DC Task Team Report - IEEE Xplore

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DC Task Team Report Erling Hesla, Life Senior Member, IEEE Appointed Team Members Barry Brusso ([email protected]), Liang Downey ([email protected]), Bob Giese ([email protected]), Erling Hesla, Chair ([email protected]), Giuseppe Parise ([email protected]), Marcelo Valdes ([email protected]) Supporting Team Members Kurt Clemente ([email protected]), Carey Cook ([email protected]), Tom Dionise ([email protected]), Philip Garland ([email protected]), Gary Fox ([email protected]), Lanny Floyd ([email protected]), Mark Halpin ([email protected]), Mike Hittel ([email protected]), Rob Hoerauf ([email protected]), Barry Hornberger ([email protected]), Tom E. Johnson ([email protected]), Kenneth W. Kozol ([email protected]), Ed Larsen ([email protected]), Wei-Jen Lee ([email protected]), Bruno Lequesne ([email protected]), Claudio Mardegan ([email protected]), L. Bruce McClung ([email protected]), Don McCullough ([email protected]), T. David Mills ([email protected]), Chuck Mozina ([email protected]), Daleep Mohla ([email protected]), Massimo Mitolo ([email protected]), Dan Neeser ([email protected]), Brian Patterson ([email protected]), Dev Paul ([email protected]), Dave Scheuerman ([email protected]), David Shipp ([email protected]), Peter Sutherland ([email protected])

Abstract—In light of the rapid growth of dc loads, ICPS created a small team to outline design considerations for dc distribution and controls. Broad interest in the subject brought in a large group who provided substantial support for the Team. The report begins with a brief background followed by discussion of design considerations that affect ICPS and IAS. The key part of the report is Part IV, which outlines in detail a path forward for ICPS and for IAS. Appendix A outlines an approach toward developing dc standards or recommended practices for design of industrial and commercial power systems. Appendix B lists some of the organizations and individuals that are working on related dc issues at present. Index Terms—AC–DC power converters, direct-current, energy efficiency, power distribution, power sources, power supply, power system, standards organizations.

I. I NTRODUCTION

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HE AC-DC Task Team, created at ICPS2011 under the auspices of the Power Systems Protection Committee, was assigned the task of outlining design considerations for dc distribution and control technology for loads and power sources. Recognizing that the ultimate functions of dc and ac electrical Manuscript received January 29, 2013; accepted January 19, 2014. Date of publication March 18, 2014; date of current version September 16, 2014. Paper 2013-PSPC-048, presented at the 2013 IEEE/IAS Industrial and Commercial Power Systems Technical Conference, Stone Mountain, GA, USA, April 30–May 3, and approved for publication in the IEEE T RANSACTIONS ON I NDUSTRY A PPLICATIONS by the Power Systems Protection Committee of the IEEE Industry Applications Society. (Coordinating author: Erling Hesla.) E. Hesla, retired, resides in Camano Island, WA 98282-8712 USA (e-mail: [email protected]). The authors are members of the DC Task Team, Power Systems Protection Committee, Industrial and Commercial Powers Systems Department, IEEE Industry Applications Department. Digital Object Identifier 10.1109/TIA.2014.2311512

systems are alike, the Team recommends that investigation of dc system design be based on fundamentals presented repeatedly in Color Books [1], [2], in the IEEE 3000 [3, typical] series of standards for ac systems, and in current papers. As noted in the following bullets these say, in essence, that for given loads and power sources, design an electrical system to provide power to the loads. • “2.1 General Discussion. The electric power distribution system in a building exists solely to serve the loads . . .” [IEEE Std 241-1990 (Reaff. 1997); Gray Book] • “2.4.1.1 Load survey • Obtain a general plant or facility layout, mark it with the known major loads . . . determine the approximate total plant load . . .” [IEEE Std 141-1993; Red Book] • “16.2 Information required • A load survey . . . • Availability of utility power . . .” II. BACKGROUND In the late nineteenth century ac inventions of Nikolai Tesla pushed Thomas Edison’s dc power aside, but dc never went away despite dominance of ac. Applications such as mass transportation, certain applications in chemical and metallurgical plants, use of ac/dc and ac/dc/ac conversion for motor drives, continued to grow. Some Public Utilities retained dc distribution until late in the nineteenth century. Commonwealth Edison in Chicago had rotary converters or motor-generator sets which changed dc to ac and ac to various frequencies in the early- to mid-20th century, serving dc loads such as elevators, fans and pumps. There were still 1600 dc customers

