meeting nec for selective coordination
TRANSCRIPT
Meeting the NEC Meeting the NEC Selective Selective
CoordinationCoordinationRequirementsRequirements
Robert E. Fuhr, P.E.Robert E. Fuhr, P.E.
Power Systems EngineeringCovington, WA
AgendaAgenda
NEC Code RequirementsNEC Code RequirementsDefinitionsDefinitionsFuse Selective CoordinationFuse Selective CoordinationBreaker Trip Unit TypesBreaker Trip Unit TypesBreaker Selective CoordinationBreaker Selective CoordinationProcedure to Achieve Selective CoordinationProcedure to Achieve Selective Coordination–– FusesFuses–– BreakersBreakers
ExamplesExamples
Fuses vs. Fuses vs. Circuit Circuit
BreakersBreakers
Special ThanksSpecial Thanks
Square D CompanySquare D CompanyData BulletinData Bulletin““Enhancing Short Circuit Selective Enhancing Short Circuit Selective Coordination with Low Voltage BreakersCoordination with Low Voltage Breakers””http://ecatalog.squared.com/pubs/Circuithttp://ecatalog.squared.com/pubs/Circuit%20Protection/0100DB0403.pdf%20Protection/0100DB0403.pdf
Emergency SystemsEmergency Systems
700.27 Coordination.700.27 Coordination.–– Emergency system(s) overcurrent devices Emergency system(s) overcurrent devices
shall be shall be selectively coordinatedselectively coordinated with with allall supply supply side overcurrent protective devices.side overcurrent protective devices.
ARTICLE 701 Legally Required ARTICLE 701 Legally Required Standby SystemsStandby Systems
701.18 Coordination.701.18 Coordination.–– Legally required standby system(s) Legally required standby system(s)
overcurrent devices shall be overcurrent devices shall be selectively selectively coordinatedcoordinated with with allall supply side overcurrent supply side overcurrent protective devices.protective devices.
ARTICLE 620 Elevators, ARTICLE 620 Elevators, Dumbwaiters, Escalators, Moving Dumbwaiters, Escalators, Moving
Walks, Wheelchair Lifts, and Walks, Wheelchair Lifts, and Stairway Chair LiftsStairway Chair Lifts
620.62 Selective Coordination.620.62 Selective Coordination.–– Where more than one driving machine Where more than one driving machine
disconnecting means is supplied by a single disconnecting means is supplied by a single feeder, the overcurrent protective devices in feeder, the overcurrent protective devices in each disconnecting means shall be each disconnecting means shall be selectively selectively coordinatedcoordinated with any other supply side with any other supply side overcurrent protective devices.overcurrent protective devices.
ARTICLE 517 Health Care FacilitiesARTICLE 517 Health Care Facilities
Essential Electrical Systems must meet Essential Electrical Systems must meet Section 700 (except as amended by 517)Section 700 (except as amended by 517)ImpliesImplies that Essential Electrical Systems that Essential Electrical Systems must be must be selectively coordinatedselectively coordinated. (700.27 & . (700.27 & 701.18)701.18)
ARTICLE 100 DefinitionsARTICLE 100 Definitions
Coordination (Selective). Coordination (Selective). –– Localization of an overcurrent condition to Localization of an overcurrent condition to
restrict outagesrestrict outages to the to the circuitcircuit or or equipment equipment affectedaffected, accomplished by the choice of , accomplished by the choice of overcurrent protective devices and their overcurrent protective devices and their ratings or settings.ratings or settings.
517.2 Definitions517.2 Definitions
Emergency System. Emergency System. –– A A systemsystem of circuits and equipment intended of circuits and equipment intended
to to supply alternate powersupply alternate power to a limited number to a limited number of prescribed functions vital to the protection of prescribed functions vital to the protection of life and safety.of life and safety.
701.2 Definitions701.2 Definitions
Legally Required Standby Systems. Legally Required Standby Systems. –– Those systems required and so classed as Those systems required and so classed as
legally required standby by municipal, state, legally required standby by municipal, state, federal, or other codes or by any federal, or other codes or by any governmental agency having jurisdiction. governmental agency having jurisdiction. These These systemssystems are intended to are intended to automatically automatically supply power to selected loadssupply power to selected loads (other than (other than those classed as emergency systems) in the those classed as emergency systems) in the event of failure of the normal source.event of failure of the normal source.
701.2 Definitions701.2 Definitions
FPN:FPN:–– Legally required standby systems are Legally required standby systems are
typically installed to serve loads, such as typically installed to serve loads, such as heating and refrigeration systems, heating and refrigeration systems, communications systems, ventilation and communications systems, ventilation and smoke removal systems, sewage disposal, smoke removal systems, sewage disposal, lighting systems, and industrial processes, lighting systems, and industrial processes, that, that, when stoppedwhen stopped during any interruption of during any interruption of the normal electrical supply, the normal electrical supply, could create could create hazards or hamper rescue or firehazards or hamper rescue or fire--fighting fighting operations.operations.
