A grounding autotransformer is used to create which type of electrical system?

• A. Three-phase, 3-Wire Grounded System
• B. Three-Phase, 3-Wire Ungrounded System
• C. Single-Phase System
• D. Three-Phase, Four-Wire Wye System

Answer: (B)

Grounding autotransformers establish a neutral reference for a three-phase system without adding a neutral conductor that serves the loads. By deriving and grounding a neutral point through the transformer, fault currents can return to earth if a line-to-ground fault occurs, which helps protective devices operate. At the same time, the normal load primarily runs between the three phase lines, so there isn’t a neutral conductor used by the loads, keeping the arrangement as a 3-phase, 3-wire setup. That’s why this setup is described as a Three-Phase, 3-Wire Ungrounded System—the system uses three phase conductors for power, with earth grounding provided for protection rather than a loaded neutral conductor.