1 Quality Assurance Framework for Mini -Grids ohit Singh, I an Baring- Gould, K Burman, M ari Sean Esterly and National Renewable Energy Laboratory R ose Mutiso and Caroline McGregor U.S. Departmen t of Energy NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Technical Report NREL/TP -5000- 67374 November 2016 08GO28308 Contract No. DE - AC36 -
2 Quality Assurance Framework Grids for Mini- Gould, K Ian Baring- ari Burman, M ohit Singh, and S ean Esterly National Renewable Energy Laboratory Rose Mutiso and Caroline McGregor t of Energy Departmen U.S. Prepared under Task No. D SMG .1000 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Labor atory (NREL) at www.nrel.gov/publications. Technical Report National Renewable Energy Laboratory 15013 Denver West Parkway 67374 -5000- NREL/TP November 2016 Golden, CO 80401 303 3000 • www.nrel.gov - 275 - Contract No. DE AC36 - 08GO28308 -
3 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, its endorsement, recommendation, trademark, manufacturer, or otherwise does not necessarily constitute or imply or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. This re port is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications . Available electronically at ech Connect http:/www.osti.gov/scitech SciT Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN 37831- 0062 OSTI http://www.osti.gov Phone: 865.576.8401 Fax: 865.576.5728 Email: [email protected] Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5301 Shawnee Road ia, VA 22312 andr Alex NTIS http://www.ntis.gov Phone: 800.553.6847 or 703.605.6000 Fax: 703.605.6900 Email: [email protected] Cover Photos by Dennis Schroeder: (left to right) NREL 26173, NREL 18302, NREL 19758, NREL 29642, NREL 19795. . NREL prints on paper that contains recycled content
4 Preface Providing clean and affordable energy services to the more than 1 billion people globally who lack access to electricity development , and is a critical driver for poverty reduction, economic improved health and social outcomes. More than 84% of populations without electricity are -effective; therefore, distributed located in rural areas where traditional grid extension is not cost -grids are critica l. The International Energy Agency (IEA) projects energy solutions such as mini that to achieve universal energy access by 2030, more than 40% of total investments must be directed toward mini -grids ( IEA 2010) . Diesel engines have been used quite successfully to provide electric and ot her energy services to communities that cannot be reached by extensions of the existing grid. However, utilizing diesel s; the rising cost of technology has inherent drawbacks: limited improvements in diesel engine delivered diesel fuel ; and the environment al impacts of diesel fuel transportation, use, and storage . Therefore, efforts to expand energy access must include options beyond diesel . Although conventional and new mini -grid technolog ies have improved greatly over the past 10 years, successful efforts to provide energy services by utilizing advanced mini -grids have remained elusive. -term power to un- With growing interest in the use of mini- grids to supply near electrified communities across sub- Saharan Africa and Asia, the need to expand beyond traditi onal energy echnology and business models continue delivery and financing models has become apparent. T to evolve, and the following are still needed: developing methodologies allowing project bundling ; developing the ability to assess long -term project risks ; reducing project costs by expanded community learning and localizing the development process; collectin g system information to allow data ; and providing guidance to -driven technology assessment organizations, both financial and governmental, on how to implement large -scale isolated power system deployment programs. The implementation of grid -based electrification at a huge scale has been greatly facilitated by the adoption of a series of defined quality assurance measures. This document describes a s imilar framework that can be applied to the mini- he authors expect that with grid market sector. T widespread implementation of these or similar quality assurance procedures ; reliance on appropriate, credible , and consistent technology standards ; and the de velopment of viable business models, large -scale mini- grid -based rural electrification can be completed using a combination of public and private sector funding sources. Success in such an endeavor will greatly impact rural communities, providing all of th e benefits that have been documented by improved access to advanced energy systems : improved health, education, and personal security ; improved economic possibilities ; and a more stable population through political and food security. iii This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
5 Acknowledg ments U.S. The authors would like to acknowledge the support of the U.S. Department of Energy ( DOE) International Affairs Office for supporting the development and implementation of the for m ini -grid power systems Quality Assurance Framework was funded by the U.S. . This work DOE , U.S. Department of State, and the U.S. Agency for International Development. This work is also an activity under the Clean Energy Ministerial’s Global Lighting and Energy Access Partnership (Global LEAP) initiative, Power Africa’s Beyond the Grid initiative, the U.S.- India Promoting Energy Access through Clean Energy (PEACE) initiative, and the S nergy ustainable E for All High Impact Opportunity on Clean Energy Mini -Grids . We would especially like to thank the following individuals who served on a technical review committee for this document and the QAF project : • Chris Greacen, Ph.D: Independent consultant • Arne Jacobson, Ph.D: D irector , Schatz Energy Research Center at Humboldt State University Lilienthal: CEO, HOMER Energy . • Peter related to electrical standards for t he Quality Assurance Framework for mini Technical support - grid development was also provided by Robert Preus, PE: S enior engineer , National Renewable Energy Laboratory . Additionally, we would like to thank the participants of several stakeholder consultation workshops during which the ini -grid s was reviewed in Quality Assurance Framework for m detail. The challenges of providing power to rural populations are many and multi -faceted. It is hope d that the concepts portrayed in the Quality Assurance Framework for m ini -grid s will help to address some of these challenges, an outcome made more likely by the guidance and insight provided by the people named above. iv This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
6 Abbreviations and Acronyms alternating current AC American National Standards Institute ANSI direct current DC Global Lighting and Energy Access Partnership Global LEAP International Energy Agency IEA IEC International Electrotechnical Commission IEEE Institute of Electrical and Electronic Engineers kW kilowatt kV kilovolt MW megawatt NREL National Renewable Energy Laboratory O&M operations and maintenance rms root -mean -square PEACE Promoting Energy Access through Clean Energy (India) P-SAIDI Planned System Average Interruption Duration Index P-SAIFI Planned System Average Inter ruption Frequency Index pu per unit peak pk- pk -to-peak (in terms of voltage fluctuations) QA ssurance quality a QAF Quality Assurance Framework SAIDI System Average Interruption Duration Index SAIFI System Average Interruption Frequency Index U.S. DOE U.S. Department of Energy Volt V v This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
7 Executive Summary Providing clean and affordable energy services to the more than 1 billion people globally who is a critical driver for poverty reduction, economic development , lack access to electricity without electricity are improved health, and social outcomes. More than 84% of populations located in rural areas where traditional grid extension may not be cost , -effective; therefore distributed energy solutions such as mini -grids are critical. The International Energy Agency (IEA) projects that to achieve universal energy access by 2030, more than 40% of total grids investments must be directed toward mini- . ( IEA 2010) , and f inancially viable mini- To address some of the root challenges of providing safe, quality er systems to remote customers , the U.S. Department of Energy (DOE) teamed with the grid pow National Renewable Energy Laboratory (NREL) to develop a Q uality A ssurance Framework (QAF) grid power system s. The QAF for mini -grids aims to address some root for isolated mini- challenges of providing safe, quality , and affordable power to remote customers via f inancially viable mini- grids through two key components : (1) ervice framework : Defines a standard set of tiers of end -user service and links Levels of s them to technical parameters of power quality, power availability, and power reliability. These levels of service span the entire energy ladder, from basic energy service to high- quality, high- e (often considered “grid parity”) reliability, and high- availability servic (see Table ES -1). (2) Accountability and eporting f ramework : Provides a clear process of performance r by providing trusted information to customers, funders, and/or validating power delivery regulators. The performance reporting protocol can also serve as a robust monitoring and evaluation tool for mini -grid operators and funding organizations . -grids will provide a flexible alternative to rigid top -down standards for mini - The QAF for mini grids in energy access contexts, outlining tiers of end- user service and linking them to relevant technical parameters. In addition, data generated through implementation of the QAF will provide the foundation for comparisons across projects, assessment of impacts, and greater confidence -up in this sector. T he QAF implementation that will drive investment and scale process also defines a set of implementation guidelines that help the deployment of mini -grids on a regional or national scale, helping to insure successful rapid deployment of these relatively new remote energy options. Note that the QAF is technology agnostic, addressing both alternating current (AC) and direct current (DC) mini , and is also applicable to renewable, fossil -fuel, -grids and hybrid systems. The QAF is being joint .S . DOE and NREL as a program of the Clean ly developed by the U Energy Ministerial’s Global Lighting and Energy Access Partne rship (Global LEAP) initiative. The QAF project was initiated as a priority activity within the PEACE (Promoting Energy Access thro ugh Clean Energy) Action Plan, the energy access initiative of the bilateral U.S. - India Partnership to Advance Clean Energy ’s Beyond the . The QAF is also part of Power Africa Grid initiative and Sustainable Energy for All’s High Impact Opportunity on Clean Energy Mini - Grids. The QA F can drive improved sustainability , greater market confidence, and expanded investment in this important off -grid sector by achieving the following: vi This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
8 • ry of power through mini -grids. The Facilitating safe, quality, and affordable delive QAF levels of service ensure basic safety while matching service delivery to customer This in turn can help strengthen a project’s revenue flows and needs and ability to pay. s financial optimize its system design and operability, which will increase the project’ viability . QAF • Providing a formalized, common standard for classifying energy consumers levels of service also allow a common basis for assessment of community energy needs, community assessment and site selection efforts, as well as facilitating streamlining improved forecasting of energy needs across a community, region, and nation. • -grid projects and unlocking private investment. A Facilitating aggregation of mini suppor ted by common classification system for customers and level of service provided, the QAF’s standard monitoring and performance reporting protocols, will make it easier , facilitating access to larger -scale fi nance at more competitive to bundle projects together . Data generated from implementation of the QAF can be a source of robust sector - rates wide market intelligence on the typical technical and non- technical characteristics of mini- grid systems (e.g., payment collection rates, customer characteristics, and electrification rates), which over time will increase investor confidence and lower the risk grid s, further decreasing barriers to private investment a nd profile of mini- power system driving scale in the sector. Inform ing • while helping to standardize regional policy and regulatory frameworks rural electrification depl oyment efforts . Defining a standard set of customers and an accountability -based reporting framework forces structure on larger rural electrification efforts using mini- grid power systems, providing regulatory clarity while hopefully minimizing the regulat ory burden by providing a simple set of reporting requirements aligned with specific project stakeholder . Defining specific customer reporting also needs leads , resulting in a better to the implementation of simple consumer protections consumer service tha t will be reflected in willingness to pay for a high -quality energy service. The following f how key stakeholders (investors, government s, igures summarize developers/ for , and customer s) are involved in the development of mini -grid systems suppliers -1) and how the QAF the provision of energy services (Figure ES can be applied to facilitate the -2). provision of energy services (Figure ES vii This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
9 Governments Investors • Enact policy to support energy access May support initial project development efforts • • • Develop rules and regulations for the provision Provide funding for energy projects of energy services Provide funding for companies that supply • energy services or energy service technology • May supply funding or other services to support expansion of energy access May define conditions or requirements for • May support initial project development efforts, funding, depending on organizational goals • including information gathering • Define design, reporting, and operational traits Institute that should be common across multiple . • reporting requirements projects and power systems . electrification Developers/Suppliers Customers • pay Assess energy needs for a community/region Use energy services as needed or able to • for operate Develop, construct, commission, and/or • energy systems providing power • Pay energy providers for the energy consumed • Collect revenue from the sale of energy services • Report issues with e nergy service to the utility or regulatory organization. Conduct long- • term energy needs planning for power systems under their purview . -grids sector Figure ES -1 . Stakeholder involvement and roles in the mini viii This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
10 Governments Investors • Integrate level -of-service concepts into • Integrate level -of-service concepts into community and initial system assessments community and initial system assessments • Use QAF concepts as part of system • Use QAF concepts to inform definition performance criteria, including specification of developer/ supplier selection process a minimum level of service as appropriate • Use QAF concepts to inform definition of concepts as part of system QAF Use appropriate performance criteria • developer/ supplier selection process through robust performance tracking Implement • Implement long- • term performance tracking standard QAF processes for key technical and operational indicators • Collect performance data to ensure • compliance long- assessment performance term Facilitate sustainability improving and forecasting, and more actionable data mproved Provide i • • Enable aggregation and bundling of projects on rural energy use and needs • -grids Enable increased understanding of mini • Provide customers with a grievance process . risk profile • . data on rural energy use and needs Improve Developers/Suppliers Customers Access • • -of-service concepts into Integrate level safe, quality, and affordable energy community and initial system assessments services their level of Know how to determine whether • Use level -of-service information to optimize • paid for design system service meets the service -of-service and customer affordability • • Use level Better understand the level of service they are purchasing, which defines expectations of rate structure that can information to identify a availability cover costs energy Collect data to demonstrate operation, service • Alert regulators or power providers of any • levels, and payment . concerns -of-service concepts to understand • Use level load growth, leading to an customer understanding of system expansion needs term performance assessment Facilitate long- • forecasting. and Figure ES -2. Main applications and benefits of QAF to mini -grids sector stakeholders The QAF defines three basic levels of power quality, bracketing service between a basic level that protects consumers and a high, grid parity level of service. Table ES.1 provides a high- level summary of these standards from a power quality and system performance perspective. ix This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
