Net Metering and Utility Interconnection

1. Net Metering and Utility Interconnection Presented by: Bill Brooks Brooks Engineering

2. Technical Interconnection Issues: Codes and Standards

3. Who Has a stake in the PV Industry? • Million Solar Roofs Partnerships • Electric utility companies • Electric customers wanting to install a PV system • PV component manufacturers • PV equipment and system dealers • Local jurisdictions enforcing building codes

4. Why Do We Need PV Codes and Standards? • To facilitate the broad acceptance of the technology among local jurisdictions and interconnecting utilities. • To maintain minimum requirements for PV products and their installation. • To standardize and reduce the cost of testing and certification.

5. Who sets codes and standards? • National Fire Protection Association (NFPA) • National Electrical Code (NEC)- Electrical Power System Installation--developed in conjunction with electrical trade and industry experts. • Underwriters Laboratory (UL) • Standards for Electrical Equipment Safety--developed in conjunction with manufacturers. • Institute of Electrical and Electronic Engineers (IEEE) • Standards for electrical and electronic equipment--developed in conjunction with applicable industry experts. • International (IEC, CENELEC, etc…)

6. What are the applicable codes and standards for PV systems? • NEC Article 690 - Solar Photovoltaic Systems - Building codes - UBC, SBC, BOCA, local codes • UL Standard 1703, Flat-plate Photovoltaic Modules and Panels • IEEE 929-2000, Recommended Practice for Utility Interface of Photovoltaic (PV) Systems (approved in January 2000) • UL Standard 1741, Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems (published in May 1999)

7. What are the common interests of Utilities and PV manufacturers? • Provides predictable requirements for design and installation. • Utility protection departments need to reduce costs. • Inverter manufacturers need to standardize their designs to keep costs lower. • Over 3000 utilities with a similar number of interconnection requirements. • Consensus IEEE standard makes it unnecessary for utilities to utilize an independent standard. • Inverter manufacturers can build one design that is widely applicable.

8. Utility Interconnection Issues • Personnel safety • Equipment protection • Service reliability • Power quality

9. Utility Interconnection Requirements • IEEE standard 929 • UL standard 1741 • Utility practice and requirements • Public utility commission statutes

10. UL 1741 Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems • First released in May of 1999 • Has been revised to match IEEE 929-2000 • Compliance with revised document required on November 7, 2000) • New title reads “Standard for inverters, converters, and controllers for use in Independent Power Systems.”(Nov 8)

11. What is UL 1741 and how does it relate to IEEE 929? • First official version published in May of 1999. “Final” version released November of 2000. • 1741 incorporates the testing required by IEEE 929 (frequency and voltage limits, power quality, non-islanding inverter testing) • 1741 testing includes design (type) testing and production testing. • Line-tie inverters should have the words“Utility-Interactive” printed directly on the listing label—this makes identification of the listing much more straightforward (several inverter manufacturers currently using this designation).

12. How Does a Utility, or a PV-System Purchaser, Know If An Inverter Meets The Requirements of IEEE 929? If it meets the testing requirements of test standard UL 1741 and has the words “Utility-Interactive” printed directly on the listing label

13. Terms and Conditions for Interconnection • May involve the following: • Metering options • Size restrictions on metering options • Carryover credit on monthly billings • Net Meter or differing buy and sell rates • Outdoor disconnect requirements • Insurance requirements • Interconnection costs

14. Net Metered Systems in California(Similar to some other states) • Requires a contract with the serving utility company. • Inverter must be acceptable to utility for interconnection. • Utility also may have a list of acceptable manual disconnects to choose from. • Starting January 1, 1999, systems are to be billed on annual basis. • Starting January 1, 2001, systems may elect time-of-use net metering (up to 30% increased financial benefit)

15. IEEE 929-2000 • Passed by IEEE Standards Board in January, 2000. • Represents an excellent primer on PV inverter interconnection issues.

