While National Grid serves the vast majority of its customers from radial primary overhead distribution systems, DG installations on distribution secondary network systems require study to ensure the DG does not degrade the reliability, power quality, safety, or operation of the network system. Therefore, customers in the downtown districts of Pawtucket or Providence should contact National Gridís Distributed Generation Services (DGS) department (Distributed.Generation@nationalgrid.com) to determine if the proposed location is served by a distribution secondary network system.
Customers can also click here to view maps of National Gridís Secondary Networks.
This should be done while the project is still in the planning stage, and certainly before purchasing equipment or beginning installation. If it is determined that the proposed location is served by a secondary network, National Gridís DGS will review the Customerís plans and discuss options with the Customer.
More about Secondary Networks
Unlike radial distribution systems that deliver power to each customer in a single path from source to load, underground secondary area network systems deliver power to each customer through a complex and integrated system of multiple transformers and underground cables that are connected and operate in parallel.
The connection of customer DG on networks is an emerging topic, which poses some issues for National Grid to maintain adequate voltage and worker safety and has the potential to cause the power flow on network feeders to shift (reverse) causing network protectors within the network grid to trip open. Therefore, to ensure network safety and reliability, additional information will be required for National Gridís analysis:
For more technical information on parallel generator installations, please refer to the Companyís ESB 756 and its Appendix D on the Companyís web site at: http://www.nationalgridus.com/non_html/shared_constr_esb756.pdf.