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The current density distribution between layers of steel‐reinforced conductors having an odd number of aluminum layers is modified by the transformer effect, as a result of the steel core magnetisation. This redistribution of current affects the conductor alternating current resistance, the transitory temperature radial distribution, and depends on the total current intensity, and the core permeability, which varies with temperature. Although some steel‐cored conductors are designed to operate at high temperatures to maximise their current capacity, the core magnetic properties in this scenario need to be further investigated. This paper presents the results of experimental work on an ACSR conductor, and on its steel core to investigate the steel core magnetic properties over an extended temperature range, and how they affect the transformer effect. Results show an unexpected hump‐shaped variation of the permeability with temperature in a specific range of magnetic field strength, with maximum permeability values occurring at a temperature ranging from 150 to 170 ∘C , which were not covered in previous studies. A similar behaviour is seen in the variation of the axial magnetic flux with increasing conductor temperature, causing the flux to decrease at high temperatures, and thus weakening the transformer effect during the conductor operation.

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