An interconnector (also known as a DC Tie in the USA) is a structure which enables electricity to flow between electrical grids. An electrical interconnector allows electricity to flow between separate AC networks, or to link synchronous grids. They can be formed of submarine power cables or underground power cables or overhead power lines. The longest interconnection as of 2016 was the undersea NorNed link between Norway and the Netherlands, spanning nearly 600 km and delivering 700 MW of high voltage direct current power.