517.2 Definitions517.2 Definitions
Essential Electrical System. Essential Electrical System. –– A A systemsystem comprised of alternate sources of comprised of alternate sources of
power and all connected distribution systems power and all connected distribution systems and ancillary equipment, and ancillary equipment, designed to ensure designed to ensure continuity of electrical powercontinuity of electrical power to designated to designated areas and functions of a health care facility areas and functions of a health care facility during disruption of normal power sources, during disruption of normal power sources, and also and also designed to minimize disruption designed to minimize disruption within the internal wiring systemwithin the internal wiring system..
DefinitionsDefinitions
MCCB MCCB –– Molded Case Molded Case Circuit BreakerCircuit Breaker
DefinitionsDefinitions
ICCB ICCB –– Insulated Case Circuit BreakerInsulated Case Circuit Breaker
DefinitionsDefinitions
LVPCB LVPCB ––Low Low Voltage Voltage Power Power Circuit Circuit BreakerBreaker
Time Current CurvesTime Current Curves
Time Current Curve (TCC)Time Current Curve (TCC)The logThe log--log graph of time versus current.log graph of time versus current.Each breaker, fuse, and relay has a time Each breaker, fuse, and relay has a time current characteristic curve current characteristic curve
Fuse Fuse TCCTCC
3-6 Sec
5 kA
@15 kA
This Fuse is Current Limiting –Clearing time is 0.004 seconds
Thermal Thermal Magnetic Magnetic BreakerBreaker
20 kA0.01-0.025 Sec
4 kA
20-50 Sec
Solid Solid State TripState Trip
SQ D NW SQ D NW 40H40H4000 Amp4000 AmpMicrologicMicrologic
100 kA
0.01-0.06 Sec
6 kA
0.08-0.12 Sec 30 kA
170-210 Sec
Manufacture Manufacture TCCTCC
SQ D NW SQ D NW 40H40H4000 Amp4000 AmpMicrologicMicrologic
Manufacture Manufacture TCCTCC
SQ D NW SQ D NW 40H40H4000 Amp4000 AmpMicrologicMicrologic
Manufacture Manufacture TCCTCC
SQ D NW SQ D NW 40H40H4000 Amp4000 AmpMicrologicMicrologic
ManufactManufacture TCCure TCC
SQ D NW SQ D NW 40H40H4000 Amp4000 AmpMicrologicMicrologic
What is Selective Device What is Selective Device Coordination Coordination
Devices closest to the fault must operate Devices closest to the fault must operate first.first.Upstream devices trip in sequenceUpstream devices trip in sequenceNo overlap on TCCsNo overlap on TCCs
Sample Sample One LineOne Line 3-MSWBD MAIN
SWBD
XFMR-UTILSS
P 2- XFMR-UTILS
5-Fdr to ATS-E
6-PNL-A MAIN
PNL-A - 250 A
E N
ATS 260 Amp
11
22
33
Selective Selective CoordinaCoordina--
tiontionThree Three Breakers in Breakers in SeriesSeriesNo OverlapNo OverlapEasy Right?Easy Right?
Problems with this Code Problems with this Code Requirement Requirement -- FusesFuses
Requires larger equipment than using T/M Requires larger equipment than using T/M CBsCBsLarger Electrical Room Larger Electrical Room –– Less rental or Less rental or usable building spaceusable building spaceReduces Levels of downstream equipmentReduces Levels of downstream equipmentFusible Panelboards and Elevator Modules Fusible Panelboards and Elevator Modules are more expensive than T/M circuit are more expensive than T/M circuit breakersbreakers
Problems with this Code Requirement Problems with this Code Requirement ––Circuit BreakersCircuit Breakers
Most breakers have an instantaneous trip Most breakers have an instantaneous trip function.function.–– Breaker trips instantaneously (no time delay)Breaker trips instantaneously (no time delay)
No Selective Coordination Testing for No Selective Coordination Testing for Thermal/Magnetic BreakersThermal/Magnetic BreakersLimited equipment w/o InstantaneousLimited equipment w/o InstantaneousHigher fault current = Increases Higher fault current = Increases complexity to selectively coordinatecomplexity to selectively coordinate
Problems with this Code Requirement Problems with this Code Requirement ––Circuit BreakersCircuit Breakers
Requires larger frame breakers with Solid Requires larger frame breakers with Solid State Trip unitsState Trip unitsLarger Framed Breakers Means Larger Larger Framed Breakers Means Larger Electrical Room Electrical Room -- Less rental or usable Less rental or usable building spacebuilding spaceNot all trip units function the same way Not all trip units function the same way Difficult to obtain competitive bidsDifficult to obtain competitive bids
RealityReality
Very Expensive to Design and Very Expensive to Design and ComplyComply
This new Section of the code will This new Section of the code will radically change the way we all radically change the way we all design emergency and standby design emergency and standby
power systems.power systems.
