HVDC back-to-back link extension between Northwest and Central China Lingbao I back-to-back station of 360 MW, located on the border between the provinces Henan and Shaanxi in central China, has been in operation since October 2005. The new Lingbao II extension project will expand the existing asynchronous interconnection by an additional 750 MW and thus increase the possibilities for power sharing between the two networks For this extension, ABB will deliver valves and control system components. The project will use six-inch thyristors rated at 4,500 A, which so far is the highest rating in the world. The control system equipment will be ABB's MACH 2, the world's most commonly used control platform for HVDC and FACTS projects. The project is expected to be in commercial operation by December 2009.