Cable Insulation Resistance Testing

Insulation resistance testing is a key test for electrical cables as it is a measure of how effectively the cable is insulated. Poor insulation may result in short circuit, electric shock or fire.

This cable test, conducted as specified in BS EN 50395, is designed to test the insulation at the cable's maximum operating temperature. This maximum operating temperature is defined by the material types used in insulation and sheathing. At temperatures over-and-above this maximum operating temperature the material will not be suitable for continuous operation and will eventually break down causing premature cable failure.

Insulation resistance testing is one of the many quality assurance tests and processes that our cable experts use to check the compliance of our cable portfolio. Our state-of-the-art facility also offers independent testing on cables sourced from third-parties to ensure that non-compliant cables do not enter our wider supply chain. 

Insulation resistance testing requires a water bath, temperature controlled and capable of maintaining the temperature within defined tolerances as specified by the relevant cable standard, as well as insulation resistance measuring equipment.

The test is conducted on cable samples, generally 5 metres in length, which have been prepared by stripping the insulation from the ends before connecting these two ends together. Keeping these connected ends out of the water, the rest of the cable is submerged and the sample remains in the water at this temperature for the period of time specified in the cable standard.

After two hours, the insulation resistance between the conductor ends and the water in the water bath is then measured by applying a voltage of the magnitude and duration as specified in the cable standard, with the result expressed in MO/km. The results are expressed as a pass or fail.

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