Conductor Resistance Test of Electrical Power Cables

This test is used to determine the DC resistance of copper or aluminum conductors. Resistance of a conductor tells us how easily a conductor allows the flow of current through it. Higher the resistance, lesser the current will flow though the conductor. Resistance of a conductor is influenced by conductor dimension and construction, conditions like, temperature and resistivity. It is normally expressed as ohms per km.
This test will make use of either Kelvin Double Bridge with accuracy of 0.2 percent or Wheatstone Bridge with accuracy of 0.5 percent.
Test specimen is selected as indicated below.

  • All solid circular conductor Drum length of 1 m
  • All stranded or sector shaped solid conductors up to and including 25 mm2 size Drum length of 5 m
  • All stranded or sector shaped solid conductors greater than 25 mm2 size Drum length of 10 m

Note – The length of the test specimen is the length which lies between the potential terminals.

Procedure of Conductor Resistance Test

Connect the specimen to the resistance measuring bridge and make sure that proper considerations are taken into account about the contact resistance.
Measure the resistance and note down the temperature.
Measured resistance is converted to the standard temperature and length.

Observation and Report

Sample no Nominal conductor size in mm2 Length (m) Material Al/Cu Class of conductor Temperature oC Observed Resistance Specified Resistance


Observed Resistance at a particular temperature,

Rt = Observed Resistance
K = Temperature correction factor
L = Length of specimen in m.
Conclusion – The sample meets/does not meet the requirements of the specification.

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