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1
Jörgens, Christoph, and Markus Clemens. "Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment." Energies 14, no. 16 (August 11, 2021): 4910. http://dx.doi.org/10.3390/en14164910.
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For long distance electric power transport, high-voltage direct current (HVDC) cable systems are a commonly used solution. Space charges accumulate in the HVDC cable insulations due to the applied voltage and the nonlinear electric conductivity of the insulation material. The resulting electric field depends on the material parameters of the surrounding soil environment that may differ locally and have an influence on the temperature distribution in the cable and the environment. To use the radial symmetry of the cable geometry, typical electric field simulations neglect the influence of the surrounding soil, due to different dimensions of the cable and the environment and the resulting high computational effort. Here, the environment and its effect on the resulting electric field is considered and the assumption of a possible radial symmetric temperature within the insulation is analyzed. To reduce the computation time, weakly coupled simulations are performed to compute the temperature and the electric field inside the cable insulation, neglecting insulation losses. The results of a weakly coupled simulation are compared against those of a full transient simulation, considering the insulation losses for two common cable insulations with different maximum operation temperatures. Due to the buried depth of HV cables, an approximately radial symmetric temperature distribution within the insulation is obtained for a single cable and cable pairs when, considering a metallic sheath. Furthermore, the simulations show a temperature increase of the earth–air interface above the buried cable that needs to be considered when computing the cable conductor temperature, using the IEC standards.
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Korotkevich, M. A., and S. N. Azarov. "The Evaluation of Impact of Cable Power Lines on the Environment." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 62, no. 5 (October 4, 2019): 422–32. http://dx.doi.org/10.21122/1029-7448-2019-62-5-422-432.
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The thermal impact of cable power lines and structural materials of cables on the environment has been considered. A quantitative evaluation of the thermal impact of electrical cables with cross-linked polyethylene insulation on the environment was carried out using the Elcut program. Analysis of the temperature field near the loaded cable line of 10 kV demonstrated high values of soil temperature that negatively affects its redox potential and living organisms. To evaluate the environmental impact of electrical cable materials, an approach has been developed that takes into account not only the toxicity of the materials but also their volumetric content in the cable. Cable lines with cables with traditional paper-oil insulation cause more damage to the environment than cable lines with cables, insulated with crosslinked polyethylene. The environment, in turn, also has an impact on the electrical cables: the values of long-term permissible load currents depend on the ambient temperature (when laying cables in the open air, in an earthen trench or in cable rooms). The impact of solar radiation on the thermal conditions of the electric cable is estimated. A comparative analysis of the complex environmental impact of electric cables with traditional insulation and insulation of crosslinked polyethylene demonstrated that unarmored cable with crosslinked polyethylene insulation at a voltage of 10 kV (regardless of the type of its shell) causes less damage to the environment than the same traditional cable throughout the considered temperature range on their surfaces.
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Diban, Bassel, and Giovanni Mazzanti. "The Effect of Insulation Characteristics on Thermal Instability in HVDC Extruded Cables." Energies 14, no. 3 (January 21, 2021): 550. http://dx.doi.org/10.3390/en14030550.
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This paper aims at studying the effect of cable characteristics on the thermal instability of 320 kV and 500 kV Cross-Linked Polyethylene XLPE-insulated high voltage direct-current (HVDC) cables buried in soil for different values of the applied voltages, by the means of sensitivity analysis of the insulation losses to the electrical conductivity coefficients of temperature and electric field, a and b. It also finds the value of dielectric loss coefficient βd for DC cables, which allows an analytical calculation of the temperature rise as a function of insulation losses and thermal resistances. A Matlab code is used to iteratively solve Maxwell’s equations and find the electric field distribution, the insulation losses and the temperature rise inside the insulation due to insulation losses of the cable subjected to load cycles according to CIGRÉ Technical Brochure 496. Thermal stability diagrams are found to study the thermal instability and its relationship with the cable ampacity. The results show high dependency of the thermal stability on the electrical conductivity of cable insulating material, as expressed via the conductivity coefficients of temperature and electric field. The effect of insulation thickness on both the insulation losses and the thermal stability is also investigated.