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in downtown New York City in 2005, until service was finally disconnected on November 4, 2007. Control of speed and torque of dc motors was well established over a century ago, yet limitations of low voltage dc transmission handicapped power distribution. AC overcame transmission and distribution problems and made the induction motor attractive but induction motors are fixed speed machines that are locked to the supply frequency. Recent developments in solid state (electronic) devices make it possible to convert ac power to dc, and then to invert the dc to the desired frequency so the induction motor can be driven at an adjustable speed. Comparative technical merits and economic constraints of ac and dc systems that have been known for decades are seen in a new light because of recent development in solid state devices that introduce an entirely new approach to the use of dc power. Current technology provides the means to convert ac/dc, dc/ac, and ac/dc/ac conveniently and economically, typically with conversion equipment near the load. As dc loads and inverter loads have grown, engineers have developed dc power distribution to the point where dc distribution now appears in many applications, particularly for Data Centers. Increasingly, trade and technical magazines carry articles covering one or more aspects of dc applications such as lighting and data centers. The article entitled The New AC/DC Debate [3] by Karen George, project Manager for EPRI’s Smart Grid Demonstration Project, is a good example. An earlier article AC-DC Data Center Debate Heats Up [4] by Tom Zind provides useful information on voltage choices for DC systems. IAS Transactions paper DC Distribution for Industrial Systems: Opportunities and Challenges [5] by Baran and Mahajan treats power distribution. The publication IEEE power & energy magazine [7] devoted an entire issue to dc, including articles that relate to ICPS fields of interest. The long history of dc in transportation, shipboard applications, and in the electro-chemical industries warrants thorough research as well. Search engines such as Google are available; for an example, one can narrow the search to such things as a search for dc appliances. A catalog prepared by Berkeley [8] provides information on dc appliances and power systems. NEMA [9] described installation requirements in their 1999 publication. Darnell Group [10] offered a conference in December 2012 to discuss dc distribution systems in buildings, hybrid distribution architectures, dc micro grids, and the smart grid. The paper DC Microgrids: Benefits and Barriers [11] describes the operation of DC microgrids, potential national benefits, barriers to deployment, and policy measures that could accelerate this deployment. This is but a sampling of what is being done in the field of dc. Present ac models are not appropriate for dc power distribution design because they fail to correspond in detail with dc realities. Clearly the time is ripe for IEEE-IAS-ICPS to take a leadership role in developing sound engineering practices in the field of dc power distribution, to replace random probes with scientific vigor. III. D ESIGN C ONSIDERATIONS Two questions must be answered before a power distribution system can be designed. What are the loads? What are the sources of power?

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Once loads and source(s) are known, tasks become: How shall the system be designed to deliver and control power from source to load? What equipment is available? Which Codes, Standards and Regulations apply? A. Loads Given that the sole purpose of an electrical system is to serve loads, the first task is to identify loads and their characteristics. This study attempts to identify major loads without describing them in detail. It provides limited references to sources of information concerning such loads. Specific load requirements will be determined through work in cooperation with other IAS Societies and other entities. Typical loads include: • drives: adjustable frequency drives, inverter driven; dc drives; single and multiple motor drives; • transportation: automobiles, mass transit; • lighting: electronic drivers and ballasts for LEDs, fluorescent, HID light sources; • electrostatic loads; • chemical processes; • metal processes: plating, melting; • data centers; • residential loads; • rural loads; • industrial loads: manufacturing, pulp & paper, mining, petrochemical, marine, etc. B. Power Sources Power and energy can come from many sources, sources that well may grow in variety in coming years with dc potentially growing in importance. Power sources promise to become more complex, more critical, more demanding of careful consideration of how to interface these sources with the providers of power, the Utilities. Utilities will continue to be major providers of power, certainly as ac and possibly as dc. Utilities will continue to transmit and distribute ac power that the customer may elect to convert to dc at the point of service or near major dc loads. Alternatively, the customer may prefer to purchase dc power, with the Utility providing conversion equipment. Size and nature of the ac and dc loads will be significant factors affecting the choices, as will the impact on the Utility’s power system. Utilities will continue to be justifiably concerned about safety when local non-utility generation is connected to their systems. Recent work on power conversion equipment suitable for residential services presents interesting aspects. One approach is to provide a conversion unit with the necessary dynamic response to supply customers with closely regulated ac and dc power, to mitigate transfer of harmonics in either direction, and to accommodate wide variations in supply voltage while reflecting a high power factor load to the Utility’s system. Integration of distributed dc sources such as solar power into a dc power system should eliminate the inverter, may simplify interface requirements, and may boost the economics of residential solar power.

