1 © 2013 Eaton. All Rights Reserved. UL/ANSI/NEMA Low Voltage Circuit Breakers

1© 2013 Eaton. All Rights Reserved.

UL/ANSI/NEMALow Voltage Circuit Breakers


Product

Standards and

Certification

InstallationCodes

Safe Products and Safe

Installations

Inspection and

Enforcement

(verification)

“System” Consideration


UL Standards for LV components

• UL 98: Enclosed and Deadfront Switches

• UL 508: Industrial Control Equipment

• UL 489: Molded Case Circuit Breakers

• UL 1066: LV Power Circuit Breakers


UL Standards for LV Assemblies• UL 67: Panelboards

• UL 891: Switchboards

• UL 1558: LV Switchgear

• UL 845: Motor Control Centers

• UL 857: Busway

• UL 508A: Industrial Control Panels


IEC Standards for LV Components

• IEC 60947: LV Switchgear and Controlgear

• Part 1: General rules

• Part 2: Circuit breakers• Part 3: Switches, disconnectors…

• Part 4 series: Contactors and motor-starters

• Part 5 series: Control circuit devices and switching elements

• Part …

• Part …


IEC Standards for LV Assemblies

• IEC 61439: LV Switchgear and Controlgear Assemblies

• Part 1: General rules

• Part 2: Power Switchgear

• Part 3: Distribution boards operated by ordinary persons

• Part 4: Construction sites

• Part 5: Distribution in public networks

• Part 6: Busbar Trunking Systems (Busways)

• Part 7: Marinas, camping sites, market squares, EV charging


National Electrical Code, NEC • NFPA 70, contains “installation” rules

- Cable connections = AWG sizes- Wire bending spaces- Enclosure type designations- Grounding- Working spaces- Creepage/Clearance distances- Temperature rises- Mentions “Listed” products

o References “product” Standards (Annex A)


UL conformity assessment

• UL Listing provides- Independent confirmation of original

design- On-going factory inspections- Periodic follow-up testing


Support the installed “system”

IEC Components

IEC Assemblies

UL Components

UL Assemblies

SAFE


Do not “intermix”

IEC Components

IEC Assemblies

UL Components

UL Assemblies

UNSAFE


System Considerations - Summary

Support your installed electrical infrastructure Concerns extend beyond individual components Need alignment with Installation requirements Certification confirms initial & continued

compliance Do not intermix IEC and UL products, it will

compromise safety!


UL 1066, Low-Voltage AC and DC Power Circuit Breakers Used in Enclosures

Background/Evolution: LV Power Breakers


Low Voltage Circuit Breaker Standards

IEC & UL

IEC 60947-2Low Voltage Switchgearand Controlgear-Part 2

Circuit Breakers

IEC 60898Circuit-breakers for

overcurrent protection for household and similar installations

UL 489UL Standard for

Molded-Case Circuit Breakers

UL 1066UL Standard for

Low Voltage AC and DCPower Circuit Breakers

used in Enclosures

MouldedCase

CircuitBreakers

Air(Power)Circuit

Breakers


Key differences Power Circuit Breakers have compared to Molded Case Circuit Breakers

Electronic Trip Only Used Primarily in Draw-out Switchboards Serviceable and Maintainable Typically used upstream from Molded Case

Circuit Breakers Provide a Higher Level of Selective Coordination Stored Energy Mechanism


Many Standards differences between IEC 60947-2 and UL 1066, including

• Testing Approach- For example, Short Circuit Interrupting Capability

• Performance Requirements- For example:

- Temperature Rise- Overload

• Follow Up Test Requirements- For example, periodic UL 1066 Follow Up

Testing


Power Circuit Breakers: Short Circuit Capability

UL requires defined/vigorous short circuit verifications and single pole interruption.

