Q: My megger has 500V, 1000V, 2500V, 5000V, and 10kV. Which should I choose for LV, MV, and HV?
A: Applying too little voltage won't stress insulation. Too much can cause a destructive punch-through. Follow the matching table.
Standard DC Test Voltage Selection:
| Cable Rated Voltage (U0/U) | Insulation Class | Recommended DC Test Voltage | Safety Limit (Max) |
| Low Voltage (LV) < 0.6/1 kV | Low Voltage | 500V to 1000V DC | 1000V DC |
| Medium Voltage (MV) 6/10 to 20/35 kV | Medium Voltage | 2500V or 5000V DC | 5000V DC |
| High Voltage (HV) 66 to 220 kV+ | High Voltage | 5000V or 10,000V DC | 10,000V DC |
Why use DC for IR? A DC supply does not continuously draw capacitive charging current after the first few seconds, allowing measurement of the tiny resistive leakage current (micro-amps) flowing THROUGH the insulation.