Effects of alternating and direct current, power frequency, temperature, and tension on the electrical parameters of ACSR conductors

Many high-voltage transmission lines are constructed with aluminum conductors, steel reinforced (ACSR). The stranded steel core supports much of the tension and the aluminum strands conduct most of the current. The current flowing in the strands spiraling around the core causes a longitudinal magnetic flux in the core, which increases its permeability and causes a redistribution of the currents in the layers of aluminum strands. This redistribution and skin effect, hysteresis, and eddy current losses in the core cause changes to the resistance and inductance of the conductor. This paper describes measurements, in a specially constructed nonmetallic hut, of the DC and 50-Hz resistances and the internal inductance of a 54/2.26-mm aluminum + 19/3.74-mm steel (Pawpaw) ACSR conductor, having three layers of aluminum wires. The effects of current, temperature, and tension were determined, and the effective radial thermal conductivity was derived. Measured values are compared with those calculated from the electromagnetic model, and the model is used to study the effect of frequency, in the range from 25 to 60 Hz, on the resistance and internal inductance.