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Zhang, Yiyi, Xiaoming Chen, Heng Zhang, Jiefeng Liu, Chaohai Zhang, and Jian Jiao. "Analysis on the Temperature Field and the Ampacity of XLPE Submarine HV Cable Based on Electro-Thermal-Flow Multiphysics Coupling Simulation." Polymers 12, no. 4 (April 20, 2020): 952. http://dx.doi.org/10.3390/polym12040952.
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The operating temperature and the ampacity are important parameters to reflect the operating state of cross-linked polyethylene (XLPE) submarine high voltage (HV) cables, and it is of great significance to study the electrothermal coupling law of submarine cable under the seawater flow field. In this study, according to the actual laying conditions of the submarine cable, a multi-physical coupling model of submarine cable is established based on the electromagnetic field, heat transfer field, and fluid field by using the COMSOL finite element simulation software. This model can help to analyze how the temperature and ampacity of the submarine cable are affected by different laying methods, seawater velocity, seawater temperature, laying depth, and soil thermal conductivity. The experimental results show that the pipe laying method can lead to the highest cable conductor temperature, even exceeding the maximum heat-resistant operating temperature of the insulation, and the corresponding ampacity is minimum, so heat dissipation is required. Besides, the conductor temperature and the submarine cable ampacity have a linear relationship with the seawater temperature, and small seawater velocity can significantly improve the submarine cable ampacity. Temperature correction coefficients and ampacity correction coefficients for steady-state seawater are proposed. Furthermore, the laying depth and soil thermal conductivity have great impact on the temperature field and the ampacity of submarine cable, so measures (e.g., artificial backfilling) in areas with low thermal conductivity are needed to improve the submarine cable ampacity.
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Vu, Tu Phan, and Long Van Hoang Vo. "Application of the hp-finite element method to modeling thermal fields of high voltage underground cables buried in multi-layer soil." Science and Technology Development Journal 16, no. 3 (September 30, 2013): 72–83. http://dx.doi.org/10.32508/stdj.v16i3.1612.
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In this paper, we investigate the application of the adaptive higher-order Finite Element Method (hp-FEM) to heat transfer problems in electrical engineering. The proposed method is developed based on the combination of the Delaunay mesh and higher-order interpolation functions. In which the Delaunay algorithm based on the distance function is used for creating the adaptive mesh in the whole solution domain and the higher-order polynomials (up to 9th order) are applied for increasing the accuracy of solution. To evaluate the applicability and effectiveness of this new approach, we applied the proposed method to solve a benchmark heat problem and to calculate the temperature distribution of some typical models of buried double- and single -circuit power cables in the homogenous and multi-layer soils, respectively.
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Yildiz, Anil, and Ross A. Stirling. "Investigating green infrastructure as potential medium for ground heat exchangers." E3S Web of Conferences 205 (2020): 06013. http://dx.doi.org/10.1051/e3sconf/202020506013.
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Space heating and cooling comprises a significant portion of the overall energy consumption. Ground heat exchangers (GHE), are a sustainable alternative to conventional, non-renewably powered heating and cooling systems. Space is a scarce resource in densely urbanised areas, allocating dedicated locations to build GHE systems can result in high initial capital costs and an inflexibility in retrofitting. An alternative solution is to utilise existing, multi-benefit and resilient Sustainable Drainage Systems (SuDS) in cities. An investigation into the feasibility of utilising SuDS as sites for potential GHEs requires an understanding of their thermal and hydrological behaviour and boundary conditions. This study utilises a heavily-instrumented, vegetated lysimeter setup, exposed to atmospheric conditions, to test a pilot-scale SuDS heat exchanger. Heat rejection into the substrate of a SuDS has been simulated with the application of heat via voltage-controlled heating cables at a depth of 850 mm for 72-hour durations (at three different power inputs) with 96-hours between each power input. These heat dissipation periods are reflected in measured soil temperature profiles. Volumetric water content, matric suction, soil temperature and heat flux are monitored at various locations in the lysimeter. A finite difference modelling scheme has been developed to simulate the variation in soil temperature due to heat rejection.