Real Problem or a Perceived Real Problem or a Perceived (Paper) Problem?(Paper) Problem?
On paper, breakers with instantaneous trip On paper, breakers with instantaneous trip units will not coordinate.units will not coordinate.In the real world…is this a problem?In the real world…is this a problem?How many times has this happened to How many times has this happened to you?you?–– Incorrect trip unit settings do not countIncorrect trip unit settings do not count–– Poor maintenance or defective trip units do Poor maintenance or defective trip units do
not countnot count
Selective Coordination Selective Coordination -- FusesFuses
FusesFuses have been have been testedtested for for coordinationcoordination..Relatively Relatively easyeasy toto select equipment to select equipment to coordinatecoordinate..Pick FusesPick Fuses from Manufacturer’s Fuse from Manufacturer’s Fuse Selective Coordination ChartsSelective Coordination Charts
FerrazFerraz--ShawmutShawmut1600 Ampere Main1600 Ampere Main
600 Ampere Branch600 Ampere Branch
BussmannBussmann
Fuse not in ChartFuse not in Chart
Fuse Fuse II22tt is the is the best toolbest tool for assuring for assuring coordinationcoordinationTotal clearing ITotal clearing I22tt of the of the downstreamdownstream fuse fuse << melting Imelting I22tt of the main of the main upstreamupstream fusefuse
Selective Coordination Selective Coordination –– FusesFuses
Most ratios are 2:1 or higherMost ratios are 2:1 or higherReduces # of Levels of CoordinationReduces # of Levels of CoordinationExample Example –– 1600 Ampere Main (6 Levels)1600 Ampere Main (6 Levels)–– Feeder 1 Feeder 1 –– 800 Ampere800 Ampere–– Feeder 2 Feeder 2 –– 400 Ampere400 Ampere–– Feeder 3 Feeder 3 –– 200 Ampere200 Ampere–– Feeder 4 Feeder 4 –– 100 Ampere100 Ampere–– Feeder 5 Feeder 5 –– 50 Ampere50 Ampere–– Feeder 6 Feeder 6 –– 25 Ampere25 Ampere
Fused PanelboardsFused Panelboards
BussmannBussmann Coordination Module™Coordination Module™
208/120 & 277/480 V208/120 & 277/480 V200 Ampere Maximum200 Ampere MaximumMain Lug Only (MLO)Main Lug Only (MLO)12, 24, 36, & 42 Circuits12, 24, 36, & 42 CircuitsBranch Circuit 0Branch Circuit 0--30 Amperes30 AmperesShort Circuit Rating Short Circuit Rating –– 100 kA100 kA
Issues with FusesIssues with Fuses
Upstream FusesUpstream Fuses with with Downstream Circuit Downstream Circuit BreakersBreakers–– They have not been tested for Selective They have not been tested for Selective
CoordinationCoordinationMust use all fusesMust use all fusesRare Exception Rare Exception –– Fault current is less than Fault current is less than the current limiting operation of the fuse. the current limiting operation of the fuse. Tip#1 Tip#1 –– Avoid intermixing fuses and Avoid intermixing fuses and circuit breakers.circuit breakers.
Circuit Breaker Trip UnitsCircuit Breaker Trip Units
Thermal MagneticSolid State– LI (Long Time & Instantaneous)– LSI (Long, Short Times & Instantaneous) – LS (Long Time and Short Time)– G (Ground Fault)
Not all Solid State Trip Units are alike!!!
Thermal Magnetic Thermal Magnetic Trip UnitTrip Unit
Thermal Thermal Magnetic Magnetic Trip UnitTrip UnitThermal Thermal Unit is Unit is FixedFixedInstantInstant--aneousaneous–– FixedFixed–– AdjustableAdjustable
Solid Solid State Trip State Trip
UnitUnitVaries for Varies for each Trip each Trip Unit!Unit!Some Some Functions Functions are Not are Not Adjustable!Adjustable!
Long Time Pickup (LTPU)
Long Time Delay (LTD)
Short Time Pickup (STPU)
Short Time Delay (STD)
Instantaneous (I)
Short Time Delay I2T-IN
(I2T)
Solid Solid State Trip State Trip
UnitUnitSQ D NW SQ D NW 40H40H4000 Amp4000 AmpMicrologicMicrologic
Current SensorsRating Plugs
Current Setting
Solid State Trip UnitSolid State Trip Unit
Why is Why is this this
Difficult?Difficult?Three Three Breakers in Breakers in SeriesSeriesNo OverlapNo OverlapEasy Right?Easy Right?
