p/1 NEMA/NFPA/UL LVDC Conference April 8, 2011 Product Standards Ken Boyce Underwriters Laboratories Inc.

p/2 DC equipment has been used in many focused applications in the past, dating back to Thomas Edison as a vocal proponent Product standards & codes have addressed these focused applications, with much evolution LVDC standards development

p/3 “Farm Lighting Plants” 1905 NEC contained requirements for Direct Current systems; “Low Potential” was specified as 550 Volts Source: powerstream.com 1920 NEC, Rule 43B addressed “Isolated Light and Power Equipments for Less Than 50 Volts” This grew into Art. 720 by the 1953 NEC, which addressed circuits such as “farm lighting plants” operating at about 32V

p/4 Today Much has changed since the early days of DC power distribution… but today we see elevated interest in DC distribution based on a variety of factors. This produces the need for codes & standards to adequately address them

p/5 LVDC Systems Generation Storage Distribution Use

p/6 Generation DC distributed generation sources use is expanding Typical sources are photovoltaic (PV); some increase in use of fuel cells DC power supplies & batteries used in specific equipment applications

p/7 Photovoltaic systems

p/8 Photovoltaic systems Photovoltaic systems typically generate (& distribute) DC power on premises Modules may or may not be “low voltage” - ~0.5V/cell Increasing voltage means more attention to mitigating hazards such as shock, ground faults and arcing

p/9 Variations in PV systems Module outputs vary based on design, number of cells and technology Crystalline modules up to ~36V; Thin film modules up to ~80V System operating voltage varies based on number of modules, application & configuration

p/10 PV Requirements Installation addressed by NEC Art. 690 UL has developed a suite of publications to address PV equipment and related wiring/distribution devices UL 1703 the primary standard for PV

p/11 PV Experiences & Learnings System voltages trending upward Special consideration for standards is needed Efforts underway to standardize connector & module port configurations Ground faults not unusual based on wiring practices

p/12 Fuel Cells Fuel Cells addressed by a number of standards: Source: Stationary: ANSI FC-1 Portable: ANSI FC-3 Hand-held: UL Sub 2265A Industrial Trucks: ANSI/UL 2267

p/13 Storage Storage may take many forms In practicality, today it’s typically accomplished through batteries Batteries expected to remain the primary storage technology for the near future

p/14 Battery Standards Stationary: UL 1973 Vehicle: UL 2580 (and others) – relevant for V2G & plans to repurpose auto batteries for second life Portable & cells – many standards including UL 1642 Lithium, UL 2054 Household, UL 2575 Battery Systems for Appliances

p/15 Storage issues moving forward Developing/refreshing codes and standards as needed – e.g. V2G Addressing safety of evolving technology as well as concerns like relative performance Repurposing and other practical use issues

p/16 Distribution Standards may be needed to address unique aspects of DC distribution New use for existing products or new requirements and products? PV platform includes Sub 4703, Subs 6703/6703A, Sub 2759, Sub , and Sub 98B

p/17 Grid issues Grid connectivity a primary concern addressed by UL 1741 and IEEE 1547 Much effort dedicated to standards for smart grid use to enable more sophisticated use and distribution Efforts also underway to develop standards for microgrids to maximize power distribution on campuses

p/18 Electric Vehicle Supply Equipment UL has been active in developing EVSE safety standards, including Sub 2594 Addresses a critical concern for distributing DC to the point of use Special protective measures to mitigate user access and electric shock concerns

p/19 Use DC presently used in many places: Lighting Information technology (IT) rooms Photovoltaic systems …..and many more are on the horizon

p/20 Lighting Low voltage lighting systems addressed by UL 2108 and NEC Article 411 Source: LED Lighting addressed by UL Sub 8750 and other standards Source:

p/21 Suspended ceiling grid LV lighting Recently Listed by UL to Sub 2577 Originally envisioned for lighting and other equipment (e.g. hot spots) Presently limited to use in lighting applications based on NEC Article 411 provisions

p/22 Ceiling Grid DC System Source:

p/23 Movement to more DC distribution The ceiling grid concept showed movement to establishing an LVDC grid within a premises We have seen other product concepts with similar approaches Product standard and Code issues both come into play

p/24 Focus on components and materials UL working to address component requirements specific to DC issues: Research work on characterization of polymers to DC sources (up to 1kV) based on potential for different response to DC than AC Components such as DC appliance couplers for data centers

p/25 Materials Polymers extensively assessed for reaction to AC conditions Reaction to DC use may be different UL reviewing issues such as tests for DC tracking resistance and resistance to arcing from DC

p/26 Couplers for DC Data Centers Variety of designs Being addressed by development of UL Sub 2695 and IEC Ratings up to 400Vdc Source: The Green Grid

p/27 On the horizon Increasing community/local energy storage, DC generation and DC distribution within premises Increasing issues with infrastructure for DC distribution Need product standard & Codes to address key issues such as safety, interconnection, and interoperability

p/28 Standards development Many organizations active in developing standards to address the phenomenon of DC distribution These organizations include UL, NFPA, IEEE, IEC, EMerge Alliance, Solar ABCs Holistic efforts needed to address key issues for the public, including safety

p/29 Conclusion Products standards & codes address focused LVDC applications and new uses Standards development will be required to address key issues such as safety, interconnectivity, and interoperability Collaboration by key stakeholders is needed to generate a cohesive set of standards & codes supporting safe deployment

p/30 Thank you