National Grid recently completed a major upgrade to its portion of a 960-mile, 450 kilovolt high-voltage direct-current, or HVDC, transmission system that has been delivering clean, carbon-free electricity from Canada to New England for the past 25 years. National Grid is the majority owner of the US portion of the system, which it operates on behalf of some 35 other energy providers. The $27 million project took approximately three years and was completed on time and on budget.