Why is Why is this this
Difficult?Difficult?SWBD MainSWBD Main–– SS w/ LISS w/ LI
FeederFeeder–– SS w/ LSISS w/ LSI
Panel MainPanel Main–– T/MT/M
Panel BranchPanel Branch–– T/MT/M
3-MSWBD MAINSQUARE D NW40H Sensor/Trip 4000 A
SWBD480 V
XFMR-UTILS480 V
S
P 2- XFMR-UTILS
5-Fdr to ATS-ESQUARE D LE Sensor/Trip 250 APlug 250 A
6-PNL-A MAINSQUARE D LA Sensor/Trip 250 A
PNL-A - 250 A480 V
E N
ATS 260 Amp
12-Lrgst FdrSQUARE D FH Sensor/Trip 100 A
Why is Why is this this
Difficult?Difficult?Instantaneous Instantaneous FunctionFunctionPer UL & Per UL & NEMA NEMA ––Required on Required on MCCBs & MCCBs & ICCBsICCBsLVPCBs LVPCBs –– Not Not RequiredRequired
SolutionSolution
EliminateEliminate the Instantaneous Function by:the Instantaneous Function by:–– Reducing the fault currentReducing the fault current–– Setting Instantaneous above fault current.Setting Instantaneous above fault current.
Instantaneous Instantaneous Function Function ––T/M TripT/M Trip
Selectively Selectively coordinates coordinates only if only if difference difference in fault in fault currentcurrent
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Instantaneous Instantaneous curve ends at curve ends at available fault available fault currentcurrent100,000 Amps100,000 Amps
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Instantaneous Instantaneous curve ends at curve ends at available fault available fault currentcurrent60,000 Amps60,000 Amps
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Instantaneous Instantaneous curve ends at curve ends at available fault available fault currentcurrent30,000 Amps30,000 Amps
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Instantaneous Instantaneous curve ends at curve ends at available fault available fault currentcurrent25,000 Amps25,000 Amps
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Instantaneous Instantaneous curve ends at curve ends at available fault available fault currentcurrent15,000 Amps15,000 Amps
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Instantaneous Instantaneous curve ends at curve ends at available fault available fault currentcurrent10,000 Amps10,000 Amps
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Adjust Adjust Instantaneous Instantaneous curve above curve above the available the available fault currentfault current3X3X
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Adjust Adjust Instantaneous Instantaneous curve above curve above the available the available fault currentfault current4X4X
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Adjust Adjust Instantaneous Instantaneous curve above curve above the available the available fault currentfault current6X6X
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Adjust Adjust Instantaneous Instantaneous curve above curve above the available the available fault currentfault current8X8X
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Adjust Adjust Instantaneous Instantaneous curve above curve above the available the available fault currentfault current10X10X
InstantaneousInstantaneousFunction Function ––
SS TripSS Trip
Adjust Adjust Instantaneous Instantaneous curve above curve above the available the available fault currentfault current12X12X
Problem Problem –– Large EquipmentLarge Equipment
Switchboard Feeder and Panelboard Mains Switchboard Feeder and Panelboard Mains many times are ICCBmany times are ICCBTip #2 Tip #2 –– Eliminate Main Breakers in Eliminate Main Breakers in Panelboards.Panelboards.
Switchgear & Switchboard
Switchgear and switchboard, Panelboard structures are built and tested to different standards:
SwitchgearSwitchgear
ANSI standard C37.20.1UL standard 1558NEMA standard SG-5Switchgear uses power circuit breakers (PCB) – ANSI C37.13– NEMA SG-3 – UL-1066
Unfused switchgear short circuit tested 30 cycles
SwitchgearSwitchgear
Instantaneous trip function not required for LVPCBs.
SwitchboardsSwitchboards
Group MountedSwitchboards Standards – NEMA PB-2– UL-891.
Switchboards may use a combination of protective devices
Switchboards Switchboards –– Devices to UseDevices to Use
Insulated case (ICCB)Molded-case circuit breakers (MCCB)Fusible switchesPower circuit breakers
GroupGroup--mounted Switchboards,mounted Switchboards, ––Short Circuit TestingShort Circuit Testing
Short Circuit tested for only 3 cyclesProtective devices must have instantaneous for UL 891 labelThis Instantaneous trip function reducesselectivity between the main and feedercircuits breakers.
Compartmented Switchboards
Short Circuit tested for 30 cycles.UL 891 Listed
SWBDSWBD& SWGR & SWGR TestingTesting
ANSI, NEMA, & ANSI, NEMA, & ManufacturersManufacturers….. We need ….. We need an I2T an I2T Withstand Withstand Curve!!!!Curve!!!! SWBD W/S Tested for SWBD W/S Tested for
3 Cycles (0.05 Seconds)3 Cycles (0.05 Seconds)
SWGR W/S 65 KA SWGR W/S 65 KA
@ 30 Cycles (0. 5 Seconds)@ 30 Cycles (0. 5 Seconds)
SWBD W/S 65 KA SWBD W/S 65 KA
More TipsMore Tips
Tip #3Tip #3–– T/M breakers must have a 3:1 ratio to T/M breakers must have a 3:1 ratio to
selectively coordinate.selectively coordinate.
