Selective Coordination & Arc Flash...
Transcript of Selective Coordination & Arc Flash...
Selective Coordination & Arc Flash Mitigation
This presentation will review the hazards and risks associated with an Arc Flash & Arc Flash incidents and provide suggested mitigation solutions using these GE technologies: • I-ZSI (Instantaneous Zone Selective Interlocking) • WFR (WaveForm Recognition)
Kevin Henkes Spec Engineering Leader LATAM & the Caribbean
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Note: While most of the material in the presentation refers to Nema products and standards, the same features are available on some of our IEC rated breakers.
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Outline
I. What is Arc Flash? and What Affects Arc Flash Energy?
II. What is Selective Coordination?
III. The Trade-Off Dilemma
IV. Introduction to WFR and I-ZSI
V. Implementing WFR and I-ZSI
VI. System Solutions
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What is Arc Flash?
Sensory Damage (Ear, Eye)
Severe Burns
Blunt Force Trauma
Internal Organ Damage
• Temperatures over 27,000°F • Pressure Wave in excess of 2000 lbs/ft2 • Parts of Molten & Vaporized Conductors Ejected at Supersonic Speed • 165db Sound Levels • IR/UV/Visible Radiation • Radiant Heating Instantly Raises Nearby Surfaces to Melting Points
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What is Arc Flash? An Arc Flash is Dangerous: • Death can occur from electrical injury • Also cause injuries that can lead to many days away from work • It is one of the top leading causes of fatality in the construction industry • And account for about 5% of all occupational fatalities
An Arc Flash is Expensive: • Electrical injuries can have very high direct and indirect costs to employers.
• Arc flash events can typically cause extensive damage to distribution equipment. Often requiring full replacement or extensive refurbishment (with a lengthy outage).
• Arc flash events can severely impact the balance of the system, exposing transformers, cables, etc. to severe duty cycle stresses
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What is Arc Flash? Hierarchy of Hazard Control Measures
Most Effective 1. Elimination of the hazard
2. Substitution of less hazardous equipment or materials
3. Engineering control to reduce exposure or severity
4. Warnings, signs, and other communications
5. Administrative control, including safe work practices
Least Effective 6. Personal Protective equipment
ANSI Z10-2005
Standard for Occupational Health and Safety Management Systems
“… The purpose of the standard is to provide organizations an effective tool for continual improvement of their occupational health and safety performance. An OHSMS implemented in conformance with this standard can help organizations minimize workplace risks and reduce the occurrence and cost of occupational injuries, illnesses and fatalities. …”
• If PPE is required, then there is hazard
• If PPE is reduced, then there is hazard • If in doubt, then there is hazard
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What is Arc Flash?
Factors that Influence Arc Flash Energy
Arc Flash energy is a function of:
• A function of the protective device acting upon the arcing current
Arcing fault clearing TIME is the critical factor Arcing Fault Clearing Time Sensitivity of the Breaker/Trip Unit
• Voltage
• Available short circuit current
• Working distance
• Arc gap
• Arcing fault clearing time
• Sensitivity of Breaker/Trip Unit
• Fixed
• Based on system design and source
• Arms are only so long
• Determined by equipment type
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Incident energy dependent on event time
Low level of incident energy requires fast mitigation.
• ~ ½ cycle interruption or less is best (CL CB or fuses)
• Large switchgear CB provide HRC-2 type protection IF they are operating in their instantaneous range
0
1
2
3
4
5
6
7
8
9
10 20 30 40 50 60 70 80 90 100Ibf
Cal/C
m2
3 cycle (large CB)
clearing time (50ms)
1.5 cycle (MCCB)
clearing time (25ms)
0.5 cycle clearing
Time, or less,
Preferred (8ms)
HRC-2
HRC-1
1.2
Cal/cm2
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What is Selective Coordination?
• It is NOT a New Idea • It does Localize Fault Response • It is Code Mandated
• NEC2005/2008/2012, NFPA99 • IEC 61947-2
• It is a Sound Design Principle
• It does Enhance System Reliability • It is Simple in Concept, BUT Can be
Complex in Implementation
Coordination (Selective). Localization of an overcurrent
condition to restrict outages to the circuit or equipment
affected, accomplished by the choice of overcurrent
protective devices and their ratings or settings. NFPA70
2012 – Article 100 Definitions
ATS
Emergency
Source
N E
Normal
Source
Opens
Unnecessary Power Loss
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What is Selective Coordination?
• Very Sensitive,
• Fast Acting Protection;
• Response in milliseconds
• Insensitive,
• Slow Acting Protection
• Good Coordination
• Good System Reliability
• Good Protection
• System Safety
• Difficult Coordination
Near the Source
Near the Load Protection
20A Branch
Molded Case Circuit
Breaker
400A Main PANEL
Molded Case Circuit Breaker
1200A SWBD Feeder
4,000A SWBD Main
400A Feeder
Molded Case Circuit Breaker
Reliability
Traditional system design
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The Impossible Compromise?
