The design, seen as competition to the Westinghouse-developed AP1000 and Europe's EPR, is deployed in the 1,150-megawatt Fuqing Unit 5 in the southeastern province of Fujian.

Hualong One is designed to have a 60-year lifespan and its reactor core needs refuelling every 18 months.

"(The successful grid connection) indicates that China has broken the monopoly of overseas nuclear technology and has officially become a country with advanced nuclear techniques," CNNC said in a statement.

The second Hualong One at Fuqing, Unit 6, is scheduled for completion in 2021.

China currently has six overseas Hualong One projects under construction.

(Reporting by Muyu Xu and David Stanway, Editing by Sherry Jacob-Phillips)