Download Electrical Safety and High Energy Physics 1 Dr. Perry L Anthony

Electrical Safety and High Energy
Physics
Dr. Perry L Anthony
SLAC Electrical Safety Officer
International High Energy Physics Technical Safety Forum
1
4/11/2005
Electrical Hazards in High
Energy Physics
„
High Voltage detector components
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High current power supplies
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Generally low current, mostly represent a “startle
hazard”
Possible burns from shorting items across terminals
Stored energy
„
Possible burns from shorting, internal damage
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What determines the hazard?
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Voltage
Current
Duration
Energy
International High Energy Physics Technical Safety Forum
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What determines the
Damage? I = V
R
Circuit
Path
Voltage
Resistance
Environment
Current
Waveform
Energy
Duration
Determines
Immediate
Impact
International High Energy Physics Technical Safety Forum
P=IxV
E=Pxt
Damage
Done
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Injury from R&D Equipment
burn
injury
arc
flash
electric
shock
reflex
International High Energy Physics Technical Safety Forum
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Typical Examples
magnet lab generator
electroplating supply
computer power supply
computer circuits
CRT monitor
photon detector
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Results of Electric Injury
„
Burn from tool across
terminals for a low
voltage, high current
device
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Results of Electric Injury (cont.)
„
High Voltage
breakdown of skin
with entrance/exit
wounds
International High Energy Physics Technical Safety Forum
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Results of Electrical Injury (cont).
„
Arc Flash Burns:
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Protecting from hazards
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Engineering controls
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Keep the hazard isolated
Interlocks
Administrative Controls
„
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Personnel Protective Equipment (PPE)
Procedures (application of Lock Out Tag Out)
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When/What protection is
necessary?
„
Codes and Standards specify
when/where protection is required:
„
In the US:
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OSHA
NEC
NFPA-70E
DOE Electrical Safety Handbook
Also Facility standards and procedures
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US: NFPA-70E Standard for
Electrical Safety in the Workplace
„
„
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Must protect against both electric shock and
possible arc flash
Preferred method is to de-energize the
equipment
Special procedures for testing, troubleshooting,
voltage measuring, and similar activities on
energized parts
Permit with special procedures for other
activities on energized parts
International High Energy Physics Technical Safety Forum
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NFPA-70E: Shock Protection
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Triggered when working “on or near” exposed
energized parts:
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Over 50V
On = tool or body part touching
Near = any activity within the “limited approach
boundary” (voltage dependent)
Requires all body parts within the “Prohibited
Approach Boundary” to be insulated against the
voltage
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Limited and Prohibited Approach
Boundaries for Electrical Shock
„
Voltage dependent:
„
„
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Prohibited = point where the voltage could
jump the air gap
Limited = larger region, activity in this region
could result in accidental contact
Example:
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120V: Limited = 42 inches; Prohibited = contact
480V: Limited = 42 inches; Prohibited = 1 inch
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Arc Flash Protection Boundary
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Boundary set at point where energy of
arc may just cause a 2nd degree burn
(blistering)
Depends on many factors (e.g. current,
duration)
May be larger than Limited Approach
Boundary for Shock
International High Energy Physics Technical Safety Forum
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What does that give us?
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New labels on equipment:
„
Arc Flash hazard labels
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More arc flash labels
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Equipment Inspection Labels
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All electrical equipment must be listed for use by
a Nationally Recognized Testing Laboratory
(NRTL) or other agency certified by the local
Authority Having Jurisdiction (AHJ)
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Is this enough for the HEP
community? NO!
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Good for shock hazard.
Not enough for burn hazards:
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NFPA-70E and IEEE-1584 give formulas for
60 Hz AC systems only!
Nothing about capacitor Banks
Nothing about high current low voltage
power supplies
Nothing about RF systems
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DOE Electrical Safety
Handbook
„
Only 2 out of 11 chapters applicable to
HEP:
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Chapter 9: Enclosed Electrical/Electronic
Equipment
Chapter 10: Research and Development
Gives guidelines for construction
Limited guidance for protection
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Where does that leave the
HEP Community?
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Each facility has needed to develop
guidance to ensure worker safety
Hazards may not be recognized
Standards not uniform
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Six US Facilities
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Where do we go from here?
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Capitalize on the expertise in the HEP
community to develop standards for
situations and equipment not covered by
existing codes (e.g. RF, capacitor banks)
Use forums like this one to work towards
uniform standards
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Initial steps
„
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The DOE Electrical Safety Handbook is a
step in this direction.
Efforts are underway to establish an
international committee under ISA to
develop standards for High Energy R&D
Electrical Systems.
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High-Power Research and
Development Electrical Systems
Standards Committee
„
Scope
„ To develop standards, recommended practices,
technical reports and related information documenting
design, fabrication, installation, operation, and
maintenance of high power electrical systems, and
their associated control, monitoring, safety, and
protection systems for national and international
research programs in accelerators, pulsed power
applications, and high power lasers.
- From the 2005 R&D Electrical Safety Meeting and Workshop held at SLAC March 28-31
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