1、 IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary etworks NIEEE Standards Coordinating Committee 21 Sponsored by the IFEEE Standards Coordinating Committee 21 on uel Cells, Photovoltaics, Dispersed Generation, and Energy Storage I
2、EEE 3 Park Avenue New York, NY 10016-5997 USA 12 September 2011 IEEE Std 1547.62011 IEEE Std 1547.6-2011 IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary Networks Sponsor IEEE Standards Coordinating Committee 21 on Fuel Cells, Pho
3、tovoltaics, Dispersed Generation, and Energy Storage Approved 10 September 2011 IEEE-SA Standards Board Approved 17 January 2013 American National Standards Institute Abstract: Recommendations and guidance for distributed resources (DR) interconnected on the distribution secondary networks, includin
4、g both spot networks and grid networks, are provided. This document gives an overview of distribution secondary network systems design, components, and operation; describes considerations for interconnecting DR with networks; and provides potential solutions for the interconnection of DR on network
5、distribution systems. IEEE Std 1547.6-2011 is part of the IEEE 1547 series of standards. IEEE Std 1547-2003 provides mandatory requirements for the interconnection of DR with EPSs and focuses primarily on radial distribution circuit interconnections. For DR interconnected on networks, all of IEEE St
6、d 1547-2003 needs to be satisfied. IEEE Std 1547.6-2011 was specifically developed to provide additional information in regard to interconnecting DR with distribution secondary networks. Keywords: distributed resources, distribution grid, distribution secondary networks, electric power systems, grid
7、 networks, IEEE 1547.6, interconnection, spot networks, utility grid The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright 2011 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 12 September 2011.
8、 Printed in the United States of America. IEEE is a registered trademark in the U.S. Patent +1 978 750 8400. Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. Introduction This introduction is not pa
9、rt of IEEE Std 1547.6-2011, IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary Networks. The IEEE 1547 series of standards was created to develop a national consensus on using distributed resources (DR) in electric power systems (EP
10、Ss). IEEE Std 1547-2003 provides mandatory requirements for the interconnection of DR with EPSs.aIt focuses primarily on radial feeder interconnections. For DR interconnected on networks, all of IEEE Std 1547-2003 needs to be satisfied. IEEE Std 1547.6-2011 is part of the IEEE 1547 series of standar
11、ds. IEEE Std 1547.6 provides recommendations and guidance for DR interconnected on EPS distribution secondary networks, including both spot networks and grid networks. IEEE Std 1547.6 was specifically developed to provide additional information in regard to interconnecting DR with distribution secon
12、dary networks. This document contains several clauses that address various aspects of DR interconnection with distribution secondary networks. Clause 1 provides an overview including the scope, purpose, and limitations of the document. Clause 2 provides normative references that must be understood a
13、nd used with IEEE Std 1547.6, and Clause 3 lists definitions, acronyms, and abbreviations used in the document. Clause 4 identifies that IEEE Std 1547-2003 provides mandatory requirements for the interconnection of DR with EPSs. Clause 5 gives an overview of distribution secondary network systems de
14、sign, components, and operation. Clause 6 describes considerations for interconnecting DR with networks. And Clause 7 provides potential solutions for the interconnection of DR on network distribution systems. Notice to users Laws and regulations Users of these documents should consult all applicabl
15、e laws and regulations. Compliance with the provisions of this standard does not imply compliance to any applicable regulatory requirements. Implementers of the standard are responsible for observing or referring to the applicable regulatory requirements. IEEE does not, by the publication of its sta
16、ndards, intend to urge action that is not in compliance with applicable laws, and these documents may not be construed as doing so. Copyrights This document is copyrighted by the IEEE. It is made available for a wide variety of both public and private uses. These include both use, by reference, in l
17、aws and regulations, and use in private self-regulation, standardization, and the promotion of engineering practices and methods. By making this document available for use and adoption by public authorities and private users, the IEEE does not waive any rights in copyright to this document. aInforma
18、tion on references can be found in Clause 2. iv Copyright 2011 IEEE. All rights reserved. Updating of IEEE documents Users of IEEE standards should be aware that these documents may be superseded at any time by the issuance of new editions or may be amended from time to time through the issuance of
19、amendments, corrigenda, or errata. An official IEEE document at any point in time consists of the current edition of the document together with any amendments, corrigenda, or errata then in effect. In order to determine whether a given document is the current edition and whether it has been amended
20、through the issuance of amendments, corrigenda, or errata, visit the IEEE Standards Association web site at http:/ieeexplore.ieee.org/xpl/standards.jsp, or contact the IEEE at the address listed previously. For more information about the IEEE Standards Association or the IEEE standards development p
21、rocess, visit the IEEE-SA web site at http:/standards.ieee.org. Errata Errata, if any, for this and all other standards can be accessed at the following URL: http:/standards.ieee.org/reading/ieee/updates/errata/index.html. Users are encouraged to check this URL for errata periodically. Interpretatio
22、ns Current interpretations can be accessed at the following URL: http:/standards.ieee.org/reading/ieee/interp/ index.html. Patents Attention is called to the possibility that implementation of this recommended practice may require use of subject matter covered by patent rights. By publication of thi
23、s recommended practice, no position is taken with respect to the existence or validity of any patent rights in connection therewith. The IEEE is not responsible for identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the legal validity or scope of P
24、atents Claims or determining whether any licensing terms or conditions provided in connection with submission of a Letter of Assurance, if any, or in any licensing agreements are reasonable or non-discriminatory. Users of this recommended practice are expressly advised that determination of the vali
25、dity of any patent rights, and the risk of infringement of such rights, is entirely their own responsibility. Further information may be obtained from the IEEE Standards Association. v Copyright 2011 IEEE. All rights reserved. Participants At the time this recommended practice was submitted to the I
