What is the primary purpose of insulation resistance testing (megger) in electrical safety?

• A. To check insulation integrity between conductors and ground, identify deterioration, and verify insulation health during commissioning or maintenance
• B. To measure soil resistivity
• C. To test grounding conductor continuity only
• D. To verify current-carrying capacity of conductors under load

Answer: (A)

Insulation resistance testing with a megger checks how well the insulation separates live parts from each other and from the ground. By applying a high DC voltage and measuring the insulation resistance, you can tell whether the insulation is healthy or showing signs of deterioration, moisture, contamination, or damage. A high resistance means solid insulation, while a low resistance indicates leakage paths that could lead to insulation failure or safety hazards. This test is typically done during commissioning and during maintenance to verify insulation health and catch problems early before they cause faults. Other options don’t fit because measuring soil resistivity relates to grounding design, testing grounding conductor continuity only checks a path exists (not insulation quality), and verifying current-carrying capacity under load concerns how much current a conductor can carry, not insulation integrity.