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DESIGNING OF BUSBAR DESIGNING OF BUSBAR SYSTEMSYSTEM

BUSBAR SYSTEM DESIGN BUSBAR SYSTEM DESIGN PART 1PART 1

• BASIC REQUIREMENTSBASIC REQUIREMENTS

• DESIGN PARAMATERSDESIGN PARAMATERS

BASIC REQUIREMENTSBASIC REQUIREMENTS

THE BUSBAR SHOULD BE ABLE TO CARRYTHE BUSBAR SHOULD BE ABLE TO CARRY

• The Rated CurrentThe Rated Current

• The Current That Would Flow Under Abnormal The Current That Would Flow Under Abnormal ConditionsConditions

BASIC REQUIREMENTSBASIC REQUIREMENTS

BUSBAR SYSTEM SHOULD ALSO BE BUSBAR SYSTEM SHOULD ALSO BE PROTECTED AGAINSTPROTECTED AGAINST

• VERMIN, FALLING TOOLS & VERMIN, FALLING TOOLS & HARDWARES WHICH INITIATES HARDWARES WHICH INITIATES ARCING FAULTSARCING FAULTS

• DUST & CONDUCTING DEPOSITS DUST & CONDUCTING DEPOSITS WHICH ACCELERATE TRACKINGWHICH ACCELERATE TRACKING

DESIGN PARAMETERSDESIGN PARAMETERS

• THE CONFIGURATION OF BUSBARTHE CONFIGURATION OF BUSBAR

• THE ORIENTATION OF BUSBARTHE ORIENTATION OF BUSBAR

• CLEARANCE & CREEPAGE DISTANCECLEARANCE & CREEPAGE DISTANCE

• INSULATING SUPPORTSINSULATING SUPPORTS

• INSULATION OF BUSBARSINSULATION OF BUSBARS

• SINGLE OR MULTI BARSINGLE OR MULTI BAR

• BUSBAR JOINTSBUSBAR JOINTS

• BUSBAR MATERIALBUSBAR MATERIAL

CONFIGURATION OF CONFIGURATION OF BUSBARSBUSBARS

100118 125 128

154 157160

120

80

40

0

ALTERNATING CURRENT CAPACITIES FOR SAME CROSS-SECTIONAL AREA

%UPRATING

VARIOUS TYPES OF CONFIGURATION

ORIENTATION OF BUSBARSORIENTATION OF BUSBARS

1) HORIZONTAL1) HORIZONTAL 2) VERTICAL ORIENTATION2) VERTICAL ORIENTATION

ss ss´

s´

INVARIABLY S´ > S

SHORT CIRCUIT FORCE FOR VERTICAL ORIENTATION IS LESS THAN THAT FOR HORIZONTAL ORIENTATION

CLEARANCE & CREEPAGE CLEARANCE & CREEPAGE DISTANCEDISTANCE

CLEARANCECLEARANCE IS THE SHORTEST DISTANCE BETWEEN TWO IS THE SHORTEST DISTANCE BETWEEN TWOCONDUCTORS AT DIFFERENT POTENTIAL.CONDUCTORS AT DIFFERENT POTENTIAL.

CREEPAGE DISTANCECREEPAGE DISTANCE IS THE DISTANCE BETWEEN TWO IS THE DISTANCE BETWEEN TWOCONDUCTORS AT DIFFERENT POTENTIAL, MEASUREDCONDUCTORS AT DIFFERENT POTENTIAL, MEASUREDALONG THE SURFACE OF INSULATING SUPPORT.ALONG THE SURFACE OF INSULATING SUPPORT.

