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The per unit value of a 2 Ω resister at 100 MVA base and 10 kV base is
4 pu
2 pu
0.5 pu
0.2 pu
2 pu
Given: Resistance R = 2 Ω,Base Power S_{base} = 100 MVA, Base Voltage V_{base} = 10 kV
Resistance R = 2 Ω,Base Power S_{base} = 100 MVA, Base Voltage V_{base} = 10 kV
Zpu=ZbaseRactual=(Vbase)2Ractual×Sbase
Calculate Base Impedance
The base impedance Zbase is calculated using the base voltage and base power as Zbase=Sbase(Vbase)2. Given Vbase=10kV and Sbase=100MVA.
Zbase=100×106(10×103)2=100×106100×106=1Ω
Calculate Per Unit Resistance
Substitute the actual resistance Ractual=2Ω and the base impedance Zbase=1Ω into the per-unit formula Zpu=ZbaseRactual.
Rpu=12=2pu
B is correct because the calculated per unit resistance for the given base values is 2 pu.
This concept is fundamental for load flow studies and fault analysis; always remember that Zbase=(Vbase,kV)2/Sbase,MVA.