Transcript Slide 1

NEMA/NFPA/UL LVDC Conference
April 8, 2011
Product Standards
Ken Boyce
Underwriters Laboratories Inc.
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LVDC standards development
• 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
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“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
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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
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LVDC Systems
Generation
Use
Storage
Distribution
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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
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Photovoltaic systems
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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
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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
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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
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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
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Fuel Cells
Fuel Cells addressed by a number of
standards:
Source: www.slipperybrick.com
•
•
•
•
Stationary: ANSI FC-1
Portable: ANSI FC-3
Hand-held: UL Sub 2265A
Industrial Trucks: ANSI/UL 2267
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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
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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
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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
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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 4248-18,
and Sub 98B
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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
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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
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Use
DC presently used in many places:
• Lighting
• Information technology (IT) rooms
• Photovoltaic systems
…..and many more are on the horizon
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Lighting
• Low voltage lighting systems
addressed by UL 2108 and
NEC Article 411
Source: www.lightsoutlighting.com
• LED Lighting addressed by UL Sub 8750
and other standards
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Source: www.lightsoutlighting.com
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
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Ceiling Grid DC System
Source: www.armstrong.com
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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
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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
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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
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Couplers for DC Data
Centers
• Variety of designs
• Being addressed by
development of UL Sub
2695 and IEC 62695
• Ratings up to 400Vdc
Source: The Green Grid
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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
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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
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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
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Thank you
[email protected]
847.664.2318
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