HVDC Conversion Technology
Neptune Project Converter Station, Long Island, NY
The technological core of the Hudson Project is a converter station located at 1 Railroad Avenue, Ridgefield, New Jersey, formerly the site of a warehouse. Using Siemens technology and equipment, the converter station will convert Alternating Current (AC) power from the PJM system to Direct Current (DC), and then back to AC within the same site (called “back-to-back conversion”). The AC-DC-AC conversion means that up to 660 MW of power can be controlled very precisely and reliably to serve NYPA’s New York City customers.
Power conversion takes place within a “valve hall” using banks of thyristors. The HVDC technology used for Hudson is identical to that used in the Neptune project and dozens of other such project worldwide. It is well proven in terms of reliability and ease of maintenance.
The converter station will not generate power, burn fuel, or produce atmospheric emissions or hazardous levels of electro-magnetic fields.
Land-Based Cable
The main land-based cable is a 345-kilovolt AC cable, manufactured by Prysmian, originating at the converter station and entirely buried along a route that largely uses public streets or railroad rights-of-way. From the station, it will proceed southward to the existing New York Susquehanna & Western (“NYS&W”) railroad, and then turn east for about a mile through an inactive NYS&W tunnel. After exiting the tunnel, it will be buried underneath New River Road in Edgewater, New Jersey, and along the southern boundary of the Edgewater Mall shopping center before entering the Hudson River.
In New York City, the upland cable will proceed underground from W. 52nd Street for less than three blocks along the West Side Highway. It will turn into an entrance point at the ConEdison W. 49th Street substation and will be interconnected to the ConEdison system within the substation.
Marine Cable
After entering the Hudson River in Edgewater, the cable will be buried a minimum of 10 feet below the bottom of the Hudson River. It will cross an existing federal navigation channel roughly parallel to W.75th Street in Manhattan, then proceed southward down the river on the New York side for about three miles before turning toward a landfall point between Piers 92 and 94.
Undersea Cable Installation
The cable will be installed using “jet plow” technology: A specially designed device with an adjustable blade, or plow, rests on the river bottom and is towed by a surface vessel. The plow creates a narrow trench at the designated depth, while water jets fluidize the sediment within the trench. The cable is fed through the plow and is laid into the trench as it moves forward. The fluidized sediments then settle back down into the trench and bury the cable.
Jet plow technology has been shown to minimize impacts to marine habitat and excessive dispersion of bottom sediments. Its most recent application in the New York area was for the Neptune RTS project, in which more than 50 miles of cable was installed using a jet plow.
New Jersey System Upgrades
The Hudson Project will be responsible for nearly $200 million worth of reinforcements and improvements to the existing electric transmission system in northern New Jersey mandated by PJM to assure no loss of reliability due to the project. These upgrades promote reliability by facilitating the increased flow of power to meet demand and improving the stability of the grid during system emergencies. Examples include: repositioning and/or upgrading the conductors and cables of existing power lines; replacing or adding to existing equipment at local electric substations (switches, circuit breakers, transformers, etc.); and adding strategically-placed new devices that will improve the electric system performance during disturbances to the grid.
