouts as in the United States currently, the country narrowly avoided power cuts only last month in another wintry spell.
Utilities and independent power providers got another jolt at the weekend when a 7.3-magnitude earthquake struck off the coast of Fukushima, northern Japan, and sent plants into automatic shutdown, briefly knocking out power for nearly 1 million people.
Power companies restarted some units on Tuesday after checks for quake damage. Wholesale electricity prices for peak-hour delivery on Thursday reached a three-week high of 38.80 yen (37 cents) per kilowatt hour, up more than 40% from Wednesday.
"Japan's weather is getting colder, with the forecast pushing demand up quite considerably into Thursday," said James Whistler, global head of energy derivatives at SSY Futures.
"Thursday's load forecast is up 20% on Monday, or about 10 gigawatts, which gives you a sense of the size of the Japanese power market," he said.
JERA Co., Japan's biggest power generation company, told Reuters on Tuesday it had brought online another of the units at its Hirono coal power station that were shut down in the earthquake.
Japan Petroleum Exploration Co said it had resumed partial operations on Tuesday of its liquefied natural gas (LNG) terminal but the nearby gas powered generation unit was still shut down.
Other units remained down and were undergoing checks.
The magnitude 7.3-earthquake injured more than 150 people, causing damage throughout the northern region, including Fukushima, where the meltdowns after a massive quake and tsunami 10 years ago left Japan without its fleet of reactors that supplied about a third of the country's electricity.
Nine reactors have been licensed to restart but only four are presently in operation, leaving Japan ever-reliant on imported fossil fuels or solar power generation that this winter has been snowed out.
The country's power generators were caught on the hop trying to get cargoes of LNG on demand last month. Operations of some U.S. LNG export terminals have been suspended as freezing weather in Texas sent power prices spiralling more than 100 times higher.
The Japan Meteorological Agency issued warnings of snow storms, blizzards and high waves over a wide swathe of northern eastern and western Japan.
Blizzard conditions are expected to be the worst in "several years" and people should stay in shelter, the weather agency said. ($1 = 105.9200 yen)
(Reporting by Aaron Sheldrick; Editing by Susan Fenton and Tom Hogue)
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