Which test is commonly used to verify insulation integrity by applying a high voltage between conductors and earth?

Which test is commonly used to verify insulation integrity by applying a high voltage between conductors and earth?

• A. Continuity test
• B. Voltage drop test
• C. Megger test
• D. Polarity test

Answer: (C)

Testing insulation integrity by applying a high voltage between a conductor and earth is done with a megger. A megger is an insulation resistance tester that applies a high DC voltage and measures the resistance between the conductor and ground. If the insulation is sound, the resistance appears very high (in the megohm range); if moisture, contamination, or damage creates leakage paths, the resistance drops, signaling insulation problems. This method isolates the insulation path so you’re evaluating how well the insulation resists leakage, not the conductor’s continuity or general circuit behavior. Other tests perform different checks: a continuity test looks for a complete, low-resistance path to confirm wiring is continuous, not insulation quality; a voltage drop test assesses how much voltage is lost along a conductor under load, which helps identify undersized or loose connections; a polarity test ensures the correct identification of live, neutral, and ground, which is a safety check rather than insulation integrity.

Testing insulation integrity by applying a high voltage between a conductor and earth is done with a megger. A megger is an insulation resistance tester that applies a high DC voltage and measures the resistance between the conductor and ground. If the insulation is sound, the resistance appears very high (in the megohm range); if moisture, contamination, or damage creates leakage paths, the resistance drops, signaling insulation problems. This method isolates the insulation path so you’re evaluating how well the insulation resists leakage, not the conductor’s continuity or general circuit behavior.

Other tests perform different checks: a continuity test looks for a complete, low-resistance path to confirm wiring is continuous, not insulation quality; a voltage drop test assesses how much voltage is lost along a conductor under load, which helps identify undersized or loose connections; a polarity test ensures the correct identification of live, neutral, and ground, which is a safety check rather than insulation integrity.