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Development of new power architectures may enable more efficient integration of variable sources such as solar power, wind power, combined heating & power plants, energy storage devices such as batteries and capacitors, plus other innovative devices. Many loads such as UPS equipment and large dc supplies for Data Centers may feed power back into the system. Without doubt, such distributed resources introduce both opportunities and complications to the design of power systems. Developments in the areas of metering, billing and “smart grids” continue to grow rapidly. The paper by Savage et al. [11] gives significant insights. In this report several potential opportunities noted as important areas for future study are not analyzed in this study. The Team anticipates close cooperation between application engineers and Utility engineers in establishing practices in this field. The end result will be that engineers in the field of ICPS will work ever more closely with Utility engineers at the “point of common coupling”. Considerations noted above apply with equal force to independent non-utility local generation. C. System Design Intuitively, approaches used for ac power should apply equally well to dc systems. While this may appear to be so, more likely ac will serve simply as a starting point for dc design. For example, what are the subtle implications of providing two dc feeders to serve one load center? Of providing two dc busses with a tie breaker? Do these and other designs introduce unique operating constraints or opportunities? What are the factors that affect power quality, and what limits or constraints should apply? Are any field data available from existing or historical installations? The System Planning section of the Red Book covering ac design will need to be re-studied for dc design. Both NEC and IEC will have to be studied carefully to see the impact on and by these standards, with particular attention to considerations related to safety. IAS may find it desirable to become increasingly involved with both standards as they relate to dc, given that these standards often drive product standards. The new IEEE 3000 series of design guidelines and the forerunner Color Books will serve well as models. It follows that the power source (typically a Utility source) shall meet load requirements, with the corollary that loads may be controlled to respond to power availability (such as peak shaving, variable billing rates, intermittent generation from solar and wind sources). Two criteria offer possible approaches to modeling a distribution system: • macro system approach for satisfying general needs and standardized quality performances on a common power system; these may differ for network and distribution levels; • micro system approach for satisfying local needs and specific local quality performances with due consideration for special components, energy and cost savings, islanded systems, integrated smart micro-grids, and the like. Traditional ac design analysis focusses on system response at power frequencies with consideration of transients usually

limited to special cases. For dc applications in the broad sense, design calculations and analyses must consider both steadystate and transient conditions, particularly switching transients. Guidelines in the Color Books [1], [2] and the successor IEEE 3000 series of standards provide extensive information on the subject. A suggested outline of parallel dc information is shown in Appendix A, X001 and X002, as a starting point for future ICPS activities. System protection, relaying, will undergo change when applied to dc systems. For example, unlike ac systems that experience high short circuit currents under fault conditions (e.g., default value around 1500% of transformer nameplate rating), dc sources provide lower currents that are in the order of load currents (default value 150% of rectifier rating). Recognition of low-current dc faults requires quite a different approach to system protection. This subject, which is beyond the scope of the Team, is identified here so that experts in protection can devise solutions. Grounding or bonding and cathodic protection: These subjects directly affect both system performance and system safety. They are noted here as key subjects for early investigation. Most likely, interrelationship between ac and dc power systems, instrumentation requirements, and lightning protection systems will play a significant part of such studies. A suggested approach to grounding standards is shown in Appendix A, X004 series. A related subject is system grounding, grounding of the power system. Grounding of ac systems has been studied at great length because it is so important—corner grounding, neutral grounding, impedance grounding, and on and on. Associated relaying has an equally long history of study. Similar consideration must be given for dc system grounding. When should a dc system be grounded? Should the ground connection be at the positive, negative or mid-point terminal? What are the merits of solid grounding versus resistance, inductive or capacitive grounding? What will be the impact on other systems such as instrumentation and communications? Which mathematical procedure is best suited for such analyses? This is a vast field that will require study in cooperation with many entities in addition to ICPS. Preferred voltage levels demand study and resolution. EMerge Alliance released an open 24 V standard to the market in 2009. European Committee for Electrotechnical Standardisation (CENELEC) and the European Telecommunications Standards Institute (ETSI) have bee exchanging information with EMerge Alliance have been exchanging information in order to harmonize certain DC standards. Society of Automotive Engineers (SAE) is working on automotive charging standards. Norwegian ship owner Myklebusthaug Management expects delivery of a 5000 ton support vessel in 2013 that will use a dc power grid operating at 1000 V nominal. Data Centers appear to use 380 V for many applications. Clearly agreeing upon preferred dc voltage levels is a matter of immediate concern. Designing for safety is paramount. Appendix A, X007, gives a recommended outline of standards for safety under Maintenance, Operations & Safety. The Team urges that work be started on such aspects for dc at the earliest opportunity. Safety of the system as it relates to protection of equipment, continuity

