Insulation testing is performed at ______ voltages and could be hazardous if touched.

• A. Direct Current
• B. Alternating Current
• C. Pulsed Direct Current
• D. Direct Current and Alternating Current

Answer: (A)

Insulation testing uses a voltage stress to reveal leaks in insulation, and that stress is applied with direct current. A steady DC voltage provides a stable, constant stress, so the leakage current or insulation resistance can be measured reliably. Using DC avoids the capacitive charging currents and reactive effects that come with alternating current, which would distort readings and make it harder to judge the insulation condition. Pulsed DC isn’t the standard approach for this test, and using both DC and AC isn’t typical practice for insulation resistance testing. Since the test voltages are high, touching them can be hazardous, which is why the equipment is insulated and safety precautions are essential.