Tip #4Tip #4–– Impedance aids in selective coordinationImpedance aids in selective coordination–– Long feeder lengthsLong feeder lengths–– Air core reactorsAir core reactors–– TransformersTransformers
Tip #5 Tip #5 –– Feeders to Feeders to Downstream MainsDownstream Mains
Feeders to Equipment Main Feeders to Equipment Main Devices, do not need to Devices, do not need to coordinate.coordinate.They feed the same load!They feed the same load!Impossible to do with SS Trip Impossible to do with SS Trip Breakers. (LTPU Region)Breakers. (LTPU Region)Impossible to do with fuses.Impossible to do with fuses.
3-MSWBD MAINSQUARE D NW40H Sensor/Trip 4000 A
SWBD480 V
XFMR-UTILS480 V
S
P 2- XFMR-UTILS
5-Fdr to ATS-ESQUARE D LE Sensor/Trip 250 APlug 250 A
6-PNL-A MAINSQUARE D LA Sensor/Trip 250 A
PNL-A - 250 A480 V
E N
ATS 260 Amp
12-Lrgst FdrSQUARE D FH Sensor/Trip 100 A
11
22
22
33
Panelboard Panelboard Mains Mains -- MCSMCS
Use Caution when Use Caution when using Molded Case using Molded Case Switches (MCS)Switches (MCS)May have very low May have very low self self --protecting protecting instantaneous instantaneous functionfunction
Transformer ProtectionTransformer Protection
NEC Table 450.3(B) Maximum Rating or NEC Table 450.3(B) Maximum Rating or Setting of Overcurrent Protection for Setting of Overcurrent Protection for TransformersTransformersDeltaDelta--Wye LV Transformers requireWye LV Transformers require–– Primary Protection @ Primary Protection @ << 250% 250% ratingrating–– Secondary Protection @ Secondary Protection @ << 125%* 125%* ratingrating–– *Use next highest standard rating allowed *Use next highest standard rating allowed
(see Table 240.6)(see Table 240.6)Tip #6 Tip #6 –– Keep Table 240.6 within reachKeep Table 240.6 within reach
S
P T-3
T-3 PRIM
T-3 SEC
12-Lrgst Brnch
PNL-A - 250 A
13-Pnl C MAIN
PNL-C
Tip #7 Tip #7 –– Primary & Primary & Secondary ProtectionSecondary Protection
Primary & Secondary Devices, Primary & Secondary Devices, do not need to coordinate.do not need to coordinate.They feed the same load!They feed the same load!Difficult to do with fuses. No Difficult to do with fuses. No Fuse selectivity tables.Fuse selectivity tables.Possible with CBsPossible with CBs
11
11
More TipsMore Tips
Tip #8Tip #8** -- Use SS Trips with LSUse SS Trips with LSI(0ff)I(0ff) or or FixedFixed Instantaneous Instantaneous OverrideOverrideTip #9Tip #9** –– Specify that SS Trip Units have Specify that SS Trip Units have adjustableadjustable::–– LTPU / LTDLTPU / LTD–– STPU / STD / I2TSTPU / STD / I2T–– INST(OFF) or Instantaneous Override INST(OFF) or Instantaneous Override (above (above
110% fault current at downstream device)110% fault current at downstream device)* * -- Do not forget the generator breakerDo not forget the generator breaker
Elevator Selective Coordination
Elevator Circuits must be selectively coordinated.