HESLA: DC TASK TEAM REPORT

of service, and quality of power is addressed repeatedly within the several other suggested standards in Appendix A. D. Equipment This report considers hardware and software under one heading because the two are closely related in practice. Direct application of ac equipment is highly questionable; hardware and software designed for ac applications must be evaluated very carefully before applying to a dc application. Fortunately, firms developing and providing hardware/software are starting to provide the information essential for application design, as they develop it. The amount of information available at this time is small compared to that for the mature ac market, however, the Team anticipates that dc information will be forthcoming as the market for dc products develops. The Team anticipates that the path of dc development will follow market development just as it has in the past, for major funding will be driven by market requirements. Transformers and DC Transformation: Conventional ac transformers are expected to dominate for the foreseeable future, with DC/DC transformation growing alongside ac/dc. DC performance characteristics similar to ac ones such as impedance, inrush, short circuit or let-through currents, harmonics, losses, insulations, and others will demand careful evaluation. Engineers in the fields of power electronics and power conversion now have, and will continue to have, major impact through their designs for conversion equipment. Undoubtedly ICPS engineers will choose to work closely with them as the field develops. Electronic transformation units for residential loads offer benefits for the Utility when compared to conventional poletop transformers. Present state-of-the-art devices make possible transformation units that accept wide swings in ac voltage, deliver closely regulated ac and dc voltages, mitigate harmonics, and reflect a near-unity power factor load to the serving Utility. The dc feature should facilitate integration of customer’s dc power sources such as solar photovoltaic systems. Switches, Breakers, Switchgear, Control Gear, Fuses, Motor Starters, Contactors, Hardware: The list does not pretend to be comprehensive, nor does it address current efforts by manufacturers. Work has been started to see if standards UL891 for switchboards and UL1558 for switchgear can be extended beyond their historic limits of 600 V AC/DC but detailed consideration is beyond the scope of the Team. That said, the Team emphasizes the need for catalog information adequately supported by data for all of such equipment. The practicing engineer relies on such data for evaluation and design. Several manufacturers have started to provide information on new and existing products for dc applications. IEEE Xplore is another source to search for current information. Although these developing sources are not yet as extensive or as well structured as ac information sources, substantial information can be found through diligent searching. There definitely is a need for a comprehensive index or bibliography concerning what is available today. The engineer is advised that at present, catalog information must be used with caution until such time as product standards and the market develop.

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Drives: Today, adjustable-frequency or variable-frequency drives dominate the field. Basically, power units for such drives convert fixed frequency power to dc and then invert the dc to a variable frequency for single-motor or multi-motor drives. A typical multi-drive line for table rolls in the aluminum industry may operate up to thirty 10–15 hp motors in sections. A single rectifier/inverter operating in V/Hz scheme can serve several motors, each with its own protection. Another approach is to have a larger ac/dc converter serve a dc bus that has several dc/ac inverters, each serving one or several motors with individual protection. With power from a dc bus available, the power unit can be simplified to just the inverter section, and such inverters are on the market now. This opens the possibility that the inverter can be mounted directly on the motor with a fiber or copper control link connected to a module providing control logic. Evaluation of cost and performance impacts on electrical room requirements, equipment and wiring, installation, maintenance, and similar factors are open to immediate investigation. The Team encourages interested engineers to begin such investigations, which in a sense parallels work that has been done regarding the merits of providing dc power to Data Centers. Further, availability of dc power will contribute to advancements that have been made in dc speed and torque control systems hence these systems may represent new loads to consider. Conductors: Both medium and low voltage conductor design involves establishing rated voltage levels, dc current ratings, effect of dc fields on insulation systems, single conductor and multiple conductor configurations, impedance, transient withstand ratings, and terminations. DC current ratings are expected to change for larger conductors, absent consideration of ac “proximity” and “skin effect”. Past studies have shown that the chemical structure of insulations affects directly their performance under dc, and that it is not the same as when used for ac. Early studies of the design of conductors and insulation systems warrant review for the insights they can offer. Standardization of terminations and connectors, on which some work is in progress, are an early requirement for dc distribution. Cable manufacturers have much data both historical and recent. The Team encourages presentation and publication of reviews of past work as well as new developments for wire and cable. E. Related Design Factors Distribution Branch Circuits: Investigation of dc design for distribution branch circuits will follow the pattern established for conductors and equipment. This area of power distribution, covered in detail for ac in both the Red Book and Gray Book, will continue to be covered in the forthcoming IEEE 3000 series of standards. Emergency and Standby Power: Current designs use batteries, UPS equipment, standby generators, and the like for dc applications. These practices provide a solid foundation for designs that will form an important part of the coming dc power systems. Appendix A, X005 series, offers an approach to the broad subject of Emergency & Standby Power Systems. Instrumentation, Sensors, Transducers, Communications: These subjects require the same consideration as noted above.

