50ka fault levelcalc
DESCRIPTION
Sample sizing calculation for busbarTRANSCRIPT
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PARAMETERS
Size of Aluminium Bus Bar Proposed 1x125x6 mm2
Site Ambient Temperature 45oC
Rise in Temperature allowed 40oC
Final Temperature Permitted 85oC
Fault current 50 kA
A. MINIMUM CONDUCTOR SIZE
Area of cross section
t = (k/100) ( Isc/A)2 (1+ 20 . ) .t( Ref: Industrial Power Engineering and application
Handbook page no. 999)t= temperature rise above operating temp. in deg. CIsc= symmetrical fault current in r.m.s in Amps.
A= cross sectional area of conductor in mm220=
0.00363 for Aluminium alloy & 0.00403 for pure Alluminium= operating temperature of the conductor at which the fault occursk= 1.166 for aluminium and 0.52 for coppert= duration of fault in seconds
Final temp. allowed for busbar after short circuit is 185 deg C By putting all values in the above equation
100 = (1.166/100) ( 50000/A)2 (1+ 0.00403 x 85) x 1A= 625.6 mm2
CALCULATION FOR AL BUS BAR SUITABLE FOR 50KA FAULT LEVEL
temperature coefficient of resistence at 20 deg C/deg C
Considering 6mm thickness for Aluminium flat for Main horizontal bus bar , we have provided 125x6mm size. For vetical droppers minimum cross section 625sq. mm shall be provided.
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