11 Table 1. Summary of Level of Service ES- Level of Base Level of Standard Level of High Issue Service Service Service AC Power Quality Phenomena <10% Voltage <2% imbalance <5% protection Surge protection No protection Transients Surge voltage duration Short <5/day <1/day <1/week variations voltage duration Long <10/day <5/day <1/day variations 48 Hz < f <52 Hz 49 Hz < f <51 Hz 49.5 Hz < f <50.5 Hz Frequency variations DC Power Quality Phenomena <10% <5% <2% Resistive voltage drop 50% peak to peak -pk Percent ripple 10% pk 20% pk -pk -pk) (pk DC ripple & switching Transient noise Ripple noise also Unfiltered minimized minimized noise Transients No protection Surge protection Surge protection <5 per day <2 per day <1/day Faults allowed per day Reliability Power (1,3) <2 per year Unplanned- <52 per year <12 per year SAIFI XX <876 hours (90% <438 hours (95% <1.5 hours (99.99% (1,3 ) Unplanned- SAIDI XX reliability) reliability) reliability No requirement but No requirement but (1,2 ) SAIFI Planned- <2 per year XX should be defined should be defined No requirement but No requirement but 100% <30 minutes - (1,2) Planned- SAIDI XX should be defined reliability should be defined (1) System Average Interruption Frequency Index (SAIFI) measures the average number of power outages that an average customer Total Number of Customer Interruptions/Total Number of Customers experiences in a year and is defined as Served. (2) System Average Interruption Duration Index (SAIDI) measures the average number of minutes that an average customer is without power over the defined time period, typically a year . (3) SAIFI and SAIDI are typically assumed for power systems that are specified to provide full -time energy service 24 or systems th hours/day. A s ubscript is used in this report f at provide partial hours/day service since the number of planned and unplanned interruptions and length of any interruptions should be normalized by the percent of hours of service. x This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
12 Additionally, the QAF defines power availability levels that mirror the multi- ramework tier f Bhatia but defines them separately, giving defined by the World Bank ( and Angelou 2015) system designers and operators the flexibility to specify the amount of energy consumers can expect. Like the m tier f ramework, power availabil ity is defined by three parameters : power ulti- draw, energy availability, and the duration of daily service. Through the accountability framework, the QAF defines guidelines for customer and utility ems are operating in a defined and reporting, helping all stakeholders better understand how syst outwardly consistent way. Utility accountability is defined with both technical and business information, including: • Technical information: Measurements addressing system performance, energy usage, safety concerns, and op erational issues • Business information: Measurements that allow an understanding of overall energy usage, payment rates, cost of system operations and . Through the implementation of the QAF , developers of multiple mini- grid projects will benefit tency and inter reporting requirements , including the from consis -system learning. Specifying that reporting is accurate, helps to frame what to date has been a verification process to insure very unstructured development process. The application of the independently developed QAF implementation guide ( to be released s oon) will also help provide guidance on the ways that the QAF can be implemented as part of a larger development process. If you wish to discuss this report or any information contained within it, please contact: Ian Baring -Gould National Renewable Energy Laboratory 15013 Denver West Parkway Golden, CO 80401 USA Ian.Baring [email protected] 7021 303- 384- xi This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
13 Table of Contents iii Preface ... ... Introduction 1 1 ... Definitions 1.1 1 -Grids to Support Universal Energy Access 1.2 1 Mini ... Key Barriers to Scaling up Mini -Grids ... 3 1.3 Mini -Grids as Mini -Utilities ... 1.4 4 -Grid Power Systems ... 5 1.5 Standards Associated with Mini Introduction to the Quality Assurance Framework 8 2 ... Overview of the Quality Assurance Framework ... 8 2.1 Levels of Service Framework Overview 9 2.2 ... ... 9 2.2.1 Power Quality Power Availability ... 10 2.2.2 2.2.3 10 Power Reliability ... Accountability Framework Overview 11 2.3 ... Customer Accountability ... 11 2.3.1 Utility Accountability 11 2.3.2 ... ... 12 2.3.3 Monitoring and Performance Reporting Process Levels of Service Framework ... 13 3 13 3.1 Power Quality ... ... 15 3.2 Power Availability Peak Available Power (Amps or Watts) ... 16 3.2.1 ... 16 Energy Available per Time Period 3.2.2 Duration of Daily Service ... 17 3.2.3 ... Time of Daily Service 17 3.2.4 3.3 ... 18 Power Reliability Accountability and Performance Reporting Framework 21 4 ... Consumer Accountability 22 ... 4.1 Level of Service Verification ... 22 4.1.1 Service Agreement ... 23 4.1.2 Utility Accountability ... 23 4.2 Technical Reporting ... 24 4.2.1 ... 26 4.2.2 Business Reporting Monitoring Processes ... 27 4.2.3 Conclusion ... 30 5 ... References 31 Bibliography ... 32 Appendix A: Power Quality (AC) ... 33 A.1 ... 33 Voltage Imbalance ... 33 A.2 Transients Short -Duration Voltage Variations ... 34 A.3 Long Duration Variations ... 35 A.4 Frequency Variations A.5 36 ... Appendix B: Power Quality (DC) ... 37 B.1 Resistive Voltage Drop ... 37 B.2 ... 37 DC Ripple B.3 Switching Noise ... 38 B.4 Transients ... 39 39 B.5 Short - and Long -Duration Variations ... Appendix C: Sample Customer Disturbance Recording Form ... 40 41 Appendix D: Sample Technical Reporting Form ... ... Appendix E: Sample Business Reporting Form 43 xii This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
14 List of Figures 1. Stakeholder involvement and roles in the mini -grids sector ... viii Figure ES- 2. Main appl ications and benefits of QAF to mini -grids sector stakeholders ... ix Figure ES- -voltage. By Biezl (own work) [public domain], via Wikimedia Commons. Figure 1. Transient over ... 34 https://commons.wikimedia.org/w/index.php?curid=4676389 ... 34 Figure 2. Oscillatory transients Figure 3. DC ripple based on the output of a rectified AC power source. Image from Spinning Spark, https://en.wikipedia.org/wiki/File:Smoothed_ripple_gray_background.svg ... 38 List of Tables Table ES -1. Summary of Level of Service ... x Table 1. Summary of Levels of Service for Power Quality ... 13 Ta ble 2. Peak Power Levels ... 16 Table 3. Energy Use per Service Level ... 17 Table 4. Duration of Daily Service ... 17 Table 5. Time of Day Service 18 ... Table 6. Unplanned Power Interruptions, Assuming 24- ... 19 Hour Service Table 7. Planned Power Interruptions ... 20 Table 8. Levels of Service for % Voltage Imbalance ... 33 Table 9. Protection against Transients for D ... 34 ifferent Levels of Service Table 10. Number of Short -Duration Variations for Level of Service ... 35 Table 11. Number of Long- Duration Variations for Level of Service ... 36 Table 12. Range of Frequency for the Level of Service 36 ... Table 13. Percent Voltage Drop for a Level of Service ... 37 Table 14. Ripple for Given Level of Service ... 38 Table 15. Switching Noise for a Given Level of Service ... 39 Table 16. Transient Protection for a Given Level of Service ... 39 39 Table 17. Number of Faults Allowed Per Day for a Given Level of Service ... xiii This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
15 1 Introduction -level public -private roundtable on mini One of the key recommendations from a high -grids at the , in 2013 was to “develop standards to set a Fourth Clean Energy Ministerial in New Delhi, India level playing field, encourage investment, and drive down prices.” As a result of this recommendation, the U.S. Department of Energy (DOE) teamed with the National Renewable Laboratory (NREL) to develop a Quality Assurance Framework (QAF) for isolated mini- Energy power system s. This project was initiated in 2014 as a central component of the U.S grid -India Promoting Energy Access to Clean Energy (PEACE) initiative and is also part o f the Clean Global Lighting and Energy Access Partnership (Global LEAP) initiative, Energy Ministerial’s Grid initiative, and the Sustainable Energy for All Clean Energy Power Africa’s Beyond the Mini -Grids High Impact Opportunity. 1.1 Definitions Building on the International Electrotechnical Commission (IEC) 62257 series definition of a 1 2 -grid , the QAF micro -grids is as follows: ’s proposed definition for mini “A m ini -grid is an aggregation of loads and one or more energy sources operating as a sin isolated from a main gle system providing electric power and possibly heat power grid . A modern mini -grid may include renewable and fossil fuel -based generation, energy storage, and load control. Mini -grids are scalable so that additional generation capaci ty may be added to meet growing loads without compromising the stable operation of the existing mini- grid system. ” This proposed definition encompasses small, AC -based systems serving multiple - and DC customers through community -based power systems typical anging between approximately 5 ly r kW kilowatts ( MW ) in size and with only distribution- level electrical ) to 1 megawatt ( interconnection. System voltage levels are less than or equal to the country’s distribution voltage level ( typically 13 kilovolts, or kV , and in some cases 33 kV ). Note that in energy access contexts grid and micro- grid are often used interchangeably, and the proposed , the terms mini- definition above captures both terms with respect to isolated (i.e., not grid connected) systems relevant to energy access contexts. 1.2 Mini -Grids to Support Universal Energy Access Providing clean and affordable energy services to the more than 1 billion people globally who lack access to electricity will be a critical driver for poverty reduction, job creation, and improved health and social outcomes. More than 84% of populations without electricity are located in rural areas where traditional grid extension is not cost -effective; therefore, distributed -grids are critical. national Energy Agency (IEA) projects energy solutions such as mini The Inter 1 The IEC 62257 series Recommendations for Renewable Energy and Hybrid Systems for Rural Electrification provides a definition for a micro -grid that focuses more on the distribution netwo rk of small, isolated electrical systems (IEC TS 62257 -1:2015). 2 -grid ” has developed added specificity in some circles to include energy systems that typically The term “micro operate directly connected to a larger central grid but can also operate discon nected from that grid. For this reason, the term “ mini -grid ” uses generally the same definition but assumes that the power system will not be connected to a - larger central grid; and if it eventually is connected, it becomes a subset of that grid or can the n become a micro grid, which can be connected or disconnected from that grid as desired. 1 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
16 that to achieve universal energy access by more than 50% of unserved people will receive 2030, grids IEA 2010) . service through mini- power systems ( There are several advantages to utilizing mini -grids and other decentralized solutions instead of extending the centralized grid. In some cases, extending the central grid, which is typically a -term and resource -intensive effort, may not be economically feasible , pa longer rticularly for rural and remote populations in the near, mid, or even long In contrast , mini -grids can be term. deployed more rapidly ed to local needs , and can better utilize local energy , can be customiz resources. Mini -grids are also scalable and expanda ble to match demand as it grows. Hybrid mini- grids —systems that combine renewable energy generation with fossil -fuel -powered generators —can be used to increase reliability and provide 24 -hour power. Beyond residential -grids can also powe -level uses that drive local applications, mini r productive and community -economic development. Finally, modern mini -grids incorporate smart and efficient socio technologies, improving load management and overall system operation. Despite the growing interest in mini- grids a nd the relative maturity of the technologies underlying them, there are a number of barriers to scaling up deployment. Demonstrating commercially sustainable models and attracting low -cost financ ing are two particularly significant challenges are linked to a number of factors , such as significant up -front . These issues investments required, difficulty in assessing local energy needs , uncertainty over a customer ’s ability and willingness to pay for service, typically limited local technical capacity, as well as limited proven track record and high perception of risk by investors. In addition, uncertain policy and regulatory environments in many countries (e.g., lack of clarity on grid extension plans, interconnect ) significantly impede ion, and others tariff structures, licensing procedures, grid mini- grid development. Lack of l - ocal technical expertise to enable maintenance and ensure long mini- grids are custom term sustainability, lack of standardization (most , and lack of designs) standard operating procedures and quality standards are all barriers. While flexibility must be maintained to allow for local conditions, some level of standardization would decrease risk and cost for system development . Finally , all players (investors, governments, customer s, developers) require sufficient data and information about the sector to better evaluate the market and strengthen confidence in mini- grids as a viable electrification pathway. Many s olutions have been proposed to address these concerns , including : • Encouraging l ocal involvement and ongoing training/capacity building Support • ing R&D and demonstration projects to enable experimentation with technologies and business models Developing a pproaches to strengthen business models , business practice, • l and operationa , such as: efficiencies economic development opportunities and incorporatin Inclu ding o g anchor tenants o Develop ing and incorporating smart technologies such as theft protection, pre - payment meters , and load management technologies -use o Promoting use of super -efficient appliances, equipment , and other end . technologies 2 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
