Controlling System Voltage
Without capacitors, the voltage drop across a system is:
or
Vd = voltage drop across system leading to the load
kVA = 3-phase load kVA
kV = phase to phase voltage at load
cos theta = cosine of the power factor angle
R = resistance of system leading up to the load (ohms)
X = inductive reactance of the system leading up to the load (ohms)
The percent voltage rise at a load due to the addition of a capacitor bank is:
Vr = % voltage rise at load
kVAR = 3-phase capacitive kilovar
kV = phase to phase kilovolts
X = inductive reactance of the system
KVAsc = 3-phase short circuit kVA
The percent voltage rise from primary to secondary of a transformer is:
Where:
Vr = the percent voltage rise at the transformer
kVAR = 3-phase kilovar applied
kVAt = 3-phase kVA of the transformer
Xt = transformer reactance in percent
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