ELEV-2
CB-ELEV-2
23-ELEV ST
22-FDR ELEV-2
PNL-A - 250 A
ELEV-2 MOTOR
Tip #10 Tip #10 –– Elevator Elevator Circuit CoordinationCircuit Coordination
Feeder and Shunt Trip Devices, Feeder and Shunt Trip Devices, do not need to coordinate.do not need to coordinate.They feed the same load!They feed the same load!Impossible to do with fuses if Impossible to do with fuses if fuses are same size.fuses are same size.Impossible with CBsImpossible with CBs
Elevator Elevator Circuit Circuit
CoordinationCoordination
ELEV-1 ELEV-3
CB-ELEV-3CB-ELEV-1
SWBD
3-MSWBD MAIN
ELEV-1 MOTOR ELEV-3 MOTOR
28-ELEV 3 ST
27-FDR ELEV-3
30-ELEV 1 ST
29-FDR ELEV-1
11
11
22
22-GEN
23-GEN MAIN #1
GEN
SWBD-EMSB-1
24-FDR PNL F
PNL-F
Generator Generator CoordinationCoordination
Must Coordinate as Must Coordinate as wellwellGood News! Good News! -- Lower Lower Fault CurrentsFault CurrentsEasier to CoordinateEasier to Coordinate
11
22
GenGenPDCPDC
Decrement Decrement CurveCurveFault Current < Fault Current < Instantaneous Instantaneous SettingSetting
Series Rating of DevicesSeries Rating of Devices
Two or More Devices are Short Circuit Tested in Two or More Devices are Short Circuit Tested in SeriesSeriesCombinations can beCombinations can be–– Circuit BreakerCircuit Breaker–– FusesFuses–– Fuses and Circuit BreakersFuses and Circuit Breakers
Last device AIC (SC) Rating < AvailableLast device AIC (SC) Rating < AvailableAllAll Devices will operateDevices will operate
SWBD41638 Amps 3P
PNL-B36029 Amps 3P
25-Fdr Pnl-BInterruptingRating 65 kA
26-Lrgst BrnchInterruptingRating 25 kA
Series Rating Series Rating of Devicesof Devices
UL Listed UL Listed Combination is Combination is Series Rated 65 kASeries Rated 65 kANo Selective No Selective CoordinationCoordinationTip #11 Tip #11 –– Do Not Do Not Use Series Rated Use Series Rated DevicesDevices
11
11
Steps to Meet the CodeSteps to Meet the Code
Obtain Utility DataObtain Utility Data–– Maximum size of transformer (kVA)Maximum size of transformer (kVA)–– ImpedanceImpedance–– Winding ConnectionsWinding Connections–– Maximum available primary three phase and Maximum available primary three phase and
line to ground short circuit currentline to ground short circuit current
Steps to Meet the CodeSteps to Meet the Code
Model the distribution system in computerModel the distribution system in computerPerform Short Circuit StudyPerform Short Circuit StudyDetermine Equipment Full Load Ratings Determine Equipment Full Load Ratings (FLA)(FLA)
Steps to Meet the CodeSteps to Meet the Code
Determine protective device Determine protective device –– Standard Ampere Rating (NEC 240.6)Standard Ampere Rating (NEC 240.6)–– Short circuit interrupting rating (AIC)Short circuit interrupting rating (AIC)–– Downstream coordination current (DCC)Downstream coordination current (DCC)
Tip #12 Tip #12 –– Put the SC numbers on the One Put the SC numbers on the One Line DrawingLine Drawing
Steps to Meet the Code Steps to Meet the Code -- Circuit Circuit BreakersBreakers
Choose a device manufacturerChoose a device manufacturerUse NEC, DCC and Circuit Breaker Use NEC, DCC and Circuit Breaker Selection TableSelection TablePick circuit breakers with instantaneous Pick circuit breakers with instantaneous trips above the DCC.trips above the DCC.
Steps to Meet the Code Steps to Meet the Code -- Circuit Circuit BreakersBreakers
Plot breaker curves toPlot breaker curves to–– Verify selective coordinationVerify selective coordination–– Determine device settingsDetermine device settingsFor new design projects For new design projects –– Repeat above steps for other manufacturesRepeat above steps for other manufactures–– Create Create detaileddetailed specifications for competitive specifications for competitive
biddingbidding–– Specify the Breaker Trip Unit Specify the Breaker Trip Unit Types (T/M or Types (T/M or
SS)SS) and and Instantaneous OverrideInstantaneous Override ValuesValues..
Steps to Meet the Code Steps to Meet the Code -- Circuit Circuit BreakersBreakers
Tip #13 Tip #13 -- Add to Project Specifications:Add to Project Specifications:
“Where indicated on one line drawing, “Where indicated on one line drawing, breakers must have trip units with breakers must have trip units with Instantaneous setting or override ampere Instantaneous setting or override ampere rating 110% above the values shown on rating 110% above the values shown on one line drawing.”one line drawing.”
Steps to Meet the Code Steps to Meet the Code -- FusesFuses
Use Selectivity Ratio Guide to determine Use Selectivity Ratio Guide to determine fuse sizesfuse sizesVerify Verify Generator BreakerGenerator Breaker and and Downstream Downstream FusesFuses will coordinate.will coordinate.
517.17 Ground517.17 Ground--Fault Protection.Fault Protection.
(C) Selectivity. (C) Selectivity. –– GroundGround--fault protection for operation of the fault protection for operation of the
service service and and feederfeeder disconnecting means shall disconnecting means shall be fully be fully selectiveselective such that the feeder device, such that the feeder device, but not the service device, shall open on but not the service device, shall open on ground faults on the load side of the feeder ground faults on the load side of the feeder device. device.
GroundGround--Fault ProtectionFault Protection
Code Code RequiresRequires Ground Fault Selective Ground Fault Selective Coordination for Coordination for MainMain and and FeedersFeeders(medical facilities) only.(medical facilities) only.Code Code does notdoes not state that Ground Fault state that Ground Fault Protection Must Coordinate with the Phase Protection Must Coordinate with the Phase Protection.Protection.Considered a different protection schemeConsidered a different protection schemeMaximumMaximum PickupPickup setting is setting is 1,2001,200 AmperesAmperesMaximum Time DelayMaximum Time Delay setting is setting is 0.5 sec0.5 sec..