17 • Increasing public and private financing options, including leverag ing public -sector private capital inflows into the sector funding to catalyze increased • Strengthen ing enabling policy and regulatory frameworks Collecting and sharing information that track s demand, assess • energy resources, ing document ing best practices , and allow ing new ideas to build on the documented success es and failure of other projects • Track ing min i-grid development and performance , including through c ollecting d ata on existing mini- grid companies and projects ing investment flows and document Develop ing regional development or deployment models to expand the economies of • scale through leveraging mul tiple projects. These are complex, multi -faceted challenges, but crucial fora such as the Sustainable Energy for 3 All’s High Impact Opportunity on Clean Energy Mini -Grids are working to convene stakeholders to strengthen the overall ecosys tem for mini- grid development. The rem ainder of this report will focus on the QAF for mini -grids, an effort that aims to address a few of the root challenges discussed above. -Grids Key Barriers to Scaling up Mini 1.3 While the fundamental electrical engineeri ng principles of mini- grids are well established, the grid construction and operation vary considerably in practice, and projects can details of mini- experience extreme var iations in power quality and reliability. The lack of common operation, nd financial practices results in a high -risk market of many individual projects that reporting, a discourages private investment, which limits funding opportunities. Demand for electrification accurate billing, low through mini -grids is hampered by uncertainty about the quality of service, reliability, and safety. This creates a major barrier to the scale- up and aggregation needed to reduce transaction costs and attract the commercial financial investments that are required for rapid and widespread deployment. Developing successful business models that will allow this up remains challenging. scale- Business models for utilities in mature energy markets work because the foundational roles and relationships among the stakeholder groups are well defined. Although a wide array of viable business concepts are used in rural energy markets, all of these have been developed based on a standard set of foundational principles. In the case of rural electrification, th e utility models break down as a result of three main chal lenges: The high cost of providing power to remote customers • • Inconsistent cash flows from customers to the power supplier • Poorly understood investment risk profile due to the small number and high variability of projects . Mini -grids also differ based on the region, customers, and the available resources , which complicate the investment and development landscape . Because of their unique characteristics , mini- grids require separate development and performance guidelines that address those 3 mini -grids http://www.se4all.org/hio_clean -energy- 3 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
18 differences. Additio -utility r egulations could make mini -grid options nally, traditional large the unique needs of rural and remote regions, such as operations unaffordable and do not address and maintenance (O&M) challenges . Mini -Grids as Mini -Utilities 1.4 The modern utility sector is a model developed to address many of the challenges identified in this sector. Although this may seem obvious, many of the simple processes that are employed in -grids . Some of the utility sector are not employed in the development or consideration of mini these standard practices include: • Standard customer classifications • Defined power -quality provisions • customer and the utility Defined contractual relations between the Collection and maintenance of customer • and other general information • Developm ent of economies of scale to reduce development, deployment, and operational costs . Although it is understood that the utility sector is not considered a model of best practice (man y utilities in developing countries struggl e to provide basic ener gy services while globally maintaining a viable business model ), the sector in many mature economies such as the U nited States and Europe has been very successful. One of the goals for the QAF is to help lay the the mark foundation in the mini et to develop by incorporating many of the ing -grid sector , allow successful features of the developed- world utility model. grids are generally small, support a clearly defined service area, and are Given that mini- typically being implemented as new power systems, the use of ut ility principles as defined in the nsure wider success of the sector, even if the larger electric utility industry for QAF will help e that region is struggling . There are many aspects of a small , community -based mini -grid -style power system that may make it more successful than larger utility -style systems. There are several qualities of a utility model that , if applied to the off -grid market sector in a consistent way, will help the industry sustainably expand. These include: : • Standardization of customers Since energy use is quite uniform across families and communities (i.e., the statistical distribution of energy needs in one community is s), the classification of user energy needs unlikely to be that different from its neighbor on of customers. This aggregation allows economies of scale as allows for easy aggregati easier to plan and predict future energy needs once a baseline of well as making it much information has been obtained. Because of this standardization of customer information, data collected f rom communities served by other providers can be used in planning for both initial implementation and growth , further reducing known risks. • Diversification of risk: Utilities are typically well diversified, with many customers over relatively large areas . This partially insulate s utilities from micro -scale market and technology changes. In rural electrification , diversification also assists in reducing overall , but if the utility is diversified, ; a power plant or transmission line may stop working risk 4 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
19 the revenue streams and economies of scale of the larger supply network help limit s. By its nature , one mini impacts on customer -grid is very dependent on local conditions, grids with the same development -utility or investor that operates multiple mini- but a mini and reporting structures different ) gains diversification that will ( even if the technology is help define the sustainability of all the mini- grids. Long- • Successful utilities collect information about current energy term data gathering: usage. This information ( power generation, sales, payment and disconnect rates, losses, th by customer class , etc. ) not only allows the utility to operate more efficiently load grow but also greatly improves planning and provides a solid record of account balances , which greatly reduces the potential risks that concern investors. • Economies of scale across a utility system: The ability of a utility system to aggregate large numbers of customers allows increasing economies of scale throughout the O&M system. -grid s deployed to date , however , typically lack many of the successful characteristics found Mini in modern utilities. First grids deployed to provide initial energy services in under - , mini- developed areas provide a high -cost service to customers who are, in general, economically challenged . Although additional funding sources can be used to make providing services more 4 affordable ( , development grants, identification of anchor clients , subsidies economic development assistance, etc. ), the basic b usiness model of energy supply for remote, rural electrification remain s challenging. In addition, the small number of customers for each mini - grid and the lack of economies of scale for most remote power applications can lead to reduced power quality and reliability, typically resulting in reduced project income as customers are reluctant to pay for low issues associated with -quality service; this situation in turn compounds company viability and equipment reliability. Lastly , a small sults in the number of projects re or transparency limited availability in performance information, which further limits economic investment in the companies that make up this sector. The implementation of a str onger utility an address some of these challenges. model, including the bundling of multiple projects, c Although the QAF does not provide a direct solution to all of these issues, it s standard level of service tiers and accountability and performance reporting elements provide a consistent foundational framework to help a ddress many of the critical faults currently found in the mini- grid market sector -needed flexibility . while retaining much 1.5 Standards Associated with Mini -G rid Power Systems 5 International and domestic standards are a major force in the development and implementation of the electric sector, helping to ensure high -quality, safe, and reliable energy services. 4 is a large private ( or in some context s public ) energy power systems An anchor client in the context of isolated that can provide a consistent source of project income from high -value energy sales . In many rural customer schools or health clinics , a local industry, cellular provider, or government services ( e.g., ) can act as communities anchor client promptly. In many cases , power can be provided to such clients at a lower cost than the s if they pay entities are paying for energy services directly, creating additional benefits across the community. T he existence of strong anchor clients can help reduce the perceived risk by private sector investors as they can provide a defined source of long- term revenue. 5 The generic term “standards ” typically encompasses a wide array of accepted and agreed -upon co nditions that can , and actual standards. Each cover a range of different understandings , including guidelines, technical specifications s a different level of general market consensus that new or differing results will not be of these terms designate 5 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
20 International standards typically try to set common frameworks that allow equipment and ied widely, creating economies of scale across the power sector. Domestic services to be appl standards expand upon and in some cases modify international standards based on local needs n the absence of a national standard and design practices. International standards may be applied i or if a project will be applied over several nation states, again lowering overall project costs. The role that international standards have played in the development of the power sector should not be underestimated. The ability of equipment to be designed and built universally and then -cost products that can be sourced allows companies to provide lower applied almost globally almost anywhere. Common design standards allow power sector workers to move freely, building ing consisten t syste ms and equipment . Without such common frameworks, the or repair world would be a very different place. 6 Some of the more accepted standards include those by the IEC and the Institute of Electrical and 7 8 ). using American The National Fire Protection Association Electronic Engineers ( IEEE 9 National Standards Institute (ANSI) al Code procedures developed the U.S. National Electric international deployment of power systems. Additionally, organizations that is used widely in the t practice guides which , although not standards, have such as the World Bank have funded bes function in been adopted widely across the developing world and in many ways serve a similar international standards. the absence of In the design and development of mini -grid power systems, several types of standards are applicable. Initially the IEC developed design and safety standards for many of the components that make up power systems, such as IEC 61215, Crystalline Silicon T erre strial P hotovoltaic 10 nsure that the Other standards help e ype A odules . (PV) M - Design Q ualification and T pproval additional elements of the power system are designed in a consistent way IEC 60287, (e.g., which specifies the ratings of electrical cables that may interconnect equipment , or IEC 60364- 7- nstallations of B uildings Electrical I which addresses the electrical interconnection of 712:2002, , a building ). (TC s) and Project C ommittees (PC s) that develop The IEC is divided into Technical Committees 11 of primary interest for mini- grid Although not an exhaustive list, the committees standards. power systems are the following: TC 2 : Rotating machinery • TC 4 • : Hydraulic turbines (hydropower) • : Systems aspects for electrical energy supply TC 8 found. For example , a guideline is issued when the developing organization s that a specification is warranted feel but new ideas or technologies may be identified that would fall outside of or make th e guideline obsolet e. This document uses the words “standard” or “standards” to cover all of these descriptions. 6 http://www.iec.ch/ 7 http://www.ieee.org/index.html 8 http://www.nfpa.org/ 9 https://www.ansi.org/ 10 http://ulstandards.ul.com/standard/?id=61215_1 11 A list is available at http://www.iec.ch 6 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
21 • TC 13 : Elect rical energy measurement and control : Secondary cells and batteries • TC 21 TC 64 : Electrical installations and protection against electric shock • • TC 82 : Solar photovoltaic energy systems • TC 88 : Wind energy generation systems • TC 114: Marine energy – w ave, tidal, and other water current converters • Smart grid user interface PC 118: • Electrical e nergy storage s ystems . TC 120: Other standards , such as ANSI C84.1: Voltage R atings for Electric Power Systems and 12 13 Equipment Recommended Practice for Mo nitoring Electric Power Quality , and IEEE 1159: provide guidance on the electrical output of power systems and how they should be monitored. Recommendations for Small 62257: Lastly, standards such as IEC technical specification TS/ Renewable Energy and Hybrid Systems for Rural Electrification 200 5) provide design ( IEC -grid power systems, although they do not guidance on the development and installation of mini provide strong guidance on the interconnection and integration of different generation sources as ated power system. part of an isol As described in S 1.1, micro -grid technology has developed quite extensively , and ection currently there are efforts to develop more defined best practices and standards for these systems. Because these power systems are designed to connect and disconnect from the grid, the need for required. At the time of this writing , more advanced technology, control, and communications is no defined international accepted standards with respect to micro -grids have been developed. It is also unclear if these standards would be applicable to isolated power system s. For the benefits of standards to be r ealized, they need to be enforced. In areas with strong governmental control and institutional functionality, power system developers and operators must operate within defined national standards. A process to document adherence to the appropriate standards is clearly defined and implemented. In other locations, especially in rural areas, government regulat are weak and in many cases not applied. However, to be ions successful over the longer term , companies, funding agencies , and the population should insist , even if they are enforced by government procedures. on the incorporation of standards -grid power systems The QAF was envisioned to fill a known gap in the wide deployment of mini that largely lies outside of existing standards. In fact iate for many of the QAF , it is not appropr concepts to become standards because they lack technical specificity and there is a need to maintain reporting flexibility. Although not defined as standards, expanded uniformity in performance requirements, consumer needs identifi cation, and data collection is helpful. The development of the QAF also helps the industry by introducing a more common language in reference to mini -grid power systems, allowing comparisons between different market suppliers and solution providers. 12 https://www.nema.org/Standards/ComplimentaryDocuments/Contents -and -Scope -ANSI -C84 -1-2011.pdf 13 https://standards.ieee.org/develop/project/1159.html 7 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
