Electrical resistance test

Electrical resistance test according to IEC 60228 / UNE-EN 60228 / UNE-HD 605.

However all materials, even conductors, show opposition to the flow of electricity. This resistance causes the heating of the conductor leading to an efficiency loss, since part of the energy carried is wasted as heat. In extreme situations this may even cause an accident.

That is why it is so important to guarantee the proper resistance value for our cables according to the installation requirements, to ensure efficiency and safety. The way to measure electric resistance is to check it according to the requirements of this test. Performing this test, we can check if the quality and amount o copper used is the right one for a certain nominal cross-section and therefore the product is suitable for use.

The samples of bare or insulated copper conductors are placed on the measuring equipment so the conductor is exposed and in contact with the brackets where the measuring is done, 1 m apart from each other.

The resistance measuring device is based on a Wheatstone bridge circuit.

Its measuring unit is Ω/km at 20ºC.

Major factors are length, temperature, and the material which the conductor is made of.

Length and temperature contribute directly to the resistance value: the bigger the length or the temperature, the higher the resistance. That why the test is always performed on a 1 m length, to make results comparable. Regarding the temperature, the measuring equipment uses a correction factor that, based on the lab room temperature, automatically corrects the readings so the result is converted to the equivalent resistance at 20ºC.

Each conductor material has different inherent resistance. All our conductors are manufactured with electrolytic copper of the highest purity which ensures an optimal resistance. Besides the purity, the amount of copper also determines the resistance, which is higher in smaller conductor cross-sections: under equal conditions smaller conductors have higher resistance values.

Under normal circumstances, silver is a better conductor than copper, and aluminium is worse. Copper is the material with the better combination of cost, malleability, mechanical resistance, weight, and electric resistance, and because of that is the most widely used material in electric cables manufacturing.

Superconductors work at extremely low temperatures and therefore cannot substitute copper for everyday use.

Copper purity directly determines the cable resistance, electrolytic copper has the best performance. Cables RCT uses only electrolytic copper.

The manufacturing process of the cables also determines the outcome and that’s why resistance quality control is essential and Cables RCT controls it between every production step, included final packaging.

The Word copper comes from the name of the island Cyprus where huge reservoirs were found in ancient times. Copper is one of the first metals used by humans for different purposes, pure or mixed in alloys such as bronze.