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Jörgens, Christoph, and Markus Clemens. "A Review about the Modeling and Simulation of Electro-Quasistatic Fields in HVDC Cable Systems." Energies 13, no. 19 (October 5, 2020): 5189. http://dx.doi.org/10.3390/en13195189.
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In comparison to high-voltage alternating current (HVAC) cable systems, high-voltage direct current (HVDC) systems have several advantages, e.g., the transmitted power or long-distance transmission. The insulating materials feature a non-linear dependency on the electric field and the temperature. Applying a constant voltage, space charges accumulate in the insulation and yield a slowly time-varying electric field. As a complement to measurements, numerical simulations are used to obtain the electric field distribution inside the insulation. The simulation results can be used to design HVDC cable components such that possible failure can be avoided. This work is a review about the simulation of the time-varying electric field in HVDC cable components, using conductivity-based cable models. The effective mechanisms and descriptions of charge movement result in different conductivity models. The corresponding simulation results of the models are compared against measurements and analytic approximations. Different numerical techniques show variations of the accuracy and the computation time that are compared. Coupled electro-thermal field simulations are applied to consider the environment and its effect on the resulting electric field distribution. A special case of an electro-quasistatic field describes the drying process of soil, resulting from the temperature and electric field. The effect of electro-osmosis at HVDC ground electrodes is considered within this model.
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Bulinski, A., and J. Densley. "High voltage insulation for power cables utilizing high temperature superconductivity." IEEE Electrical Insulation Magazine 15, no. 2 (March 1999): 14–22. http://dx.doi.org/10.1109/57.753927.
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Yahya, Muhammad Bin, and Muhammad Nazrolni Azmi Bin Izani. "Cable Test and Breakdown Voltage Determination of Joysense Cable Insulation." Indonesian Journal of Electrical Engineering and Computer Science 8, no. 1 (October 1, 2017): 177. http://dx.doi.org/10.11591/ijeecs.v8.i1.pp177-183.
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Cross-linked Polyethylene (XLPE) has been used as the insulation for polymeric power cables for its superior advantages. This type of cable insulation are famously known and used for their good dielectric properties, mechanical properties, thermal properties, and probability to be utilized at high temperature. This study is of four (4) parts; designing suitable method for cable test, accelerated testing procedures applied to XLPE insulation for high voltage cables, online partial discharge determination, and aging test. To study the insulation durability to AC high voltage operation, the breakdown strength and aging were investigated under different setting of temperature. The breakdown voltages of XLPE were measured at different temperatures of 30<sup>0</sup>C, 50<sup>0</sup>C and finally at 70<sup>0</sup>C. Lastly, the aging effect of cable insulation was observed by conducting the AC breakdown voltage test after the aging process. Results showed that the breakdown voltage and aging of XLPE cables will decrease with increase of temperature setting.<em> </em>
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Stewart, M. G., W. H. Siew, L. C. Campbell, and C. Ferguson. "Sensor System for Monitoring Soil Moisture Content in Cable Trenches of High-Voltage Cables." IEEE Transactions on Power Delivery 19, no. 2 (April 2004): 451–55. http://dx.doi.org/10.1109/tpwrd.2004.824410.
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Shcherba, A. A., A. D. Podoltsev, and I. M. Kucheriava. "SYSTEM FOR REMOTE MONITORING OF HIGH-VOLTAGE CABLE LINE STATE." Praci elektrodinamiki Nacionalanoi akademii nauk Ukraini Institutu 2020, no. 57 (December 2, 2020): 10–14. http://dx.doi.org/10.15407/publishing2020.57.010.
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The article proposes a device for remote monitoring of high-voltage cable line state. The device gives a possibility to measure simultaneously several diagnostic characteristics, i.e. the temperature of cable outer sheath, electric current in cable core, capacitive current to earth and uses a specially designed internal electric power source that directly converts the energy of cable electromagnetic field into electric energy with necessary parameters. By computer simulation, the temperature field distribution in the cable cores of 330 kV cable line is determined and the quantitative relationship between the directly measured temperature on the cable outer sheath and the temperature values of the cable core and insulation, which are important diagnostic characteristics of the thermal state of power cables is revealed. References 5, figures 3.
