Conductor strength test

Test method

The conductor strength test with a cable or sample of the conductor of at least 1 m long is measured in accordance with the standard IEC 60228. The test determines the continuous strength of Class 1, Class 2, Class 5 and Class 6 conductors for smooth copper, metal, aluminium and aluminium alloy coated copper, either round or shaped. The cable or conductor standard specifies the area of the nominal cross section in a range from 0.5 mm2 to 2500 mm2, and the results are expressed in ohm/km.

The conductor strength test equipment that is employed is usually a Kelvin Double Bridge or a Wheatstone Bridge, using the principle of balancing voltage between resistances known as determining the unknown resistance. The sample and test room must be at a temperature as near to 20ºC as possible.

The accuracy of the test is typically 0.2% to 0.5%. A formula is used to correct deviations from 20ºC and then to compare the results with the standard for each conductor type and size.