22 2 Introd Quality Assurance Framework uction to the -grid business models to be effective as a means to expanding energy access , In order for mini power must be affordable to a customer base that is typically cost sensitive ( limited ability to pay) and provid e quality and reliable service that meet the customer’s needs (willingness to pay). As a result, the ability to deliver value while minimizing costs is a key determinant of the success of mini -grid projects. Yet achieving this balance is challenging due to the high up- front costs for mini- grids and is exacerbated by the ad -hoc and fragmented approach to developing mini- grid s, characterized by a lack of standard technologies and operational best practices, limited sector s. data, and lack of enabling environment The QAF for mini -grids aims to address some of the root challenges of providing quality and -grids by defining (1) affordable power to remote customers through financially viable mini standard technical specifications for power quality, reliability, and availability that are appropriate for different tiers of end- user service, and (2) a standard accountability and performance reporting framework that will provide a clear process of validating power delivery to customers, funders, and/or regulators. The fr amework addresses both AC and DC mini -grids and is applicable to renewable, fossil -fuel, and hybrid systems. The concepts behind the QAF are also independent of the business mode -grid business, but they help ls used for operating a mini define several of th e foundational concepts on which the businesses can be built. The QAF will provide a flexible alternative to rigid top -down standards for mini -grids in energy access contexts, outlining a standard set of tiers of end- user service and linking them to releva nt technical parameters, coupled with a complementary framework for performance tracking and hese core elements of the QAF aim to preserve flexibility while providing a reporting. T e utility in scale and foundational structure that can put the sector on track to resemble a matur sophistication. In addition, data generated through implementation of the QAF will provide the foundation for comparisons across projects, assessment of impacts, and greater confidence that -up in this sector. will drive investment and scale 2.1 Overview of the Quality Assurance Framework Th e QA F has two components: • It define s different levels of service , including appropriate thresholds for power quality, reliability, and availability , which can be used throughout the energy supply proces s, from community assessment through system operations and long -term planning . These levels of service span the entire energy ladder, from basic energy service to high- quality, high reliability, and high- the equivalent to what is available in most availability service ( central grid power systems, sometimes referred to as “grid parity ”) and provide a common technical basis for classifying mini- grids and energy customer . It should also be understood that the definitions of the di fferent levels are intended to be notional ( though in some cases with legal or regulatory backing ) and should not be considered absolute. • It will specify a common accountability and performance reporting framework based on utility models in developed energ y markets that will define a clear process for validating power delivery by providing trusted information to customers, funders, and regulators. The performance reporting protocol can also serve as a robust monitoring and -grid oper ators and funding organizations . This framework will evaluation tool for mini 8 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
23 lay the foundation for sustainable business models in the mini -grid space by clearly . defining the roles and relationships of the various stakeholders The goal of th e QAF is not to mandate a specific lev el of service but rather to define service levels that ensure safe, quality, and affordable delivery of basic grid parity service and to provide an accountability framework that can be used to determine whether an agreed- upon level of service is delivered. It is also understood that any such framework, even if adopted as an international standard, would not supersede domestic standards but would be applied or adapted to support those . standards 2.2 Levels of Service Framework Overview The QAF levels of energy service have three components covering power quality , reliability , and availability. For each of these, the QAF defines technical specifications corresponding to different service tiers. An expanded discussion of the elements that define the l evels of s ervice is 3 of this document provided in Section , while discussions on how the levels of service would be applied are present ed in Section 4 The suggested range for key parameters presented in the QAF has been determined through liter ature searches into similar codes, stakeholder meetings , and interviews with mini- grid installers. The value of a common definition of levels of service goes well beyond simply codifying an agreement between a supplier and consumer of energy services. The following provides some examples of the benefits of the levels of service framework: • Allows a regulator or project funder to define minimum performance criteria for energy supply Allows a utility to aggregate customer s within and across disparate power sy • stems • Provides a common methodology to classify energy users and assess energy needs across communities, nations , or regions • Allows a common methodology for reporting energy usage and assessing trends over time, informing planning activities by project de velopers, operators, and rural electrification agencies . 2.2.1 Power Quality This section of the guidelines defines power quality parameters using common electrical codes in nited S the U tates and Europe as the upper bounds and the minimum power quality that will not damage common electrical appliances (lighting, , etc. ) as the lower bound. household appliances As appropriate, this defined range is also segmented to reflect differing power quality needs based on the expected load types. Both AC and DC systems are addressed from a power quality perspective. Power quality in the QAF is characterized by the following elements: • Voltage imbalance (AC) ning (AC, DC) Transients often caused by light • 9 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
24 • Short -duration variations (AC, DC) -duration variations (AC, DC) • Long • Freque ncy variations (AC ) Resistive voltage drop (DC) • • DC ripple (DC) Switching noise (DC). • 2.2.2 Power Availability Power availability can be defined by three basic parameters , as introduced in the World Bank’s multi- ramework developed by Mikul Bhatia and N icolina Angelou ( Bhatia and Angelou tier f 2015) : • Power d raw (in a mps or w atts ): The maximum power draw in amps or watts available to a customer or a class of customers. Six service levels are specified between a minimum of 3 watts through greater than 5,000 watt s. A lthough 3 watts is considered small in terms of service for mini -grids, conversations with system operators indicate that systems providing service as low as 20 watts are being implemented and 3 watts maintains consistency wit h the multi- tier f ramework . customer • : The amount of energy available that a Energy available ( over a time period) or class of customer s would be expected to use . This is i ndependent of how the customer tier energy consumption. Expanding on the ranges provided in the multi- is charged for structure, aggregated energy usage starting from 365 W att -hour /month (12 framework -hour /day and 4.38 kWh/year) through greater than 600 kWh/month (20 kWh/day Watt currently being considered. This value is high for a standa rd rural and 7,300 kWh/year) is residence but may not be appropriate for a home with an integrated small business. Duration of daily s ervice: Independent of system reliability, energy service can be • power 24 hours -service per day or may only be provided for spe provided for full cific hours per day. Additionally, the specific time of day when service is provided is also can be defined on a consumer needs basis . Service relevant. Duration and time of day tiers under this category are defined based on the level of certainty with whi ch hours of service are guaranteed. These parameters will directly impact the size and type of power system that will optimally provide the specified levels of service. Additionally, an increase in any of these parameters means an increased level of service that could result in a different service charge due to additional power system capacity required to provide that service. The QAF does not attempt to specify a price for service or even the means for collection, serving only as a framework that specifies different expectations of service for both the consumer and provider. 2.2.3 Power Reliability -grid, Beyond power quality, the reliability of that power is also relevant. In the context of a mini power reliability can be addressed through two common assessment terms for electrical outages, considering both the frequency and duration of those outages: 10 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
26 reporting also allows regulators, funders, and other organizations a better unde rstanding of the - and long near -term condition of businesses in the utility sector, both technical and financial. This allows a better understanding of the market risks for current and future investments and is documented through two levels of formal performance reporting: • Technical information: Measurements addressing system performance, energy usage, safety concerns, and operational issues, such as: Periodic, random, and documented end user voltage surveys to ensure proper o service, primarily focused on customer power quality o Central station power quality o System efficiency (including measures of distribution losses [kWh generated vs. kWh sold] and power production [kWh generated vs. measure of fuel]) Percent of renewable energy contribution over a defined t ime period. o • Business (non- technical) information: Measurements that allow an understanding of overall energy usage, payment rates, and cost of system operations, such as: o Electrification and payment rates of customer o Customer characteristics, including load growth by market sector o O&M, repair, and management costs Safety issues or incident reports. o In addition to the above -mentioned operation and financial reporting, other documents should be ssioning reports, O&M logs, and ready available, such as generic user agreements, system commi standard rate schedules. 2.3.3 Monitoring and Performance Reporting Process of data collection General accountability will only be achieved if a defined and validated process . This monitoring and performance reporting process would likely and reporting is maintained include a combination of automated and manual data recording, with defined reporting systems that would be independently verified. If the QAF is implemented as part of a national or sub- national, multi- communi ty electrification program, developing and document ing the data collection , reporting , and validation process will need to be implemented as part of early program development. Additional guidance on monitoring and reporting processes is provided in 4, and sample technical and business reporting forms are provided in Appendices C and Section D. This guidance is based on a combination of industry best practices from the mature utility sector and input from mini -grid stakeholders during QAF consultation workshops. However, while the QAF provides general guidance and recommendations, it does not prescribe detailed monitoring and reporting procedures (e.g., instrumentation, measurement frequency, data management, etc.) in order to preserve flexibility on the part of project regulators, investors, and developers. The base level of information recommended may be extensive and too costly for a small, low -cost system but insufficient for a larger, multi- technology mini -grid system. More specific information is being developed as part of the forthcoming QAF implementation guide, technical validation documentation, and through the initial implementation of the QAF on real widely. earning from these activities will be shared mini- grid syste ms. L 12 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
27 3 Levels of Service Framework s an overview of the levels of service and the three : power 2 provide Section related factors quality, power availability, and power reliability. Each of these factors is discussed in more detail in the following sections. 3.1 Power Quality This section presen ts in detail the different level of service elements for power quality within the QAF. Three tiers of power quality are specified for each characteristic: base, standard , and high. is commensurate with The base level ensures a minimum threshold of safety, while the high level grid systems. Table 1 provides a high- level summary of the levels of service for power mature quality that are presented in the remainder of this section. Table 2. Summary of Level s of Service for Power Quality Base Level of Standard Level of Level of High Issue Service Service Service AC Power Quality Phenomena imbalance <10% Voltage <5% <2% Transients No protection Surge protection Surge protection Short -duration voltage <1/week <5/day <1/day variations Long voltage- duration <1/day <5/day <10/day variations 49 Hz < f <51 Hz 49.5 Hz < f <50.5 Hz variations 48 Hz < f <52 Hz Frequency DC Power Quality Phenomena Resistive <5% <2% voltage drop <10% 50% peak to peak 14 ripple Percent 20% pk -pk 10% pk-pk (pk-pk) DC ripple & switching Transient noise Ripple noise also Unfiltered minimized minimized noise protection Transients No protection Surge Surge protection <5 per day Faults allowed per day <2 per day <1/day Power Reliability (1) Unplanned- SAIFI <52 per year <12 per year <2 per year XX 14 It should be noted that how and where percent ripple is measured has the potential to greatly impact the results of the measurements. See http://www.eetimes.com/document.asp?doc_id=1273282 13 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
28 Level of Issue Level of Standard Level of Base High Service Service Service <1.5 hours (99.99% <438 hours (95% <876 hours (90% (1) SAIDI Unplanned- XX reliability) reliability reliability) No requirement but No requirement but (1) Planned- SAIFI <2 per year XX should be defined should be defined No requirement but No requirement but 100% <30 minutes - (1) Planned- SAIDI XX should be defined should be defined reliability (1) SAIFI and SAIDI are typically assumed for power systems that are specified to provide full time, 24 hours/day, of energy serv ice. A subscript is used for systems that provide partial hours/day service since the number of planned and unplanned in this report interruptions and length of any interruptions should be normalized by the percent of hours of service. There are many common de finitions of power quality (Bollen 1999 ); however , the one that captur es the primary end result is : “maintaining the near sinusoidal waveform of power distribution bus voltages and et al. 2011) . currents at rated magnitude and frequency ” ( Chattopadhyay An assessment of p ower quality is basically the documentation of the deviations of voltage , setting characteristics (symmetry, frequency, magnitude, and waveform) from the ideal ; thus characteristics of the voltage within standards on power quality is related to maintaining the certain limits. Power quality is an economic issue for utilities and customers. Poor power quality ower supply costs , whereas poor for the utility leads to unsatisfied customers and increased p , equipment damage, and power quality for the customer may lead to equipment inoperability reduced system safety . -grids are simpler than AC mini- grids with respect to power quality. Conceptually, DC mini for the quality of DC . Voltage magnitude -based power delivery However, no real standards exist is the only concern because there is no frequency or phase -related issues. Imbalance, harmonics, , and frequency variations are also not a problem in DC systems . In low -voltage DC flicker oltage drop is the limiting factor and will determine the ge systems, v ographical footprint of a DC mini- grid. Electrical t ransients are similar across AC and DC systems as large sources are switched on and off. The following . summarize the AC and DC power quality phenomena Detailed information on AC and DC power quality and the levels of service provided in Table 1 can be found in , respectively. Appendices A and B • Voltage imbalance (AC) : T he voltage imbalance is the maximum deviation from the average of the three -phase volta ge or current divided by the average three -phase voltage or current and is expressed in percent. Voltage imbalance occurs only in three- phase AC power systems , not in single -phase or DC -power systems . • Transients (AC, DC) : A transient is a sudden change in the steady -state condition of , or both. voltage, current Transients in electrical distribution networks result from the effects of lightning strikes and/or network switching operations, such as capacitor banks. 14 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
