20120504 LISAT slides Dube

ARC FLASH MITIGATIONSTRATEGIES

forMETALCLADSWITCHGEAR

The Sign of Quality

PEDERSEN POWER PRODUCTS

Discussion Topics

Arc Flash Standards Arc Flash Prevention Arc Flash Protection Mitigation Techniques

Molten MetalDroplets

Copper Solid toVapor Expansion67,000 Times

Toxic Gases

PressureWave

IntenseLight Flash

Flying Objects& Shrapnel

SoundBlast

Arc Flash HazardsIntense Heat35,000F

ARC FLASHSTANDARDS

The Sign of Quality


IEEE Standard 1584

Contains calculations used to determinesafe boundary distances for unprotectedpersonnel and the incident energy at theworking distance for qualified personnelworking on energized equipment.

Incident Energy Calculation forArc Flash in a Cubic Box

E =1038.7D-1.4738 x T[0.0093F2-0.3453F+5.9675]E = Incident Energy in cal/cm2D = Distance to arcing pointT = Time to clear arcing faultF = Available bolted fault short circuit current

IEEE Standard 1584

NFPA-70E-2009

Utilizes IEEE 1584 methods forcalculating incident energy onspecific electrical equipment andprovides guidelines for the PPEclothing required based on theincident energy level.

Standard for Electrical Safetyin the Workplace

National Electric Code

Requires labeling of electrical equipmentto warn qualified personnel of the dangerof electric arc flash.Refers to NFPA-70E as a guide forquantifying the hazard.

Arc Flash Warning Label

Compliance with National Electric Code

Arc Flash Warning Label

OSHA 29 CFR Part 19101910.333 Selection and Use of Work PracticesSafety-related work practices to prevent injuries resultingfrom either direct or indirect electrical contact, whenwork is performed near or on equipment or circuits whichmay be energized.1910.335 Safeguards for Personal ProtectionPPE shall be used to protect employees fromelectrically related injuries while that employee isworking near exposed energized parts.

Subpart S, Appendix AReferences NFPA-70E forElectrical Safety Practices

ARC FLASHPREVENTION

The Sign of Quality


DONTWORK ON

ENERGIZEDELECTRICAL

EQUIPMENT!

Arc Flash Prevention

Causes of Electric Arc Flash Contact with Live Parts Unsafe Work Procedures Misoperation Insufficient Maintenance Overvoltages Insulation Failure Entry of Small Animals

Arc Flash Prevention Maintain Sound Safety Practices Prevent Entry of Critters Use IEEE Metalclad Standards Prevent Moisture Ingress Proper Insulation System Design Monitor for Partial Discharge Monitor Bus Temperatures

IEEE Standard C37.20.7

There is little likelihood of an internal arc inequipment meeting the requirements of IEEE StandardC37.20.1-2002 or IEEE Standard C37.20.3-2001. Thereis even less likelihood of an internal arc in equipmentthat has insulated bus, compartmentalization, barriers,and interlocks, such as those described in IEEEStandard C37.20.2-1999.

Metalclad Switchgear Design Standard

Uninsulated Bus

LoadTerminals

Ground bus

Load breakair switch

Fuse

LineTerminals

Everything in SameCompartment

ExposedLive Parts

withDoor Open

Metal Enclosed Switchgear

Metalclad SwitchgearRelay, Controls

andInstrumentation

BreakerCompartment

Loadbus

Main bus

Ground bus

CT

CT

Primary circuits,relays, meters,and controlsisolated in owngrounded metalcompartments

Primary buses andconnections coveredwith insulation

CT barrier

MovableShutters

Shutters coverPrimaries whenno breaker installed

Metalclad SwitchgearRelay, Controls

andInstrumentation

Loadbus

Main bus

Ground bus

CT

CTVacuumBreaker

Steel barrier

No primary circuitsexposed withbreaker installed

Arc Flash Prevention Maintain Good Safety Practices Prevent Vermin Entry Use IEEE Metalclad Standards Prevent Moisture Ingress Proper Insulation System Design Monitor for Partial Discharge Monitor Bus Temperatures

IEEE Tested Enclosure DesignMoisture Prevention

Use Extended Life Sealants Ventilate Cable Compartment Maintain Filters/Screens Use Dual Strip Heaters Monitor Strip Heaters Seal Unintentional Openings Apply Quality Protective Finish

IEEE C37.20.2 Section 6.2.10Test Criteria

7.1 gallons per minute flow rate 60psi min water pressure 10 ft. Min Distance from Joints Against 2 Surfaces at each Joint


Fluidized Bed Epoxy Bus Insulation

Insulation Materials

PVCInsert

Cycloaliphaticbus supports

95kV BIL Rated Insulators


Signalsent toInsulGardRelay

Partial Discharge Monitoring

RFCT #1 detects partialdischarges internal toswitchgear compartment.RFCT #2 detects partialdischarges in Customerscables up to 100 ft fromswitchgear

