Network Interconnection
What are spot and area networks?
The majority of the Massachusetts electric grid is structured as a radial distribution system where power moves in one direction from the distribution substation to an individual customer. If drawn in a diagram, this type of system would look like the branches of a tree, with a main line connecting to a series of smaller circuits that then branch off to serve each customer individually. The interconnection process is largely designed for distributed generation connected to these radial systems.
However, certain high-density or high-load areas throughout the state are served by spot network systems and area network systems, where power flows through a complex web of power lines that connect to individual customers through multiple paths. These systems were built to ensure reliable power for customers in these areas.
A spot network system typically serves one or more customers at a single location (such as a high-rise office building) through two or more paths. Where a radial customer is served by a single utility line connected to one transformer that then connects to the building, a spot network customer has two or more lines, transformers, and building connections through which power can flow.
An area network system typically serves a broader group of customers located in a high-density area (such as a group of city blocks). Area network systems differ from spot network systems in that they not only have multiple lines, transformers, and building connections but also interconnections between the buildings. This means that power is flowing through even more paths and in many different directions.
In terms of complexity, radial systems are generally the least complex, followed by spot network systems, with area network systems being the most complex form of distribution. These levels of complexity determine the different reviews and criteria for interconnecting to each system.
Why are spot and area networks important?
Because spot and area network systems allow power to flow through multiple paths, adding a distributed generation generator to these systems introduces the risk of sending power into the grid when the grid is not delivering power to the site, due to maintenance or system failures. This presents significant risks to the safety of utility workers, performance of the distribution system equipment, and power quality of other customers on the same network. Because of these risks, utilities must evaluate proposed distributed generation on these systems more exhaustively than they do for radial interconnections.
How does being located on a network system affect the review process?
The Massachusetts interconnection standards include distinct reviews and protection requirements for spot network interconnections. Because area network systems are of such complex structure, the utilities do not currently allow interconnections to these systems.
Spot Network Systems: A project eligible for the simplified review process (less than 10 kW and inverter based, among other requirements) that is on a spot network system will be evaluated using the simplified spot network review, which is slightly longer than the simplified review. Projects on spot network systems that do not qualify for the simplified review process must go through the standard review process.
Area Network Systems: Because distributed generation presents significant safety and reliability concerns when interconnected to an area network, such projects are considered through the standard review process. If your project is found to be on an area network system, you will receive a letter from your utility explaining your alternatives to interconnection. These may include:
. Transferring your site's load from an area network to a radial distribution system and interconnecting the generator on this system
. Interconnecting the generator to a nearby radial distribution system
. Operating the load to be served by the generator off the grid
Each of these options has the potential to significantly increase project costs. If you receive a letter from your utility on this matter, you should contact them to discuss these options further.
Am I on a network system?
In general, both area network and spot network systems serve downtown areas of major cities like Boston, Worcester, and Springfield along with several others. Isolated spot network systems also serve some large customers (such as hospitals, office parks, or industrial facilities) around the state.
Area network systems serve downtown areas in 11 cities around the state. To gain a general sense of where these systems are located, you can use the list below for reference. However, it is also critical to note that a small minority of customers within these areas may be served by radial or spot network systems overlapping with the area network system. You must contact your utility directly to determine whether your site is served by an area network.
Because spot network systems are more scattered and often serve privately owned sites, it is not possible to provide a public list of every system in the state. To determine whether you are on a spot network system, you must contact your utility directly.
Fitchburg Gas and Electric Light (Unitil)
City/Town |
Approximate Location |
Fitchburg |
Area around Main St. stretching from Summer St. to River St. |
To determine whether a specific project in Fitchburg is served by the area network system, you must contact FG&E.
Massachusetts Electric Company and Nantucket Electric Company (National Grid)
City/Town |
Approximate Location |
Brockton |
Bounded by Montello St., Warren Ave., Court St., Allen St. |
Lynn |
Bounded by Shepard St. , Union St. , Harvard St. , Lynnway. |
Worcester |
Bounded by Lincoln Sq., Chandler St., Harvard St., Worcester Center Blvd. |
To determine whether a specific project in one of these locations is served by an area network system, you must contact Massachusetts Electric.
NStar
City/Town |
Approximate Location |
Boston: Main Area Network |
North / east boundaries: Charles River, Boston Harbor, Fort Point Channel |
Boston: Additional Networks |
Columbus Ave., Tremont St., Washington St. in the South End |
Cambridge: Inman Square |
Bounded by Springfield St., Oak St., Court St., Hampshire / Antrim Sts. |
Cambridge: Harvard Square |
Bounded by Massachusetts Ave., Bow St., Eliot St., Appian Way |
Cambridge: Arsenal Square |
Bounded by Massachusetts Ave., Waterhouse St., Berkeley St., Craigie / Chauncy Sts. |
Cambridge: Peabody Terrace |
Bounded by Banks St., Akron St., Memorial Drive, Flagg St. |
Cambridge: Garfield |
Bounded by Prentiss St., Massachusetts Ave. (east and west boundary), Mellen St. |
Cambridge: Davenport |
Bounded by Davenport St., Massachusetts Ave. (east and west boundary), Porter Rd. |
Cambridge: Fresh Pond |
Bounded by Concord Ln., Alewife Brook Parkway, Boston & Maine Railway, New St. |
Cambridge: City Hall |
Bounded by Massachusetts Ave. / Hancock St. (north and east boundary), Massachusetts Ave. / Inman St. (south and west boundary) |
Cambridge: Central Square |
Bounded by Austin St., Massachusetts Ave. / Main St., Green St., Temple St. |
Cambridge: Tech Square |
Bounded by Portland St., Boston & Maine Railway, Albany St. |
Cambridge: 3 rd & Cambridge |
Bounded by Cambridge St., Second St., Thorndike St., Third St. |
New Bedford |
Bounded by County St., Middle St., Front St., School St. |
To determine whether a specific project in one of these locations is served by an area network system, you must contact NSTAR.
Western Massachusetts Electric Company (Northeast Utilities)
City/Town |
Approximate Location |
Greenfield |
Contact WMECo |
Pittsfield |
Contact WMECo |
Springfield |
Contact WMECo |
West Springfield |
Contact WMECo |
Small sections of these cities are served by an area network system. If your project is in one of these towns, you must contact WMECo to determine whether your location is served by an area network system.
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