All distribution transformer tanks and __________ conductor(s) of all transformer secondary circuits should be grounded to protect life and property.

• A. the right
• B. all
• C. the left
• D. one

Answer: (D)

Grounding provides a safe fault path and keeps metal enclosures at earth potential, which protects people and equipment. The distribution transformer tank is a metal enclosure, so it is bonded to earth to prevent the surface from rising to dangerous voltages if insulation fails. In addition, grounding exactly one conductor of the secondary circuit gives the system a defined reference to ground. If a fault causes a live part to contact a grounded surface, fault current has a low-impedance path back to the source through that single grounded conductor and the tank, which makes protective devices trip quickly and reliably. Grounding all secondary conductors isn’t necessary and can create unnecessary ground paths or loops, while “left” or “right” don’t apply to grounding requirements.