## 7 Conclusions  
This paper has analyzed the DC and AC resistance of stranded conductors for overhead transmission lines, since their temperature is highly dominated by resistive losses, as they are the main heat source. Although stranded conductors seem to be simple elements, the reality is quite different, since the resistance depends on several parameters, some of which are not quantifiable or can vary between different conductors. The electrical conductivity of the aluminum strands has a profound effect on the resistance of the conductor, but other factors also play a role, such as the lay length of the various aluminum layers, the effective cross-sectional area of the conductor, or the contact resistance between adjacent strands, which depends on the condition of the surface layer between the strands. It is reasonable to assume that some of these parameters may evolve as the conductor ages. In addition, eddy current effects in stranded conductors do not have explicit exact equations. In the case of ACSR conductors, the magnetization of the core wires also plays an important role. The combined action of the above effects results in the impossibility of obtaining exact equations to predict the AC resistance of stranded conductors with or without a magnetic core.  
A comparison between experimental results and those obtained from explicit equations has been presented for three types of stranded conductors, i.e., AAAC, ACSR, and ACCC/TW-HTLS conductors. It has been shown that the largest differences between measured and calculated values are found in the case of ACSR conductors, especially for single-layer and two-layer configurations. This is because ACSR conductors have a magnetic core, so the current distribution between the strands is more difficult to predict and formulate due to the transformer effect, the intensity of which depends on effects such as the current dependence of the magnetic permeability and the non-linear magnetization of the magnetic core. Therefore, in ACSR conductors, the AC resistance depends on the current level, and this dependence is characteristic of each specific conductor, so there are no explicit exact equations to quantify this effect.  
The results presented in this paper have shown the difficulty of accurately calculating the electrical resistance of helically stranded conductors, especially those with a magnetic core, and the importance of performing accurate laboratory or on-line measurements of the AC resistance. These results enable the development of accurate line models, which are key elements in the development of reliable DLR approaches. DLR provides valuable tools for grid operators to provide information about current line capacity, make informed decisions about the amount of power a particular line can safely carry, manage power flows more efficiently, manage alerts when line ratings are close to their safe limits, and optimize the use of transmission lines during periods of congestion or high demand.  
**Funding:** This research was funded by the Generalitat de Catalunya under grant number 2021 SGR 00392 and by Ministerio para la Transformacion Digital y de la Funcion Publica under grant number PID2023-147016 OB-I00.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data are contained within the article.  
**Acknowledgments:** The author is grateful to SICAME Spain and the SICAME group for their technical support and for providing the samples analyzed in this paper.  
**Conflicts of Interest:** The author declares no conflicts of interest.