Partial Discharge Monitoring


Wireless Parasitically PoweredTemperature Detectors forMedium Voltage Switchgear(under development)

Temperature Monitoring

BusJoint

StraightBus

Protection system configurationTemperature input from sensorsCurrent Input from CTsCalculate and Predict a ProblemEmail/Alarm notification

Output Through Internet

ARC FLASHPROTECTION

The Sign of Quality


Train Personnel Wear Proper PPE Install Warning Labels Maintain Good Safety Practices Build Sturdy Enclosure Reduce the Human Interface Redirect the Blast Energy

Arc Flash Protection

De-Energize EquipmentUse Lockout/Tagout ProceduresLatch and Secure All PanelsLabel Line and Load Side Bus Isolate Potential BackfeedsOpen Tie Breaker/Redundant SourcesGround De-Energized Conductors

Safety Practices

First G&T Standard Established Formal G&T Tests BIL Withstand AC Hipot 1-minute Momentary For 10 Cycles Per

C37.20.2 K*I 2 Seconds Per C37.20.2 Interlocking (Upper & Lower) 500 Insertions and Removals

IEEE C37.20.6-2007Safety Practices

G&T TESTING STANDARD

Safety PracticesBall Type Ground & Test Device

Safety Practices

Ground Conductor Sizing31.5kA for 2 seconds

Requires three (3) 500mcmcables per phase

(total of 9 grounding cables)

Ground Conductor Sizing25kA for 2 seconds

Requires three (3) 350mcmcables per phase

(total of 9 grounding cables)

Safety Practices



Use Only 11 Gauge Steel Weld Cubicles Two Walls Between Sections Heavy Duty Door Hinges Heavy Duty Door Latches

Sturdy Enclosure Design

Train Personnel Wear Proper PPE Install Warning Labels Maintain Good Safety Practices Build Sturdy Enclosure Reduce Human Interface Redirect the Blast Energy


Reduce Human InterfaceOpening & Closing Breaker Relocate control switch Use remote communications Use local HMI Use remote control station Use Remote Operator Use Time Delay Control Switch

RemoteControlStation

Remote Breaker ControlSmartReduce Human Interface

Remote Breaker ControlELECTROSWITCH

Reduce Human Interface

Remote BreakerRacking Motor

RemoteBreakerRackingMotor

Remote Breaker RackingReduce Human Interface







NOT A DESIGN STANDARD

A procedure for testing and evaluatingthe performance of medium-voltagemetal-enclosed switchgear for internalarcing faults and identifying thecapabilities of the equipment relativeto specific zones of protection.


Equipment designed to withstandthe effects of an internal arcingfault as indicated by successfullymeeting the requirements of IEEEStandard C37.20.7-2007.

Arc-Resistant Definition:


Term Arc Resistant can be misleading.In the event of an internal arcing fault,the dangerous effects of the arc arevented away from the zone ofprotection for personnel.Term Arc Venting is more accurate

Arc Venting Switchgear

48 min

95

Duct can exit to theleft, right, or rear


Exhaust Vent Duct Design Tested on the switchgear Must vent to safe area Fire rated at wall opening No external air allowed in Prevent buildup of ice and snow Prevent critter ingress



Intended to provide an additional degree ofprotection to the personnel performing normaloperating duties in close proximity to the equipmentwhile equipment is operating under normalconditions

Not intended to provide this additional degree ofprotection to operating personnel who, in the normalperformance of their duties, would be required toopen enclosure doors or panels or otherwise alter theequipment from its normal operating conditions.


IEEE does not require that metalcladswitchgear to be manufactured topass the IEEE Standard C37.20.7Testing Procedures.


Zonesof

Protection

Zones of Protection

Switchgear with arc-resistant designs orfeatures at the freelyaccessible front of theequipment only.

Type 1

Zones of Protection

Switchgear with arc-resistant designs orfeatures at the freelyaccessible exterior(front, back and sides)of the equipment only.

Type 2

Zones of Protection

That arcing does notcause holes in the freelyaccessible front of theenclosure or in the wallsisolating the low-voltagecontrol or instrumentcompartments.

Type 1B

Zones of Protection

That arcing does notcause holes in the freelyaccessible front, sidesand rear of the enclosureor in the walls isolatingthe low-voltage control orinstrumentcompartments.