MEASUREMENT OF MEASUREMENT OF CREEPAGE DISTANCECREEPAGE DISTANCE

INSULATINGINSULATINGMATERIALMATERIAL

2mm2mm

2mm2mm

CONDUCTINGCONDUCTINGPARTPART

CONDUCTINGCONDUCTING PARTPART

CREEPAGECREEPAGEDISTANCEDISTANCE

INCLUSION OF A GROOVE IN CREEPAGE DISTANCEINCLUSION OF A GROOVE IN CREEPAGE DISTANCE

MEASUREMENT OF MEASUREMENT OF CREEPAGE DISTANCECREEPAGE DISTANCE

INSULATINGINSULATINGMATERIALMATERIAL

2mm2mm CONDUCTINGCONDUCTINGPARTPART

CONDUCTINGCONDUCTING PARTPART

CREEPAGECREEPAGEDISTANCEDISTANCE

INCLUSION OF A RIDGE IN CREEPAGE DISTANCEINCLUSION OF A RIDGE IN CREEPAGE DISTANCE

MINIMUM VALUES OFMINIMUM VALUES OF CLEARANCES & CREEPAGE CLEARANCES & CREEPAGE

DISTANCES (IS 4237 : 1982)DISTANCES (IS 4237 : 1982)RATEDRATEDINSULATIONINSULATIONVOLTAGEVOLTAGE

CLEARANCESCLEARANCES mmmm

CREEPAGESCREEPAGES mm mm

I I 63 A I 63 A I 63 A I 63 A I 63 A I 63 A I 63 A 63 A

L - L L - A L - L L - A L - L L - A L - L L - AL - L L - A L - L L - A L - L L - A L - L L - A

UP TO 50 2 3 3 5 2 3 3 4UP TO 50 2 3 3 5 2 3 3 461 TO 250 3 5 5 6 3 4 5 8 61 TO 250 3 5 5 6 3 4 5 8 251 TO 380 4 6 6 8 4 6 6 10251 TO 380 4 6 6 8 4 6 6 10381 TO 500 6 8 8 10 6 10 8 12381 TO 500 6 8 8 10 6 10 8 12501 TO 660 6 8 8 10 8 12 10 14 501 TO 660 6 8 8 10 8 12 10 14 661 TO 750 ac 10 14 10 14 10 14 14 20661 TO 750 ac 10 14 10 14 10 14 14 20661 TO 800 dc 661 TO 800 dc 751 TO 1000 ac 14 20 14 20 14 20 20 24751 TO 1000 ac 14 20 14 20 14 20 20 24801 TO 1200 dc 801 TO 1200 dc

CLEARANCE & CREEPAGE CLEARANCE & CREEPAGE DISTANCEDISTANCE

ASSUMPTION AS GIVEN IN INDIAN STANDARDASSUMPTION AS GIVEN IN INDIAN STANDARD

““THE VALUES OF CLEARANCES & CREEPAGE DISTANCESTHE VALUES OF CLEARANCES & CREEPAGE DISTANCESSPECIFIED IN THIS STANDARD ARE BASED ON THE SPECIFIED IN THIS STANDARD ARE BASED ON THE

ASSUMPTIONASSUMPTIONTHAT THE AIR IS CLEAN & ITS RELATIVE HUMIDITY THAT THE AIR IS CLEAN & ITS RELATIVE HUMIDITY

DOESN’TDOESN’TEXCEED 50 PERCENT AT TEMPERATURE OF 40°C ”EXCEED 50 PERCENT AT TEMPERATURE OF 40°C ”

INSULATING SUPPORTSINSULATING SUPPORTSDESIRABLE PROPERTIESDESIRABLE PROPERTIES

• HIGH MECHANICAL STRENGTHHIGH MECHANICAL STRENGTH

• HIGH DIELECTRIC STRENGTHHIGH DIELECTRIC STRENGTH

• HIGH TEMPERATURE WITHSTANDHIGH TEMPERATURE WITHSTAND

• NON FLAMMABLE PROPERTIESNON FLAMMABLE PROPERTIES

• NON HYGROSCOPIC PROPERTIESNON HYGROSCOPIC PROPERTIES

• HIGH COMPARATIVE TRACKING HIGH COMPARATIVE TRACKING INDEX (CTI)INDEX (CTI)

TRACKINGTRACKING

(A) LEAKAGE CURRENT THRU’(A) LEAKAGE CURRENT THRU’THE CONDUCTIVE LAYERTHE CONDUCTIVE LAYER

(B) CONDUCTIVE LAYER(B) CONDUCTIVE LAYERCONTINUITY BREAKSCONTINUITY BREAKS

(C) ABRUPT STOPPAGE OF(C) ABRUPT STOPPAGE OFCURRENT CAUSES OVERCURRENT CAUSES OVERVOLTAGE RESULTING IN SPARKVOLTAGE RESULTING IN SPARK

(D) SPARKS CAUSE (D) SPARKS CAUSE BREAKDOWN OF SURFACEBREAKDOWN OF SURFACERESULTING IN SPREADRESULTING IN SPREADOF TRACK MARKSOF TRACK MARKS

CTICTI

CTI IS A MEASURE OF THE SUSCEPTIBILITY OF THE CTI IS A MEASURE OF THE SUSCEPTIBILITY OF THE INSULATION MATERIAL TO ELECTRICAL TRACKING.INSULATION MATERIAL TO ELECTRICAL TRACKING.