29 • Short -duration voltage variations (AC, DC) : S hort -duration voltage variations encompass -mean ute and are root -square (rms) deviations at power frequencies for less than 1 min caused by fault conditions, energizing large loads that require high starting currents, or intermittent loose connections in power wiring. Long -duration voltage variations (AC, DC) : Long -duration variations encompass rms • deviations at power frequencies for longer than 1 minute . When the supply voltage has been zero for a period of time in excess of 1 minute, the long- duration volt age variation is considered a sustained interruption. • Frequency variations (AC) : D eviation of power system supply frequency from the specified nominal value is directly related to rotational speed of generators. The main causes of frequency variations are faults on bulk transmission system, large loss of load, and large loss of generation. This is more likely to be a problem in a system with a high contribution of variable generation sources and often occurs in an isolated system. • Resistive voltage drop (DC): Electrical resistance increases the farther current flows through an electrical wire; a higher resistance reduces the voltage. Therefore t he farther the load is from the power source, the higher a distribution system -induced resistive voltage drop wi ll be , simply decreasing the DC voltage at the load. Voltage drop will limit the geographical footprint of a DC mini- grid. • DC ripple (DC): DC ripple is an artifact of the AC -to-DC conversion process as it is ting current. This is a concern only if AC -to- difficult to remove all variation in the alterna DC conversion (rectification) is employed. DC ripple can cause additional wear on devices designed to operate at a fixed DC voltage, including radios and televisions. DC -only power systems. ripple should not be a concern for DC Switching noise (DC): Switching noise, a higher • -speed variation in the DC voltage, is caused by operation of power electronic switches. Switching noise can be eliminated or reduced by expanded filtering, but this increases equipment costs so it is more of a problem with low -quality power electronics. 3.2 Power Availability Power availability is the amount of energy services being provided to customers and should be associated to the customers’ ability and willingness to pay for that service. T he power availability can be expected to change over the life of the utility -customer relationship. Three main criteria drive power availability: • Power : Maximum draw in amps or watts • Energy : Total energy available (kWh) over a defined time period (month, year) • Duration of d aily s ervice: Number of hours in a day that power is available ( hours/day) . In developing the different levels of service defined below, we used the mu tier f ramework lti- (Bhatia and Angelou 2015) as a guide. Unlike the QAF, the multi- tier framework does not provide sufficient detail to inform technical specifications for power system design because it combines all attributes into one tier, which reduces the information that is used by project tier framework designers and developers. The multi- provides a very good methodology to 15 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
30 classify different levels of energy services but generally does not allow the level of detail needed , the to assess consumer energy usage from a power system operator perspective. Additionally tier framework is designed around the level of service available to a consumer and not the multi- level of services that are used by the customer , which is important to power system operators . The QAF is aligned with the multi- for each of the levels of service described tier framework above except that the QAF has an additional high level to account for high- energy -consumption customers. 3.2.1 Peak Available Power (Amps or Watts) This parameter largely defines what types of devices or equipment can be used. Minimum and maximu for different customers, although typically only a m levels of service could be specified e.g. maximum value is defined ( can draw (use) up to a maximum power rating but if , a customer they chose to use no power at all, that is also acceptable ). Peak power levels are typically regulated at the consumer level by the fuse installed at the load , or a threshold value can be set when using a smart meter. Rates for power delivery for different levels of service could be applied . Table 2 defines the various power l evels. Table 2. Peak Power Levels Peak Level (W) Power Level Level 1 >3 >50 Level 2 Level 3 >200 Level 4 >800 Level 5 >2,000 Level 6 >5,000 3.2.2 Time Period Energy Available per The energy available is typically tabulated over a period of time, usually a month or a year. Although customers typically pay for energy consumed ( e.g. , by the kWh) , defined rates are charged based on the total amount of energy supplied. As with the tabulation of power availability, usually only a maximum energy usage is defined, with a customer allowed to consume no energy if desired. Rates may also change based on many factors , such as time of day or the cost of the power being generated to supply the energy service. Additionally, in some cases a flat rate is charged based on the application, such as for a defined number of lights and a fan. In all of these cases , however, any of these different rate structures can be converted to an Table 3 provides an index of expected energy use over time for different customer classes. energy availability for different levels of service. 16 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
31 3. Energy Use per Service Level Table Energy Level Pe ak Level ( kWh/ year ) Level 1 >4. 38 Level 2 >73 Level 3 >365 Level 4 >1,250 Level 5 >3,000 Level 6 ,000 >73 Duration of Daily Service 3.2.3 the general number of hours in a day that power The duration of daily service is used to specify is available (hours/day). In place of defining levels based on pre -determined hours of service , we have chosen to allow the system operators flexibility to define the amount of time for which service will be provided. Level 1 specifies that no guarantee number of hours of is given that any service is to be provided, which may be typical of a renewable -only system with no back- up generator or limited energy storage , so the duration of service is simply driven by the availability of the renewable resource. With adeq uate system modeling, a power provider can develop a level, and system that will supply power for a specified time period within a defined confidence In each of these cases, power availability finally providing full power availability is possible. would be (Section 3.3) and will also need to be considered. subject to defined power reliability For example, a system could be defined as Level 3, providing full -time power, but is still subject to defined levels of planned and unplanned power outages. Table 4 de fines the level of service and the hours that power is available. 4. Duration of Daily Service Table (1) Availability Level Power Availability Daily Service No guarantee of availability Level 1 certainty Variable certainty: x hours a day with y Level 2 Level 3 Full certainty: planned continual availability (1) power reliability conditions described below. Availability is subject to defined Time of Daily Service 3.2.4 is also important as it allows for decisions The provision for the time of day of power availability on the load types that can be applied. For example, if power cannot be provided during the day with any confidence, then providing power for government services or productive uses may not be applicable. In place of a more exacting parameter that tries to define when energy is supplied, the QAF allows the energy provider to specify energy services during two key times of day : evening loads ( most relevant to residential and light commercial) and daytime loads ( most ). As with duration of daily service, a relevant to government services and other productive uses confidence level is provided to allow flexibility in design. Table 5 defines the level of service and the hours during which power is available. 17 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
32 Table Service 5. Time of Day Availability Time of Day Service Power Availability Level No guarantee of availability Level 1 Variable night -time certainty: x hours per day with y % Level 2 certainty during the evening certainty % Variable full -day certainty: x hours per day with y Level 3 during the day and evening Full certainty: Planned continual availability Level 4 3.3 Power Reliability Power reliability represents how consistently the power system provides power , specifically between the defined levels of service and the actual service provided . T he QAF addresses power reliability through two common assessment terms for electrical outages, SAIFI and SAIDI, respectively . considering the frequency and duration of those power outages The SAIFI measures the average number of p ower outages that an average customer experiences in a year and is defined as: Interruptions Customer of Number Total = 푆푆푆푆푆푆푆푆푆푆 Number of Customers Served Total The SAIDI measures the average number of minutes that an average customer is without power over the defined time period, typically a year, and is defined as: Interruption Customer Total Minutes of = 푆푆푆푆푆푆푆푆푆푆 Number of Customers Served Total SA IFI is the total number of interruptions ; SAIDI is the total length of interruptions. SAIFI and SAIDI measures are commonly implemented in larger grid networks where specific feeders may In s) while the power system remains operational. customer be turned off ( blackouts for specific the case of mini , it i s much more common for the entire power system to drop -grid systems offline, impacting all customers. In the developed utility sector, it is generally assumed that power will always be provided with high availability, even though i n m any areas this is not the case. , several modifications to the commonly used utility approach have to be In the mini -grid market applied. The most important consideration is that SAIFI and SAIDI are typically assumed to be -time power. In the case of a mini -grid applied on a power system that is expected to provide full system that is only expected to provide service for part of the day (e.g., 18 hours ), SAIFI and in the context of the mini SAIDI -grid should only be calculated on the expectation of 18 hour s of service. In both cases , t his could be confusing when comparing the reliability of power systems It is thus important that are expected to provide service for different numbers of hours per day. that hours of service for which power is not to be provided should be annotated. Additionally, the interruption associated with partial time of day power should not be considered as a reduction in 18 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
33 reliability , this d ocument adds new notations to distinguish from the . To highlight this difference of SAIDI The notation is also used to distinguish that the traditional utility notation and SAIFI. power system was not designed to provide full -time energy service. different lengths of time, then the values for SAIDI and However, if a power system operates for SAIFI for a defined level of service must also be adjusted. For systems that provide partial hours/day service , then the number of interruptions and length of any unplanned interruptions hours . For example, a base level of should be normalized by the percent of planned service per day) service for a power system that was expected to provide continuous power (24 hours would be less than 52 unplanned interruptions per year. I f a system provides 12 hour s per day of service (50% of 24 hours per day service) , then the “base ” level of service for unplanned power interruptions would be less than 24 interruptions (50% of the 52) per year . Similarly, the base . To case for SAIDI in the same example would be 26,280 minutes (50% of 52,560 minutes) allow comparison to the broader utility sector , which is expected to provide power for 24 hours per day, it is important to document if a specified mini -grid is intended to provide only partial power. Thus, the QAF introduces a subscript notation to reflect a lower number of service hours, SAIFI and SAIDI in the example above . If 24 -hour -per -day service is being provided, the 12 12 notation can be droppe d. The common use of SAIFI and SAIDI in the utility context is for unplanned outages. Because mini- grids may be designed to have planned outages , we make a designation between unplanned and planned outages: xx) SAIFI • Unplanned System Average Interruption Frequency I ndex ( ). • Interruption Duration Index ( SAIDI Unplanned System Average XX Table 6 provides guidance for SAIFI and SAIDI for different levels of service. Table 6. Unplanned Power Interruptions , Assuming 24- Hour Service Level of Service SAIFI * SAIDI Interruption Duration * Interruption Frequency 24 24 Base <52 per year <52,560 minutes (876 hours) 90% reliability Standard <12 per year <26,280 minutes (438 hours) 95% reliability High <90 minutes (1.5 hours) 99.99% reliability <2 per year *SAIDI and SAIFI values provided assume 24 hours per day of expected service. If fewer than 24 hours per day are to be provided, an adjustment of the specific threshold values for SAIFI and SAIDI should be made and a subscript added to reflect hours of service per day. the expected Planned power outages may be required for basic maintenance if system redundancy is not incorporated into the power system. In modern utility systems , backup generation and distribution infrastructure are used to minimize service interruptions for standard system maintenance. In these systems , the only planned service outage would be periodic maintenance of the local distribution system or specific service drops. Lower -cost mini- gri d systems may not be implemented with that level of power generation and distribution redundancy , resulting in the need to shut off power when equipment undergoes regular maintenance. For example, a power undergoes regular system with only one generator will not pro vide power while that generator maintenance. 19 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
34 In renewable , lower levels of service may be provided due to resource -only power systems a monsoon. The expected reductions in constraints during certain periods, such as during expected service can be estimated using computational models and reported as a planned outage. only power system s, could be designed into Because planned outages, especially in renewable- s of service are not defined in Table 7 but normal system operation, base and standard level should be specified in the customer agreement. A high level of planned interruptions has been defi ned consistent with grid -parity energy services. Given that planned interruptions are not typica he following new notations are used to indicate lly identified in central power generation, t that the outages represented are expected and should be assumed by the customer as part of normal operation: • Planned System Average Interruption Frequency Index (P -SAIFI) • Planned System Average Interruption Duration Index (P -SAIDI ). XX Table 7. Planned Power Interruptions Interruption Duration* P-SAIDI Interruption P-SAIFI 24 24 Level of Service * Frequency No requirement but should be defined requirement but should be No Base defined No requirement but should be Standard No requirement but should be defined defined High <2 per year <30 minutes - 100% reliability *P-SAIDI and P -SAIFI values provided assume 24 hours per day of expected service. If fewer than 24 hours per day are to be DI and P FI should be made and a subscript added to provided, an adjustment of the specific threshold values for P-SAI -SAI reflect the expected hours of service per day. 20 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
