Publications resulting from the project
Publications resulting from the project
Embedded Files
Low Wind Speed Heat Loss Analysis for DLR Applications
Riba, J.-R., IEEE Access, Accepted 07/10/2025.
Riba, J.-R., Measurement, 258 (2026) 119184, pp. 1-9. DOI: 10.1016/j.measurement.2025.119184. Accepted 28/09/2025.
Abstract
Corona discharges have many industrial applications, but in high-voltage systems, they often create unwanted effects that need to be addressed. Therefore, design engineers need simple tools to control their effects and, when they do occur, to determine the potential impact. Since the mean free path and mean energy of corona-generated electrons are key indicators of plasma characteristics and the efficiency of various processes occurring within the discharge, these parameters provide important information about the intensity and performance of the discharge. In this work, an easy-to-apply method is developed to determine the mean free path and mean energy of corona-generated electrons once the local electric field is known, which can be determined from finite element method simulations. The mean electron free path and mean electron energy can then be determined from published experimental data relating the total electron collision cross sections with air molecules to the mean electron energy and the mean electron energy to the reduced electric field. The method presented here is applied to experimental data obtained at different supply frequencies and different pressures typical of aircraft systems, which, due to the imperative need for electrification, are exposed to a higher risk of discharges due to the higher operating voltages, higher supply frequencies, and low pressure environment.
On the Calculation of the Mean Free Path and Electron Energy in Atmospheric Corona Discharges
Riba, J.-R., European Journal of Physics, 2025. 2025 Eur. J. Phys. 46 045804 DOI: 10.1088/1361-6404/adeb12 Published 22/07/2025.
Abstract
This work proposes a practical or guided project for graduate physics or electrical engineering courses to determine the mean free path and the mean energy of electrons in atmospheric air. To this end, concepts such as the total scattering cross section of the electrons with air particles, the electric field strength at which corona occurs for given electrode geometries, and on the electron energy distribution function are analyzed. In addition, this paper provides a complete set of data that can be used directly to develop the practical or guided project, or depending on the extension of the practical or guided project, the students can also acquire their own data using a simple setup similar to the one described in this paper.
Riba, J.-R., Electric Power Systems Research, Volume 247, October 2025, 111794. DOI: 10.1016/j.epsr.2025.111794, Volume 247, October 2025, 111794, Accepted 29/04/2025.
Abstract
The surface voltage gradient (SVG) is probably the most important factor in determining the likelihood of a corona discharge occurring on the surface of round conductors or tubular substation busbars. There are several standards that propose simple formulas to determine the SVG of various configurations involving round conductors. However, such formulas are not exact, so this paper analyzes their accuracy by comparing the results provided by such formulas with the results obtained by Finite Element Method (FEM) models. This comparison highlights the difficulty in accurately calculating the average and maximum SVG of round conductors and tubular busbars using simple formulas.
Analysis of the Relationship between Light Intensity and Electrical Power of Corona Discharges
Riba, J.-R., European Journal of Physics, 46(1), 015202, 12/12/2024, DOI: 10.1088/1361-6404/ad955a.
Abstract
This work analyzes the intensity of the light emitted by corona discharges using a smartphone camera, which is compared to the electrical power associated with the corona discharges. The raw images from the camera provide essential information for the experiment. Data at different atmospheric pressures are also provided to help students understand that at lower pressures, due to the increased mean free path of the electrons, they are more efficient at ionizing neutral air molecules. An analysis of the data obtained also makes it possible to estimate the values of the energy of the electrons involved in the discharge process, the mean free path of the electrons and the cross section for electron collision, using much simpler equipment compared to other studies. The data and approach presented in this paper can be adapted for a group project or a guided practical session for both undergraduate and graduate courses.
Analyzing the effect of corona losses on dynamic line rating models for overhead transmission lines
Riba, J.-R.; Moreno-Eguilaz, M., International Journal of Electrical Power & Energy Systems,
Volume 166, 2025, 110546, ISSN 0142-0615, https://doi.org/10.1016/j.ijepes.2025.110546.