Protection Or Reliability…
Selective
Coordination Arc Flash
Performance
System Reliability System Protection
• High Set or Non INST Breakers Sacrifice Protection for Coordination • Maintenance Mode , Reduced Energy Let-Thru (RELT) Sacrifices
Coordination for Protection • Arc Resistant Gear is Protective ONLY when Doors are Closed
Don’t Compromise
GE’s Solution = Protection + Reliability
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WFR + I-ZSI = Sensitive Trip Units with Intelligent Response
Instantaneous ZSI and WaveForm Recognition
EntelliGuard® Family Trip Unit
Upstream Selectivity
I-ZSI
Downstream Selectivity
WFR
What I-ZSI Does
You don’t have to know how they work, Just understand what they do.
Think of I-ZSI as a telephone call between neighbors. When a fault happens, the circuit breaker closest to a fault calls his neighbors and lets them know the fault is being taken care of… quickly enough to control an arc flash event
What WFR Does Like I-ZSI, WFR is an intelligent response to a downstream fault. With WFR, upstream circuit breakers sense when a fault is being cleared by a downstream device, and determine if a trip should happen… without the phone call, and
quickly enough to control an arc flash event
ZSI = Short Time & Ground Fault = Enhanced Protection
I-ZSI = Instantaneous,
Short Time & Ground Fault
= Enhanced Protection
+
Coordination
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Instantaneous ZSI and WaveForm Recognition
• Very Sensitive,
• Fast Acting Protection;
• Response in milliseconds
20A Branch
Molded Case Circuit
Breaker
400A Main PNL
Molded Case Circuit Breaker
1200A SWBD Feeder
4,000A SWBD Main • Insensitive,
• Slow Acting Protection
400A Feeder
Molded Case Circuit Breaker
• Good Coordination
• Good System Reliability
• Good Protection
• System Safety
• Difficult Coordination
Near the Source
Near the Load
I-ZSI Means Better Protection
Near the Source
WFR Makes Coordination Easier
Near the Load
With
Protection
Reliability
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What is Waveform Recognition (WFR)?
As mentioned in the previous slide, zone selective interlocking is communication between breakers via a twisted pair of copper conductors. This is easily achieved on trip units on larger circuit breakers (≥ 400A) and when the main and feeder circuit breakers are within the same enclosure or within a reasonable distance. Smaller circuit breaker (<400A) normally have thermal magnetic or solid state trip units to make them economical. They do not have the ability to generate a zone selective interlocking signal. However, they are most often current limiting by design and this feature has been innovatively used by GE to enhance the protection of equipment connected downstream of the EntelliGuard TU trip unit. The feature is called “Waveform Recognition” (WFR) . It works between the ETU trip unit of the circuit breaker feeding the LV MCC, panelboard or other equipment, that contain current limiting MCCBs or MCPs.
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…continued What is WFR?
Peak Let-through selectivity method
(Previous GE and other manufacturers electronic trip units)
The instantaneous algorithm in electronic trips is often a peak sensing algorithm or circuit. Though the trip is calibrated in rms amperes and the associated Trip Time Curve is drawn in rms amperes, the trip operates based on instantaneous peak amperes. The conservative assumption is that the trip is calibrated to operate at 1.41 times the rms value shown on the time current curve. Hence a trip nominally set at 10,000A rms is sensitive to 14,100A peak. Allowing for a 10% tolerance the 10,000A rms setting means the trip will not actuate if the peak current is below 12,690A (10,000X1.41X0.9). Using the knowledge that the that an upstream electronic trip is sensitive to peak current will allow the circuit breaker to have its instantaneous algorithm on and set below prospective bolted fault current. The circuit breaker may achieve a significant level of selectivity due to the current-limiting action of the downstream CL OCPD, if the setting is chosen correctly based on the current limiting effect of the downstream OCPD.
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Waveform recognition (WFR) selectivity method (GE Entelliguard TU)
The industry’s most advanced electronic trip uses an algorithm that considers a combination of peak current and time to determine if the fault current shows the characteristic wave shape of a current and energy limiting fault current interruption. Since peak currents and time are being considered the trip may be described as capable of waveform recognition (WFR) or energy sensing. A trip able to detect that the waveform is truly energy limiting can be set more sensitively (lower pickup) than one that only considers peak current. The next slide illustrates the difference between the different trip sensing methods. In that slide, the line identified as “Maximum Possible Peak”, is the setting in peak amperes (ignoring trip sensing and processing tolerance) that a line side CB would need to be selective at the prospective fault current in peak amperes, if determined from a normal Time Current Curve (TCC) coordination study and considering DC offset. The Maximum Let-Through Peak Current is the setting the same trip could employ if the peak let-through of the downstream current limiting OCPD is considered. The “WFR setting” is what the trip setting at the same upstream device could be if the trip employed our advanced waveform recognition, or energy, sensing algorithm.
