KUNMING - China's third-largest hydropower station became operational Monday with the world's largest power generating unit officially starting work.

The No 7 generator with a capacity of 800,000 kw, at the Xiangjiaba hydropower station, started working at 4:30 p.m. after a three-day test run, its operator China Three Gorges Corporation said.

The other of the first batch of generators to be put into use, the No 8 unit, is still being tested.

The station, designed with eight 800,000-kw generators, has a total generating capacity only after the Three Gorges and Xiluodu hydropower stations.

Construction of the Xiangjiaba hydropower station, located in the Jinsha River, a major headstream of the Yangtze in the southwestern Yunnan and Sichuan provinces, started in late 2006. It started water storage on October 10 this year.

The station is designed to generate 30.8 billion kwh a year after all its generators become fully operational. Apart from helping to meet demand in provinces of Sichuan and Yunnan, it will mainly supply power to the country's east.