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Presentation to the Massachusetts DG Collaborative Gene Shlatz Stan Blazewicz

Interconnecting DG into Network Distribution Systems. Presentation to the Massachusetts DG Collaborative Gene Shlatz Stan Blazewicz. January 10, 2003. Background.

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Presentation to the Massachusetts DG Collaborative Gene Shlatz Stan Blazewicz

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  1. Interconnecting DG into Network Distribution Systems Presentation to the Massachusetts DG Collaborative Gene Shlatz Stan Blazewicz January 10, 2003

  2. Background • This work has been supported by the Massachusetts Renewable Energy Trust and was directed by Raab Associates, Ltd (facilitator of the Massachusetts Distributed Generation Collaborative). • The views expressed in this presentation represent only those of Navigant Consulting, Inc and the presenters. • This presentation is not complete without the accompanying oral remarks.

  3. Table of Contents 1 Key Terms and Definitions 2 Radial versus Network Distribution Systems 3 Network Interconnection Opportunities and Challenges 4 Approaches from Other States and Jurisdictions 5 Conclusion

  4. Table of Contents 1 Key Terms and Definitions 2 Radial versus Network Distribution Systems 3 Network Interconnection Opportunities and Challenges 4 Approaches from Other States and Jurisdictions 5 Conclusion

  5. Key Terms and Definitions We have developed some key terms & definitions that should help us in addressing network interconnection. • Network Systems – Power delivery systems that provide highly reliable, continuous service via alternate supplies. • Primary Network Distribution Lines or Feeders – Higher voltage distribution lines (4,000 volts to 35,000 volts) that deliver power to secondary grid or spot networks. • Secondary Network Lines – Lower voltage distribution lines (208 volts to 480 volts) that distribute power to customers located on secondary grid or spot networks. • Network Transformers – Converts higher distribution voltages to lower voltages used to serve secondary networks. Power (current) is intended to flow in one direction: high to low voltage. • Grid or Street Networks – Low voltage lines connected in a grid arrangement, typically serving many customers over several city blocks.

  6. Key Terms and Definitions We have developed some key terms & definitions that should help us in addressing network interconnection (continued). • Spot Networks – Low voltage lines typically serving one large customer or high-rise building in one or a few city blocks. • Faults (Radial or Network) – Equipment failures or conditions that must be interrupted to limit equipment damage, minimize the number of customers interrupted and eliminate potential safety hazards to workers and public. • Network Protectors – Devices that interrupt power when flows are from the secondary grid into the high voltage distribution system. The protectors are usually attached to the low voltage side of the network transformer. • Circuit Breakers – Devices that interrupt power flows on a primary line, usually to isolate and clear faults. Normally located in the substation, although many utilities install reclosers on lines to limit outage exposure. • Reverse Power Flow – When power flows from the low voltage side (secondary) into the high side (primary) of the network transformer, thereby causing network protectors to operate.

  7. Table of Contents 1 Key Terms and Definitions 2 Radial versus Network Distribution Systems 3 Network Interconnection Opportunities and Challenges 4 Approaches from Other States and Jurisdictions 5 Conclusion

  8. Radial versus Network Distribution Systems Simplified Illustrations SIMPLIFIED ILLUSTRATIONS Three distribution systems could be addressed in interconnection standards and requirements. Radial System Spot Network Grid Network Substation Substation Substation HV HV HV Load TX & NP TX & NP Load Load Load TX & NP TX & NP Loads designated by arrows Load LV LV Loads NP = Network Protector TX = Transformer HV = High Voltage LV = Low Voltage

  9. Issue/Description Radial Systems Spot Networks Grid Networks No. of Primary Feeders (Typical) 1 2-4 4-8 Voltages 4000 volts to 35,000 volts 480 volts 208 volts Locations Urban, Suburban or Rural Urban and Suburban Urban Area Served (Typical) Up to 30 to 40 miles. 5-10 miles for main feeder One Building Complex, High Rise or Single Customer Several City Blocks; Sometimes Larger Length of Secondary Circuits Typically less than 300 feet to meter. Typically less than 100’ to customer switchgear Individual sections can be up to 500’ to 600’ feet Construction Type Overhead or Underground Almost Always Underground Almost Always Underground Level of reliability Typically 1 to 3 interruptions per yr Reliability improved by a factor of 5-10 Reliability improved by a factor of 5-10 Relative Cost Base-Urban systems typically higher than rural/suburban High, due to redundancy and high cost equipment Very high, due redundancy and urban location Circuit loadings All load served by a single circuit Loads balanced equally on network transformers Relative loadings may vary on network transformers Radial versus Network Distribution Systems Key Differences In general, there are key differences between radial, spot network and grid network distribution systems.