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Lee, Chun-Kwon, Gyu-Sub Lee, and Seung-Jin Chang. "Solution to Fault of Multi-Terminal DC Transmission Systems Based on High Temperature Superconducting DC Cables." Energies 14, no. 5 (February 26, 2021): 1292. http://dx.doi.org/10.3390/en14051292.
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In this paper, we developed the small-signal state-space (SS) model of hybrid multi-terminal high-voltage direct-current (HVDC) systems and fault localization method in a failure situation. The multi-terminal HVDC (MTDC) system is composed of two wind farm side voltage-source converters (VSCs) and two grid side line-commutated converters (LCCs). To utilize relative advantages of the conventional line-commutated converter (LCC) and the voltage source converter (VSC) technologies, hybrid multi-terminal high-voltage direct-current (MTDC) technologies have been highlighted in recent years. For the models, grid side LCCs adopt distinct two control methods: master–slave control mode and voltage droop control mode. By utilizing root-locus analysis of the SS models for the hybrid MTDC system, we compare stability and responses of the target system according to control method. Furthermore, the proposed SS models are utilized in time-domain simulation to illustrate difference between master–slave control method and voltage droop control method. However, basic modeling method for hybrid MTDC system considering superconducting DC cables has not been proposed. In addition, when a failure occurs in MTDC system, conventional fault localization method cannot detect the fault location because the MTDC system is a complex form including a branch point. For coping with a failure situation, we propose a fault localization method for MTDC system including branch points. We model the MTDC system based on the actual experimental results and simulate a variety of failure scenarios. We propose the fault localization topology on a branch cable system using reflectometry method. Through the simulation results, we verify the performance of fault localization. In conclusion, guidelines to select control method in implementing hybrid MTDC systems for integrating offshore wind farms and to cope with failure method are provided in this paper.
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Szczegielniak, Tomasz, Dariusz Kusiak, and Paweł Jabłoński. "Thermal Analysis of the Medium Voltage Cable." Energies 14, no. 14 (July 9, 2021): 4164. http://dx.doi.org/10.3390/en14144164.
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The use of high voltage power cables in distribution and transmission networks is still increasing. As a result, the research on the electrical performance of cable lines is still up to date. In the paper, an analytical method of determining the power losses and the temperature distribution in the medium voltage cable was proposed. The main feature of the method is direct including the skin and proximity effects. Then the Joule law is used to express the power losses in the conductor and screen, and the Fourier-Kirchhoff equation is applied to find out the temperature distribution in the cable. The research was focused on a cable with isolated screen and return current in the screen taken into account. The proposed method was tested by using the commercial COMSOL software(5.6/COMSOL AB, Stockholm, Sweden) as well as by carrying out laboratory measurements. Furthermore, the results obtained via the proposed method were compared with those given in literature. The differences between the temperature values calculated by the analytical method, numerical computations and obtained experimentally do not exceed 10%. The proposed analytical method is suitable in prediction the temperature of the power cables with good accuracy.
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Zakarka, Mindaugas, Šarūnas Skuodis, Giedrius Šiupšinskas, and Juozas Bielskus. "Compressive strength and thermal properties of sand–bentonite mixture." Open Geosciences 13, no. 1 (January 1, 2021): 988–98. http://dx.doi.org/10.1515/geo-2020-0289.
