We continue to receive numerous requests from local distribution companies (LDC’s) for new transmission to distribution (T-D) interconnections. These interconnection requests generally are categorized into one of four different types of projects:
Constructing new T-D substations
This type of interconnection typically involves constructing a new T-D substation to serve normal load growth. They are usually located adjacent to an existing transmission line which is tapped or looped into the new substation. If the new substation site cannot be located adjacent to the transmission line, the ATC Best Value Planning (BVP) process helps evaluate the optimal transmission system solution to interconnect the new substation. Depending on the re–distribution of the load and type of new interconnection, the transmission system performance may be materially impacted. Generally, a new network line may have a greater impact on the transmission system performance than just connecting a new substation to existing lines.
Adding or replacing T-D transformers at existing substations
This type of interconnection involves modifying an existing T-D substation to accommodate a new T-D transformer. Typically, this type of interconnection is a way for a distribution company to increase capacity to meet growing customer demand. The scope may also include increasing reliability by replacing old infrastructure and/or equipment at the substation. This type of project may require transmission system reinforcements depending on how the distribution of load affects transmission system performance.
Distributed energy resource projects
This type of project supports the interconnection of a distributed energy resource (DER) to the LDC’s distribution system. Depending on the amount of DER and the load pocket it is connecting to, the transmission system may absorb some of the DER during part or all of the year. ATC may perform system impact study and insulation/protection coordination review to ensure the DER can be safely and reliably connected. Minor substation upgrades may be needed depending on the DER type, size, and substation configuration.
Economic development projects
This type of project is designed to accommodate a large new load. These may include a new industrial load or an existing industrial load that is expanding their operation. There may be a need for transmission system reinforcements, or a new substation, to reliably serve the new load. ATC works closely with the LDC on the BVP process to determine the required interconnection configuration and any necessary network upgrades to meet the customer’s demand and timeline.
A list of T-D interconnection requests that have been or are being jointly evaluated between ATC and each LDC is available on ATC’s Web site: www.atcllc.com/customer-relations/connecting-to-the-grid/.