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

currentpower

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?

\$S=\sqrt{3}VI\text{*}\$