° ° °

DROPS OF NHDROPS OF NH44CLCL

4mm4mm

TEST FOR CTITEST FOR CTI

COMPARISION OF SOME COMPARISION OF SOME INSULATING MATERIALINSULATING MATERIAL

MECHANICALSTRENGTH

LOW BRITTLE HIGH HIGH

DIELECTRICSTRENGTH

HIGH HIGH HIGH HIGH

CTI (VOLTS) 133 500 1000 800

TEMP.WITHSTAND

120 HIGH 250 200-250

INFLAMMABLE YES NO NO NO

MOISTUREABSORPTION

HIGH LOW LOW LOW

MOULDING TOSHAPES

NO DIFFICULT YES YES

HYLUM PORCELAIN EPOXY SMC/DMCHYLUM PORCELAIN EPOXY SMC/DMC

INSULATION OF BUSBARSINSULATION OF BUSBARS

• MINIMIZES OCCURENCES OF ARCING MINIMIZES OCCURENCES OF ARCING FAULTSFAULTS

• ARRESTS SPREAD OF ARCING IF AT ALL ARRESTS SPREAD OF ARCING IF AT ALL FAULT OCCURSFAULT OCCURS

• BLACK SLEEVES IMPROVES HEAT BLACK SLEEVES IMPROVES HEAT DISSIPATION (BUT INSIGNIFICANT)DISSIPATION (BUT INSIGNIFICANT)

• BECAUSE OF SLEEVES BUSBARS ARE BECAUSE OF SLEEVES BUSBARS ARE NEVER IN DIRECT CONTACT WITH THE NEVER IN DIRECT CONTACT WITH THE SUPPORTSSUPPORTS

ARCING FAULTSARCING FAULTS

• CAUSE MAXIMUM DAMAGECAUSE MAXIMUM DAMAGE

• LOW CURRENTS (5 TO 10 kA COMPARED LOW CURRENTS (5 TO 10 kA COMPARED TO 50 kA S/C CURRENT)TO 50 kA S/C CURRENT)

• HIGH TEMPERATURES UPTO 3000°CHIGH TEMPERATURES UPTO 3000°C

• FROM POINT OF INITIATION, IT TRAVELS FROM POINT OF INITIATION, IT TRAVELS AWAY FROM THE SUPPLY SOURCEAWAY FROM THE SUPPLY SOURCE

• VERY HIGH SPEED OF TRAVEL VERY HIGH SPEED OF TRAVEL 550 550 m/Secm/Sec

REDUCING RISKS OF REDUCING RISKS OF ARCING FAULTSARCING FAULTS

• INCREASE CLEARANCE BETWEEN INCREASE CLEARANCE BETWEEN PHASESPHASES

• SLEEVING OF BUSBARSSLEEVING OF BUSBARS

• SHROUDING BUSBARS JOINTSSHROUDING BUSBARS JOINTS

• PROPER SUPPORT PROPER SUPPORT MATERIAL/PROFILEMATERIAL/PROFILE

SINGLE BAR OR MULTIPLE SINGLE BAR OR MULTIPLE BARBAR

SKIN EFFECTSKIN EFFECT IS THE PHENOMENON BY WHICH THE IS THE PHENOMENON BY WHICH THE CURRENT DISTRIBUTION IN THE BUSBARS ISCURRENT DISTRIBUTION IN THE BUSBARS ISDISTORTED DUE TO THE INDUCTIVE EFFECT OF THE DISTORTED DUE TO THE INDUCTIVE EFFECT OF THE CURRENT IN THE CONDUCTOR ITSELF.CURRENT IN THE CONDUCTOR ITSELF.

PROXIMITY EFFECTPROXIMITY EFFECT IS THE PHENOMENON BY WHICH IS THE PHENOMENON BY WHICHTHE CURRENT DISTRIBUTION IN ONE CONDUCTOR IS THE CURRENT DISTRIBUTION IN ONE CONDUCTOR IS DISTORTED BY THE CURRENT IN THE ADJACENT DISTORTED BY THE CURRENT IN THE ADJACENT CONDUCTORS.CONDUCTORS.

SINGLE BAR OR MULTI BARSINGLE BAR OR MULTI BARSIZE IN MM 1 BAR 2 BARS 3 BARS 4 BARSSIZE IN MM 1 BAR 2 BARS 3 BARS 4 BARS25.4 25.4 6.35 356 715 970 1100 6.35 356 715 970 110038.1 38.1 6.35 520 1020 1350 1535 6.35 520 1020 1350 1535 50.8 50.8 6.35 670 1290 1705 1940 6.35 670 1290 1705 1940 63.5 63.5 6.35 812 1510 2000 2260 6.35 812 1510 2000 226076.2 76.2 6.36 958 1740 2310 2620 6.36 958 1740 2310 2620 101.6 101.6 6.35 1235 2140 2800 3200 6.35 1235 2140 2800 3200 127.0 127.0 6.35 1505 2510 3240 3700 6.35 1505 2510 3240 3700152.4 152.4 6.35 1780 2860 3680 4240 6.35 1780 2860 3680 4240 50.8 50.8 9.53 830 1500 1970 2260 9.53 830 1500 1970 2260 76.2 76.2 9.53 1180 2050 2660 3030 9.53 1180 2050 2660 3030 101.6 101.6 9.53 1495 2480 3150 3560 9.53 1495 2480 3150 3560127.0 127.0 9.53 1860 2930 3660 4200 9.53 1860 2930 3660 4200152.4 152.4 9.53 2120 3340 4080 4680 9.53 2120 3340 4080 4680 203.2 203.2 9.53 2750 4150 4900 5740 9.53 2750 4150 4900 574076.02 76.02 12.7 1355 2240 2830 3240 12.7 1355 2240 2830 3240101.6 101.6 12.7 1740 2720 3360 3900 12.7 1740 2720 3360 3900 127.0 127.0 12.7 2080 3120 3900 4550 12.7 2080 3120 3900 4550152.4 152.4 12.7 2420 3500 4400 5100 12.7 2420 3500 4400 5100203.2 203.2 12.7 3060 4450 5300 6150 12.7 3060 4450 5300 6150254.0 254.0 12.7 3640 5000 6000 6850 12.7 3640 5000 6000 6850








