Workers test the 500-kilovolt submarine cable on Jan 3 in Zhoushan. [Photo/zj.zjol.com]

The 500-kilovolt submarine cable laid between Ningbo and Zhoushan one and a half months ago proved ready for operations as it passed a technical test on Jan 3.

The 17-kilometer cable, developed by the State Grid Zhejiang Electric Power Co and related national research institutes and cable manufacturers, is the first domestic-made 500kv submarine cable, and also the world's first 500kv cross-linked polyethylene insulated submarine cable. 

It is an important part of the 500kv power transmission project, which includes building two 380-meter-high power transmission towers in Zhoushan, the highest of their kind in the world, and stringing a 34km wire, apart from laying the cable. 

The project, worth 4.8 billion yuan ($700 million), is the largest and most difficult cross-sea power transmission project in the history of the State Grid Zhejiang, and will increase electricity supplies for the China (Zhejiang) Pilot Free Trade Zone in Zhoushan.

One of the two 380-meter-high power transmission towers (red) under construction in Zhoushan [Photo/zj.zjol.com]