…continued What is WFR?
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If peak-let-through is ignored, upstream CB must be set above prospective fault current’s maximum possible peak. (traditional thermal-magnetic breakers)
If upstream trip is peak sensing it can be set just above known expected maximum let through peak current. (most other electronic trip breakers)
Trips with waveform recognition capability may be set even lower
(GE breakers with Entelliguard trip unit)
Understanding branch & feeder behavior allows better pickup settings
(80,000)
(60,000)
(40,000)
(20,000)
-
20,000
40,000
60,000
80,000
100,000
- 0.005 0.010 0.015 0.020
Seconds
Am
pe
res
Prospective
Let-through
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WFR Implementation Representation of WFR on Time-Current Curves
Record Plus FG600
EntelliGuard G 2000 (INST = 10.5x)
Our WFR Example…
The Current Limiting Step
Graphically Shows the Minimum INST Pickup Setting for Full Selectivity
Downstream: Current Limiting Molded Case
Upstream: Any EntelliGuard Family Trip Unit
EntelliGuard Trip Set above “the Step” = INST Selectivity
Without Using Tables
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Documenting selectivity • Since the value is associated with
the branch (downstream device) it is that device that must document required setting.
• Traditional Instantaneous clearing times shown on TCC are very conservative…
• New method of drawing curves allows communication of required setting and achieved selectivity… voltage dependent
0.01
0.10
1.00
10.00
100.00
1000.00
100.00 1,000.00 10,000.00 100,000.00
Se
co
nd
s
Amperes
Line identifies threshold
for upstream setting
Adjustable Electronic
instantaneous tripping
Mechanical current limiting
clearing the ETU can understand
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Add a CB with the ETU
0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000
Se
co
nd
s
Amperes
• Drawing the curves allows you to set the CB exactly where it needs to be… just like the old fashioned way
• Overlap with sloped portion of the curve does not matter because the algorithm filters out Current Limiting behavior
Only system in the industry that
allows user to “see”
instantaneous selectivity on the
TCC and allows “optimized”
instantaneous setting of the
upstream CB
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0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000Amperes
Se
co
nd
s
Selectivity you can see
X (A)
X (B)
• For a fault at (A), the lower pickup
setting in the instantaneous time
range at CB1 allows for faster
clearing
• For a fault at (B), there is full
selectivity in the instantaneous time
range and the downstream MCCB
(CB2) trips
• Minor overlap does not indicate lack
of selectivity – selective CB pair
tables are published by GE
• Note 12ms commit time and 50ms
(3 cycle) clearing. Selectivity seen
on TCC – used to identify selective
portion of algorithm
0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000Amperes
Se
co
nd
s
Current limiting portion of MCCB curve as
recognized by the trip unit
CB1
CB2
EG TU
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WFR Implementation
From: GE DET-760B Guide to Instantaneous Selectivity www.geindustrial.com/i-zsi
Example of a 2000A Main + 600A Branch/Feeder on a 65kA system
Downstream: Record Plus ®FG w/ 600A Maximum Trip Upstream: EntelliGuard G UL489
Selectivity Limit: Up to withstand rating…
Instantaneous Setting Must Be: ≥ 20.36kA EntelliGuard G UL489: INST Pickup Range = 2-15X Rating Plug Amperes
Without WFR…
In a 65kA Switchboard, 30kA is above the arcing current! Marcelo sheet?
Minimum INST Setting = Max (15x Rating Plug) = 30kA According to IEEE 1584: Isc=65kA, 480V with 25mm Gap At 18” Working Distance Iarc = 27.6kA available
20,360A (Selectivity Limit)
2000A (Rating Plug A) = 10.18 (INST Pickup)
2000A EntelliGuard G, with INST set to 10.5x or higher is selective above FG600
That means no INST protection from an arcing fault!
… and < 8 Cal/cm2
(And not Fully Selective)
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While most of the material in the presentation refers to Nema products and standards, the same features are available on some of our IEC rated breakers.