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The list in the heading is not comprehensive, nor does it address current efforts by manufacturers. Detailed consideration is beyond the scope of this Team. That said, the Team emphasizes the need for catalog information adequately supported by data for all such equipment. The practicing engineer relies on such data for evaluation and design. Software: Several firms offer software programs for power systems that have been updated or created for dc applications. They will continue to develop software for dc analyses to meet market demands. At present the mathematics for the programs is in place but the library of manufacturers’ data for devices is small. Application engineers are cautioned to be particularly diligent and careful when using the limited data available. Protection: Design and application of protective relays will involve modified use of present devices or the use of new devices. The resulting information will form a vital part of software programs. The Team anticipates that protection of the dc system will be integrated with protection of the associated ac system. See the X004 series in Appendix A for a suggested approach.

F. Codes, Standards, Regulations IEEE “Recommended Practice” standards are developed by volunteer engineers, based on their knowledge and experience. The Economist stated “. . .standards are usually drafted by industry bodies after wide consultation. . .” (The Economist, October 6, 2012, p54) It follows that a corpus of “knowledge and experience” is a prerequisite. The Team recommends that ICPS begin development of an outline of anticipated dc standards or of addenda to standards in order to expedite publication when adequate knowledge and experience is in hand. Appendix A offers an approach to development of dc standards. Applicable codes for each legal jurisdiction will be studied to determine their applicability to dc power systems, and may well involve significant expansion of such codes and standards. DC concerns have received limited attention to date. Article 690 in the 2011 edition of NFPA 70 was introduced rather quickly to cover solar photovoltaic systems; other than that, NEC devotes about a page to grounding in Article 250 VIII, a sentence to lighting in 410.134, and touches briefly on dc grounding in articles 692 and 694. UL standards are mentioned in Section IV. The paper by Savage et al. speaks to regulatory constraints and requirements that have a great impact on development of dc power systems. Obviously IEC 603-64-01 which addresses dc design standards is a starting point for any study of dc standards. This is a global issue, complex both technically and politically. Governmental rules, regulations, codes, and standards for dc installations must become a part of future studies. It is incumbent upon ICPS to work diligently in cooperation with other entities toward establishment of technically sound Codes, Standards, and Regulations. With due recognition of the associated problems, complications, and inevitable delays, the Team recommends an early start on Codes and Standards

with particular attention to any current proposals for DC standards. G. Economics Every step of introduction and expansion of dc power applications introduces an economic impact. Economics, always the critical factor, the major driving factor, must be given serious consideration at every step of development of dc power applications and systems. To reiterate, the Team notes that the path of dc development will follow market development, for major funding will come from market requirements just as it has in the past. Varying methods for addressing economic factors will be resolved at each level of development. Energy efficiency, energy conservation, and “green” power aspects will change. Recent reports tell of substantial energy savings when dc sources are used for Data Centers, with a substantial reduction in energy needed for air conditioning. An article [6] by Peter Curtis reports that a demonstration project showed energy savings of up to 28% achieved by using dc-based power distribution systems for data center energy, however, the article does not explore in depth the details of the savings comparison. A paper [12] to be presented at ICPS 2013 that covers certain aspects of installation costs and energy savings for industrial distribution design using equipment that is on the market at present, concludes that a dc system offers cost and energy savings for power distribution to adjustable speed motor drives. The nature of residential services will be driven by economics. One approach that has been voiced is to duplicate wiring throughout the building, which tends toward doubling the initial capital cost. Another approach is to substitute two smaller services in place of the current large ac service, with dc for mechanical loads such as laundry and HVAC and ac for other loads. This opens the possibility of using Smart Grid control to modulate motor speeds rather than resorting to on-off control, and of integrating dc power sources such as solar photovoltaic systems. From the Utility’s standpoint, the reflected load from a dc conversion unit appears attractive because of the improved power factor and tolerance of wider voltage swings. Total costs for support structure and parts may increase, as they certainly will in the near-term when both ac and dc systems must be supported. Several manufacturers claim that space requirements for equipment will be reduced—a cost saving. Initial training for dc will be a cost item; whether training costs will ultimately increase, decrease, or remain the same is difficult to forecast. The critical field of economic justification will require study of all cost factors, such as those outlined in detail in IEEE Std 141, The Red Book, or in the corresponding IEEE 3000 standards when they are released. Reliability; Energy Management; Communications: All three areas will involve considered investigation as dc applications advance. The Team chose not to attempt to delineate these areas except for reference to series X006 standards proposed in Appendix A. The economic impact of dc reliability and availability is an open question, dependent in large part on equipment and system design. Appendix A, X006, offers an approach from a reliability standpoint.