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Abstract Sand–bentonite mixtures are used in road embankments as a protective material for protecting underground high-voltage cables and utility pipelines supplying water and gas etc. The sand–bentonite mixtures provide benefits while laying high-voltage cables. The purpose of this study is to determine the proportions as well as mechanical and thermal properties of a dry-mixed sand–bentonite mixture and to investigate the suitability of such mixtures for installation around high-voltage underground power lines in road embankments. When selecting a sand–bentonite mixture, the following requirements must be ensured: the compressive strength must be greater than 0.5 MPa after 24 h; the thermal resistivity must be greater than 1.2 K m/W (thermal conductivity 0,833 W/(K m)); and the moisture content of the sand–bentonite mixture must be less than 13%. The following materials were used when selecting the bentonite mixture: bentonite, 0–4.0 mm fraction sand, cement (CEM I 42.5R), and water. In this study, six groups of samples were formed, in which the parts of concrete, sand, cement, and water were added in different proportions. The strength and thermal conductivity of the samples were analyzed. Studies about the use of bentonite around high-voltage cables have revealed the need for wet mixing of bentonite suspensions. The required thermal conductivity properties of the soil were not achieved by dry mixing. This method of mixing can be useful only in cases when the thermal conductivity of the mixed soil is not relevant, because the work can be continued after a day.
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Zaytsev, Evgeny. "Development of Calculation Methodology of Thermal Equivalent Circuit’s Parameters for Predicting Temperature of High Voltage Cable Lines 110 - 500 kV." Applied Mechanics and Materials 792 (September 2015): 272–79. http://dx.doi.org/10.4028/www.scientific.net/amm.792.272.
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This paper is concerned with the development of techniques to the calculation of the thermal equivalent circuit parameters for the high-voltage cable line laid in the ground. The topology of the scheme was developed in author’s previous publication. This article discusses the parameters of the circuit which simulate the environment of the cable line. Calculation techniques of these parameters are described for cables laid in a plane and a trefoil pattern. The proposed scheme allows one to predict heating of cables on the day ahead in order to prevent thermal degradation of the insulation.
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Loos, Florian, Karl Dvorsky, and Hans-Dieter Liess. "Determination of temperature in automotive high-voltage cables of finite length with dynamic current profiles." Mathematical and Computer Modelling of Dynamical Systems 20, no. 5 (September 2, 2013): 433–51. http://dx.doi.org/10.1080/13873954.2013.833120.
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Arpaia, P., C. Baccigalupi, and A. Esposito. "Low-complexity voltage and current sources for large-scale quench detection of high-temperature superconducting cables." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 920 (March 2019): 73–80. http://dx.doi.org/10.1016/j.nima.2018.12.042.
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Lebedev, V. D., and E. S. Zaytsev. "Calculation of core temperature of single-phase high-voltage cables with XLPE insulation in real time." Vestnik IGEU, no. 4 (2015): 11–16. http://dx.doi.org/10.17588/2072-2672.2015.4.011-016.
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Kientzl, Imre, János Dobránszky, and János Ginsztler. "Heat Treatment and Impact Testing of Composite Wires." Key Engineering Materials 345-346 (August 2007): 1273–76. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.1273.
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The reinforcement of high voltage electric power cables is a promising application field of the composite wires. The temperature of the power cables can reach 200-300 °C due to an over-loaded electrical grid. The composite wires have to stand these high temperatures for a long time in the power cables. Long term heat treatments have been done to examine the eligibility of the composite wires. After heat treatment impact test was applied to measure the changes of the mechanical properties of composite wires. With the instrumented impact tester the process of the failure was examined. In this paper the continuous production method of ceramic fibre reinforced metal matrix composite wires and their properties are shown.
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Kim, Jeong Guk, Seung Koo Baek, Chang Young Lee, and Sung Cheol Yoon. "Deterioration and Thermographic Analyses of Electrical Units in Diesel Locomotive." Key Engineering Materials 417-418 (October 2009): 729–32. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.729.
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The electrical units of diesel electric locomotives, which were used for over 30 years, were characterized for deterioration evaluation through insulation resistance measurement, degradation testing, and infrared thermography method. Especially, an infrared camera and thermocouples were employed for the evaluation. The thermocouples were attached on high-voltage cables connected to traction motors, for in-situ measurement of abnormal heating during test running. After test running, the thermographic images were obtained for the inspection of high-voltage cables using the infrared camera. The thermographic results were quantitatively analyzed, and compared with temperature changes during running. In this investigation, various analysis techniques for the safety characterization of diesel electric locomotives have been introduced, and the analysis results have been used to provide the deterioration or wear information in current locomotive systems.
