PHNOM PENH, July 12 -- The Lower Sesan II Hydropower Plant, which is Cambodia's biggest hydropower dam, will begin testing its first-phase operation on July 15 after more than three years of construction, the Electricity Authority of Cambodia (EAC) said on Wednesday.

The 400-megawatt hydropower dam, situated in northern Cambodia's Stung Treng province, is a joint venture between China's Hydrolancang International Energy holding 51 percent of the stake, and Cambodia's Royal Group and Vietnamese EVN International Joint Stock Company possessing 39 percent and 10 percent, respectively.

The project's investment worth is about 928 million U.S. dollars.

"This is a huge achievement of the Cambodian government in developing a stable, qualitative electricity sector," the EAC said in a Facebook post.

The project is a concessional contract of a 45-year build-operate-transfer (BOT), of which, five years are for construction and 40 years for operations.

When the dam is operational, the electricity will be sold to the Electricity of Cambodia at the fixed price of 6.95 U.S. cents per kilowatt-hour.

China is the largest investor in building hydroelectric dams in this Southeast Asian nation.