HESLA: DC TASK TEAM REPORT

H. Safety

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A. Recommended Initial Actions BY ICPS

Safety is considered under “design” and repeated here because of its importance. Of particular concern is the safety of employees (workers) who may have close interface activities while working near or in contact with energized dc conductors or devices. Effects on the body of dc current are similar to the effects of ac current, but not quite the same. DC Safety demands the research and investigation accorded to AC Safety, starting with work that has been presented and published in recent years. Recent developments in ac arc-flash levels and related personal protective equipment bring attention to the same subject in dc systems, however, if dc systems experience much lower fault currents does that necessarily mean that dc arcflash hazards are also lower? And what are the implications for PPE? Basic considerations of maintenance, operations, and safety for ac systems apply equally to dc systems. Details will be re-evaluated in light of new products, differing fault and arcflash levels, personal protection equipment, and similar factors. Concern regarding retained (capacitive) charges on lines and equipment will be more significant for dc than it has been for ac. Standards and Safety leaders in an IAS article under the banner “Breaking New Ground” express the need for safe installation and maintenance practices for all applied dc systems. A partial outline of recommended dc practices is presented as X007 in Appendix A. The Team urges an early beginning on dc safety.

IV. PATH F ORWARD Clearly there is a need for the fundamental building blocks of dc power utilization, a need so great that IEEE cannot do it alone. A dynamic approach toward cooperation with others, with definition of the scope and territory of each, will prove vital. A starting point is to look at the existing situation to see what we have in common and then decide on what should be added, and by whom. Terminology must be defined. IEC provides a good starting point with its listing of dc standards and practices covering voltages, topologies, and related subjects. The consensus of the Team is that such work will extend over a period of years, that it will involve many members, that it will be a work in progress rather than a structured program. It is a global task, not an IEEE task. The DC Task Team recommends that ICPS make a dedicated, long-term commitment to development of standards of recommended practice for the design and the safe operation of DC Power Distribution Systems. For ICPS, the Team recommends a biological/organic approach, keeping parts that flourish, divide, and grow new cells, dropping parts that wither and die. In the event, direction of the work will be determined by those ICPS members who are active participants and contributors. Given that the path of dc development will follow market development with major funding coming from market requirements, the Team encourages all members to explain to their employers the benefits that accrue through supporting their related activities in IEEE and specifically in IAS.

• ICPS: Start immediately by assigning modest, attainable program tasks to several Working Groups so each subject will get focused attention. To expedite the flow of information, individual WGs may choose to develop white papers first, followed by formal papers as the subject matures. • ICPS: Identify a coordinator who will: • maintain an index of dc WG activities and of existing and new White Papers; • identify subjects that warrant study, and encourage such study; • develop a “position paper” describing the field of interest that ICPS intends to cover. • ICPS: Solicit active participation from IAS groups that focus on uses of power. Lighting, appliances, and rural loads are typical of these areas. Their input is essential to providing mutual compatibility between sources and loads. • ICPS and IAS: Establish active participation with other interested Societies in IAS. An example is the paper [13] to be presented at REPC 2013. • ICPS: Establish fruitful communications with other organizations (such as EPRI) that are involved in dc power distribution. Another example can be found in the work by Dr. J. W. Kolar (IEEE Fellow, PELS Distinguished Lecturer) under the auspices of the Swiss Federal Institute of Technology Zurich [14]. • ICPS: In an effort to get wider participation and faster response, consider ways to supplement formal IAS papers for present on-going and future dc efforts. Possibilities include webinars, white papers, invited papers, electronic communications, chat groups. Approach other organizations, both IEEE and non-IEEE, to accelerate development and avoid overlap. • ICPS: Develop the following subjects by early attention, technical papers, white papers, invited papers: • outline of standards similar to IEEE 3000, or DC addenda to 3000; • rationale for preferred voltages; • research of arc phenomena and arc interruption; • power interface devices for residential loads; • power interface devices for rural loads; • comparisons of ac and dc power distribution designs, with examples; • information regarding equipment available at present; • search literature for relevant dc papers, including applications from metals and chemical industries, cranes, draglines; • investigate potential impact on Codes.

B. Recommended Actions With Other Societies • Approach other organizations, both IEEE and non-IEEE, to coordinate and accelerate dc development and avoid overlap. • Develop specific joint task groups to address common problems.

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• Develop a bibliography of technical papers, white papers, research, text books, and similar basic materials. • Investigate and suggest academic subjects for theses and research. • Identify at least some dc testing labs, with their ranges of capabilities. • Take advantage of liaison opportunities through engineers such as Thomas Key, IEEE Fellow, who directs an R&D program in EPRI, and who has membership in both organizations.

