How is the formula for the base current value derived in a three-phase per-unit system


When analysing a power system using the per-unit system for a three phase system, why is \$S_b = \sqrt{3}*V_b*I_b\$, where as shown in the link, \$S_b\$ is the base power value, \$V_b\$ is the base voltage value and \$I_b\$ is the base current value?

Best Answer

Three phase circuits in power systems can be connected in two ways, delta connection or a wye connection. Luckily, both of these circuits have the same equation for apparent power.


It is this insight that allows for the current formula, despite the relation between line/phase voltage/current being different for the delta and the wye circuit.