Abstract
High-voltage transmission lines tend to generate corona activity. The value of corona losses is highly dependent on several parameters such as line configuration, conductor geometry, surface condition, operating voltage and weather conditions. International guidelines and standards such as Cigré, IEEE and IEC recommend that corona losses should not be considered when developing thermal conductor models, so such losses are typically omitted when developing dynamic line rating (DLR) applications. DLR is a set of techniques based on dynamically changing the thermal ratings of transmission lines based on changes in environmental conditions (wind, temperature, etc.). To develop accurate DLR models that include corona losses, a large amount of line data is required, including operating voltage, complete conductor information (materials, dimensions, etc.), bundle and line geometry, phase layout, and ground clearance, among others. To validate the accuracy of such models, part of the complete line data, long-term measurements of instantaneous corona losses in existing lines, operating voltage and weather conditions are required. However, the development of DLR approaches and the inclusion of corona losses in such models is severely limited by the lack of experimental work that includes a complete description of all this information. Based on experimental corona losses already published in the literature, this paper uses an accurate conductor model that accounts for radial heat transfer to show that, under certain conditions, corona losses are comparable to and even greater than Joule losses, which are usually the main source of conductor heating, suggesting that corona losses should be included in the development of accurate thermal conductor models. It has also been shown that for conductors in a normal condition, operating in fair weather conditions and at rated line load, corona losses are typically less than 2% of the Joule losses, resulting in a reduction of the maximum current carrying capacity of less than 1%. However, for heavily contaminated conductors, the reduction in current carrying capacity due to the effect of corona losses can be as high as 15%.
Quantification of Corona Discharge Intensity Applied to Sphere-Plane Configurations
Pradeep Kumar Gupta, Pau Bas-Calopa, Jordi-Roger Riba, Kaur Tuttelberg, Jako Kilter,
IEEE Transactions on Dielectrics and Electrical Insulation, DOI: 10.1109/TDEI.2025.3562196.
Abstract
This paper proposes several experimental methods for the quantification of the intensity of corona discharges under alternating current (AC) and positive and negative direct current (+DC and –DC) power supplies. These methods are based on the measurement of voltage and corona current, the energy associated with the corona pulses using high-frequency probes and a high-frequency oscilloscope, the apparent charge using a partial discharge (PD) detector coupled to a coupling capacitor, and the intensity of images taken with a digital camera. The experimental results presented are based on a sphere-plane electrode. However, many other electrode geometries can be studied based on the developments made in this work. In addition, an analysis of the advantages and disadvantages of the different methods is presented.
The Role of AC Resistance of Bare Stranded Conductors for Developing Dynamic Line Rating Approaches
Jordi-Roger Riba,
Applied Sciences 2024, 14(19), 8982. https://doi.org/10.3390/app14198982.
Abstract
Overhead transmission line conductors are usually helically stranded. The current-carrying section is made of aluminum and/or aluminum alloys. Several factors affect their electrical resistance, such as the conductivity of the conductor material, the cross-sectional area, the lay length of the different layers of aluminum, and the presence of a steel core used to increase the mechanical strength of the conductor. The direct current (DC) and alternating current (AC) resistances per unit length of stranded conductors are different due to the effect of the eddy currents. In steel-reinforced conductors, there are other effects, such as the transformer effect due to the magnetization of the steel core, which make the AC resistance dependent on the current. Operating temperature also has an important effect on electrical resistance. Resistive losses are the main source of heating in transmission line conductors, so their temperature rise is highly dominated by such power losses, making it critical to know the value of the AC resistance per unit length when applying dynamic line rating (DLR) methods. They are of great interest especially in congested lines, as by applying DLR approaches it is possible to utilize the full line capacity of the line. This paper highlights the difficulty of accurately calculating the electrical resistance of helically stranded conductors, especially those with a magnetic core, and the importance of accurate measurements for the development of conductor models and DLR approaches.
Milad Jalilian, Jordi-Roger Riba, Pooya Parvizi,
Materials 2024, 17, 4536. https://doi.org/10.3390/ma17184536.