C. Recommended Long Term Actions by IAS • IAS: Given that the broad scope of dc applications exceeds by far the purview of ICPS, the Task Team recommends that IAS establish a position at Board level to coordinate activities of IAS Societies affected by the growing dc applications. • IAS: Recognizing the potentially wide involvement by many Societies within IEEE as well as extensive global interaction, the Team recommends that IAS sponsor similar coordination at the IEEE Corporate level. • IAS: Develop a “position paper” describing the field of interest that IAS intends to cover, similar to that under study by the Power Electronics Society (PELS). • IAS: Check all the PARs within IEEE that relate to dc, and respond in accordance with the actions outlined above.

A PPENDIX A As examples, a limited selection of possible new standards to be developed as recommended practices for use in industrial and commercial dc power systems are outlined below. Alternatively, dc standards may become addenda to the corresponding IEEE 3000 standards. Essentials (Base) Standard (X000) Power System Design—(X001 Series) • X001.a, “Preferred DC Voltages” • X001.b, “Recommended Practice for Evaluating the electrical Service Requirements of DC Industrial and Commercial Power Systems” • X001.c, “Recommended Practice for the Instrumentation and Metering of DC Industrial and Commercial Power Systems” • X001.d, “Recommended Practice for the DC Lighting of Industrial and Commercial Facilities” • X001.e, “Recommended Practice for Application of Power Distribution Apparatus in Industrial and Commercial DC Power Systems” Power System Analysis—(X002 Series) • X002.a, “Recommended Practice for Conducting DC Motor-Starting Studies in Industrial and Commercial Power Systems” • X002.b, “Recommended Practice for Conducting Harmonic-Analysis Studies of Industrial and Commercial DC Power Systems”

• X002.c, “Recommended Practice for Conducting Switching-Transient Studies of DC Industrial and Commercial Power Systems” Power Systems Grounding—(X003 Series) • X003.a, “Recommended Practice for the System Grounding of Industrial and Commercial DC Power Systems” • X003.b, “Recommended Practice for Equipment Grounding and Bonding in Industrial and Commercial DC Power Systems” Protection and Coordination—(X004 Series) • X004.a, “Recommended Practice for the Application of Instrument Transformers in Industrial and Commercial DC Power Systems” • X004.b, “Recommended Practice for Generator Protection in Industrial and Commercial DC Power Systems” • X004.c, “Recommended Practice for Bus and Switchgear Protection in Industrial and Commercial DC Power Systems” Emergency & Stand-By Power Systems—(X005 Series) • X005.a, “Recommended Practice for the Application of Stored-Energy Systems for Use in Emergency and StandBy DC Power Systems” • X005.b, “Recommended Practice for Improving the Reliability of Emergency and Stand-By DC Power Systems” • X005.c, “Recommended Practice for the Application of Metering for Energy Management of Industrial and Commercial DC Power Systems” Power Systems Reliability—(X006 Series) • X006.a, “Recommended Practice for Determining the Reliability of ‘24 × 7’ Continuous DC Power Systems in Industrial and Commercial Facilities” • X006.b, “Recommended Practice for Analyzing Reliability Data for Equipment Used in Industrial and Commercial DC Power Systems” • X006.c, “Recommended Practice for Collecting Data for Use in Reliability, Availability, and Maintainability Assessments of Industrial and Commercial DC Power Systems” Maintenance, Operations & Safety—(X007 Series) • X007.a, “Recommended Practice for the Operation and Management of Industrial and Commercial DC Power Systems” • X007.b, “Recommended Practice for the Maintenance of Industrial and Commercial DC Power Systems” • X007.c, “Recommended Practice for Electrical Safety in Industrial and Commercial DC Power Systems” A PPENDIX B The following is a limited list of individuals and organizations working in dc fields at the time this report was prepared. It is by no means comprehensive, and is offered only as a “starting point” for future activities. Andy McMillan, BACnet International; [email protected]; 770-971-6003 (tel)

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Don Talka and Michael Shulman, UL; [email protected]; 631.546.2447 (tel) [email protected]; 408.754.6703 (tel) Ken Gettman, NEMA; [email protected], tel: 703-841-3254 Dennis Symanski, EPRI; [email protected]; (650) 855-1000 Electric Power Research Institute (EPRI); [email protected]; www.epri.com; 800.313.3774 EMerge Alliance, an www.EMergeAlliance.org

open

industry

association,

Other resources include—Enocean Alliance; ZigBee Alliance; US Department of Energy (DOE) Labs; NFPA; PSMA (Power Supply Manufacturers Association); IEC; Society of Automotive Engineers (SAE); European Committee for Electrotechnical Standardisation (CENELEC); European Telecommunications Standards Institute (ETSI) The following papers can be Googled: Possibilities of the Low Voltage DC Distribution Systems; Tero Kaipia, Pasi Salonen, Jukka Lassila, Jarmo Parteanen; Lappeenrata University of Technology, Lappeenrata Finland