• BUSBAR JOINTSBUSBAR JOINTS

BUSBAR JOINTSBUSBAR JOINTS

• PROPER CONTACT PRESSURE MUST BE PROPER CONTACT PRESSURE MUST BE APPLIED AND MAINTAINEDAPPLIED AND MAINTAINED

• THE SURFACE OF THE ALUMINIUM MUST THE SURFACE OF THE ALUMINIUM MUST BE CLEANED BEFORE BOLTING UPBE CLEANED BEFORE BOLTING UP

• AIR & MOISTURE MUST BE EXCLUDED AIR & MOISTURE MUST BE EXCLUDED FROM THE JOINTFROM THE JOINT

• THE OVERLAP SHOULD BE ATLEAST THE OVERLAP SHOULD BE ATLEAST EQUAL TO THE WIDTH OF BUSBAREQUAL TO THE WIDTH OF BUSBAR

BUSBAR JOINTSBUSBAR JOINTSDESIRABLE PROPERTIES OF INHIBITING DESIRABLE PROPERTIES OF INHIBITING

COMPOUNDCOMPOUND• ASSIST IN MAKING ELECTRICAL JOINTS OF ASSIST IN MAKING ELECTRICAL JOINTS OF

LOW RESISTANCELOW RESISTANCE• INHIBIT OXIDE FORMATIONINHIBIT OXIDE FORMATION• CONSISTENT PROPERTIES OVER WIDE CONSISTENT PROPERTIES OVER WIDE

TEMP. RANGETEMP. RANGE• EXCLUDE MOISTURE UNDER ALL EXCLUDE MOISTURE UNDER ALL

CONDITIONSCONDITIONS• NON TOXIC & NON CORROSIVE FOR Cu & AlNON TOXIC & NON CORROSIVE FOR Cu & Al

BUSBAR JOINTSBUSBAR JOINTSNUMBER OF HOLES IN A BUSBARNUMBER OF HOLES IN A BUSBARPART OF BUSBAR MATERIAL MAY BE PART OF BUSBAR MATERIAL MAY BE

REMOVED FOR HOLES OR SLOTS REMOVED FOR HOLES OR SLOTS PROVIDEDPROVIDED

• THE REMAINING MATERIAL AT ANY THE REMAINING MATERIAL AT ANY CROSS SECTION ALONG THE LENGTH OF CROSS SECTION ALONG THE LENGTH OF THE BUSBAR HAS AT LEAST 70% OF THE THE BUSBAR HAS AT LEAST 70% OF THE REQUIRED AMPACITYREQUIRED AMPACITY

• THE REMAINING METAL IN ANY 150 MM THE REMAINING METAL IN ANY 150 MM LENGTH OF THE BUSBAR IS AT LEAST 93% LENGTH OF THE BUSBAR IS AT LEAST 93% OF THE METAL OF A BUS HAVING THE OF THE METAL OF A BUS HAVING THE REQUIRED AMPACITYREQUIRED AMPACITY








• BUSBAR JOINTSBUSBAR JOINTS• BUSBAR MATERIALBUSBAR MATERIAL

BUBAR MATERIALBUBAR MATERIALCOPPER & ALUMINIUMCOPPER & ALUMINIUM

• DENSITY OF Al IS 2.95 gm/cc DENSITY OF Al IS 2.95 gm/cc COMPARED TO 9.7 gm/cc OF COPPERCOMPARED TO 9.7 gm/cc OF COPPER

• BECAUSE OF THE INCREASED AREA, BECAUSE OF THE INCREASED AREA, THE ALUMINIUM BUSBAR WILL RUN THE ALUMINIUM BUSBAR WILL RUN COOLER THAN THEIR COPPER COOLER THAN THEIR COPPER BUSBARBUSBAR

• Al IS EASILY AVAILABLE & OF Al IS EASILY AVAILABLE & OF LOWER COSTLOWER COST

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