26、EEE-SA Standards Board for approval, Standards Coordinating Committee 21 on Fuel Cells, Photovoltaics, Dispersed Generation, and Energy Storage had the following membership: Richard DeBlasio, Chair Thomas S. Basso, Vice Chair damage has occurred in vaults before any of the protection operates for su
27、stained faults in 480 V NPs. However, implementation of time-delay overcurrent protection, coordinated with NP fusing, may provide a proper response to secondary faults. For further discussion, see the IEEE Std C37.108-2002, which goes into more sophisticated schemes of protection. Such schemes are
28、beyond the scope of this short discussion on networks. 5.4 Secondary grid networks As defined in 3.1 and shown in Figure 3, a secondary grid network is a network system with geographically separated NUs and the network-side terminals of the NPs interconnected by low-voltage cables that span the dist
29、ance between sites. The low-voltage cable circuits of the grid networks are supplied by numerous NUs. The low-voltage cables may have customer service cables connected in manholes between the network transformer vaults. Network transformers are located at various locations throughout the grid to sup
30、ply power and support the grid voltage as required per studies. The same transformers and NPs are used here as with spot networks. Secondary grid networks are typically 208Y/120 V, although some 480Y/277 V systems were developed. Secondary grids typically have multiple sets of secondary cables per p
31、hase running between network transformers. These cables can have inline fuses (cable limiters) installed at each end to isolate a faulted cable and provide for high-current faults and thermal overload protection for the cables without interrupting service to customers or the grid. If limiters are no
32、t present or the limiters do not function as designed, the fault is isolated by the cable burning such that a gap is created at the fault site. This opening of the cable conductor and insulation is a sufficient distance to create a gap that is adequate to withstand the arc recovery voltage at the fa
33、ulted location in 208Y/120 V secondary network systems. The number of primary feeders, transformer units, and sets of low-voltage cables installed is determined by performing power-flow studies both under normal and contingency conditions to avoid circuit overloading. 8 Copyright 2011 IEEE. All righ
34、ts reserved. IEEE Std 1547.6-2011 IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary Networks Figure 3 Illustrative example of a grid network Different planning strategies may exist for a secondary grid network, but a typical scenar
35、io allows for one primary circuit to be out of service (faulted) at peak load times and two primary circuits to be out of service (one for maintenance with a subsequent fault occurring on another) at non-peak times. Power flow studies need to be run for all these scenarios to determine whether or no
36、t customers receive adequate voltage and no equipment is overloaded. Power flow studies are also presently performed to determine whether or not the secondary grid network can supply the load. The base case varies depending on the utilitys design and operating criteria, but it usually addresses the
37、peak period with the design basis contingency conditions. If, for example, the design basis included the need to supply the customer load for a peak period with a second contingency in effect, power flows would have to be performed for all combinations of second contingencies. The results of these s
38、tudies are examined to determine whether or not the customer load is supplied without equipment overload and electric service to the customer is within normal voltage range. Regarding power flow studies, the utility typically has access only to peak loads that occurred at the NP without any time sta
39、mp and customer peak demands, with or without time of day depending on the metering employed. Periodic voltage measurements are made on the grid, but they may not correspond to when specific load data were extracted. Most utilities do not monitor voltage and current on the secondary network. The uti
40、lity also has substation load data for the primary feeders that are part of the grid. This information, limited in kind and detail, is commonly the only source of information available to utility engineers asked to run power flow studies and plan secondary network grid upgrades. 9 Copyright 2011 IEE
41、E. All rights reserved. IEEE Std 1547.6-2011 IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary Networks Furthermore, there are many uncertainties associated with network power flow studies. In the majority of grid network installat
42、ions, there is a lack of real-time information on the distribution of the currents flowing in the grid conductors. Estimates of this data (currents) are available only from power flow studies, which are a snapshot of a static set of network parameters that are assumed to represent worst-case conditi
43、ons. They may or may not represent real-world operating conditions, such as the loss of one or more conductors of the multiple conductors that make up one phase of a current path. The current paths in the grid consist of multiple cables connected in parallel per phase that may or may not be sharing
44、the load current equally. It has also been noted that the failure of one or more parallel conductor(s) could go undetected for an extended period of time, resulting in a reduction of the current-carrying capacity of that current path. Finally, within a given facility served by a network, the issue o
45、f whether the customer or customers served at the site decide to install and operate DR adds the same degree of uncertainty as that posed by tenants moving in or out and customers adding load when business is growing or cutting back energy usage in a recession. At least when a DR installation is pla
46、nned, the utility needs to be notified; this can provide information about the new minimum load at the site. In contrast, customers rarely notify the utility when they are cutting back operations significantly, which also results in a drop in the minimum load (all other things equal). When a custome
47、r proposes to install a significant level (in kilowatts) of DR, it presents the opportunity for utility personnel to obtain new and useful information for conducting power flow studies with and without DR operation. 5.5 Operation In normal operation of the grid, all primary feeder circuit breakers a
48、nd NPs are closed and all secondary cables are in service at both peak and light load times. Although this is the preferred method of operation, secondary cable faults, which will be cleared by limiters or burn clear, can occur at any time. These faulted cables will not be detected until a physical
49、inspection of the grid is performed, unless the loss results in a low-voltage complaint or overloading of in-service cables with resultant smoke, fire, or other noticeable activity. NPs can be out of service for maintenance, a primary feeder fault, or a failure of the protector to close (typically a burned-out close motor). Unsupervised protectors that fail in the open position will not be detected until a physical inspection is performed. A primary feeder can trip open because of a fault, and this will cause all the protectors connected to that feeder to open. If supe
