Which statement best describes the grounding approach where neutrals of every wye-connected transformer and generator are tied to earth?

• A. Grounding is optional in many networks
• B. Only one transformer neutrals should be grounded
• C. All neutrals of wye-connected transformers and generators are tied to earth
• D. Grounding is achieved by bonding phase conductors to ground

Answer: (C)

Grounding a system by tying the neutral points of every wye-connected transformer and generator to earth creates a solidly grounded network. This establishes a single, defined voltage reference to earth and provides a low-impedance path for any fault current that travels from a phase conductor to ground.

With neutrals grounded at all sources, a line-to-ground fault quickly pulls a large fault current through the earth reference, which makes overcurrent protective devices operate promptly and reliably. It also helps limit voltages on healthy phases during faults, reduces touch potential, and keeps system voltages stable under normal and fault conditions. The approach ensures consistent fault paths across the entire network and consistent protection coordination.

Other descriptions don’t match this setup: grounding being optional would leave no defined earth reference and hinder fault-clearing; grounding only one transformer neutral wouldn’t provide a common reference for other sources; and bonding phase conductors to ground doesn’t establish a neutral reference and can create unsafe or inefficient current paths.