High-voltage overhead power lines consist of the non-insulated, densely packed round or trapezoidal aluminum strands supported by a reinforced core. This configuration may ensure the acceptable investment cost, mass per unit length, and aerodynamic effects caused by wind; however, the ampacity is lower than those of copper wires, which limits the power transmission. Today, it is especially important, since the peak power generation of, e.g., photovoltaics forces power lines to casually distribute high currents. To potentially improve long- and short-term capabilities of energy distribution, instead of a cylindrical wire, the helical structure was proposed. Preserving an identical core, the conductor was formed as many elongated helices wrapped around an aluminum tube. The design was meant to significantly enlarge the outer surface of the wire, improving the heat transfer of the line, which then allowed us to enhance its ampacity. The solution was investigated numerically utilizing a 3D model with the coupled electrical, heat transfer, and laminar flow analysis. Based on this, the parameters (unit weight, unit resistance, and aerodynamic drag) of such modified wires were identified. Then, at different current loadings and wind speeds, the conductors were studied and compared with the ACSS (aluminum conductor steel-supported). The optimal variants of helical wires were suggested and the results indicated that using the helical conductor makes it possible to increase the ampacity of power lines (with the same unit weight, resistance, and cross-section of the ACSS wire) by 44% at low wind speed, even up to 160% at higher temperatures.

This paper presents an experimental investigation of dynamic line rating (DLR) applied to aluminium conductor steel-reinforced (ACSR) overhead line conductors, with a specific focus on wind speed conditions up to 5 m/s. An experimental system was designed and implemented to provide controlled and repeatable cross-flow air conditions along a tested ACSR conductor, enabling direct measurement of wind speed in the immediate vicinity of the conductor surface. Conductor temperature, electrical current, voltage drop per unit length, the phase angle between them, and relevant meteorological parameters were continuously measured under controlled experimental conditions. Based on the measured data, the conductor heat balance was evaluated and the allowable current-carrying capacity was determined. The experimentally obtained conductor temperatures and ampacity values were compared with results calculated using thermal models and correlations recommended by IEEE, CIGRÉ, and IEC standards. The comparison demonstrates that, under low and moderate wind speed conditions, differences between standard-based predictions and experimental results can be significant, leading to deviations in the estimation of allowable current-carrying capacity. The results confirm the high sensitivity of DLR calculations to wind-related assumptions and provide an experimentally validated basis for assessing the applicability and limitations of existing standard thermal models for ACSR conductors under realistic operating conditions.

This paper provides an objective comparison of harmonic power flow (HPF) results, focusing on the methods and software tools used for harmonic analysis of distribution networks. Particular emphasis is placed on the influence of system element modeling on the accuracy of HPF results, including the modeling of linear and nonlinear loads, as well as the impact of the skin effect, harmonic current phase angles, and Thevenin equivalent impedance of the substation bus. Harmonic analysis was performed using the software tools ETAP, DIgSILENT, SINCAL, and PCFLO. The results obtained were compared with those derived using the decoupled HPF method. The testing was conducted on two widely used distribution networks: the IEEE 18and 33-bus. The results from various software tools demonstrated a high degree of agreement. The models of the tested IEEE systems, applied across different software tools, are publicly available at https://github.com/MilosFTN/Models-of-the-IEEE-18-and-33-bus-test-systems.

This paper analyzes errors in the estimation of induction-motor-equivalent circuit parameters using an improved combined two-stage Particle Swarm Optimization (PSO) method. The proposed method accounts for variations in rotor parameters based on both linear and square root speed approximations, as well as two different approaches for the stator and rotor leakage reactance ratios. The first approach assumes that the starting rotor leakage reactance is equal to the stator leakage reactance, while the second considers them as distinct. Improvement of the algorithm consists of increasing the accuracy of the approximations of parameter changes on the rotor. Thanks to more accurate determination of the initial rotor parameters, both approximations provide better results in parameter estimation. The analysis involved sixteen induction motors with four different power ratings and four different pole numbers. The analysis aimed to assess the impact of these approximations and assumptions on equivalent circuit parameter estimation errors. The estimated torque-speed characteristics closely matched the manufacturer’s reference data, including starting, maximum, and full-load torques. The deviation of the estimated torque-speed characteristics from the reference characteristics, within a defined speed range, is defined as the mean absolute percentage error. Based on the obtained results, the mean absolute percentage error is complex and depends on rotor parameter speed approximations, stator and rotor leakage reactance ratios, and the full power of the induction motor.

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.