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Graphical demonstration – 30A MCP
• At 50kA available fault current Ibf
• ~4kA motor contribution at MCC
• 30A MCP @ MCC
• Either trip can be set to protect instantaneously with arcing fault on main MCC bus, & maintain selectivity
• Waveform Recognition trip provides more margin
100
1,000
10,000
100,000
1,000 10,000 100,000Fault Current (Ibf)P
eak L
et-
Th
rou
gh
(I
pk)
Switchgear feeder Setting using WFR
Switchgear feeder Setting using peak
Arcing current
Bolted fault current Ibf
Rule of thumb: Ia is 35-50% of Ibf
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Larger motor circuit protector – 250A MCP
250A MCP or CB in MCC
• Simple peak sensing trip pickup overlaps arcing current so setting does not provide reliable instantaneous arcing fault protection
• Trip with waveform recognition (WFR) capability provides selectivity & instantaneous arcing fault protection with ~10kA of margin
100
1,000
10,000
100,000
1,000 10,000 100,000Fault Current (Ibf)P
eak L
et-
Th
rou
gh
(I
pk)
Switchgear feeder Setting using WFR
Switchgear feeder Setting using peak
Arcing current
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i-ZSI implementation example: GTU Curve, Legacy CBs, CB1 & CB2
0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000 1,000,000Amperes
Se
co
nd
s
Main Bus Fault
GTU Curve, Legacy CBs, CB1 & CB2
0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000 1,000,000Amperes
Se
co
nd
s
Feeder Fault GTU Curve, Legacy CBs, CB1 & CB2
0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000 1,000,000Amperes
Se
co
nd
s
Sub Main Fault
GTU Curve, Legacy CBs, CB1 & CB2
0.01
0.10
1.00
10.00
100.00
1000.00
100 1,000 10,000 100,000 1,000,000Amperes
Se
co
nd
s
For AF Analysis • AF ALWAYS at
minimum clearing
time.
• Selectivity is
FORCED by I-ZSI
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I-ZSI Implementation
“Maximum Instantaneous selectivity that may be
achieved using I-ZSI …. Limited by short circuit rating
of downstream device and withstand rating of
upstream device.”
Our 2000A 65kA Rated EntelliGuard G… Fully Selective with upstream 3000A, 4000A, or
any upstream EntelliGuard equipped circuit breaker… With INST “ON”
With I-ZSI…
INST Setting = 8.5x (8.5x Rating Plug) = 25.5kA
2000A and Upstream 3000A Fully Selective:
… and < 8 Cal/cm2
Without I-ZSI… 2000A and Upstream 3000A Fully Selective:
INST Setting = “OFF” (or 65+kA)
No INST Protection from Arcing Faults
From: GE DET-760B Guide to Instantaneous Selectivity www.geindustrial.com/i-zsi
I-ZSI curve and Cal/cm2 example on next screen
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Double click on file to open
i-ZSI example 2000A to 3000A
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Solutions for every level of a system!
EntelliGuard G EntelliGuardTU EntelliGuardE
Powerbreak ®II Spectra w/ micro-EntelliGuard
Record Plus FG Record Plus FE
Spectra® F Spectra E
TEYF/D/H/L Q-Line
Record Plus FB WFR
WFR
I-ZSI
WFR
Energy
AKD-20 Switchgear Entellisys™ Switchgear
Evolution™ Switchboard SenPlus & Quixtra 4000
Evolution Switchboard Evolution ™ Motor Control Center
Evolution Motor Control Center Multilin F35 UR (I-ZSI)
MV Transformer primary
M
Evolution Switchboard Spectra Panelboard
I-ZSI A-Series Panelboard
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AKD-20 Switchgear
Evolution Switchboard
Evolution MCC
Spectra Panelboard
A-Series Panelboard
Entellisys Switchgear
EntelliGuard G Air Circuit Breakers
Powerbreak II w/ EntelliGuard TU
Spectra RMS & Spectra w/ micro-EntelliGuard
Record Plus & TEYx MCCB’s
EntelliGuard TU Trip Units & Retrofit Kits
Solutions for every level of a system!
Protection from 15kV to 15A
Multilin F35 MV Relay
Find I-ZSI and WFR embedded in all these GE systems
Quixtra 4000
SenPlus
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Available IEEE Papers on topic Methods For Limiting Arc Flash Hazards While Maintaining System Selectivity
Gary H. Fox, PE, GE Energy Management, Senior Member, IEEE
Optimizing Circuit Breaker Instantaneous Trip Settings for Selectivity and Arc Flash Performance Simultaneously
Marcelo E. Valdes, P.E., GE Energy Management, Senior Member, IEEE
Steve Hansen, Ferraz Shawmut, Member, IEEE
Dr. Peter Sutherland, P.E. GE Energy Services, Fellow, IEEE
Zone Selective Interlocking On Instantaneous (I-ZSI) & Waveform Recognition (WFR)
Bernard Wright, Specification Engineer, GE Energy Management
Maurice D’Mello P.E., Senior Specification Engineer, GE Energy Management
Ronald Cuculic, Specification Engineer, GE Energy Management
GE DET-760 Guide to Instantaneous Selectivity, Circuit Breaker Engineering Reference
* All photos used in this presentation are from GE archive's. All graphs, tables and data from various GE authors.
GE_WFR_Selectivity_AF__Calculator
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English Language Website
Contact your GE Account Manager or
go to www.geindustrial.com