WWCC Arc Flash Mitigation Atlanta

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Arc Flash Mitigation

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Smart Water for
Smart Cities
Arc Flash Mitigation
Enhancing Personnel Safety
Terry L. Schiazza
Low Voltage Offer Marketing
Seneca (SC) Plant

Sponsored by the Water Wastewater
Competency Center
Atlanta, GA
May 2014

● Graduated (1980) Georgia Institute of Technology
Bachelor of Mechanical Engineering
Graduated (1991) Clemson University
Master of Human Resource Development
● Began career at Square D in 1980 and serve as
Business Development Manager for Partner Business Unit
● Member of IEEE/IAS and AIST
- IEEE/PCIC Chemical Subcommittee
- AIST Energy Applications Technology Committee
Terry L. Schiazza

● Standards Working Group member of
- IEEE 1683
- IEEE C37.20.7

Co-authored published IEEE paper
(Paper No. PCIC-2008-31) presented at the 2008
Petroleum and Chemical Industry Committee
(PCIC) conference in Cincinnati.
ELECTRONIC MOTOR CIRCUIT PROTECTORS
A fresh perspective on sizing circuit protection for
branch motor circuits in a low voltage motor
control center

Co-authored published AISTech 2012 Proceedings
(Paper 25222113) presented at the 2012 Association
for Iron & Steel Technology Conference in Atlanta.

New Approach for Intelligent Motor Control Centers
*Recipient of the 2013 AIST Farrington Award received
at the Pittsburgh Technology Conference
2

Arc Flash Principles and Theory

Arc Blast & Arc Flash occur
together. The term Arc Flash
often refers to both
phenomena. From here on,
the term Arc Flash will be
used for both terms.

Arc Flash Characteristics
Pressure
Effects

Thermal
Effects

Why is Arc-Flash Analysis Important?
• Need to provide optimal safety for electrical workers

• Increasing awareness of arc-flash hazards
• Calculation of Arc-Flash Incident Energy (AFIE) allows selection of
“adequate” Personal Protective Equipment (PPE) if equipment must be
worked while energized
• Working on or near exposed live parts: NFPA 70E requires an arc-flash
hazard analysis if equipment >50V is not placed in an electrically safe
working condition
• OSHA is enforcing NFPA 70E!
• NEC 2014 Impact Changes (Section 240.87)

NFPA 70E PPE Table
Table 130.7(C)(11) Protective Clothing Characteristics
Typical Protective Clothing Systems

Hazard/Risk
Category

Clothing Description
(Typical number of clothing layers is given in parentheses)

Required Minimum
Arc Rating of PPE
[J/cm2(cal/cm2)]

0

Non-melting, flammable materials (i.e., untreated cotton, wool, rayon, or silk, or
blends of these materials) with a fabric weight at least 4.5 oz/yd 2 (1)

N/A

1

FR shirt and FR pants or FR coverall (1)

16.74 (4)

2

Cotton underwear — conventional short sleeve and brief/shorts, plus FR shirt and
FR pants (1 or 2)

33.47 (8)

3

Cotton underwear plus FR shirt and FR pants plus FR coverall, or cotton underwear
plus two FR coveralls (2 or 3)

104.6 (25)

4

Cotton underwear plus FR shirt and FR pants plus multilayer flash suit (3 or more)

167.36 (40)

Note: Arc rating is defined in Article 100 and can be either ATPV or EBT. ATPV is defined in ASTM F 1959-99
as the incident energy on a fabric or material that results in sufficient heat transfer through the fabric or
material to cause the onset of a second-degree burn based on the Stoll curve. EBT is defined in ASTM F
1959-99 as the average of the five highest incident energy exposure values below the Stoll curve where the
specimens do not exhibit breakopen. EBT is reported when ATPV cannot be measured due to FR fabric
breakopen. (APTV = Arc Thermal Protective Value)

AF Testing & Models
• To date, there are no practical theoretical models that match
tested arc flash results
• Instead, state-of-the-art techniques use empirical models based
upon test results
• IEEE 1584-2002 gives an empirical model that, if properly applied,
gives 95% confidence that calculated PPE will be adequate or morethan-adequate for hazards associated with heat energy from an arc
• Other effects, such as pressure-wave effects and the effects of
the expulsion of molten metal, are not taken into account in the
IEEE-1584 model.

