Cable Insulation Resistance Standard

What is the standard value for the insulation resistance of cables?

If it's a 1KV cable, its insulation resistance value must not be less than 10 megohms.

For cables rated 1-3KV, the insulation resistance must not be less than 200 megohms.

For 6-10KV cables, the standard insulation resistance value should be greater than 400 megohms.

For cables rated at 20-35KV, the standard for insulation resistance value required is not less than 600 megohms.

For 220KV cables, the standard for insulation resistance is even higher, not less than 4,500 megohms.

How to Measure Insulation Resistance

Insulation resistance can be measured using an insulation resistance tester, a specialized device. It is crucial to switch off the main power supply before measurement. While doing so, discharge any ground shorts to prevent live measurements, as this can pose a safety hazard.

Ensure the condition of existing high-voltage equipment is checked, and if any induction is detected, it must be eliminated before proceeding with the measurement. Clean the surface of the object to be measured thoroughly to avoid substances that may affect the resistance value, ensuring accuracy after measurement.

Ensure the insulation resistance tester is in proper working condition. Pay close attention to the "0" and "∞" areas. Rotate the handle to reach the rated speed. If the pointer stops at the "0" area during a short circuit and at the "∞" area during an open circuit, it indicates normal operation.

The insulation resistance tester must be placed on a flat surface without any rocking or movement, and there should be no significant external current conductors or magnetic fields nearby. Once everything meets the requirements, connect the lines for testing, and the displayed values are the insulation resistance readings.