technical perspective - rmel · 2018. 3. 28. · 3) based on ieee 1584 equations. 1 inch gap, 1.641...
TRANSCRIPT
-
Page 1 www.brainfiller.com
.com P.O. Box 12024 | Scottsdale, AZ 85267, USA | 800.874.8883
Arc FlashTechnical
Perspective
Jim Phillips, P.E.
-
Arc Flash and the Technical Perspective
● Vice Chair of IEEE 1584 IEEE Guide for Performing Arc Flash Hazard Calculations● International Chair of Geneva Based IEC TC78 Committee – Live Working● Liaison Officer between IEEE 1584 and IEC TC78 Arc Flash Committees● Author of the book: Complete Guide to Arc Flash Hazard Calculation Studies● Member: Steering Committee – IEEE/NFPA Arc Flash Collaborative Research Project● Founder of the Electrical Power and Electrical Safety Training Company: Brainfiller.com● Founder of the internationally known website: ArcFlashForum.com
Jim Phillips will discuss the relevant OSHA, NESC and IEEE standards used for protecting workers from the arc flash hazard. See how to create an arc flash protection strategy by determining the severity of the thermal hazard and specifying suitable arc rated clothing and related personal protective equipment. Jim is at the forefront of arc flash standards both nationally and internationally and is:
-
Major Standards
Electrical Safety Pyramid
OSHAFederal
Regulations
Consensus Standards
NFPA 70E - General Industry
NESC - Electric Utility
Guides, Practices, Methods
IEEE 1584 - IEEE Guide for Performing Arc Flash Hazard Calculations
-
OSHA 1910.269(I)(8)(ii)
Clothing Restrictions
• The employer shall ensure that
each employee who is
exposed to the hazards of
flames or electric arcs does not
wear clothing that, when
exposed to flames or electric
arcs, could increase the extent
of injury that would be
sustained by the employee.
-
OSHA 1910.269(I)(8)
• Assess workplace for hazards from flames or
electric arcs
• If there is exposure, estimate incident energy
• Appendix E provides methods for estimating Ei
• Other methods could be used if reasonable
• Require Arc Rated clothing under certain
conditions
• Select clothing with arc rating grater than
estimated incident energy
-
Copyrig
ht ©
Obero
n
-
• Intensity
• Duration
• Distance
• Equipment Type
-
Copyrig
ht ©
Obero
n
• ATPV or Ebt
• Arc Rating is on
the Garment Label
• cal/cm2
• J/cm2
• kJ/m2
-
Higher Short Circuit + Longer Clearing Time
= Greater Incident Energy
How much short circuit current?
Arc Flash Duration?
Protective device
opening time?
-
Arc Flash Duration and Incident Energy
Incid
en
t E
ne
rgy –
ca
l/cm
2
0
2
4
6
8
10
12
3 6 9 12
Clearing Time - cycles
-
Selecting a Reasonable Incident Energy
Calculation Method
• IEEE 1584 Calculations - 3 Phase• Good for equipment in enclosures
• Empirical < 15 kV
• Theoretical > 15 kV
• OSHA 1910.269 Appendix E Tables
• NESC Tables 410-1 and 410-2
• Arc Pro - 1 Phase
-
IEEE 1584 – IEEE Guide for Performing
Arc-Flash Hazard Calculations
• Calculations based on IEEE working group
• Calculations are still evolving
• Based on statistical analysis and curve fitting
• Calculations for incident energy limitations• Voltage 208 Volts to 15 kV three phase
• 50 to 60 Hz.
• 700 Amps to 106,000 Amps short circuit
• 13 mm to 152 mm conductor gap
• Intended for three phase - Conservative if
single phase event
-
PPE / Arc Rating Selection from Study
Results Using IEEE 1584 Calculations
Arc Flash Calculation Study ResultsBrainfiller Industries
Bus NameVoltage
(kV)Equipment
TypeArc Gap
(mm)
Bolted Fault (kA)
Est. Arc Fault (kA)
Arcing Time (sec)
Est. Arc Flash
Boundary (feet)
Working Distance (inches)
Incident Energy
(cal/cm2)PPE Level
MAINSWGR
0.48 Switchgear 32 37.734 19.034 0.167 6.65 24 7.0 #2
PANEL 1A 0.48 Panel 25 27.285 15.457 0.200 5.67 18 10.6 #3
PANEL 1B 0.48 Panel 25 27.368 15.497 0.050 2.13 18 2.7 #1
MCC-1 0.48 MCC 25 21.117 12.418 0.100 2.81 18 4.2 #2
PANEL 2 0.48 Panel 25 21.164 12.442 0.033 1.44 18 1.4 #1
Incident Energy in cal/cm2
-
2017 NESC Rule 410.A.3Paraphrased
Performed by: Wylie E. Coyote
Reviewed by: Road Runner
Employer shall ensure assessment is
performed to determine arc flash hazard
Perform a detailed arc hazard analysis or
use Table 410-1, 410-2 or 410-3
Analysis includes calculation of estimated
arc energy
Employees wear clothing or clothing system
with effective arc rating not less than
anticipated level of arc energy.
