In a three-phase electrical system, three ground detecting lamps are provided. One lamp goes dark and the others increase in brightness when the "ground test" button is pushed. What is indicated?

Correct Answer: Option A — there is a ground on the line with the dark lamp

Ground-detection lamp circuits connect phase lines through lamps to a common hull ground. Pressing the test button bridges the ungrounded system; a single dark lamp indicates that phase is shorted directly to the metallic ship's hull.