Abstract
Industrial development and population growth have increased the need for higher-capacity power transmission lines. Aluminum conductor steel-supported (ACSS) conductors, a type of high-temperature low-sag (HTLS) conductor, are now widely used in new designs and reconductoring applications. ACSS conductors are preferred over traditional aluminum conductor steel-reinforced (ACSR) conductors due to their high strength, low sag, and excellent thermal stability. These attributes have garnered significant interest from researchers, engineers, and manufacturers. This paper provides a comprehensive review of the structure, properties, testing methods, and environmental behavior of ACSS conductors.
Ankit Soni, Jordi-Roger Riba, Manuel Moreno-Eguilaz,
CPE POWERENG 2025, 20-22 May 2025, Antalya, Turkey.
Abstract
Emissivity is an important parameter to consider when analyzing the heat balance of conductors and thus their temperature. Surface emissivity becomes more important at high temperature operation, as it plays a leading role in the radiation loss, since it depends on the fourth power of temperature. This paper analyzes the effect of surface oxidation on the emissivity of a solid copper rod conductor. It is shown that the emissivity changes. For this purpose, the temperature of the copper bar is varied from 20ºC to about 240ºC by applying a current of about 1450 A. A large change in the estimated emissivity value from 0.04 to 0.30 is observed, which is attributed to the oxidation of the surface of the polished copper bar. This significant change in emissivity due to the oxidation process has important consequences for the thermal behavior of copper conductors that cannot be ignored.
Ankit Soni, Jordi-Roger Riba, Manuel Moreno-Eguilaz,
23th International Conference on Renewable Energies and Power Quality (ICREPQ'25), Tenerife 25-27 June, 2025.
Abstract
Transmission conductors used in overhead power lines are typically helically stranded and often have a steel core to give the conductor mechanical strength and outer strands of aluminium or aluminium alloy to provide the current carrying capacity. The presence of a magnetic core has several effects on the behaviour of the conductors, such as the presence of an axial component of the magnetic field which interacts with the current of the different layers of conductive strands wound helically around the magnetic core. This has a major effect on the alternating current (AC) resistance of the conductor, which can be very different from the direct current (DC) resistance. When applying dynamic line rating (DLR) approaches, the surface temperature of the conductor is typically measured due to the inability to measure inside the conductor, but the average temperature determines the true value of the resistance. In this work, a thermal model of the conductor is used to account for the radial temperature distribution to more accurately determine the resistance of the conductor and the temperature coefficient of the resistance. The experimental results presented show the potential of the proposed method.
Evaluation of the sensitivity of measuring circuits for corona discharges detection
M. Soltany, J.-R. Riba, S. Bogarra,
23th International Conference on Renewable Energies and Power Quality (ICREPQ'25), Tenerife 25-27 June, 2025.
Abstract
Partial discharges (PD) play a major role in the degradation of insulation in high voltage equipment. PD occurs when localized electrical breakdowns occur in the presence of a high electric field near an insulator. A critical aspect of PD measurement is the calibration of the measurement system. Calibration results in a scale factor (k), that is used to convert the measured signal to the apparent charge. This paper presents a comparative analysis of five different measurement circuits used for PD detection. The experiments were performed using a sphere-to-plane configuration. In addition to the conversion factor, this study also examines the signal-to-noise ratio (SNR) for each measurement system.
Corona Discharge Pulse Shape Analysis: Sphere Plane Configurations
Pradeep Kumar Gupta, Maninder Choudhary, Pau Bas, Jordi-Roger Riba, Kaur Tuttelberg, Jako Kilter,
IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2025, September 14-17, 2025, Manchester, United Kingdom.
Abstract
This paper proposes the experimental corona discharge pulse shape analysis (PSA) for different sizes of spherical electrode plane configurations at different voltage levels. According to experiments, the corona discharge signal may be assessed by measuring the peak amplitude and the rise and fall times of the pulse edges. This approach might be very useful when corona discharges are being examined and assessed. In addition, the pulse width is studied as the intensity level and discharge gap for different voltage levels are varied. PSA patterns are based on the sequence of discharge occurrences. The study presents PSA simulations and corona discharge analysis on common spherical test configurations for corona discharges, conducted at AC and partially under DC test conditions.
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