Type 2B

Zones of Protection

Adds isolation fromeffects of an internalarcing fault between alladjacent compartments

Type 1BC

Zones of Protection

Adds isolation fromeffects of an internalarcing fault between alladjacent compartments

Type 2BC


Initial cost (up to 25% more) Need breaker lift device Must design room accordingly Must seal all cable entries Low voltage wiring protection Loss of protection if door/panel open

Considerations


Protection against toxic gases Protection against excessive sound Arcing within components Protection from above or below

Testing Does Not Address

ARC FLASHMITIGATION

The Sign of Quality


Arc Flash Mitigation

Incident Energy CalculationE =1038.7D-1.4738 x T[0.0093F2-0.3453F+5.9675]E = Incident Energy in cal/cm2D = Distance to arcing pointT = Time to clear arcing faultF = Available short circuit current

Complete System Analysis High Speed Differential Relay Fast Bus Tripping Maintenance Relay Settings Arc Flash Detection Hi-Speed Arc Terminator 3 Cycle Breakers Current Limiting Fuses


Fast Bus Tripping

50/62

50 50 50 50 50T

Fast Bus Tripping

50/62

50 50 50 50 50

T

Complete System Analysis High Speed Bus Differential Relay Fast Bus Tripping Maintenance Relay Settings Arc Flash Detection Hi-Speed Arc Terminator 3 Cycle Breakers Current Limiting Fuses


Relay Group Settings Feature can be enabledby a contact input, communications or ARMsSelector Switch to enable Maintenance Modeprotective settings when maintenance is beingperformed on the equipment.Maintenance Mode Protective Group settingstypically establish lower instantaneous pick-ups that can be optimized to reduce trip delaysand increase sensitivity, but avoid nuisancetrips.Remote and/or Local Visual Indication can beprovided to confirm the Relay is in MaintenanceMode.

CI - 8

a b

ARMsSelectorSwitchTB2FP5000

Relay

CI - 7

Maintenance ModeIndicating Light

Maintenance Relay Settings

ARMs Selector SwitchFP5000 Postion A Position B

Relay SettingsGroup

Group 2Maintenance Mode

Group 1Normal Mode

Relay ContactInput CI-7 CI-8



Microprocessor based high speed relaysends trip signal to breaker upon sensinga light flash with high speed light sensorsinstalled in theswitchgearcompartments.

Arc Flash Detection

Arc Flash DetectionSEL-751A Feeder Protection RelayInstantaneous OvercurrentTimed OvercurrentInstantaneous Neutral OvercurrentTimes Neutral OvercurrentUndervoltage (Bus Side)Overvoltage (Bus Side)Undervoltage (Line Side)Overvoltage (Line Side)Over FrequencyUnder FrequencySyncronism CheckAuto-ReclosingArc-Flash DetectionArc-Flash Overcurrent

Arc Flash DetectionTest Cell Without Arc Flash Detection

Arc Flash DetectionTest Cell With Arc Flash Detection

Arc Flash DetectionSwitchgear Without Arc Flash Detection

Arc Flash DetectionSwitchgear With Arc Flash Detection

Arc Flash DetectionTest Dummy Without Arc Flash Detection

Arc Flash DetectionTest Dummy With Arc Flash Detection



Detects presence of an arc flash with highspeed photo sensors and closes a highspeed switch that shorts out the the mainbus in the first cycle to create a parallelpath to the arc and quickly extinguish aburning arc

Arc Terminator

Arc Terminator

Arc Terminator

Arc Terminator

Phase A

Phase B Phase C

Arc TerminatorArc

Confines Arc Effects at Initiation Point Extinguishes Arc < Cycle Prevents Pressure Buildup No Change to Relay Coordination Integrated Into Switchgear Lineup Indicates Where Flash was Detected. Limited to 40ka Symmetrical Faults

Arc Terminator





Current Limiting FusesCurrent Limiting Protector (CLiP)Up to 5,000A Continuous @15.5kvUp to 120,000A Interrupting

Current Limiting Fuses

10ka Trigger Elementlimits peak to 17ka vs48ka

Scheme Comparison

Protection SchemeArcingTime

PercentReduction

ArcingTime

PercentReduction

Normal Coordination 800ms 0% 767ms 0%Fast Bus Trip 170ms 137ms Maintenance Settings 120ms 87ms High Speed Differential 107ms 74ms Arc Flash Detection 86ms 53ms Arc Terminator 2.3ms 2.3ms

5 Cycle Breakers 3 Cycle Breakers

NFPAPersonalProtectiveEquipment

RequirementsThe Sign of Quality


IncidentEnergyPresent(cal/cm2)

PPERiskCat

RequiredMinimumPPE Rating(cal/cm2)

Protective Clothing Required to PreventOnset of a Second Degree Burn

E 1.2 0 N/A Untreated Cotton1.2 < E 4 1 4 FR Shirt + FR Pants4 < E 8 2 8 Cotton Undergarments + FR Shirt + FR Pants8 < E 25 3 25 Cotton Undergarments + FR Shirt + FR Pants

+ FR Coverall25 < E 40 4 40 Cotton Underwear + FR Shirt + Pants

+ Multi-Layer Flash Suit (minimum of 3 layers)E > 40 N/A N/A Too Dangerous to Work On