  10. Table of Contents 1 Key Terms and Definitions 2 Radial versus Network Distribution Systems 3 Network Interconnection Opportunities and Challenges 4 Approaches from Other States and Jurisdictions 5 Conclusion

  11. Network Interconnection Opportunities and Challenges Attractive market opportunities for distributed generation may exist that require network interconnection. • Secondary networks are used in about 90% of the cities in the US having a population of >100,000 and in more than 1/3 of the cities with populations between 25,000 – 100,000.1 • Some of the more attractive and most accessible market opportunities for DG involve commercial customers in urban areas: • Relatively high electricity prices • Reasonable gas prices, accessibility to gas • Electricity can be a significant operating cost • Customers care about costs, reliability, power quality and green attributes • Technical fit • Right size (I.e. MW) for some DG technologies (microturbines, fuel cells and recip engines) • PV opportunity • Cogen opportunity • It would appear that many of these customers are in urban areas on grid or spot networks. • Standard Handbook for Electrical Engineers, 13th Edition, 1993

  12. Network Interconnection Opportunities and Challenges There are challenges with interconnecting DG into spot and grid networks. • Single greatest challenge is to address the possibility that DG will cause network protectors to open under non-fault conditions; for example, when DG output causes reverse power flows on network protector(s). • Whether the length of time required to analyze DG impacts is longer than radial systems due to greater complexity of network systems, particularly on grid networks with many primary feeders and secondary transformers. • Development of a generic standard for integration of DG presents potential challenges due to significant differences in network system design within and among utilities, particularly for grid systems that have evolved over time. • Similar to radial systems, need to ensure fault current contribution by DG does not exceed the fault duty ratings of primary and/or secondary equipment; for example, circuit breakers. • If clearing times for DG exceed those of the network protectors, need to address potential mis-coordination or de-sensitization of protection systems. • Identifying mitigation options for synchronous generators that potentially could remain on line and contribute fault current to primary and secondary faults.

  13. Network Interconnection Opportunities and Challenges Faults should be easily isolated on a radial feeder with DG.

  14. Network Interconnection Opportunities and Challenges Fault protection becomes more difficult on network feeders with DG installed. NP =Network Protector

  15. Network Interconnection Opportunities and Challenges Reverse power could also be an issue for network feeders with DG installed . Incoming Transmission Lines Substation Potential for Either Network Protector No.1 or No. 2 to Open Under R everse Power if F 1 F 2 DG Output Exceeds Flows On Feeder 1 or Feeder 2 (F1 or F2) For E xample, if Net DG O utput is 250kW and E ith er F1 or F2 is Less Than 250kW, Then the NP No. 1 NP No. 2 Network Protector Could Open DG Provider Loads NP =Network Protector F = Feeder

  16. Table of Contents 1 Key Terms and Definitions 2 Radial versus Network Distribution Systems 3 Network Interconnection Opportunities and Challenges 4 Approaches from Other States and Jurisdictions 5 Conclusion

  17. Approaches from Other States and Jurisdictions Several jurisdictions have begun to address network interconnection of DG. • Texas – Included both spot and grid networks • California – Dealt with in supplemental review • FERC ANOPR – Considered in both primary and secondary screens • IEEE – Covers spot networks only

  18. Approaches from Other States and Jurisdictions Texas-Overview The Texas rules cover network interconnection; however, there has been limited experience with using these rules for network interconnection. • The Public Utility Commission of Texas Interconnection Manual provides screens for interconnection into secondary networks. • These screens cover: • Equipment pre-certification • Size of DG • Unit size • Relative to the feeder load • Relative to the customer’s load • Technology type • If the application passes these screens, the application is approved and there is no study fee. • If the application fails any of the screens, the applicant is charged for a study and the utility will make a recommendation to the applicant on how to proceed. • The utility can always perform a study, but not always charge the customer. Regardless of who pays for the study, the utility may reject an application for safety or reliability issues. • Since the standard has been in place, there has been little activity regarding network interconnection using these rules.