IEEE 1584 Model
• Ia is the arcing current (kA), defined by IEEE-1584 as:
Ia  10K  0.662logIbf  0.0966V  0.000526G 0.5588V logIbf 0.00304G logIbf

K = -0.153 for open configurations, = -0.097 for box configurations
Ibf: Bolted fault current for three-phase faults (symm. RMS) (kA)
V: System voltage (kV)
G: gap between conductors, (mm)
• Represents current that would flow through the arc during
an arcing fault – typically 50% - 60% of bolted fault current
for 480V system

IEEE 1584 Model
• En is the normalized incident energy

En  10K1  K2 1.081logIa  0.0011G
K1 = -0.792 for open configurations, = -0.555 for box configurations
K2 = 0 for ungrounded or HRG systems, = -0.113 for grounded
systems
Ia is the arcing current (kA) (Calculated)
G is gap between conductors, (mm) (Measured)
• Represents arc-flash incident energy normalized to a
working distance of 610mm and 0.2s arcing time

IEEE 1584 Model
• E is the calculated incident energy

 t  610
E  C f En 
 x
 0.2  D

x





(cal/cm2)

Cf = 1.5 for voltages  1kV, = 1.0 for voltages > 1kV
t: Arcing time in seconds
D: Working distance (mm)
x: Distance exponent (tabulated in IEEE 1584)
• Note that once E is calculated, the process should be repeated but for Ia =
85% of the calculated value. The larger of the two values for E is the
calculated arc-flash incident energy.

What System Parameters Can be
Changed to Reduce AFIE?
• From IEEE 1584 model:





System Voltage
Bolted fault current
Gap between conductors
Arcing time

• System voltage: Generally not practical to change

• Gap between conductors: Would require different equipment
construction, not practical to change
• That leaves bolted fault current and arcing time.

Effect of Changing Bolted Fault Current
on AFIE
• Lower bolted fault current leads to
lower arcing current
• Arcing current determines arcing
time!
• Overcurrent protective devices,
which define the arcing time, may
take longer to trip with lower arcing
current due to inverse time-current
characteristics
Lower arcing current: 1s arcing time
Higher arcing current: 0.06s arcing time

Arc Flash Mitigation Methods

Enhancing Personnel Safety

5-10
2000

Number of arc flash explosions that occur in
electrical equipment every day in the United States
- According to statistics compiled by Cap-Schell, Inc.,
a Chicago-based research and consulting firm that
specializes in preventing workplace injuries and deaths

Each year the number of patients that are
emitted to burn centers due to arc flash events
- Report by research on IEEE Website

Electrical Safety
● Electrical Safety Then and Now
● http://esfi.org/index.cfm/page/Electrical-Safety-Then-and-Now/cdid/12394/pid/10272

● Workplace Electrical Injury and Fatality Statistics
● http://esfi.org/index.cfm/page/Workplace-Electrical-Injury-and-Fatality-Statistics,-20032010/cdid/12396/pid/3003

http://esfi.org/index.cfm/pid/11506

Arc Flash Mitigation Solutions
Prevention / Avoidance
System Design
De-energize Equipment
Site Safety Procedures
Intelligent MCCs
AF Mitigating Features (Equipment Design)
Electric Operated CBs

Passive Protection
Virtual Mains
Zone Selective Interlocking
Bus Differential Relays
Low Arc Flash CB
High Resistance Grounding
Arc Flash Sensing RelayVAMPTM technology

Passive Containment

AF

Energy Redirection
Installation Considerations
Plenums (ductwork)
Size of Equipment
Equipment location

Active Protection
LV Arc Flash Sensing Relay
with Arc Quenching technology
MV Arc TerminatorTM