NFPA PPE Requirements

NFPA PPE RequirementsNO CALCULATION OF INCIDENT ENERGYNFPA Table 130.7(C)(9) 1Kv 38Kv Switchgear

Tasks Performed on Energized Equipment Risk CatInspections Outside Restricted Approach Boundary 3Operate Circuit Breaker with Door Closed 2Operate Circuit Breaker with Door Open 4Operate Meter Switch 0Work on Energized Electrical Conductors 4Work on Exposed Control Energized Circuits 120V 4Racking of Breakers with Door Open or Closed 4Application of Safety Grounds After Voltage Test 4Remove Covers to Expose Energized Conductors 4Open Hinged Covers to Expose Energized Conductors 3Open PT or SST Compartment 4

NFPA PPE RequirementsNO CALCULATION OF INCIDENT ENERGYNFPA Table 130.7(C)(9) 1Kv 38Kv SwitchgearIF ARC RESISTANT SWITCHGEAR UTILIZED

(for clearing times less than 500ms)

Tasks Performed on Energized EquipmentNon ARRisk Cat

AR SwgrRisk Cat

Operate Circuit Breaker with Door Closed 2 0Operate Circuit Breaker with Door Open 4 4Work on Energized Control Circuits 120V 4 4Racking of Breakers with Door Open 4 4Racking of Breakers with Door Closed 4 0Insert or Withdraw Potential Transformers 4 0

E (cal/cm2) versus Fault CurrentProtection Scheme 25ka 40ka 50ka 63kaNormal Coordination 13.30 29.70 50.50 89.30Fast Bus Trip 2.83 6.32 10.73 18.97Maintenance Settings 2.00 4.46 7.58 13.39High Speed Differential 1.78 3.98 6.76 11.94Arc Flash Detection 1.47 3.20 5.43 9.60

Protection Scheme 25ka 40ka 50ka 63kaNormal Coordination 12.75 28.5 48.40 85.60Fast Bus Trip 2.28 5.09 8.65 15.29Maintenance Settings 1.45 3.23 5.49 9.71High Speed Differential 1.23 2.75 4.67 8.26Arc Flash Detection 0.88 1.97 3.35 5.91

3 Cycle Breaker

5 Cycle Breaker

E(cal/cm2)

PPECat

1.2 04 18 225 340 4>40 N/A

0102030405060708090

100

0 6 12 18 24 30 36

FC = 25kaFC = 40kaFC = 50kaFC = 63ka

E (cal/cm2) versus DistanceNormal Coordination (5 cycle)

PPECat

1

E(cal/cm2)

PPECat

1.2 04 18 225 340 4>40 N/A

23

4

Distance to Arcing Point (inches)

Incide

nt En

ergy (

cal/c

m2)

E (cal/cm2) versus Distance

0

5

10

15

20

25

30

35

40

0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216


Normal Coordination (5 cycle)

Incide

nt En

ergy (

cal/c

m2)

E(cal/cm2)

PPECat

1.2 04 18 225 340 4>40 N/A

PPECat

4

3

21

Distance to Arcing Point (inches)(216 = 18)

E (cal/cm2) versus Distance

0

5

10

15

20

25

30

35

40

0 6 12 18 24 30 36


Bus Differential + Arc Flash (3 cycle)

E(cal/cm2)

PPECat

1.2 04 18 225 340 4>40 N/A

PPECat

12

3

0Distance to Arcing Point (inches)

4

Incide

nt En

ergy (

cal/c

m2)

Remote Racking/Control Advantages

E(cal/cm

2)PPECat

1.2 04 18 225 340 4>40 N/A

Bus Differential Protection (107ms interrupt)Standard 5 cycle Breakers

FaultCurrent

Operation at Frontof Cubicle Door

Operation at 20 Feetfrom Cubicle Door

25kA 1.78 cal/cm2 0.11 cal/cm240kA 3.98 cal/cm2 0.24 cal/cm250kA 6.76 cal/cm2 0.41 cal/cm263kA 11.94 cal/cm2 0.73 cal/cm2

Normal Coordination (800ms clearing time)Standard 5 cycle Breakers

FaultCurrent

Operation at Frontof Cubicle Door

Operation at 20 Feetfrom Cubicle Door

25kA 8.31 cal/cm2 0.51 cal/cm240kA 18.58 cal/cm2 1.13 cal/cm250kA 31.56 cal/cm2 1.93 cal/cm263kA 55.79 cal/cm2 3.40 cal/cm2

Transformer Differential ProtectionBus Differential Protection

Arc Flash Detection

Recommended Scheme

87B Zone

Arc FlashDetectionZones

To CTs atTransformer

87T Zone

ThinkPEDERSENThink

PEDERSEN

PPP

20120504 LISAT slides Dube

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