HVDC sparks transmission growth in Eastern U.S.


Has the day finally arrived for widespread adoption of high-voltage direct current (HVDC) transmission? As the U.S. electric grid continues to age, specifically in the Eastern Interconnect, there is an emerging need for additional transmission.

The day may have finally arrived for widespread adoption of high-voltage direct current (HVDC) transmission.

Laurie Oppel, Managing Director for Energy at Navigant, said that approximately 30,000 circuit lines are estimated to be built over the next 10 years. This is equal to approximately 10 percent of the Eastern Interconnect's current installed transmission capacity. About 3,000 of the proposed 30,000 circuit miles will be HVDC, and these lines will be driven by reliability and renewable integration concerns. Navigant research also found that more than half of the HVDC lines were proposed by investor-owned utilities.

While the amount of proposed HVDC is low, there is optimism and buzz in the industry surrounding HVDC transmission as the push continues to modernize the grid.

HVDC advocates point out that the technology is more efficient than AC (alternating current) transmission lines. Efficiency improvement is achieved by eliminating the need to change direction multiple times per second (as is this case with AC flow) and directing the power through an entire conductor. Still, converting the grid from AC transmission is difficult. HVDC systems are cumbersome to operate and require installing converter substations along transmission corridors.

Approximately 30,000 circuit lines of transmission are estimated to be built over next ten years.

HVDC success in the Eastern grid

HVDC's high efficiency makes it valuable when transmitting power over long distances. As such, it has been popular outside the dense populations of the Eastern Interconnection. But new renewable generation projects -- especially offshore projects and those in remote parts of Maine and Canada -- necessitate transmitting power over hundreds of miles. Such projects are cropping up on the East Coast because of a large estimated retirement of PJM coal generation capacity.

Several projects underway demonstrate the long-distance practicality of HVDC. The 660 MW Neptune Project is an underwater, underground HVDC cable traveling 65 miles between Sayreville, New Jersey and Long Island. It was completed in 2007, on budget, and contains two converter stations. The similar Hudson Transmission Project will connect New York City and PJM through HVDC technology once completed in 2013. HVDC is also being used for renewable offshore transmission. The Atlantic Wind Connection's (AWC) Backbone Transmission Project is connecting 7,000 MW of offshore wind power to the eastern grid through HVDC lines. 

Still, there is much room for growth of HVDC technology. 

"Our view is that DC transmission is still underappreciated in spite of the success that we've had in many other places," said Ed Krapels, CEO of Anbaric Transmission, which developed Neptune and Hudson. He said the company has several other HVDC plans already in the pipeline.

Future remains murky

Though transmission projects take years to get off the ground and onto the grid, they also last for decades. As such, proposals are liable to flex and adjust as companies and utilities look at how to best reach their needs.

It's for this very reason that proposals are just that -- proposals. Nothing is set in stone, and Oppel cautioned against being too optimistic as a number of factors will determine what construction is ultimately completed, which projects are scaled back and what gets scrapped from the agenda. A November NERC report, for example, estimated that only 14,000 circuit miles (less than half of the 30,000 proposed) will be built in the next decade.

So, while the future of transmission build still has some uncertainties, the prospects remain bright for HVDC.  It will all depend on how the financing and planning processes go forward, but the need for efficient and reliable transmission is only going to grow in the coming years.

Filed Under