[3] K. George, “The new AC/DC debate,” Elect. Line Mag., vol. 18, no. 1, pp. 50–56, Jan./Feb. 2012. [Online]. Available: www.electricalline.com [4] T. Zind, “AC-DC data center debate heats up,” EC M, vol. 107, no. 1, pp. 32–39, Jan. 2008. [Online]. Available: www.ecmweb.com [5] M. E. Baran and N. R. Mahajan, “DC distribution for industrial systems: Opportunities and challenges,” IEEE Trans. Ind. Appl., vol. 39, no. 6, pp. 1596–1601, Nov./Dec. 2003. [6] P. M. Curtis, “Integrating existing and innovative strategies in data centers,” Mission Critical, vol. 5, no. 3, pp. 22–26, May/Jun. 2012. [Online]. Available: www.missioncriticalmagazine.com [7] IEEE Power Energy Mag., vol. 10, no. 6, Nov./Dec. 2012. [8] E. Orlando, “Catalog of DC appliances and power systems,” Lawrence Berkeley Nat. Lab., Berkeley, CA, USA, Rep. LBNL-5364E, Oct. 2011. [9] Electrical Installation Requirements, A Global Perspective, NEMA, Rosslyn, VA, USA, Apr. 1999. [10] Darnell Group, in DC Building Power Asia Conf., Shanghai, China, Dec. 2012. [11] P. Savage, R. R. Nordhaus, and S. R. Jamieson, DC Microgrids: Benefits and Barriers. New Haven, CT, USA: Yale School of Forestry & Environmental Studies, 2007. [12] E. Hesla, B. Giese, T. E. Johnson, and M. Mitolo, “Economics of DC power distribution for motors,” in Proc. 49th IEEE/IAS Ind. Commercial Power Syst., 2013, pp. 1–7. [13] E. Hesla, “Is DC coming to rural electric systems,” in Proc. IEEE REPC, 2013, pp. C1-1–C1-6. [14] J. W. Kolar and G. I. Ortiz, “Solid state transformer concepts in traction and smart grid applications,” in Proc. 15th Int. Power Electron. Motion Control Conf., 2012, p. 166. [15] P. E. Sutherland, “DC short-circuit analysis for systems with static sources,” IEEE Trans. Ind. Appl., vol. 35, no. 1, pp. 144–151, Jan./Feb. 1999. [16] R. W. Lye, Ed., Power Converter Handbook: Theory, Design and Application. Peterborough, ON, Canada: Canadian General Electric Company Limited, 1976, Pub. PGEI-10355A. [17] A. C. Stevenson, Power Converter Handbook: Theory, Design and Application. Peterborough, ON, Canada: General Electric Canada Inc., 2002.

Small-Scale Residential DC Distribution Systems; Kristof Engelen, Erik Leung Shun, Pieter Vermeyen, Ief Pardon, Reinhilde D’huist, Johan Driesen, Ronnie Belmans AC versus DC Power Distribution for Data Centers; Neil Rasmussen, Chief Technical Officer, American Power Conversion, White Paper #63, presented at the 2006 American Power Conference DC Power Production, Delivery and Utilization, an Epri White Paper; Karen George, EPRI Solutions, Inc.; 2006 R EFERENCES [1] H. L. Floyd, II, S. M. Halpin, and L. F. Saunders, “An overview of the IEEE color books,” in Conf. Rec. IEEE IAS Annu. Meeting, 2000, pp. 3226–3231. [2] B. McClung, “Integration of components in a power system,” IEEE Ind. Appl. Mag., vol. 17, no. 5, pp. 74–75, Sep./Oct. 2011.

Erling Hesla (S’46–M’48–SM’62–LSM’86) was born and educated in Canada, graduating from the The University of British Columbia, Vancouver, BC, Canada, in 1947 with the B.ASc. degree in electrical engineering. He was employed by Canadian General Electric Company, Cobast in Brazil, and Scott Paper Company before moving into consulting practice. He helped establish a panel manufacturing firm, a robotics control firm, and a company that manufactured devices for hearing aids and holds three patents relating to such devices. Mr. Hesla has been active in AIEE and IEEE, for example: Chair of the “Yellow Book” (1902–1998), Chair of a chapter of the “Red Book” (1941–1983), past Member-at-Large of the IAS Executive Board, and past Chair of IAS Chapters Technical and Professional Outreach Committee. He received the RAB Larry K. Wilson Transnational Award in 1998 for innovative promotion of IEEE globalization. He is Professional Engineer in several States and has served as an expert witness.