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

2 WFR & I-ZSI Webinar

1Q 2013

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.


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


Reliability

Traditional system design


1Q 2013

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


1Q 2013

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


1Q 2013

Instantaneous ZSI and WaveForm Recognition

• Very Sensitive,

• Fast Acting Protection;

• Response in milliseconds

20A Branch

Molded Case Circuit

Breaker

400A Main PNL


1200A SWBD Feeder

4,000A SWBD Main • Insensitive,

• Slow Acting Protection

400A Feeder


• 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


1Q 2013

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.


1Q 2013

…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.


1Q 2013

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?


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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)


1Q 2013

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.


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

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


1Q 2013

Double click on file to open

i-ZSI example 2000A to 3000A

http://www.geindustrial-latam.com/PDFs/i-ZSI example 2000A to 3000A.xlsm




1Q 2013

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


1Q 2013

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


1Q 2013

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

http://www.geindustrial-latam.com/PDFs/GE_WFR_Selectivity_AF__Calculator.xlsm


1Q 2013

English Language Website

Contact your GE Account Manager or

go to www.geindustrial.com

http://www.geindustrial.com/

selective coordination & arc flash...

Documents