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SOSNOWSKI, Jacek. "SUPERCONDUCTING CABLES – ANALYSIS OF THEIR OPERATION AND APPLICATIONS IN ELECTRIC GRIDS." Proceedings of Electrotechnical Institute 63 (December 15, 2016): 89–96. http://dx.doi.org/10.5604/01.3001.0009.4425.
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In this paper the use of high temperature superconducting cables for transporting electrical energy is analysed. The construction of a short model of a superconducting cable is explained, global progress in this field is examined and related electromagnetic phenomena are discussed, particularly those concerning pinning potential barrier formation. The paper analyses the results of investigations into the current-voltage characteristics of superconducting cable model working in the temperature of liquid nitrogen, allowing to reach the value of critical current equal to 45 A.
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Hunter, Britney, Dan Drost, Brent Black, and Ruby Ward. "Improving Growth and Productivity of Early-season High-tunnel Tomatoes with Targeted Temperature Additions." HortScience 47, no. 6 (June 2012): 733–40. http://dx.doi.org/10.21273/hortsci.47.6.733.
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In northern climates where the growing season is shortened by cool spring conditions, high tunnels make it possible to plant and produce tomatoes (Solanum lycopersicum L.) at least 1 month earlier than in the field. However, limited high-tunnel research has been performed in arid high-elevation regions that experience extreme diurnal temperature fluctuations. High tunnels are designed to be passively heated; therefore, additional protection from frost may be warranted if growers wish to plant significantly earlier than normal. Low tunnels built within a high tunnel reduce the energy requirement by concentrating heat around the plants, particularly when a heat source is placed inside the low tunnel. ‘Sunbrite’ tomatoes were transplanted through black plastic mulch in four high tunnels in North Logan, UT (lat. 41.73° N, long. 111.83° W, 1382 m elevation) on 17 Mar., 30 Mar., and 7 Apr. in 2009 and on 19 Mar., 30 Mar., and 9 Apr. in 2010. Low tunnels were constructed over each row, and three supplemental heat treatments (unheated, soil-warming cables, and soil-warming cables plus 40-W incandescent lights) were tested to improve plant performance. The highest total marketable yield was achieved for earliest planting dates in both 2009 and 2010. In 2009, early-season yield was significantly greater when both the soil + air were heated, but only for the earliest planting date. In 2010, soil heat alone and in conjunction with air heat significantly improved early-season yield. Information gathered in this study on planting dates, yield, and energy costs provides valuable production and economic information to growers in arid high-elevation climates who desire the benefits of growing early-season tomatoes in high tunnels.
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Bugajev, Andrej, Gerda Jankevičiūtė, and Natalija Tumanova. "The Mathematical Modelling of Heat Transfer in Electrical Cables." Electrical, Control and Communication Engineering 5, no. 1 (May 1, 2014): 46–53. http://dx.doi.org/10.2478/ecce-2014-0007.
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Abstract This paper describes a mathematical modelling approach for heat transfer calculations in underground high voltage and middle voltage electrical power cables. First of the all typical layout of the cable in the sand or soil is described. Then numerical algorithms are targeted to the two-dimensional mathematical models of transient heat transfer. Finite Volume Method is suggested for calculations. Different strategies of nonorthogonality error elimination are considered. Acute triangles meshes were applied in two-dimensional domain to eliminate this error. Adaptive mesh is also tried. For calculations OpenFOAM open source software which uses Finite Volume Method is applied. To generate acute triangles meshes aCute library is used. The efficiency of the proposed approach is analyzed. The results show that the second order of convergence or close to that is achieved (in terms of sizes of finite volumes). Also it is shown that standard strategy, used by OpenFOAM is less efficient than the proposed approach. Finally it is concluded that for solving real problem a spatial adaptive mesh is essential and adaptive time steps also may be needed.
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Zhang, Xingchao, Chengzhi Yang, and Lu Wang. "Research and application of a new soil moisture sensor." MATEC Web of Conferences 175 (2018): 02010. http://dx.doi.org/10.1051/matecconf/201817502010.
