Impact of steel permeability on ACSR impedance per unit length

Electric characteristics of Aluminum Conductor Steel Reinforced (ACSR) components, aluminum and steel conductivity values, are usually provided by the ACSR manufacturers, but not the steel core permeability. In order to explore how important the steel core permeability is, the paper deals with the impact of this characteristic on ACSR impedance per unit length. For the estimation of this impact, numerous calculations were performed and the results are shown in this paper. The value of relative steel core permeability was varied from 10 to 50000 inside three different standardized ACSR conductors, at eleven different frequencies, up to 2500 Hz (50th harmonic of fundamental frequency). All calculations were carried out numerically, applying COMSOL Multiphysics 3.5a computer program package on simplified two-dimensional model. ACSR resistance per unit length was calculated from heating losses, while the reactance and the inductance per unit length were determined via magnetic energy stored in ACSR magnetic field. Even in the case of great relative permeability value range, the paper shows that the influence of steel core permeability on any ACS conductor is much less than expected, especially at lower frequencies. This fact is the consequence of the big difference in aluminum and steel conductivity values.