IEC 60947-2 UL 1066

• Significant clause is 4.4: Utilization Categories

• Category B “Determine rated short time withstand current”

• Annex H Single Pole Interrupting – Optional

• Ics: Rated Breaking Capacity (Seq. II)

• Icu: Rated Ultimate Capability (Seq. III)

References ANSI/NEMA C37.50 for:• Short-Time Current Duty Cycle

• Carry fault current for two 0.5 second periods

• Short-Circuit Current Duty Cycle• Single Pole Test at 87% of

Interrupting Capacity (ANSI C37.50 Table 4)

• Short Circuit Current Tests required in each Test Sequence (C37.50 Table 1)


IEC UL

Philosophy different for temperature tests

Maximum Allowable Temperature Rise

80°C Enclosure not required, sample previously tested in Seq. I and Seq. II

55˚C Tested in the Enclosure, tested on a new sample (C37.50 Table 1 Sequence V)

Maximum allowable Temperature Rise At the Circuit Breaker Contacts

No value specified but no damage to adjacent parts (Table 7 Note a)

85°C

Power Circuit Breakers: Temperature


IEC UL

UL always requires overload, alsoRequires short circuit test after overload

Overload test requirements

Required for 630A and less, optional above 630A (8.3.3.4 and Test Sequence I)

Required for ALL circuit breakers (ANSI C37.50 Table 1, Seq. 1)

Tests after Overload

Short Circuit Test not required and not part of test sequence Short Circuit Test required

Power Circuit Breakers: Overload Capability


Power Circuit Breakers:Conformance Testing/Conformity Assessment

IEC UL

• Conformance to IEC Standard (CE Mark) typically justified solely by manufacturer’s self declaration

• UL Third-Party Witness of Conformance Testing

• UL Factory Surveillance• UL “procedures” document the

construction/components for on-going compliance

• UL periodic Follow-up Testing based on production volume or number of years (ANSI C37.50 Table 7)

Third-party certification assures independent verification & ongoing conformance


Emerging technology: Addressing Arc Flash Hazards

• Data is available to apply UL low voltage circuit breakers to limit arc flash energy


Circuit breakers were originally intended to protect the installed conductors:

– Protect & prevent possible damage for operating beyond their capability.

– Cut-off current below the cable damage curves.

Traditional Circuit Protection


Arc Flash Hazards

Pressure Waves

Copper Vapor:Solid to VaporExpands by67,000 times

Molten Metal

Intense Light

Hot Air-Rapid Expansion

35,000 °F

Shrapnel

Sound Waves

Pressure Waves



Molten Metal

Intense Light

Hot Air-Rapid Expansion

35,000 °F

Shrapnel

Sound Waves


IEEE 1584, Guide for Performing Arc-Flash Hazard Calculations

– Calculate Incident energy• Use fault current level and interruption time of the

overcurrent device.

– Circuit breaker calculation methods do not account for their current limiting aspects!

– Published Papers referencing circuit breaker arc flash applications are:

• “Molded-Case Circuit Breakers reduce Arc-Flash Hazard Impact” NEMA (available for free download from the NEMA Website)

• “Understanding IEEE 1584 Arc-Flash Calculations”, K. J. Lippert, D. M. Colaberardino, and C. W. Kimblin, IEEE IAS Magazine, May/June 2005.

• Applying Low Voltage Circuit Breakers to Limit Arc-Flash Energy”, G. Gregory and K. J. Lippert, IEEE PCIC, September 2006


Comparison of MCCB arc test results Incident Energy

at Bolted Fault Current (kA)

Min Mid Max 250 A MCCB with Thermal - Magnetic Trip Unit Bolted fault current Inc. Energy via IEEE 1584 Table E.1 Generic (Cal/cm

2)

Inc. Energy via IEEE 1584 & Trip Curve (Cal/cm2)

Measured Incident Energy (Cal/cm2)

3.7 kA N/A

1

27.6 0.11

35 kA 1.7 0.9 0.15

100 kA 4.7 1.8 0.13

400 A MCCB with Thermal - Magnetic Trip Unit Bolted fault current Inc. Energy via IEEE 1584 Table E.1 Generic (Cal/cm

2)



6 kA N/A

1

72 0.12

35 kA 1.7 0.7 0.2

100 kA 4.7 1.4 0.20


2)



9 kA N/A

1

46 1.22

35 kA 2.3 1.1 0.78

100 kA 5.7 1.8 0.36


2)



12 kA N/A

1

61.4 0.86

35 kA 2.3 1.7 1.14

65 kA 3.9 2.8 1.05

1200 A MCCB with Electronic Trip Unit Bolted fault current Inc. Energy via IEEE 1584 Table E.1 Generic (Cal/cm

2)



20 kA N/A

1

218 1.86

35 kA 3.5 3.5 1.20

100 kA 9.4 5.8 1.64

2500 A MCCB with Electronic Trip Unit Bolted fault current Inc. Energy via IEEE 1584 Table E.1 Generic (Cal/cm

2)



35 kA N/A

1

110 3.96

65 kA 7.7 5.4 3.48

100 kA 11.5 6.5 2.12

1.

