What characterizes a three-phase electrical system?

A three-phase electrical system is characterized by the presence of three conductors that carry alternating current (AC). This configuration allows for the generation, transmission, and distribution of electrical power with improved efficiency and performance. The alternating currents in each conductor are offset in phase by 120 degrees, which leads to a more consistent and reliable power supply.

This phase relationship allows three-phase systems to maintain a continuous power output, as at least one of the phases is always delivering power, making them particularly advantageous for powering large motors and industrial applications. Additionally, three-phase systems can deliver more power than single-phase systems using the same amount of conductor material, which contributes to reducing installation costs and material usage.

The other options do not accurately describe the three-phase system. For instance, having two conductors carrying direct current does not align with the three-phase concept. Similarly, providing a single-phase supply is not representative of what makes a three-phase system distinct, and variable frequency current is more related to specific applications like variable frequency drives rather than the fundamental characteristics of a three-phase system itself.