Interactive Protection
Energy-Reducing
Maintenance Switches

Zone SelectiveSystem
Interlocking
Coordinated
100sec

M1
3000A
tSD .3 Sec

10sec

No restraint signal
Short time delay will be
ignored

Bolted Fault
Current
62kA
Incident
Energy
24” ––20
cal/cm2
Arc Fault
Current
PPE
Category
3 – 29kA
IncidentFault
Energy
24” –– 3.33
Bolted
Current
62kAcal/cm2
PPEFault
Category
1 – 29kA
Arc
Current

1sec

.1sec

F1
800A

F2
800A

F3
800A

F4
800A

1kA

10kA

100kA

Bolted Fault Current – 62kA
Arc Fault Current – 29kA
Incident Energy 24” – 3.33 cal/cm2
PPE Category 1

19

Arc Flash Relay Systems
Primary fuse







Arc flash detection relay (1-2 msec)
(light sensors/current-optional)
Tripping of upstream breaker
Fault location identification
Multiple zones protection (optional)

Transformer

AF
Relay
MAIN CB

LV Switchgear
Fault

Zone 1

x

CB F1

Optional

Z2

CB F2

Z3

CB F3

Z4

Typical System Design

Virtual Main

Arc Terminator System Operation
• Sense a Fault Current
+
• Detect an Arc
=
• Close Shorting Switch

MasterClad Arc Resistant Ratings
Nominal Voltage

4.16 kV

7.2 kV

13.8 kV

Maximum Voltage

4.76 kV

8.25 kV

15.0 kV

60

95

95

Continuous
Current (A)

1200, 2000,
3000(*)

1200, 2000,
3000(*)

Interrupting
Current (kA)

40, 50

40

25, 40, 50

Internal Arc
Current (kA)

Up to 63, 0.5 sec

Up to 63, 0.5 sec

Up to 63, 0.5 sec

Nema 1

Nema 1

Nema 1

BIL (kV)

Enclosure Types
(*) Only for 1 High

1200, 2000,
3000(*)

Medium Voltage MCC
Compartmentalized
Construction

Pressure Relief Flaps
Arc Plenum - Optional

Top View

•Interlocked rear panel to
Frame Construction
•Top and Bottom Access
Panels
•Easy Removal

Rear View

Enclosure – AR
Type 2

Bolted Rear Panels

North America
Low Voltage Arc Resistant Offer

ANSI C37.20.7, Annex D Arc Resistant
(ANSI
4 Drawout
Switchgear)
ANSI C37.20.1
C37.20.1Power-Zone
Power-Zone
4 Drawout
Switchgear

● IIEEE C37.20.7-2007
● IEEE guide for testing metalenclosed switchgear rated up
to 38 kV for internal arcing
faults
●A procedure for testing and
evaluating the performance of
metal-enclosed switchgear for
internal arcing faults is
covered. A method of
identifying the capabilities of
this equipment is given.
Service conditions,
installation, and application of
equipment are also discussed.
Schneider Electric – SpecTech 2012, November Update

28

AR LV Equipment- Design Values
Without ArcBlokTM
(1 shot) at 65 kAIR @ 480 Vac

AR LV Equipment- Design Values
With ArcBlokTM
(1 shot) at 65 kAIR @ 480 Vac

Arc Resistant Considerations


Testing Standard



Reinforced, Compartmentalized Enclosure



Ratings






Bus and Breaker
kAIR
Accessibility Type (2A/2B)

Optional Features







Insulated Bus
Plenums
Zone Selection Interlocking
High Resistant Grounding
Energy Reduction
Maintenance Switch
Breaker Remote Racking

Schneider Electric – SpecTech 2012, November Update

31

Air Intake Design
Optimized Air Flow
Dynamic Spring
Loaded Pressure Flap

Plenums

Plenums for PZ-4

● What is the Standard
for Low Voltage
Motor Control Centers?