35 4 Accountability and Performance Reporting Framework The two elements to ensure long -term project sustainability. The accountability framework has first is to formalize the relationships and information exchange among the parties involved in mini- grid system development and operations (developers/operators, funders, regulators, and customers), which are conceptually similar to more conventional utility systems. Second, it also dissemination of information from these mini- grid defines processes for formal collection and systems, allowing increased knowledge of the systems not only internally to the organizations developing or operating them but also to the wider mini- grids sector. These goals are upheld through two mechanisms: (1) a specification of the quality of service (defined in accordance with the levels of service component of the QAF) and (2) a method to assess the technical and business condition of the power system or its operating utility . The QAF accountability thus define a clear process for validating power delivery by framework will providing trusted information to developers/operators, customers, funders, and regulators. Access to this information yields a number of wide -ranging benefits for these mini- grid sector stakeholders, including facilitating increased transparency, long- term performance tracking and forecasting, demonstrating a track record, improving risk assessment, and lay ing the foundation for aggregation and bundling of mini -grids projects. Figu re 2 provides a summary of these benefits. As discussed in Section 1.4, although applicable to any business model, the QAF is modeled on best practices from conventional utilities in mature markets, with the view of mini- grids as mini- practices include establishing a defined contractual relationship with utilities. These best -term data, and customers, employing standard classification of customers, gathering long unlocking aggre accountability the QAF gation and economies of scale. With this in mind, framework has two components: Consumer a ccountability : Focusing on the agreement between the customer and • help s to ensure that the service provider of energy services, consumer accountability expected is rendered through appropriate checks and balances, str engthening consumer . Improved confidence will increase a customer ’s willingness to pay for confidence service since there is a documented understanding of the service being provided for the payments being made. Additionally, a defined project -specific proc ess outlines recourse for customers who do not believe they are receiving the level of service expected. This documentation reduces the risks of customer s stopping payment, which in turn improves the bankability of projects. This also solidifies the concept of a business relationship between a buyer and seller of a commodity , in this case energy services. • Utility accountability : Focusing primarily on the agreement between the provider of energy services and either the government, regulator , or funders, utility accountability describes the systematic collection and dispersal of information about the system. This information can be used by the service provider (i.e., mini- utility) to improve operational gy planning, as well as externally via reporting management and facilitate long -term ener to regulators, funders, or other interested parties as appropriate. The collection of this information must be completed in a way to ensure high quality and reliability . This 21 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
36 reporting should depend on but be independent of the business model used to manage the power system. The type and quality of data collected through the accountability framework will depend on the users and uses of the data. In this document we have compiled a complete set of likely param eters , but i t should not be assumed that all systems need to collect all data parameters described or that all parties of a specific project ( the customer , utility, regulator, and investor ) will want or need all identified data. Additionally, the resolution of the data collection in terms of accuracy and frequency of collection and reporting will also vary by parameter, system size, and the intended use of that data. In addition, this document does not mandate methods of data , automated vs. manual) and the corresponding instrumentation, as this will also collection (e.g. vary. Maintaining flexibility is critical given the inherent diversity and relative nascence of the mini- grids sector. Note that additional guidelines and recommendations detailing QAF imple mentation in a range of theoretical scenarios will be published as a complement to this main QAF technical document. In addition, subsequent QAF technical validation and implementation pilots will provide examples based on operating mini- grid systems. The following sections provide further details on the QAF a ccountability f ramework, divided by consumer and utility accountability . 4.1 Consumer Accountability The consumer accountability defines, demonstrates , and validates that a specific level of service Information collected on customer energy usage can also be is bei ng provided to a customer. used to better understand local and regional energy usage over time, allowing the utility and other organizations to better manage power system operation and plans for long -term usage growth. The two main elements of the QAF consumer accountability are discussed below. 4.1.1 Level of Service Verification The level of service verification must have the following capabilities at each customer point of connection: • Ability to check voltage at service drops • Ability to record energy consumption • Ability to record hours of service at service drops . The three attributes above will give an indication of power quality, energy availability , and power reliability at the customer point of connection. Note that the level of service verification under the QAF does not require that all of these are measured continuously , although it is important to monitor these attributes at the customer level at least periodically, as well as maintain a histor ical record over time. The use of smart meters would facilitate the collection of robust real -time data across some or all of these domains but may be cost -prohibitive. Alternatively, periodic surveys using temporary meters are recommended, though the frequency, duration, and size of these surveys would vary depending on cost constraints, regulatory arrangements, and other factors. Level of service verification assessments may also be triggered w of the historical records. by a customer complaint and would also include a revie 22 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
37 Note that the relevant metric for measuring energy consumption at the customer level could vary depending on the business model. For example, tariffs may be structured on the basis of kilowatt hours consumed, services or appliances supported, or a flat fee in some cases ( although this is not recommended ). Related to the hours of service attribute , it is important to track the outages s experience. For small mini- grids, this will likely be tracked at a system- that customer wide level (see utility accountability section below), though ability to record more granular customer -level outages (e.g. , impacting specific feeders or even specific service drops) is most ideal where possible. Finally, although voltage must be measured at the customer point of connection, system frequency and , if appropriate , other power -quality -related parameters should also be monitored and recorded ; the location of this monitoring will depend on the parameter. 4.1.2 Service Agreement To ensure a common understanding , a ser vice agreement that defines the expectation between the consumer and provider of energy services must be in place . The service agreement must define the terms of service including the details of the level of service to be delivered, tariffs and fees, payment processes, compliance with applicable standards and regulations, customer responsibilities, customer complaint procedure, and other relevant information. For full transparency, the service agreement should also specify the type and frequency of service data that the utility will provide to the customer, as well as clear processes for addressing customer the appro concerns if priate service is not provided. A process to file complaints directly with the utility as well as an independent third party, such as the national regulator, should also be described. The service agreement must also describe how to address power quality impacts caused by the customer ver sus those caused by the power system. Appendix C provides a sample customer disturbance recording form . A service 15 agreement should be provided to each new customer and made available through a public process, such as available online and posted at the pow erhouse or local office in the local language . The legal justification of the agreement will depend on the jurisdiction and applicable local regulations but should, if possible, have some strong legal basis. 4.2 Utility Accountability Utility accountability allows funding or regulatory organizations to understand if the mini -grid system is safe and providing contracted service. Technical and business reporting specified under this framework provides a defined and secure methodology for utilities to provide rele vant information to regulators and project financiers that will allow a good understanding of the utility business. This information is also important for internal use by the utility to improve operational management and facilitate long -term planning. In general, the reporting of this standard information also provides the wider industry important sector data that will help reduce risks, facilitate bundling and aggregation, and inform effecti ve interventions in the sector. As discussed earlier, the QAF does not mandate the collection or reporting of all of these attributes, which will vary depending on the size of the intended users and uses of the data. In the implementation of a project, the various project participants will need to determine the metrics o f interest for each of the parties involved. For example, regulators may be most interested in issues 15 E.g., Wise Electric Cooperative in Decatur, Texas, provides a customer service agreement: http://www.wiseec.com/content/uploads/2015/09/WEC_Service_Agreement.pdf 23 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
38 of power quality and safety. Project funders may be more interested in payment rates and service ional efficiency and load growth. Sample levels, while utility operators are concerned with operat elements of utility technical and business reporting are provided in the following section, but the final selection should be driven by partner needs. The se attributes were selected during a series of QAF workshops and webinars in consultation with mini- grids sector stakeholders, who identified these as a reasonable set of key performance indicators for characterizing the soundness of the mini -grid utility. Further refinements to this list will take place following forthcoming QAF implementation pilots and ongoing stakeholder consultations. 4.2.1 Technical Reporting The main elements of technical reporting for mini- grids include assessment of power quality and reliability, energy production and consumption, generation sources, and system efficiencies. The goal of technical reporting is to not only document the performance of the power system in terms of meeting contractual delivery of energy services but also to report on the efficiency and reliability of those services . This allows consumers and regulators, as well as the utility, to understand the quality of the service, the efficiency of how energy is being generated and sold, and finally how all of this changes over time. The selection of metrics (or monitoring param eters) will determine the choice of monitoring equipment and the method of collecting data (e.g., voltage surveys for small mini -grids versus power monitoring for larger power systems). The method of collecting data also includes the triggering thresholds needed, the data storage and analysis technique to employ, and what to do with the results of the information collected. The cost of the monitoring and analysis should also be understood and included in the development of any system requirements, being car eful to balance the desire to collect data with the cost impact of doing so. Quality assurance monitoring may be provided by the utility, the user of that data (regulator or investor), or a third party, but it must adhere to a process that insures the integrity of the data being generated. Further, to be fully credible the data and data collection process must be audited, which adds additional expense. The level of monitoring may also change as the sy stem or group of systems grows. meters Technical Monitoring 18.104.22.168 Para The following list summarizes : the main elements for technical reporting • Annual electricity production during the calendar year (January 1 to December 31) (kWh) • Annual electricity purchased (if applicable) during the calendar year (January 1 to December 31) (kWh) • Annual e lectricity sales during the calendar year (January 1 to December 31) (kWh) • System losses: e nergy sales (kWh)/ energy production (kWh) • Renewable energy contribution: renewable energy production (kWh)/ total energy production (kWh) • System production efficiency: total energy production (kWh)/ total system fuel consumption (liters) • Power plant fuel efficiency (if applicable): total fuel delivered energy production (kWh)/ total system fuel consumption (liters) 24 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
39 • Duration of daily service : a verage hours of service provided per day over the reporting period (January 1 to December 31 and/or monthly) • Unplanned power outages: number and number of hours of system -wide service outages based on unplanned service interruptions ( units and hours) to al low calculation of SAIFI and SAIDI . This should be measured at the customer location or at least at XX XX the end of the feeder if possible. • Planned power outages: Number and number of hours of system -wide service outages based on planned service interruptions (units and hours) to allow calculation of P - SAIFI and P -SAIDI . This should be measured at the customer location or at least at XX XX the end of the feeder if possible. Total fuel consumption (liters ) • • Number of O&M events with short description of event and root cause analysis (distinction of planned or unplanned events should be noted) • Number of public or worker safety events with short description of event and root cause analysis quality events – report of any power quality events including the • Assessment of power magnitude and duration of the following: o Over and under voltage Voltage transient o o Power interruption o Over and under frequency o Phase imbalance o Harmonic distortion . Note that for small pro jects, all of these elements may not be necessary and cost -effective to report. An example business reporting template is provided in Appendix D the . In addition, while specifics will depend on the business model, an appropriate level of customer age energy us should also be collected to allow for billing and assess changes in customer energy use. In the event that thermal energy is also provided as an additional product of the power system, key ues from the sale of thermal summary information such as total thermal energy sold and reven information energy should also be recorded. Additional technical reporting is provided in Appendix D . 22.214.171.124 Technical Documentation In addition to the above -mentioned technical data, other documents should be ready available, such as system commissioning reports, O&M logs, power and distribution system one -line . Documentation on any monitoring diagrams , and potentially as -built technical specifications system should also be available. 25 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