GroundGround--Fault ProtectionFault Protection
Limited Equipment options for fusesLimited Equipment options for fusesMany times impossible to prevent overlap Many times impossible to prevent overlap with ground fault and phase devices.with ground fault and phase devices.
More Problems with the CodeMore Problems with the Code
Modifications or additions to a facility. Modifications or additions to a facility. How far do you go to implement selective How far do you go to implement selective coordination?coordination?Small Transformers (15Small Transformers (15--45 kVA) and 45 kVA) and PanelboardsPanelboards
More Problems More Problems with the Codewith the Code
Hospital Isolation Hospital Isolation PanelboardsPanelboards
Tools for Breaker CoordinationTools for Breaker Coordination
Square D Square D –––– Enhancing Short Circuit Selective Coordination Enhancing Short Circuit Selective Coordination
with Low Voltage Breakerswith Low Voltage Breakers
New Products coming down the pipe! New Products coming down the pipe! Eaton Electric Eaton Electric –––– Breaker Selectivity ChartBreaker Selectivity Chart–– Breaker Coordination Excel SpreadsheetBreaker Coordination Excel Spreadsheet
101010104.2150
101010104.24.2125
101010105.04.22.52.2100
101010105.04.22.52.290
101010105.04.22.52.280
101010105.04.22.52.270
101010106.04.22.52.20.860
101010106.04.22.52.20.850
101010106.04.23.42.20.840
101010108.05.03.42.21.230
101010108.05.03.42.21.220
101010101010.04.02.21.215
BR, BAB, HQP & QC
(10 kA)
R (2500 A)
N (1200 A)
LG (630A)
L(600 A)
K (400 A)
J (250 A)
JG(250 A)
F (225 A)
EG(125 A)Rating
Upstream (Main) MCCBDownstream (Branch) CB
All Values (Typical) in RMS Current Levels @ 240, 415 / 480 Vac
Coordination Table.
Job Title
Company Name
Available Fault Current CalculationEnter Available Utility Fault Current Amperes
If not known, enter transformer KVA rating 300 KVAEnter transformer impedance (Z) 5 %
Select Primary System VoltageSelect Secondary System Voltage
Transformer Calculations Primary Voltage 480 VoltsPrimary Current 361 AmperesMaximum Primary Protection per NEC 450.3(B) 902 AmperesRecommended Primary Breaker Rating 1000 Amperes
Secondary Voltage 208 VoltsSecondary Current 833 AmperesMaximum Secondary Protection per NEC 450.3(B) 1041 AmperesRecommended Secondary Breaker Rating 1200 Amperes
ISCA = Transformer FLA x 100 16,655 AmperesTransformer %Z
Short Circuit Current (RMS symmeterical) 16,655 Amperes@ Transformer Terminals
Motor Contributions 1,665 Amperes
Total Short Circuit Current 18,320 Amperes(Transformer/Utility+Motor Contribution)
Three Phase 208Y/120
Three Phase 480
Select Conductor Data Between Main MCCB and Branch MCCBSelect Conductor Type & Raceway Charisteristics
Select Conductor Size
Enter Conductor Length 100 Feet
Enter Number of Conductors / Phase 1
Fault Current @ Load Terminals of Branch MCCB 7,815 Amperes
Select Transformer Secondary MCCB
Select Downstream Branch MCCB
Coordination Level 2,300 Amperes
Results Select Larger Frame Size
Copper in Metalic Raceway
250 kcmil
JG(250 A)
F 100A
Circuit Breaker Selection TableCircuit Breaker Selection Table
Table Used to Quickly Select Breakers that Table Used to Quickly Select Breakers that maymaycoordinate.coordinate.Easily Sorted in Excel.Easily Sorted in Excel.