Low Voltage Motor Control Center
A Standard Dilemma….Resolved
•There currently is no standard or guide for
testing Low Voltage Motor Control Centers for
internal arcing faults however based on
recent decisions within IEEE, AR MCCs will
now be covered in Annex H of the IEEE
C37.20.7 standard.
•The most important test parameters
for determining equipment capability
is establishing •The preferred rated arcing duration
test (H.3)
•The means of establish an arc to
produce enough ionized gas quickly
enough to prevent premature
extinction at lower voltages (H.4)
•Current discussions within the working group
indicate that the minimum arcing duration test
will be no less than 100 ms

● IEEE PC37.20.7, Draft 6
May 2014, Annex H
● Purpose of the Annex is to
provide specific information
for test sample configuration,
testing methods, test assessment,
and additional ratings that are
specific to LV MCCs (UL845)

Plenum

Exhaust Options

Pull Box

Ceiling or obstruction above MCC

28.5 in

Baffle

14.24 in.

Plenum
UL Witnessed
Plenum Design
Top Entry thru Pull
Box
Single Plenum

10 ft.
Minimum height
from bottom of
section to
obstruction
above MCC

Front

Rear

Pull Box

Thank You

Appendix

MasterClad Arc Resistant 2-High

Main Bus
compartment

Relay &
instrument door

Cable
compartment
Circuit breaker
compartment

MasterClad Arc Resistant
with Plenum
• Plenum Required if:
– Ceiling* less than
192”
– Power Zone Center
Application
– Exhaust needed from
equipment room
– 50kA or 63kA rating
(optional use-arc
shield)

*As measured from the floor

MasterClad Arc Resistant
Arc Shield
• Arc Shield
Required if:
– 50kA or 63kA
rating (optional
use-plenum)
– Increase
likelihood of
protection for
front, rear, &
sides of
equipment

ArcBlok Patented Technology
Internal Arc Gas Management System

Prevents and
Controls Arcing

Cradle Barriers

Arc Ventilation

Cluster Shields

Exhaust Methods - Baffles
Roof Baffles
14 Guage Steel
Exhaust Flap
Louvered
10 ft. Clearence
Ceiling

Base of
Equipment

Internal Arc Gas Management
Ventilated
Mid-Shelf

Vertical Bus
Isolation

Shroud Power
Stabs

Model 6 Arc Resistant Highlights
 Testing Standard

Metal Control
Station Plate

 C37.20.7, Annex H
 UL Witnessed

 Reinforced Enclosure
 12 gauge steel
 Additional hardware
 Metal Control Station Plate
 Filter box (VFD)
 Baffle compartment assembly

Additional top
mid bracket

 Ratings
 65 kAIR @ 600 Vac
 Type 2A
 100 ms (Stage 1)
 500 ms (Stage 2)
 2000A Bus (Stage 1)
 2500A Bus (Stage 2)

Filter Box for
Thermal Ventilation

Reinforced door
with hinges

Additional bottom
mid bracket

Clip on Fast
Lead Screws

References
● Arc Flash Mitigation
● AT327/July 2013
● SE Engineering Services
● 1910BR1205
● Arc Flash Description of Services
● SAFARC01R02/12

Industry-Leading Expertise
We currently have more than 130 power
system engineers. SE Engineering
Services has completed over 10,000
power system assessments, studies,
and designs including IBM.
47

Arc Flash Analysis
An arc flash analysis is performed to estimate incident energy levels, to identify
appropriate levels of Personal Protective Equipment (PPE) and to determine flash
protection boundaries at specific points in an electrical distribution system.
The Occupational Safety and Health Administration requires employers to protect
facility workers and contractors from the hazards associated with electrical shock,
arc, and blast. The National Fire Protection Agency, producers of the National
Electrical Code, developed a set of guidelines to assist employers in complying with
OSHA laws in the NFPA 70E, Standard for Electrical Safety in the Workplace.
We offer arc flash analyses based on the results from the Short-circuit and
Overcurrent Device Coordination studies, and are calculated using the
equations provided in IEEE Std. 1584-2002.

Arc Flash Mitigation
Enhancing Personnel Safety

April 23, 2014
Terry L. Schiazza
Business Development Mgr.
Seneca, SC Manufacturing Facility

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