Magnetic properties of an ACSR conductor steel core at temperatures up to 230 ∘C and their impact on the transformer effect

Abstract

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.

On-Line Core Losses Determination in ACSR Conductors for DLR Applications

“…Due to the opposite stranding directions of adjacent aluminum layers, the axial components of the magnetic field generated by the currents from adjacent layers are in opposite directions, which reduces the total magnetic field. The greatest cancellation of the magnetic field occurs in conductors with two aluminum layers, this effect being less marked in conductors with an odd number of aluminum layers than in conductors with an even number of layers [ 23 , 25 , 26 ]. Therefore, ACSR conductors with an even number of aluminum layers have lower magnetic core losses [ 22 ].…”

“…Experimental results performed on a three-layer ACSR conductor show that the current density in the central layer is higher than in the other layers, resulting in a higher R ac / R dc ratio [ 28 ], R dc being the direct current (DC) resistance. This is mainly due to the transformer effect [ 26 , 27 ] or current redistribution among the aluminum layers, and only partially due (to a lesser extent) to the eddy currents and hysteresis losses that occur in the steel core [ 28 ].…”

Development, optimization and experimental validation of smart devices for substations and power transmission lines

“…Due to the opposite winding directions of adjacent aluminum layers, the axial components of the magnetic field produced by the currents in adjacent layers have opposite directions, thereby leading to a reduction in the overall magnetic field. The cancellation of magnetic field is most in conductors comprising two aluminum layers, with this effect being less marked in conductors containing an odd number of layers than in conductors with an even number of aluminum layers [109]- [111]. This means that ACSR conductors with an even number of aluminum layers result in reduced magnetic core losses [108].…”