Circuit Breaker Selection TableCircuit Breaker Selection Table
Example 1Example 1Determine the Determine the –– SWBD Main (4000 Amp)SWBD Main (4000 Amp)–– Feeder to ATS (200 Amp)Feeder to ATS (200 Amp)–– Panelboard Main (200 Amp)Panelboard Main (200 Amp)–– Largest Feeder is 70A KH Largest Feeder is 70A KH
AMPAMP
32-MSWBD MAIN
SWBD41638 Amps 3P41081 Amps SLG12-Fdr ATS-E
12-PNL-A MAIN
PNL-A - 250 A30933 Amps 3P27901 Amps SLG
E N
ATS 260 Amp
76-Lrgst Brnch
32-MSWBD MAINSQUARE D NW40H Sensor/Trip 4000 ASettings Phase LTPU/LTD (A 0.4-1.0 x S) 1 (4000A); 0.5 STPU (1.5-10 x LTPU) 5 (20000A) STD (INST-0.4) 0.3(I^2 T Out) INST (2-15 x S) 15 (60000A)
12-Fdr ATS-ESQUARE D NT08H Sensor/Trip 400 ASettings Phase LTPU/LTD (A 0.4-1.0 x S) 0.5 (200A); 24 STPU (1.5-10 x LTPU) 6 (1200A) STD (INST-0.4) 0.2(I^2 T Out) INST Override Fixed (40000A)
Example 1Example 1
12-PNL-A MAINSQUARE D NT08H Sensor/Trip 400 ASettings Phase LTPU/LTD (A 0.4-1.0 x S) 0.5 (200A); 16 STPU (1.5-10 x LTPU) 5 (1000A) STD (INST-0.4) 0.1(I^2 T Out) INST Override Fixed (40000A)
76-Lrgst BrnchSQUARE D KH Sensor/Trip 70 ASettings Phase Thermal Curve (Fixed) INST (5-10 x Trip) 10.0 (700A)
Example 1Example 1
Example 1Example 1Determine Determine the the –– SWBD Main SWBD Main --–– Feeder to Feeder to
ATSATS–– PNLBD MainPNLBD Main–– Largest Largest
Feeder is Feeder is 70A KH AMP70A KH AMP
Example 2Example 2Determine the Determine the –– Panel A FeederPanel A Feeder–– Panel C MainPanel C Main–– Panel C Largest Feeder is 20A QOPanel C Largest Feeder is 20A QO
Step 1 Step 1 –– Determine 208 V Fault Determine 208 V Fault in 480 V amperes.in 480 V amperes.3,094 X 208/480 = 1,341 A3,094 X 208/480 = 1,341 A
Example 2Example 2
Pick 125 Amp Feeder Breaker TPick 125 Amp Feeder Breaker T--3 3 –– Instantaneous OR > 1,341Instantaneous OR > 1,341–– 1,341 / 125 = 10.7 (Can not use T/M)1,341 / 125 = 10.7 (Can not use T/M)–– Must Use SS TripMust Use SS Trip
Pick Panel C 100 Ampere MainPick Panel C 100 Ampere Main–– Must Coordinate with Largest Branch BreakerMust Coordinate with Largest Branch Breaker
Example 2Example 213-Pnl C MAINSQUARE D PG Sensor/Trip 250 ASettings Phase LTPU/LTD (A 0.4-1.0 x S) 0.4 (100A) STPU (1.5-10 x LTPU) 10 (1000A) STD (0-0.4) 0.1(I^2 T In) INST Override Fixed (24000A)
17-Lrgst BrnchSQUARE D QO3 Sensor/Trip 20 ASettings Phase Fixed
12-PNL-A MAINSQUARE D NT08H Sensor/Trip 400 ASettings Phase LTPU/LTD (A 0.4-1.0 x S) 0.5 (200A); 16 STPU (1.5-10 x LTPU) 5 (1000A) STD (INST-0.4) 0.2(I^2 T Out) INST Override Fixed (40000A)
14-Fdr to T-3SQUARE D LE Sensor/Trip 250 APlug 250 ASettings Phase LTPU (0.5-1.0 x P) 0.5 (125A) LTD (2-14 Sec.) 2 STPU (2-8 x P) 2.5 (625A) STD (0.1-0.5 Sec.) 0.1(I^2 T Out) INST (2.5-8 x P) 8.0 (2000A)
Example 2Example 2
Example 2Example 2
SummarySummary
You must change the way you design You must change the way you design circuits for:circuits for:–– Emergency Emergency –– StandbyStandby–– ElevatorElevatorManufacturers must provide:Manufacturers must provide:–– New Equipment to meet the codeNew Equipment to meet the code–– Tools (tables, spreadsheets, charts)Tools (tables, spreadsheets, charts)–– II22T Withstand curves for EquipmentT Withstand curves for Equipment
Need more InformationNeed more Informationwww.powerstudies.comwww.powerstudies.com–– ArticlesArticles–– LinksLinks–– Specifications for Power System StudiesSpecifications for Power System Studies
Short CircuitShort CircuitProtective Device CoordinationProtective Device CoordinationArc Flash HazardArc Flash Hazard
Questions??Questions??
Thank you for your Thank you for your time! time!
Who are we? Who are we? Electrical Electrical Engineering Engineering Consulting FirmConsulting FirmWe Specialize in We Specialize in performing Power performing Power System StudiesSystem Studies90% of our 90% of our business is in business is in performing Power performing Power System StudiesSystem Studies
Where are we located?Where are we located?Our office is located in Covington, WA.Our office is located in Covington, WA.Near SeattleNear SeattleOur territory is Western third of USOur territory is Western third of USWe have also done studies for clients in We have also done studies for clients in Russia and South AmericaRussia and South America