Final answer:
In a single-phase system, the base impedance is the impedance of the system when the apparent power is equal to the rated power and the power factor is 1. In a three-phase system, the base impedance is calculated using the per-unit system and represents the impedance that would result in a power factor of 1 and a power of 1 VA in each phase.
Step-by-step explanation:
In a single-phase system, the base impedance is defined as the impedance of the system when the apparent power is equal to the rated power, and the power factor is equal to 1. It is typically represented by the symbol Zbase and has units of ohms. It is used as a reference for analyzing and designing electrical systems.
In a three-phase system, the base impedance is calculated using the per-unit system. It is defined as the ratio of the rated voltage to the rated current of the system. It represents the impedance that would result in a power factor of 1 and a power of 1 volt-ampere in each phase. It is also used as a reference for analyzing and designing three-phase electrical systems.