Which test is used to verify insulation between phase and ground when GFCI is not used?

• A. Megger between phase and ground
• B. Continuity test of ground prong
• C. Visual inspection
• D. Continuity test between phase and ground

Answer: (A)

Using an insulation resistance test with a megohmmeter (Megger) between the live conductor and ground directly checks how well the insulation between those parts is performing. The megger applies a high DC voltage and measures leakage current to calculate insulation resistance. A very high resistance means good insulation and little leakage; a low resistance indicates a leakage path or degraded insulation that could pose a shock or fault risk if energized. This is the appropriate method when a GFCI isn’t used because it assesses the integrity of the insulation itself, not just the presence of a conductor. Visual inspection can miss hidden damage, and continuity tests (either of the ground prong or between phase and ground) do not evaluate insulation quality and can be unsafe or misleading. Perform the test with equipment de-energized and follow all safety and manufacturer guidelines.