  19. Approaches from Other States and Jurisdictions Texas The Texas rules allow for simple interconnection approval and relief from study fees for network interconnection under certain circumstances. Source: Distributed Generation Interconnection Manual, Public Utility Commission of Texas, May 1, 2002, Figure 4-2: Network Secondary Study Chart

  20. Approaches from Other States and Jurisdictions Texas The Texas rules allow for simple interconnection approval and relief from study fees for network interconnection under certain circumstances (continued). “Certain aspects of secondary network systems create technical difficulties that may make interconnection more costly to implement. If the proposed site is serviced by a networked secondary, no study fee may be charged to the applicant if: ·Proposed DG equipment is pre-certified ·Aggregate DG, including the proposed system, represents 25% or less of the total load on the network (based on the most recent peak load demand) and either ·Proposed DG has inverter-based protective functions, or ·Proposed DG rating is less than the local applicant’s verifiable minimum load. Otherwise, the TDU may charge the DG applicant a fee to offset the costs of the interconnection study. The TDU must advise applicants requesting DG interconnection on secondary networks about the potential problems and costs before initiating the study. Note that these provisions do not preclude the TDU from performing a study; they simply regulate when the TDU can charge the applicant for the cost of the study. Whether or not a study fee is billable to the applicant, the TDU may reject an application for demonstrable reliability or safety issues but must work to resolve those issues to the mutual satisfaction of the TDU and applicant. The TDU must make reasonable efforts to interconnect all proposed DG, including the possibility of switching network-secondary service to a radial feed if practical and if acceptable to the applicant.” Source: Distributed Generation Interconnection Manual, Public Utility Commission of Texas, May 1, 2002

  21. Approaches from Other States and Jurisdictions Texas Major problems have not been reported in Texas, however they have little practical experience with the network interconnection using the rules. • Standards have been in place since January 2001. • No complaints have been reported to the Public Utility Commission of Texas.1 • ONCOR has processed 19 applications (2001-2002).2 This represents about 80% of all applications in Texas. • Only one application was for a network interconnection. That project was an 8MW (4x2MW recip engine) back-up power system installed in a 4kV spot network. • The network interconnection aspects of the standard do not appear to be a concern to ONCOR. The rules allow, “A utility may reject applications for a distributed generation facility under this section if the utility can demonstrate specific reliability or safety reasons why the distributed generation should not be interconnected at the requested site. However, in such cases the utility shall work with the customer to attempt to resolve such problems to their mutual satisfaction.” • Centerpoint Energy has not received any applications for network interconnection.3 • Telephone Interview with Tony Marciano, Public Utility Commission of Texas, Electric Division January 7, 2003 • Telephone Interview with Ken Brunkenhoefer, ONCOR Electric Delivery Company January 7, 2003 • Telephone Interview with Ben Gazara, Centerpoint Energy, January 8, 2003

  22. Approaches from Other States and Jurisdictions California California’s Rule 21 does not currently deal with network interconnection directly; it is unclear if this is a major concern. • The first screen in the initial review process puts network interconnection into supplemental review. • It is It has been suggested that network interconnection may be lengthening the time for supplemental review for some utilities. However, data is not readily available to support that position. • The Rule 21 Working Group is developing guidelines for supplemental review which addresses what happens if an application fails a screen.1 • Network interconnection may be addressed in these guidelines, however other screens (non-export screen and 15% screen)appear to be priorities. • SCE and SDGE have not received any applications for network interconnection.2,3,4 • SCE has processed approximately 1400 applications (1200 for PV) since Rule 21 was established. SDG&E has processed approximately 700 applications (650 for PV). • These utilities have limited network distribution in their systems. • Telephone Interview with Scott Tomashevsky, California Energy Commission, January 7, 2003 • Telephone Interview with Tom Dossey, Southern California Edison, January 8, 2003 • Telephone Interview with Mike Iammarino, San Diego Gas and Electric, January 8, 2003 • Note: PG&E could not be reached. PG&E is likely to have more network distribution systems

  23. Approaches from Other States and Jurisdictions FERC The FERC ANOPR Interconnection Procedures document addresses networks, however the details have not been worked out. • During the initial review the interconnection provider would apply primary and secondary screens to determine how the application will be treated. • If the applicant passes the primary screens the application is approved. • If the application fails one or more primary screens but passes the secondary screens it still may qualify for simple interconnection. • There are primary and secondary screens that cover network interconnection. • The details for these screens have not been worked out.