40 4.2.2 Business Reporting Reporting business information is as critical as technical information and makes up the second half of any utility accountability framework. Business information is inherently sensitive but critical to understan -sector capital is being applied. the utility sector, especially if private ding A primary objective of business reporting is to create transparency on the operational soundness, -grid operating entity. T his is important for financial condition, and growth potential of the mini the regulatory bodies, incentive providers, customers, lenders, and potential public or private investors. This reporting will help provide the basis for accurate risk assessment that can result in ence and lowe r cost of capital. a higher level of confid 126.96.36.199 Business Reporting Parameters -grids include payment collection rates, The main elements of business reporting for mini electrification rates, customer characteristics, service calls, safety concerns, etc. Additional business reporting re quirements are outlined below based on the U.S. Department of Agriculture 16 Rural Utilities Service Financial and Statistical Report and the United Republic of Tanzania’s 17 form Energy and Water Utilitie for small power producers reporting: s Regulatory Authority’s Total number of customer s (#) • • Customers by level of service (#) • Customers by sector (residential, government, commercial) (#) • Unconnected potential customers by sector (residential, government, commercial) within reach of the distribution system (#) Metered customers (if different from total customer s) (#) • • (#) New services connected by sector (residential, government, commercial) • Services retired by sector (residential, government, commercial) (#) Payment c ollection rate by service level (%) • Payment collection rate by sector (%) • Electrification (%) • Energy sales by sector (%) • • Other electric r evenue ($) • ($ and $/kWh) Cost of power purchases • Cost of power g eneration ( $ and $/kWh) 16 Form 7. Available at: U.S. Department of Agriculture Rural Utilities Service Financial and Statistical Report – -2006.pdf http://www.nmprc.state.nm.us/utilities/docs/form7 17 See “Form 7: Form for Annual SPP Reporting to EWURA” starting on page 37 of EWURA (2009). Guidelines for Developers of Small Power Projects in Tanzania . Available at: -private http://ppp.worldbank.org/public - partnership/sites/ppp.worldbank.org/files/documents/Tanzania%20Guidelines%20Small%20Power%20Projects.doc 26 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
41 Cost of power provision (distri bution) ($ and $/kWh) • • Cost of s ervice ( administrative , office support, insurance) ($ and $/kWh) • Total cost of power ($ and $/kWh) • Total fuel costs ($) ($) • Revenues by sector (residential, government, commercial) Revenues by level of service ($) • • Average revenues from power sales ($/kWh) Average sale price of power by sector ($/kWh) • • Average sale price of power by level of service ($/kWh) • Expected capacity to sell (minimum and maximum) (kWh) . • Number and nature of service calls and complaints is Reporting can be completed on any interval, although a minimum of annual reporting recommended . Some institutions may require more frequent reporting. While the level of , to be business reporting discussed above is desirable and valuable, it is also expensive. Further fully credible it must be audited , which adds additional expense. The value of detailed reporting must be balanced against the cost , and an appropriate level of tracking and reporting must be selected. The level may change as the system or group of system s grows and has more revenue and financing requirements. An example business reporting template is provided in Appendix E . 188.8.131.52 Business Documentation In addition to the above -mentioned business data, other documents should be ready available, such as generic use agreements , standard rate schedules , licenses , and permits . Monitoring 4.2.3 Processes Utility accountability will only be achieved if a process is put in place that holds utilities to the contractual commitments made to their customers, investors, regulators, and other relevant stakeholders. This, in turn, will require defined procedures for the monitoring, reporting, and verification of the technical and business elements discussed in the preceding sections. 184.108.40.206 Instrumentation for Monitoring The type of monitor that is utilized is based in part on the timeframe over which monitoring is needed. In general, portable/handheld monitors are used to troubleshoot problems in facilities or the electric distribution system using a reactive approach, although th ey can also be used for shorter -term compliance monitoring in small power systems. Permanently installed monitoring systems are used for recording longer -term system performance and reliability as well as providing data and/or alarms when power -quality -rel ated problems occur. Permanently installed monitors include dedicated power quality monitors, revenue meters with power quality functionality, statistical survey/compliance monitors, and system protection relays with some power quality functionality. onitoring process can be described in four stages. The m 27 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
42 • The first stage in the process is data acquisition. Acquiring the data for a mini- grid power -recording specific values and automated data system will likely be a combination of hand perational data , detailed diagnostic data , and calculated parameters acquisition systems. O by power system operators will likely be collected and maintained at the power system . Additional simple analysis and characterization of the data may also be completed on site by power s ystem operators. Data may be transferred for storage to a central company office. Advanced automated data collection is likely to include local data storage and potential electronic transfer to national or regional offices for expanded analysis and long -term storage. • Data summation is the second stage of the process. Based on informational needs, the type of data collection , and data delivery options, raw plant data collected in the first stage will be analyzed and summarized either locally or at a corporate headquarters . Although different stakeholders may have different data needs, efforts should be made to align the reporting requirements of the different accepting parties so as to reduce overhead burden on small utility systems. Some form of loca l data storage and potentially additional processing may also be likely on the part of the utility for their own operational use. • Summary information about the operation of the power system can then be at specific inter vals . Since different stakeholders communicated to project stakeholders require different information, data systems can be created for larger programs to en sure that the specific information is transferred securely to each of the different project stakeholders in a similar and thus more useful manor . Data submittal could be done through web portals, automatic transmittal of data from data acquisition systems , or on paper and entered by program administrators. Reports should be generated regularly for specific systems or wider deployment efforts, documenting the performance of different technologies and system developers. • For larger or multi- system projects, such as national rural electrification projects additional operations such as aggregation of data from multiple site , long -term data retent ion, and expanded analysis of some parameters may be needed to provide insight expanded long into longer trends . The availability of such -term data will allow the wider industry to analyze the performance of mini- grid systems with high renewable energy con tent, which is an important step in unlocking private -sector capital for such systems. The security of data provided by individual projects will likely be a topic of some discussion and may need to be stipulated as part of the development of larger rural electrification projects. 220.127.116.11 Reporting Beyond the collection of information around power system operation, a reporting requirement should be developed based on national or programmatic needs. Different governmental organizations may already have reporting requ irements for the power sector , which may generally be applicable for mini -grid power systems. In some cases, requirements have been developed for the mini -grids sector or some segments may be exempt from regulation altogether. ections 4.2.1 and 4.2.2 for more information about the kinds of reporting information Refer to S . and templates that could be of interest to various stakeholders 28 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
43 The frequency of technical data collection and reporting will also be driven largely by the uses of the data and will vary b y parameter and recipient. Energy regulators may only need annual data of specific parameters, while project operators may desire hourly or even sub- hourly data collection to tune system performance. Other organizations may require reports following pow er quality or safety incidents. 18.104.22.168 Verification Independent verification is a critical part of any accountability framework. Verification processes should cover the entire project timeline, incorporating a formal commissioning of the power system, commissioning of any data collection processes , and ongoing assessment of system performance and more general reporting. The intended verification process should be developed in the early stages of wider project development so that it can be integrated and implemented a s part of the project development. It is also important that project developers understand the data acquisition, reporting, and verification requirements at the start of any development so that the costs of these components can be included in any project d evelopment and operational cost projections. Finally, the organization(s) implementing the larger data monitoring and verification process must understand and prepare for the implementation of this process. Not only will new systems new hardware will (both organizational and data management) need to be developed, but also likely need to be procured, processes developed and implemented, and staff trained to implement each new step in the development process. Organizational oversight of the verification proce ss, both in terms of commissioning of new power system projects and long -term verification processes for the operation of the power systems, will require the development of in- house parties to provide over capacities or procedures to hire independent third sight of the verification process. 29 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
44 5 Conclusion The QA F for mini -grid power systems aims to provide a similar structure and transparency for isolated mini- grids as is offered by successful utility models. The QA F defines different levels of service, including appropriate thresholds for power quality, reliability , and availability to meet the needs of different segments of the off -grid consumer base. The framework’s goal is not to set clarify and advance the m ini -grid sector by specifying a a standard level of service but rather to — range of service levels from basic energy services to grid -parity service —and providing mechanisms for assessment and reporting to determine whether an agreed level of service is delivered. grid power systems aim to preserve flexibility while for mini- These core elements of the QAF providing a foundational structure that can put the sector on track to resemble a mature utility in scale and sophistication. In addition, data generated through implementation of the QAF will provide the foundation for comparisons across projects, assessment of impacts, and greater confidence that will drive investme nt and scale- up in this sector. It should be remembered that the term “framework” in the QAF was chosen intentionally. This effort doe s not provide a clear recipe; rather, it is a set of ingredients that various parties, public or private, could use based on their specific needs and goals. The QA F is also a work in progress and will develop as it is applied in different contexts. T he QAF team and partners will continue to take steps to advance the project , including development of an implementation toolkit, technical validation pilots, demonstration pilots, and additional supporting technical resources. More QAF documents will be developed over time, supporting the expanded application of the framework in individual system or large -scale deployment projects. The Clean Energy Solutions 18 Center provides an initial gateway to information that supports the development of isolated power systems. 18 https://cleanenergysolutions.org/ 30 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
45 References Bhatia, M.; Angelou, N. 2015. “Beyond Connections, Energy Access Redefined.” Energy Sector Management Assistance Program (ESMAP), The World Ban k Group, Washington, DC, USA. https://openknowledge.worldbank.org/bitstream/handle/10986/24368/Beyond0connect0d000tech nical0report.pdf?sequence=1&isAllowed=y Bollen, M.H.J. (1999). Understanding Power Quality Problems: Voltage Sags and Interruptions . Wiley -IEEE Press. http://www.wiley.com/WileyCDA/WileyTitle/productCd - 0780347137,miniSiteCd- IEEE2.html Electric Power Quality . ISBN 978- 94- .; and S. Samarjit. (2011). Chattopadhyay, S; Mitra, M 7. Springer Science 0634- and Business. 007- International Electrotechnical Commis sion. (2005 ). Recommendations for Renewable Energy and Hybrid Systems for Rural Electrification, Part 1: General I ntroduction to IEC 62257 Series 2:2005 (E). Geneva, Switzerland: International and Rural Electrification . IEC/TS 62257- Electrotechnical Commis sion. https://webstore.iec.ch/publication/23502 “Energy Poverty : How to Make Modern Energy Access International Energy Agency. 2010. Universal .” Available at http://www.iea.org/publications/freepublications/publication/weo -2010- --special -report ---how -to-make- mode rn-energy -access -universal.html Nation al Fire Protection Association. (2014) . NFPA 70: National Electric Code . Quincy, Massachusetts , USA: Natio nal Fire Protection Association. http://www.nfpa.org/codes -and - -standards?mode=code&code=70&tab=about standards/all -codes -and -standards/list- of-codes -and 31 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
46 Bibliography Africa -EU Renewable Energy Cooperation Programme (RECP). Mini -Gri d Policy Toolkit: Policy and Business Frameworks for Successful Mini -Grid Roll -outs . (2015). Eschborn, Germany: European Union Energy Initiative Partnership Dialogue Facility . http://www.ren21.net/Portals/0/documents/Resources/MGT/MinigridPolicyToolkit_Sep2014_E N.pdf Greacen, C.; Engel, R., Quetchenbach, T. (2013). A Guidebook on Grid Interconnection and p to 200 kW Islanded Operation of Mini -Grid Power Systems U 6224E. Berkeley, . LBNL- California: Lawrence Berkeley National Laboratory. https://building - microgrid.lbl.gov/publications/guidebook- grid -interconnection- and International Renewable Energy Agency (IRENA). (2015). Accelerating O ff-Grid Renewable Energy : International Off -Grid Renewable Energy Conference & Exhibition 2014: Key Find ings . Abu Dhabi, United Arab Emirates. IRENA. and Recommendations http://www.irena.org/DocumentDownloads/Publications/IRENA_2nd_IOREC_2015.pdf Layton, Electric System Reli ability Indices . Self -published. L. (2004). http://l2eng.com/Reliability_Indices_for_Utilities.pdf Schnitzer, D.; Lounsbury, D. S.; Carvallo, J. P.; Des hmukh, R.; Apt, J.; and D.M. Kammen. (2014). Microgrids for Rural Electrification: A C ritical R eview of B est P ractices B ased on Seven Case Studies . United Nations Foundation. https://rael.berkeley.edu/publication/microgrids -for- -electrification rural -a-critical -review -of-best -practices -based -on- seven -case -studies/ Tenenbaum, B 2014) C.; Siyambalapitiya, T.; and J . Knuckles. ( .; Greacen, . From the Bottom Up: How Small Power Producers and Mini -Grids Can Deliver Electrification and Renewable Energy Washington, DC: World Bank. in Africa. https://openknowledge.worldbank.org/handle/10986/16571 32 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
