In a circular regarding the intensification of wind farm security management, the State Electricity Regulatory Commission (SERC) said that wind turbines must be LVRT-capable, and that wind turbines that don't feature the technology should be upgraded as soon as possible.

LVRT refers to the capacity of wind turbines to maintain continuous operation during and after precipitous voltage dips. LVRT-capable wind turbines allow the power grid to be adjusted more quickly and improve the overall safety and stability of the grid.

The SERC has not released a timetable for the upgrades.

This circular was released along with the announcement of two incidents of wind turbines becoming disconnected from the power grid because of voltage dips. The incidents occurred on April 17 in Gansu and Hebei provinces, according to the announcement.

On April 17, 702 wind turbines were disconnected from the power grid in Gansu's city of Jiuquan. The disconnection was caused by breakdowns in two box transformers at a windfarm in Jiuquan. The accident caused a 54 percent decrease in wind power output.

On the same day, 644 wind turbines were disconnected from the power grid in Hebei's city of Zhangjiakou. This disconnection was also caused by a box transformer malfunction, and resulted in a 48.5 percent decrease in wind power output.

In late March, the SERC announced that 598 wind turbines were disconnected from Jiuquan's power grid on Feb. 24 for similar reasons.

The SERC said that the three incidents have exposed major problems in China' s booming wind power industry, particularly the absence of LVRT capability in China's wind turbines.

The SERC said that most of China's wind turbines do not feature the technology, as it was not previously required. However, the absence of LVRT capability is more likely to cause disconnections in the future if the grid continues to experience power dips, according to the SERC.

The SERC says that the three incidents indicate that the Chinese wind power industry must reevaluate its turbines and ensure that they will be more secure in the future. The Chinese wind power industry is expected to maintain rapid growth over the next five years.

Over the past five years, China' s wind power industry has realized three-digit annual growth in installed capacity. By the end of 2010, China replaced the United States to become the world' s largest producer of wind power.

Li Yinghua, deputy director of the security regulatory bureau under the SERC, said "It is not an easy task to upgrade existing wind turbines to become LVRT-capable."

"It costs several tens of thousand yuan to upgrade a single wind turbine. This will put considerable pressures on wind turbine makers and wind farm operators to upgrade China's 34,000 wind turbines," said Li.

Li said a new national standard for integrating China's wind farms into the national power grid will be finalized in the first half of this year. Li said that this standard will require these turbines to be LVRT-capable.