Work commences in Changshu, a small city in eastern Jiangsu province, on the world's first ever 1,000-kilovolt GIL power line on August 16. [Photo/ jsnews.jschina.com.cn]

Engineers in Changshu, a small city in eastern Jiangsu province, set engineering history on August 16 as work began on the world's first ever ultra-high voltage gas insulated underground power line (GIL).

When the 4.76 billion yuan ($760 million) project connecting Suzhou and Nantong is completed in 2019, it will be the first time a 1,000-kilovolt UHV GIL power line – a type of underground electric transmission system – has ever been applied worldwide.

The enormous 12-meter wide pipe will stretch 5.5 kilometers along the bottom of the Yangtze River, with the upper layer carrying the high-performance 1,000kV line and the lower layer containing a 500kV cable, communication lines, and other municipal cables.

The challenges Changshu's engineering team face in completing this project are considerable. Not only is it the first of its kind in history, the engineers will also have to deal with high hydraulic pressure and complex geological conditions while working on the river bed.

However, once completed the project is believed to offer the most efficient and reliable way of expanding the capacity of the power infrastructure in one of China's key economic regions. The new line will be part of a larger project that will eventually run all the way from Huai'nan in Anhui province through Shanghai to Nanjing, connecting many of the major cities in East China.