IEEE 1547.6-2011 pdf free download – IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary Networks.
4. Existing requirements for the interconnection of distributed resources with networks IEEE Std 1547-2003 provides mandatory requirements for the interconnection of DR with EPSs. It focuses primarily on radial feeder interconnections. For DR interconnected on networks, all of IEEE 1547 requirements need to be satisfied. In addition, IEEE Std 1547.6-2011 provides recommendations and guidance for DR interconnected on networks.
5. Overview of distribution secondary network systems: design, components, and operation
5.1 Background Secondary-voltage ac networks (secondary networks) were first developed in the 1920s to provide highly reliable electric service to concentrated load centers—primarily in the downtown areas of major cities. There are two types of secondary networks: spot networks and grid networks (also referred to as area networks and street networks). A minimum of two primary feeders is required to supply a network. The number of feeders supplying a network depends on the design parameters such as level of reliability and the load requirement of the grid network or the spot network. An area EPS may have multiple grid networks operated independently from one another within a city. Customers in a secondary network area typically take service from the network at the secondary network voltage level, with no interposing transformer.
Grid networks serve many customers over a dispersed area. A spot network serves one or a limited number of customers at one location. In either case, network service increases reliability compared to other forms of service. The higher level of reliability is a result of system design that allows one or more primary feeders to be out of service without affecting customer service. A faulted primary feeder or transformer connection to the secondary network is isolated within a few cycles and the load continues to see service without any interruption. Network transformers and protectors may be located in a separate vault below the sidewalk or street, on pole-supported structures above the street, or dispersed throughout high-rise buildings. For vault-located NPs, the parallel connections on the low-voltage side may be made in a separate room. For underground vaults, the equipment may be in a harsh environment (e.g., they are frequently submersed), complicating the interfacing with other control equipment. Network engineers often refer to a network unit (NU), which typically consists of the network transformer, low-voltage air circuit breaker, fuse, reverse power relay function, and phasing relay function. Figure 1 shows the components within a NU in detail.IEEE 1547.6 pdf download