16. The Need for PV Interconnection Standards • Many utilities were using “Rotating Machinery” requirements for PV systems • Many of the Interconnection Requirements were established in early “PURPA” days • too many requirements • telemetery and “Utility Grade” type relays • special (and costly) engineering were needed for each specific utility requirements

17. Purpose of IEEE 929 “This recommended practice contains guidance regarding equipment and functions necessary to ensure compatible operation of photovoltaic systems which are connected in parallel with the electric utility. This includes factors relating to personnel safety, equipment protection, power quality and utility system operation.” • Power Quality • Safety and Protection

18. IEEE 929 Working Group Consisted of Utilities and Industry

19. What Does IEEE 929Really Impact? PV Array Utility System M Inverter

20. IEEE 929 Outline • Introduction • 1. Overview (scope & purpose) • 2. References • 3. Definitions (inverter, islanding, PCC, quality factor, etc…) • 4. Power quality • 5. Safety and protection functions • Annexes

21. Power Quality • Power quality problems in general are rising because of proliferation of non-linear loads on utility systems -- all customers suffer • PV should not add to that problem

22. Power Quality • Power Quality • 1. Service Voltage • 2. Voltage Flicker • 3. Frequency • 4. Waveform Distortion • IEEE 519 • 5. Power Factor

23. Safety and Protection Functions • 1. Response to Abnormal Utility Conditions • a. Voltage Disturbances • b. Frequency Disturbances • c. Islanding Protection • d. Reconnect After a Utility Disturbance • 2. Direct Current Isolation • 3. Grounding • 4. Manual Disconnect

24. Response to Abnormal Utility Conditions *”Trip time” refers to the time between the abnormal condition being applied and the inverter ceasing to energize the utility line. The inverter will actually remain connected to the utility to allow sensing of utility electrical conditions for use by the “reconnect” feature.

25. Terminology • Power Conditioning Unit or Inverter • Line-Commutated Inverters • Self-Commutated Inverters • Inverter Shut Down • The PV Inverter as a UPS • Power Factor • Controls Integrated into the Inverter • Islanding

26. The PV Inverter as a UPS • Some inverters are designed to provide uninterruptible power to critical loads • The power to critical loads is maintained when the connection to the utility is severed • When the inverter ceases to energize the utility line (due to abnormal conditions, the inverter will continue to maintain the loads connected to a special distribution panel isolated from the utility, also no power flows to the utility

27. IEEE 929- Annexes • Annex A (Normative) – Minimum Test Procedure for a Non-Islanding PV Inverter • Annex B (Informative) - Bibliography • Annex C - PV Inverters and the Utility Interface (Terminology) • Annex D - Disconnect Switches & Utility Procedures • Annex E - Islanding as it Applies to PV Systems • Annex F - The PV Inverter Under Utility Fault Conditions • Annex G - Dedicated Distribution Transformer

28. ManualDisconnect Switch PV Array Local Loads Utility System M Inverter

29. Islanding Testing

30. Why do we need testing? • Utility engineers are required to do testing of system protection equipment • Testing has a profound impact on an engineer’s understanding of how things work. • Example: New York utilities require special tests. • Tests designed to pit PV inverters against notorious NY waveforms • Three utility engineers from NY visited Sandia to witness tests • After first day into three-day test procedure, they said, “Let’s do something more interesting.”

31. Anti-Islanding Requirements • “Typical” island (no balance between load and island) • Trip time - 10 cycles (to avoid interference with reclosing) • “Balanced” island (real power load between 50% and 150% of PV output, Q  2.5) • Trip time - 2 seconds

32. “non-islanding” test procedure: • The load should have a real power match as close as reasonable (at least within 20%) to the PV system output • and a Q (quality factor)  2.5, where Q=R(C/L)½ • the selected Q  2.5 equates to an uncorrected power factor of 0.37. As power factor increases, Q decreases. Thus, the test requirement that Q  2.5 equates to lines with uncorrected power factors from 0.37 to unity • RLC load that has been tuned to 60Hz

33. Sandia Anti-Islanding Method Basic Concepts • Frequency and voltage trip points are used • Error signal from frequency and voltage is calculated each ½ cycle • Frequency and voltage are then “tweaked” in the same direction as error signal • If tweaking results in change, then accelerated tweaking results to push frequency or voltage to trip points

34. Test Circuit Used at Sandia

35. “Less Than Sandia” SchemeBalanced load and generation (25% of Capacity)

36. “Less Than Sandia” Scheme(125% of Inverter Capacity)

37. “Less Than Sandia” Scheme Balanced load and generation (100% Capacity)

38. Sample Test-Using Sandia Anti-Islanding MethodNote that trip time meets “typical” criteria even though test is with “balanced” conditions

39. Sample Motor Load Tests—Using Sandia Anti-Islanding MethodRequired trip time - 2 seconds

40. Motor Load TestsGeneration to load ratio impacts

41. IEEE 1547 Standard for Interconnecting Distributed Resources with Electric Power Systems • Approved at June 2003 IEEE Standards Board Meeting

42. IEEE Standards Classification • Standards: documents with • mandatory requirements (shall) • Recommended Practices: documents in which • procedures and positions preferred • by the IEEE are presented (should) • Guides: documents in which alternative approaches • to good practice are suggested but • no clear-cut recommendations are made (may) • IEEE Standards are Voluntary.

