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Insulation strength test

Test method

The insulation strength test is the key test for electrical cables since it is a measure of the effectiveness of the cable insulation. Deficient insulation can lead to electric shocks, short-circuits or fires.

The test is designed to test the insulation on the cable at the maximum operating temperature. This temperature is determined according to the type of materials used in the cable insulation and sheath.

The insulation strength test requires a water bath, a controlled temperature and the ability to maintain the temperature within the tolerances defined in the relevant standard on cables, and the insulation strength measurement equipment.

The test is carried out on cable samples usually 5 metres long. The ends of the insulation are removed and the conductors are spliced together to comprise one of the connection points. Keeping the connected ends out of the water, the rest of the cable is submerged and left in the water at the set temperature for the duration specified in the cable standard.

After two hours, the insulation strength between the ends of the conductor and the water is measured by applying a voltage at the magnitude and for the duration specified in the cable standard, expressing the result in MO/km.