  24. Approaches from Other States and Jurisdictions FERC The details still need to be worked out for the primary screen that addresses network interconnection. “4. Screening Criteria for Determining Grid Impacts • Primary Screening Criteria 2. For interconnection of a proposed generator to the load side of spot network protectors, the proposed generator must utilize an inverter based equipment package and, together with the aggregated other inverter-based generation, will not exceed the smaller of 5% of a spot network’s maximum load or 50 kW [IP POSITION: AND MUST COMPLY WITH ALL REQUIREMENTS OF IEEE P1547, SECTION 4 “INTERCONNECTION TECHNICAL SPECIFICATIONS AND REQUIREMENTS”]. 3. [SGC POSITION: FOR INTERCONNECTION OF GENERATORS TO THE LOAD- SIDE OF SECONDARY GRID NETWORKS, THE PROPOSED GENERATOR MUST BE AN INDUCTION GENERATOR THAT DOES NOT EXCEED 50% OF THE MINIMUM LOAD OF THE HOST FACILITY OR A GENERATOR WITH AN INVERTER-BASED EQUIPMENT PACKAGE WHICH DOES NOT EXCEED THE GREATER OF 50% OF THE MINIMUM LOAD OF THE HOST FACILITY OR 20 KW NOT EXCEEDING 30% OF PEAK LOAD.] [IP/NARUC POSITION: THE PROPOSED GENERATOR CANNOT BE CONNECTED ON THE LOAD SIDE OF A SECONDARY NETWORK PROTECTOR, EXCEPT AS ALLOWED UNDER SECTION 4.a.2 (SPOT NETWORK) ABOVE.]” Source: Report to FERC on Standardization of Small Generation Interconnection Agreements and Procedures, November 12, 2002 Note: SGC POSITION - Small Generator IP POSITION - Interconnection Provider NARUC POSITION -National Association of Regulatory Utility Commissioners

