Alternating current (AC) resistance of helically （交流电阻力成螺旋形地）.pdf

TRANSMISSION Alternating current (AC) resistance of helically stranded conductors Information from Cigré The electrical resistance of bare, helically‑stranded conductors (aluminium and aluminium alloy), intended for use in overhead distribution and transmission lines, depends on the conductor cross‑section area, the conductivity of the aluminium alloy, the lay length of the aluminium layers, and the presence or absence of a steel reinforcing core. The presence of a stranded steel core can increase the resistance due to core magnetising effects. Cigré brochure 345 describes a process of AC resistance calculation for bare stranded aluminium conductors both with and without a steel reinforcing core. In order to determine the AC resistance of an ACSR conductor one The resistance per unit length R of a conductor depends on the resistivity must account for the following: ρ and the cross-sectional area A. Since the resistivity is temperature dependent, the resistance also varies with the temperature T of the • DC resistance : Increases with strand resistivity and length. conductor. • Temperature: DC resistance increases with temperature. • Skin effect : Alternating current forces current to the outer section Alternating current parameters of the strands and to the outer layers of the conductor. In order to determine the parameters that affect AC resistance, it • Core losses: Eddy current and magnetic hysteresis losses in the is necessary to study the effects on