43. 1547 Body of Standards 1547Standard for Interconnecting Distributed Resources with Electric Power Systems Guide for Networks Guide for Impacts P1547.3 Draft Guide for Monitoring, Information Exchange and Control of DR Interconnected with EPS Guide for Islanding & Anti-Islanding Guide For Interconnection System Certification 1547.1 Draft Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems P1547.2 Draft Application Guide for IEEE P1547 Draft Standard for Interconnecting Distributed Resources with Electric Power Systems DP Specifications and Performance The above schematic identifies existing standards development projects and potential future activities under discussion by P1547 Work Group members.

44. 1547: Interconnection Is The Focus Area Electric Power System (EPS) Interconnection System Distributed Resource (DR) unit

45. 1547 Interconnection Terms

46. IEEE 1547 Contents INTRODUCTION 1.0 OVERVIEW 1.1 Scope 1.2 Purpose 1.3 Limitations 2.0 REFERENCES 3.0 DEFINITIONS

47. IEEE 1547 Contents 1.1 Scope This standard establishes criteria and requirements for interconnection of distributed resources (DR) with electric power systems (EPS). 1.2 Purpose This document provides a uniform standard for interconnection of distributed resources with electric power systems. It provides requirements relevant to the performance, operation, testing, safety considerations, and maintenance of the interconnection. The requirements shall be met at the point of common coupling (PCC), although the devices used to meet these requirements can be located elsewhere. This standard applies to interconnection based on the aggregate rating of all the DR units that are within the Local EPS. The functions of the interconnection system hardware and software that affect the Area EPS are required to meet this standard regardless of their location on the EPS. The stated specifications and requirements, both technical and testing, are universally needed for interconnection of DR, including synchronous machines, induction machines, or power inverters/converters, and will be sufficient for most installations.1 1 Additional technical requirements and/or tests may be necessary for some limited situations.

48. IEEE 1547 Contents • 4.0 INTERCONNECTION TECHNICAL SPECIFICATIONS AND REQUIREMENTS • 4.1 General Requirements • 4.2 Response to Area EPS Abnormal Conditions • 4.3 Power Quality • 4.4 Islanding • 5.0 INTERCONNECTION TEST SPECIFICATIONS AND REQUIREMENTS • 5.1 Design Test • 5.2 Production Tests • 5.3 Interconnection Installation Evaluation • 5.4 Commissioning Tests • 5.5 Periodic Interconnection Tests • ANNEX A (INFORMATIVE) BIBLIOGRAPHY

49. IEEE 1547 Contents 4.1 General Requirements 4.1.1 Voltage Regulation (Don’t!) 4.1.2 Integration with Area EPS Grounding (Coordinate) 4.1.3 Synchronization (<5% voltage fluctuation, no flicker) 4.1.4 Distributed Resources on Distribution Secondary Grid and Spot Networks 4.1.4.1 Distribution Secondary Grid Networks 4.1.4.2 Distribution Secondary Spot Networks 4.1.5 Inadvertent Energization of the Area EPS (Don’t!) 4.1.6 Monitoring Provisions 4.1.7 Isolation Device (Disconnect Switch) 4.1.8 Interconnect Integrity 4.1.8.1 Protection from Electromagnetic Interference (C37.90.2) 4.1.8.2 Surge Withstand Performance (C62.41 or C36.90.1) 4.1.8.3 Paralleling Device (withstand 220% of rated voltage)

50. IEEE 1547 Contents 4.2 Response to Area EPS Abnormal Conditions 4.2.1 Area EPS Faults (detect faults, cease to energize) 4.2.2 Area EPS Reclosing Coordination (coordinate) 4.2.3 Voltage (<60V,106V – 132V, >144V) 4.2.4 Frequency (59.3 – 60.5 Hz) 4.2.5 Loss of Synchronism (not required unless there is flicker) 4.2.6 Reconnection To Area EPS (up to 5 min, C84.1 Range B) 4.3 Power Quality 4.3.1 Limitation of DC Injection (>0.5% of rated output current) 4.3.2 Limitation of Flicker Induced by the DR (Don’t) 4.3.3 Harmonics (~IEEE 519) 4.4 Islanding 4.4.1 Unintentional Islanding (Don’t) 4.4.2 Intentional Islanding (Don’t know)