N/A represents “Not Applicable” because the parameters are outside the range of the

IEEE 1584 Table E.1 generic equation.


Conclusions from Molded Case Circuit Breaker arc flash testing

• In the instantaneous region, tested incident energies are significantly lower than calculated values due to:

• Actual arcing time• Current reduction by the circuit breaker

(particularly for current limiting circuit breakers)


Zone Selective Interlocking (ZSI)

• Many modern circuit breakers have electronic trip units which make them more “intelligent”

• Electronic trips with ZSI allows breakers in the same zone to communicate with each other

• ZSI bypasses the preset short delay time (and ground fault delay time when available) on the upstream circuit breaker closest to the fault, which then trips with no intentional delay


Zone A

Feeder 1

Circuit Breaker

Circuit Breaker

Circuit Breaker

Circuit Breaker

Feeder 2 Feeder 3

Main 1

All is OK here, so I’m quiet.


I sense trouble!

Circuit Breaker

Circuit Breaker



When a fault occurs at point X...

X


Zone A

Feeder 1

Circuit Breaker

Circuit Breaker

Circuit Breaker

Circuit Breaker

Feeder 2 Feeder 3

Main 1

Circuit Breaker

Circuit Breaker


X

Without ZSI, I’d normally wait for my Short Delay time, and then open!

But with ZSI… since none of my downstream buddies are telling me that they sense trouble, I know not to wait at all, and open as quickly as I can!


Zone A

Feeder 1

Circuit Breaker

Circuit Breaker

Circuit Breaker

Circuit Breaker

Feeder 2 Feeder 3

Main 1

Circuit Breaker

Circuit Breaker

Zone Selective Interlocking (ZSI)However, when a fault occurs at point XX...

XX

I sense trouble!

I sense trouble too! Hey upstream buddy, hang in there, I’ve got it!All is OK here, so

I’m quiet.


Coordination Is Maintained!


ZSI Arc Flash Example

With ZSI = 0.08 S:7.0* Cal/cm2

FR Shirt & Pants + Cotton underwear

Cat. 2 PPE

Without ZSI = 0.5 S:43.7* Cal/cm2

Greater than Cat. 4 PPE!

FIND ALTERNATIVES!

Short Delay=0.5S

ShortDelay=0.3S

Feeder 1

Circuit Breaker

Circuit Breaker

Circuit Breaker

Circuit Breaker

ShortDelay=0.3S

ShortDelay=0.3S

Feeder 2 Feeder 3

Main 1

X35kA fault current

* Using IEEE 1584: 480V-35kA, MCC, 18” from Arc


Arc-reducing maintenance switching• Manually or Automatically enables an

instantaneous pickup• Trip Times May Vary Between Manufacturers

– Some may be same as Instantaneous– Some my be faster than Instantaneous

• Reduces arc energy to downstream equipment/personnel

• Limits energy available during maintenance

EXAMPLE:

•Normal settings calculates to 10.7 cal (Cat. 3)

•With Arcflash Reduction Maintenance Switch 2.2 cal (Cat. 1)


Arc flash mitigation system

• When activated, this technology continuously monitors current and voltage to identify an arc flash.

• When an arc flash occurs, the arc is automatically dealt with, without changes to the circuit breaker.

• Sometimes referred to as “crowbar systems”


Summary of UL circuit breaker applicationsto reduce arc flash energy

• Use Arc flash energy values published by the circuit breaker manufacturer

• Zone Selective Interlocking

• Arc Reduction Maintenance Switch

• Arc Flash Mitigation Systems


UL 489B, Outline of Investigation for Molded-Case Circuit Breakers …for Use with Photovoltaic (PV) Systems

Emerging technology: PV Circuit Breakers


• UL 489B:- First published July, 2010 - Several manufacturers have UL Listed

products

• IEC 60947-2- No published requirements yet for PV

breakers- CD circulated 2014-02-28

UL 489B and IEC


UL 489B PV Circuit Breaker Requirements

• 1500 V dc capability

• Rated/marked for 50 C

• Vigorous dc current tests

• Evaluated for reverse direction current


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1 © 2013 Eaton. All Rights Reserved. UL/ANSI/NEMA Low Voltage Circuit Breakers