Solutions for deploying PV systems in New York City´s secondary network system

New York City has set a goal to increase its installed photovoltaic (PV) capacity from 1.1 MW in 2005 to 8.1 MW by 2015. A key barrier to reaching this goal, however, is the complexity of the interconnection process on secondary network distribution systems (network). Although most areas of the country use simpler radial distribution systems to distribute electricity, many larger metropolitan areas like New York City use networks to serve their customers, increasing reliability and better utilizing utility assets. Unlike a radial distribution system, where each customer receives power through a single distribution feeder, a network utilizes a grid of interconnected distribution feeders, transformers, and special devices, to deliver power to each customer through two or more parallel circuits. This redundancy improves reliability, but it also requires more complicated coordination and protection schemes that can be disrupted by exported energy from distributed PV systems. To assess ways to improve the interconnection process, the National Renewable Energy Laboratory (NREL) conducted a review of concerns and solutions to PV interconnection in New York City-summarizing common concerns of utility engineers and network experts regarding interconnecting PV systems to networks. This paper contains detailed descriptions of nine such concerns along with proven or potential solutions, and their potential impacts. There are also detailed descriptions of four methods used to insure nonexportation of power and energy which is typically the most common approach to interconnecting PV onto networks.