  25. Approaches from Other States and Jurisdictions FERC The details still need to be worked out for the secondary screen that addresses network interconnection. “4. Screening Criteria for Determining Grid Impacts • Secondary Screening Criteria 2. [SGC POSITION: FOR INTERCONNECTION OF A PROPOSED GENERATOR TO A SPOT NETWORK CIRCUIT, THE NEW UNIT IN AGGREGATE WITH OTHER GENERATION WILL NOT EXCEED 5% OF THE SPOT NETWORK’S MAXIMUM LOAD.] [IP/NARUC POSITION: FOR INTERCONNECTION OF A PROPOSED GENERATOR TO THE LOAD SIDE OF SPOT NETWORK PROTECTORS, THE PROPOSED GENERATOR MUST UTILIZE AN INVERTER BASED EQUIPMENT PACKAGE AND, TOGETHER WITH THE AGGREGATED OTHER INVERTER-BASED GENERATION, WILL NOT EXCEED THE SMALLER OF 5% OF A SPOT NETWORK’S MAXIMUM LOAD OR 50 KW AND MUST COMPLY WITH ALL REQUIREMENTS OF IEEE P1547’S “INTERCONNECTION TECHNICAL SPECIFICATIONS AND REQUIREMENTS”.] 3. For the interconnection of a proposed generator to any network, the generator [SGC POSITION: WILL EITHER UTILIZE] [IP/NARUC POSITION: MUST UTILIZE A PROTECTIVE SCHEME THAT WILL ENSURE THAT ITS CURRENT FLOW WILL NOT AFFECT THE NETWORK PROTECTIVE DEVICES INCLUDING] reverse power relays or a comparable function [SGC POSITION: TO ENSURE THAT ITS CURRENT FLOWS CANNOT AFFECT NETWORK PROTECTIVE DEVICES]. [IP/NARUC POSITION: SYNCHRONOUS GENERATORS CANNOT BE INTERCONNECTEDINTO A SECONDARY NETWORK.] 4. [SGC POSITION: NOTWITHSTANDING SUBSECTION B. 3, FOR INTERCONNECTION OF A PROPOSED GENERATOR TO A SECONDARY GRID NETWORK WHOSE TOTAL NET GENERATING CAPACITY, IN AGGREGATE WITH OTHER EXPORTING GENERATORS INTERCONNECTED ON THE LOAD SIDE OF NETWORK PROTECTIVE DEVICES, WILL NOT EXCEED THE LESSER OF 10% OF THE MINIMUM ANNUAL LOAD ON THE NETWORK OR 500 KW.] [NARUC/IP POSITION: FOR INTERCONNECTION OF A PROPOSED GENERATOR THAT IS AN INDUCTION GENERATOR OR THAT UTILIZES INVERTER BASED PROTECTIVE FUNCTIONS, BOTH OF WHICH INCLUDE REVERSE POWER RELAY FUNCTIONS, THE GENERATOR’S TOTAL NET GENERATING CAPACITY, IN AGGREGATE WITH OTHER GENERATORS INTERCONNECTED ON THE LOAD SIDE OF NETWORK PROTECTIVE DEVICES, DOES NOT EXCEED THE LESSER OF 10% OF THE MINIMUM LOAD ON THE NETWORK OR 50 KW. A SMALL GENERATOR DOES NOT EXPORT TO ANY NETWORK.] “ Source: Report to FERC on Standardization of Small Generation Interconnection Agreements and Procedures, November 12, 2002

  26. Approaches from Other States and Jurisdictions IEEE IEEE 1547 will provide little guidance on network interconnection outside of spot networks. “4.1.4.2 Distribution Secondary Spot Networks 3 Network protectors shall not be used to separate, switch, serve as breaker failure backup or in any manner isolate a network or network primary feeder to which DR is connected from the remainder of the Area EPS, unless the protectors are rated and tested per applicable standards for such an application. Any DR installation connected to a spot network shall not cause operation or prevent reclosing of any network protectors installed on the spot network. This coordination shall be accomplished without requiring any changes to prevailing network protector clearing time practices of the Area EPS. Connection of the DR to the Area EPS is only permitted if the Area EPS network bus is already energized by more than 50% of the installed network protectors. The DR output shall not cause any cycling of network protectors. The network equipment loading and fault interrupting capacity shall not be exceeded with the addition of DR. DR installations on a spot network, using an automatic transfer scheme in which load is transferred between the DR and the EPS in a momentary make-before-break operation, shall meet all the requirements of this clause regardless of the duration of parallel. 3When required by the authority who has jurisdiction over the DR interconnection, a study may be conducted to determine that all of the requirements of this clause can be met when the aggregate DR installed on a spot network exceeds 5% of the spot network’s maximum load.” • IEEE 1547 only covers spot networks, secondary grid networks may be included in future revisions. • IEEE 1547.2 is a guidebook that is under development and may cover network interconnection. Source: IEEE 1547, Draft 10

  27. Table of Contents 1 Key Terms and Definitions 2 Radial versus Network Distribution Systems 3 Network Interconnection Opportunities and Challenges 4 Approaches from Other States and Jurisdictions 5 Conclusion

  28. Conclusion Conclusion • We have established key definitions and a framework for thinking about network interconnection. • There are opportunities and challenges for network interconnection. • Other jurisdictions have done work on establishing standards and rules for network interconnection, however there is little practical experience with these standards.

  29. Conclusion Defining the scope of the Collaborative’s work on developing network interconnection standards • What can the Collaborative leverage from the radial work? • Timelines • Fees • Process flow diagram • Are there other parts that should be similar to radial? • Agreements • ADR • Can the Collaborative address spot networks by the end of February? • Can the Collaborative address grid networks by the end of February? • Can the Collaborative use screens for network interconnection? • Can the Collaborative use Texas or the ANOPR as a starting point?

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