C-Tech Corp., the operator of the generator, has stopped the 18 other generators at Wind Park Kasatori that stands over the Mie Prefecture cities of Tsu and Iga, and is poised to launch a probe to clarify the cause of the accident.
At around 8 p.m. on April 7, workers at Wind Park Kasatori found one of its 19 wind power generators and its three blades had plunged to the ground. The 65-meter-high pole that supported the generator also broke off. C-Tech believes the generator was blown to the ground by strong winds.
The generator, including its three 40-meter blades, weighs approximately 140 tons, and its output was 2,000 kilowatts.
The generator was designed to withstand winds of up to 70 meters per second but the maximum instantaneous wind speed in Tsu on that day was 27.9 meters per second.
In principle, apart from nuclear reactors, power generators are inspected by their own operators, according to the ministry. C-Tech inspects its wind power generators twice a year, and when it examined the generator in question on March 15, it found no problem, company officials said.
The 19 generators at Wind Park Kasatori have a combined output of 38,000 kilowatts, according to the website of Chubu Electric Power Co., the parent company of C-Tech.
In the wake of the accident, the Economy, Trade and Industry Ministry will instruct power companies that operate 105 wind power generators produced by Japan Steel Works Ltd. to inspect the machines. Noting that a wind power generator manufactured by another company fell down in Ine, Kyoto Prefecture, last month, officials said the ministry is also poised to encourage other power companies to voluntarily examine all of their large-scale wind power generators with an output of over 2,000 kilowatts.
Some serious accidents involving wind power generators have occurred over the past decade.
In September 2003, three generators collapsed on Miyako Island, Okinawa Prefecture, after being hit by a powerful typhoon which registered a maximum instantaneous wind speed of 74.1 meters per second.
A wind power generator fell to the ground at Iwaya Wind Farm in Aomori Prefecture in January 2007 after the pole supporting the machine broke off from its base.
It has been confirmed that the generators in Okinawa were unable to withstand winds stronger than they were designed to withstand while the Aomori accident occurred because one of the two bolts necessary to firmly fix the generator was missing.