Abstract
This paper investigates the influence of temperature- and current-dependent variations in alternating current (AC) resistance on the estimation of the operating temperature of aluminium conductor steel-reinforced (ACSR) conductors, with particular emphasis on the differences arising from the use of tabulated and experimentally determined resistance characteristics. Special attention is devoted to the current dependence of AC resistance in the single-layer ACSR conductor 48-AL1/8-ST1A, where pronounced resistance variations occur due to the electromagnetic interaction between the aluminum strands and the steel core. Experimental investigations were conducted under controlled laboratory conditions using a dedicated measurement system capable of the synchronized acquisition of electrical and thermal quantities in real time. Based on the obtained measurements, AC resistance characteristics were determined as functions of both conductor temperature and current, and their influence on conductor temperature estimation was subsequently evaluated. The results demonstrate that neglecting the current dependence of AC resistance may lead to conductor temperature estimation errors of up to approximately 2.5~°C under current loadings close to the rated value, indicating that this effect should not be disregarded in thermal analyses of single-layer ACSR conductors. However, the study also reveals that conductor emissivity has a substantially larger influence on temperature estimation. Specifically, varying the assumed conductor surface emissivity from 0.3 to 0.9 results in calculated conductor temperature differences exceeding 15 °C, significantly outweighing the influence of current-dependent AC resistance. The obtained findings indicate that accurate determination of conductor emissivity is essential for reliable thermal analysis and Dynamic Line Rating (DLR) applications, while the use of experimentally determined AC resistance characteristics further improves the accuracy of conductor temperature and ampacity assessments.