Exception: If clothing can create a greater
hazard then an arc rating less than required
may be worn
-
NESC Table 410-1 Clothing and clothing
systems for 50 V to 1000 V (ac)
Equipment TypeNominal Voltage Range and cal/cm2
50 V to 250 V 251 V to 600 V (14) 601 V to 1000 V
Self-contained meters / cabinets 4 (2) 20 (4) 30 (8)
Pad mounted transformers 4 (9) 4 (9) 6 (8)
CT meters and control wiring 4 (2) 4 (5) 6 (8)
Metal-clad switchgear / motor
control centers8 (3) 40 (6) 60 (8)
Pedestals / pull boxes / hand
holes4 (2) 8 (7) 12 (8)
Open air (includes lines) 4 (2) 4 (7) 6 (8)
Network protectors 4 (10) (11) (11)
Panel boards – single phase (all) /
three phase ( 100A)4 (2) (13) (13)
2017 National Electrical Safety Code – always consult the latest editionNote: Use the NESC table
-
NESC Table 410-1
Notes – Partial List
1) Developed from fault testing based on equipment type and is
independent of fault current unless otherwise noted.
2) Industry testing shows arc does not sustain more than 2 cycles
3) Based on IEEE 1584 equations. 1 inch gap, 1.641 distance
factor, 208V, 1000 kVA transformer, 500 MVA source, max
duration 10 cycles
4) Industry testing did not exceed 20 cal/cm2
5) Industry testing did not exceed 4 cal/cm2
6) Based on IEEE 1584 equations. 1 inch gap, 1.641 distance
factor, 480 V, 12.47 kA, max duration 85 cycles
7) Incident analysis does not exceed table values
8) Engineering analysis shows using 150% multiplier is conservative
9) Industry testing shows values do not exceed 4 cal/cm2
2017 National Electrical Safety Code – Consult the standard for the complete list. Always consult the latest edition
-
NESC Table 410-1
Notes – Partial List
10)Industry testing shows values do not exceed 4 cal/cm2
11)Industry testing shows arc will not self extinguish and heat flux
rates will exceed 60 cal/cm2/second at 24 inch working
distance – perform analysis.
12)Industry testing shows values do not exceed 8 cal/cm2
13)Industry testing shows arc will not self extinguish and heat flux
rates will exceed 60 cal/cm2/second at 18 inch working
distance – perform analysis.
14)IEEE 1584 original test data indicates there is no significant
difference between heat flux rates for 400V class and 600V
class equipment.
2017 National Electrical Safety Code – Consult the standard for the complete list. Always consult the latest edition
-
Transformer Secondary Blind Spot
Forensic Analysis
Sleeve burned through
Leather burned through, rubber
line is intact
Example of an arc rated FR shirt (5 - 6 cal/cm2) and
gloves worn by a person who was burned in a
secondary fault while hooking up some 120/208V.
leads to a pad mounted transformer. He came out
of it with just some 2nd degree burns on his arm.
-
Arc Rated Clothing and PPEC
opyr
ight
© O
bero
n
-
NFPA 70E 130.7(C)(10) (b)(1)
Head Protection < 12 cal/cm2
Arc rated face shield with
arc rated balaclava for
head protection when head
is within arc flash boundary.
Arc rated hood is permitted
instead of face shield and
balaclava
-
NFPA 70E 130.7(C)(10) (b)(2)
Head Protection > 12 cal/cm2
When the incident energy
exposure is greater than 12
cal/cm2, an rated hood shall
be used.
-
Head Protection
OSHA 1910.269(i)(8)(v)(C) thru (E)
1910.269(l)(8)(v)(C)
Arc-rated protection is not necessary for the employee's head when the employee is
wearing head protection meeting § 1910.135 if the estimated incident energy is less
than 9 cal/cm2 for exposures involving single-phase arcs in open air or 5 cal/cm2 for
other exposures,
1910.269(l)(8)(v)(D)
The protection for the employee's head may consist of head protection meeting §
1910.135 and a faceshield with a minimum arc rating of 8 cal/cm2 if the estimated
incident-energy exposure is less than 13 cal/cm2 for exposures involving single-
phase arcs in open air or 9 cal/cm2 for other exposures, and
1910.269(l)(8)(v)(E)
For exposures involving single phase arcs in open air, the arc rating for the
employee's head and face protection may be 4 cal/cm2 less than the estimated
incident energy.
-
Face Protection
Face shields must have
sufficient arc rating and a
wrap-around guarding to
protect the face, chin,
forehead, ears and neck.
-
Hand Protection
Heavy duty leather gloves or
arc-rated gloves shall be worn
Leather protectors shall be worn
over rubber insulating gloves.
-
Clothing Material Characteristics
• Non-AR fabrics that ignite
(start to burn) will continue
to burn and can increase
the severity of the burn.
• AR fabric can ignite but will
extinguish itself after the
ignition source is gone.
• AR materials provide
thermal protection.
-
NFPA 70E
130.5(H) Equipment Labeling
130.5(H)(1) Nominal system voltage
130.5(H)(2) Arc flash boundary
130.5(H)(3) At least one of the following:
Incident Energy and Working Distance Selected
-
Thank You!
.com
-
Stay Connected!
Brainfiller https://twitter.com/brainfiller
BrainfillerTV https://www.youtube.com/user/BrainfillerTV
Jim Phillips Brainfiller.com
Brainfiller https://www.linkedin.com/in/brainfiller