47 Appendix A: Quality (AC) Power in the Specific parameters for each of the defined AC conditions of power quality are discussed following sections. A.1 Voltage Im balance -phase system, voltage imbalance takes place when the magnitudes of phase or line In a three voltages are different from one phase to the next or the phase angles differ from the balanced conditions, or both. This is typically caused by single- phase loads being distributed unevenly among the three phases. T he voltage imbalance is the maximum deviation from the average of the three- phase voltage or current divided by the average three -phase voltage or current and is expressed in percent. Voltage imbalance occurs only in three -phase AC power systems , not in single DC -power systems . -phase or A common source of voltage imbalance occurs when a fuse opens in one of the single -phase loads on a three -phase circuit. Si nce most remote villages only require single -phase service, three- phase service to three sets of loads. Voltage phase generators will often send single- imbalance will occur when these loads are very different. , and large quipment that are affected by voltage imbalance are transformers, motors Types of e phase loads. three- Generators may experience torque oscillation due to imbalanced loading of the different phases. Table 8 provides the maximum allowed value of voltage imbalance evel of service . recommended for each l Table 8. Levels of Service for % Voltage Imbalance Level of Service Voltage Imbalance Limits Base <10% Standard <5% High <2% Transients A.2 Transient over -voltages in electrical distribution networks result from the effects of lightning -voltages strikes and/or network switching operations, such as capacitor banks. Transient over can be classified as being impulsive or oscillatory. -voltages hav e the potential to result in damage to equipment , potentially leading Transient over to a loss of production. Equipment affected from transient over -voltage includes electronics , instrumentation, and winding insulation for transformers or motors. An impulsive transient is a sudden, non- power frequency change in the steady -state condition of voltage, current, or both that is unidirectional in polarity (primarily either positive or negative). The rise time for impulsive transient ov er-voltages is in nanoseconds. Impulsive transients can -off of inductive loads, such as large motors. Lightning arrestors and also be caused by switch surge suppressers can be installed along the distribution lines or at homes to limit the potential damage of impulsive transients. 33 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
48 . 1. Tra over -voltage . By Biezl ( own work) [p Figure nsient ublic domain], via Wikimedia Commons https://commons.wikimedia.org/w/index.php?curid=4676389 An oscillatory transient is also a sudden, non- power frequency change in the steady -state condition of voltage, current , or both that includes both positive and negative polarity . As the name implies The lower - , an oscillatory transient oscillates along the fundamental frequency. frequency oscillatory transients propagate in essentially the same way as the 50 -Hz fundamental voltage. In rural areas , capacitor banks are rarely used , which will limit the likelihood of oscillatory transients. 2. Oscillatory transients Figure 9. Protection against Transients for Different Levels of Service Table Level of Service Quality Base No protection Surge protection Standard Surge protection High Short A.3 -Duration Voltage Variations Short -duration voltage variations encompass rms deviations at power frequencies for less than 1 require high starting and are caused by fault conditions, energizing large loads that min ute currents or intermittent loose connections in power wiring. Depending on the fault location and 34 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
49 the system conditions, the fault can cause temporary voltage drops (sags), vol tage rises (swells), or a complete loss of voltage (interruptions). The fault condition can be close to or remote from the point of interest. In either case, the impact on the voltage during the fault condition is of the -duration variation until prot ective devi ces operate to clear the fault. short , or interruption based on fault intensity, location , and duration. Fault can cause sag, swell A sag is a decrease in voltage to between 0.1 and 0.9 percent nominal per unit (pu) in rms • voltage or current at the po wer frequency for durations from 0.5 cycle to 1 minute . • A swell is an increase in voltage from 1.1 pu to 1.8 pu from 0.5 cycle to 1 minute. • An interruption is voltage <0.1 pu for <1 minute. Table 10 lists the number of short riod that is recommended in -duration variations per time pe each level of service. Table 10. Number of Short- Duration Variations for Level of Service Level of Service Quality Base <5/day Standard <1/day <1/week High A.4 Long Duration Variations -duration variations encompass rms deviations at power frequencies for longer than 1 Long ute . ANSI C84.1 specifies the steady -state voltage tolerances expected on a power system. A min voltage variation is considered to be long duration when the ANSI limits are exceeded for greater than 1 minute . Long -duration variations can be over -voltages or under -voltages. Over -voltages and under - voltages generally are not the results of system faults but are caused by load variations on the system and system -switching operations. of the nominal An over -voltage is an increa se in the rms AC voltage to greater than 110% voltage -voltage is usually the result of load switching (e.g., . Over for longer than 1 minute switching off a large load or energizing a capacitor bank). The over -voltages result because either t he system is too weak or voltage controls are inadequate. Incorrect tap settings on transformers can also result in system over -voltages. An under -voltage is a decrease in the rms AC voltage to less than 90% of the nominal voltage for longer than 1 minute . Under -voltages are the results of switching events that are the opposite of the events that cause over -voltages. A load switching on can cause an under -voltage until voltage regulation equipment on the system can bring the voltage back to within tolerance s. Overloaded circuits can also result in under -voltages. - , the long When the supply voltage has been zero for a period of time in excess of 1 minute duration voltage variation is considered a sustained interruption. Voltage interruptions longer 35 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
50 than 1 minute . often require human intervention to repair the system to return it to service an cause overheating and insulation damage for motors and Repeated interruptions c transformers. ong -duration variation parameters: Summary of the l Over -voltage: RMS AC volta ge > 1.1 pu for longer than 1 minute • • Under -voltage: RMS AC voltage < 0.9 pu for longer than 1 minute • Sustained i nterruption: Voltage <0.1 pu for longer than 1 m inute . Table 11 lists the number of long -term duration variations per time period that is recommended in each level of service. Table 11. Number of Long -Duration Variations for Level of Service Level of Service Quality <10/day Base Standard <5/day High <1/day A.5 Frequency Variations Deviation of power system supply frequency from the specified nominal value is directly related to rotational speed of generators. Frequency variation is a more likely problem in a system with a high contribution of variable generation sources and often occurs in an isolated system. The main causes of frequ ency variations are faults on bulk transmission system, large loss of load, and large loss of generation. One of the main effects of frequency variations is that it slows down or speeds up motors on the system . Consistent low frequency can also cause overs aturation of transformers, leading to . premature transformer failure, a costly problem Table 12 outlines the range of acceptable frequenc y for a given level of service. Table 12. Range of Frequency for the Level of Service Level of Service Quality Base 48 Hz < f < 52 Hz Standard 49 Hz < f < 51 Hz 7.5 Hz < f < 50.5 Hz High 36 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
51 Appendix B: Power Quality (DC) or phase in DC power systems, including phase Because there is no frequency -related issues imbalance, harmonics, or flicker , they are conceptually much simpler than AC mini -grids with ariations in v oltage magnitude respect to power quality. V , including voltage drop on distribution lines and induced transients on the DC voltage , are the primary concerns. Electrical variations superimposed on the DC voltage are broken into two types based on their frequency . DC ripple is low frequency, an artifact of AC to DC rectification. Switching noise is generally much higher frequency (in the kHz or above) and is caused by the rapid switching of semiconductors , such as field effect transistors . DC transients are similar to transients in AC systems as both result from the effects of lightning strikes and/or network- switching operations. The following section reviews the common DC power -quality issues and proposed level of service thresholds. B.1 Resistive Voltage Drop The farther the load is from the power source, the higher a distribution system -induced resistive voltage drop, simply decreasing the DC voltage at the load. Voltage drop will limit the geographical footprint of a DC mini- grid. Voltage drop depends on: • Length of conductor • Area of conductor wire Conductor material (copper/aluminum) • • Power flowing through the line . are: The causes of excessive voltage drop Overdraw of power • Improper conductor choice, poor -qualit y conductors • Poor connections. • There are no defined standards that address voltage drop, so the following values in Table 13 should act as an approximate guide. Table 13. Percent Voltage Drop for a Level of Service Level of Service Quality Base Within 30% of sending- end voltage Standard Within 20% High Within 10% B.2 DC Ripple -to-DC conversion process DC ripple is an artifact of the AC as it is difficult to remove all variation in the alternating current. This is a concern only if AC -to-DC conversion (rectification) 37 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
52 is employed. DC ripple can cause additional wear on devices designed to operate at a fixed DC , including radios and televisions -only power voltage . DC ripple should not be a concern for DC systems. -to-DC conversion process is shown in Figure 3 below with the dashed The DC output of the AC . S moothing is accomplished by using a capacitor at the line showing the simple rectified ripple output of the rectifier, as shown in the red line , but it never completely removes all high- speed variation i n the final DC voltage . Increased ripple is typically due to a lack of filtering and is more prevalent in low -quality charge controllers or power converters. Figure 3. DC ripple based on the output of a rectified AC power source . Image from Spinning Spark, https://en.wikipedia.org/wiki/File:Smoothed_ripple_gray_background.svg Table 14 provides the percent pk- pk ripple allowed for a given level of service. Ripple for Given Level of Service 14. Table Level of Service Quality Base 10% of pk-pk Standard 5% of pk-pk 2% High of pk-pk Switching Noise B.3 Switching noise , a higher -speed variation in the DC voltage, is caused by operation of power electronic switches . The potential problem with switching noise is electromagnetic interference. Switching noise can be eliminated or reduced by expanded filtering , but this increases equipment . Table 15 provides a general costs so is more of a problem with low -quality power electronics grid power systems. guide for switching noise in mini- 38 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
53 Table Switching Noise for a Given Level of Service 15. Level of Service Quality Base Unfiltered Transient noise minimized Standard High Ripple noise minimized B.4 Transients DC voltage t ransients are similar to what is found in AC systems and can occur when loads or gen eration sources are switched on or off , causing sudden changes in system voltage. Higher - speed voltage t or other sudden external eve nts . ransients can also be caused by lightning strikes As with AC systems , DC transients can be addressed by the purchase of loads that include some sort of power smoothing (soft starts) and by the inclusion of surge suppressors to address the more damaging high -voltage transients. Table 16 provides a gen eral guide for the type of transient protection to be used in mini -grid power systems. Table 16. Transient Protection for a Given Level of Service Level of Service Quality No additional protection Base Standard Surge suppressors Surge suppressors High Short - and Long-Duration Variations B.5 By their nature , voltage variations are common in DC -based power systems. DC voltage will vary between defined thresholds based on battery state of charge and power system currents coming into and out of the system. These voltage variations are normal and typically kept within a safe range, using charge controllers on the upper level and low -voltage disconnects to protect against low voltages. Short -term voltage variations can be caused by changes in large loads (specifically motors, electrical shorts, or during the transitions between battery charging and -term variations, over approximately a minute, are more likely the discharging states ). Longer of the application of large loads or the failure of specific pro tection systems, such as result - low voltage disconnects or charge regulators. Table 17 provides a general guide for the frequency of faults in mini- grid power systems. 17. Number of Faults Allowed P er Day for a Given Level of Service Table Level of Service Qualit y Base <5 per day Standard <2 per day <1 per day High 39 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
54 C: Sample Customer Disturbance Recording Appendix Form Disturbance description Date: Time: Address: Description of disturbance: Restoration Restoration time: Equipment back in service: Equipment affected Equipment type manufacturer: Equipment rating: Based on IEEE Std . 1159- 2009: IEEE Recommended Practice for Monitoring Electric Power Quality 40 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
55 D: Sample Technical Reporting Form Appendix Power quality Voltage surveys for small system Expanded power monitoring for larger systems Renewable energy contribution (kWh) Cost energy sales Energy production (kWh)/ ($/kWh) Power availability service Duration of d aily Hours per day electricity provided daily Percent of days service provided below contracted value Percent of days service provided above contracted value Average number of hours of service provided during the day (6 a. m./6 p.m.) Average number of hours of service provided during the evening (6 p.m./12 p.m.) Efficiency energy System losses ( energy sales (kWh)/ production (kWh)) System efficiency (kWh/l) Diesel system efficiency 41 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
56 adjusted to reflect average hours of service per day ) Unplanned power outages ( Number of unplanned service events System Average Interruption Frequency Index (SAIFI) System Average Interruption Duration Index (SAIDI ) XX Planned power outages (adjusted to reflect average hours of service per day) Number of planned service events Planned System Average Interruption -SAIFI) Frequency Index (P Planned System Average Interruption Duration -SAIDI Index (P ) XX maintenance, and safety Operation, Number of O&M events with short description of event and root -cause analysis Number of public or worker safety events with short description of event and root -cause analysis 42 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
57 Appendix E: Sample Business Reporting Form Customers by level of service Customers by sector (residential, government, commercial) New services connected Services retired Total services in place Payment collection rate % of customers current on payments by level of service % of customers that are more than 6 months behind by level of service % of customers current on payments by sector % of customers that are more than 6 months behind by sector Number and % of customers in community electrified with electrical service that meets power quality requirements by sector Percent (%) of load by sector Total service interruptions supplier Power Extreme storm Prearranged All other Number and nature of service calls and complaints Safety issues and workplace injuries Total number of customer s Total kWh sold Other electric revenue Total kWh purchased Total kWh generated Cost of purchases and generation 43 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
58 Revenues by sector (residential, government, commercial) Revenues by level of service Average revenues from power sales ($/kWh) Average cost of power ($/kWh) by segment Generation (fuel, maintenance) Provision (distribution) Service (office support, insurance) Total cost of electric service Expected capacity to sell Minimum Maximum Annual electricity production during the calendar year (January 1 to December 31) Annual electricity sales during the calendar year (January 1 to December 31) Amount of electricity sold to distribution network operators Amount of electricity sold to retail customers 44 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
INTERNATIONAL OUT-OF-DELIVERY-AREA AND OUT-OF-PICKUP-AREA SURCHARGES International shipments (subject to service availability) delivered to or picked up from remote and less-accessible locations are a...More info »