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The measurement of soil moisture is the basis for the refinement of agriculture to implement water-saving irrigation. A new soil moisture sensor was designed based on its theoretical basis and analysis of the dielectric constant characteristics of soil. It mainly consists of probes, electronic circuits and wiring cables. The calibration test of the sensor was conducted under the working voltage of 2.5 ~ 5.5V. Using the experimental data to analyze the regression function, it was found that the output voltage of the sensor should have a linear negative correlation with the volumetric moisture content of the soil, and the coefficient of determination R2>0.986.The accuracy of the sensor was verified by soil samples with different moisture content. The average absolute value of absolute errors is less than 2.5%. The results show that the sensor has stable and reliable working performance, high measurement accuracy and good linearity, and is suitable for moisture measurement in most types of soil.
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Zarubin, V. S., G. N. Kuvyrkin, and I. Yu Savelyeva. "Temperature State of the Electrical Insulation Layer of a Superconducting DC Cable with Double-Sided Cooling." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 4 (97) (August 2021): 71–85. http://dx.doi.org/10.18698/1812-3368-2021-4-71-85.
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For the reliable operation of a high-voltage DC cable with high-temperature superconducting current-carrying conductors with a sufficiently high difference in electrical potentials, it is necessary to maintain a fixed temperature state not only of the conductors but also of other cable elements, including the electrical insulation layer. In this layer, despite the high electrical resistivity of its material, which can be polymer dielectrics, Joule heat is released. The purpose of this study was to build a mathematical model that describes the temperature state of an electrical insulation layer made in the form of a long hollow circular cylinder, on the surfaces of which a constant potential difference of the electric field is set. Within the study, we consider an alternative design of a cable with central and external annular channels for cooling liquid nitrogen. Using a mathematical model, we obtained integral relations that connect the parameters of the temperature state of this layer, the conditions of heat transfer on its surfaces, and the temperature-dependent coefficient of thermal conductivity and electrical resistivity of an electrical insulating material with a given difference in electrical potentials. A quantitative analysis of integral relations is carried out as applied to the layer of electrical insulation of the superconducting cable. The results of the analysis make it possible to assess the possibilities of using specific electrical insulating materials in cooled high-voltage DC cables under design, including superconducting cables cooled with liquid nitrogen
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Rizzo, Giuseppe, Pietro Romano, Antonino Imburgia, Fabio Viola, and Guido Ala. "The Effect of the Axial Heat Transfer on Space Charge Accumulation Phenomena in HVDC Cables." Energies 13, no. 18 (September 15, 2020): 4827. http://dx.doi.org/10.3390/en13184827.
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To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating the ageing of the dielectric material. However, the reference standards for the thermal rating of cables are mainly thought for alternating current (AC) cables and do not adequately take into account the effects related to high thermal drops over the insulation. In particular, the difference in temperature between the inner and the outer surfaces of the dielectric can be amplified during load transients or near sections with axially varying external thermal conditions. For the reasons above, this research aims to demonstrate how much the existence of “hot points” in terms of temperature drop can weaken the tightness of an HVDC transmission line. In order to investigate these phenomena, a two-dimensional numerical model has been implemented in time domain. The results obtained for some case studies demonstrate that the maximum electric field within the dielectric of an HVDC cable can be significantly increased in correspondence with variations along the axis of the external heat exchange conditions and/or during load transients. This study can be further developed in order to take into account the combined effect of the described phenomena with other sources of introduction, forming, and accumulation of space charge inside the dielectric layer of HVDC cables.
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Tamayo Ávila, Idalberto, José Manuel Nieto Jalil, Jorge Viteri, Juan Belana, and José Antonio Diego. "Study of Space Charge in SC Shield / XLPE Interface and Mid-Voltage Cable Perfomance." Nova Scientia 6, no. 11 (October 8, 2014): 12. http://dx.doi.org/10.21640/ns.v6i11.63.
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Three experimental mid-voltage cables C2, C3 and C4 with cross-linked polyethylene (XLPE) isolation, rated respectively as Medium, High and Low in perforation tests over 150KV, are studied. All these cables have been systematically measured by Electroacoustic Pulse (PEA) and Thermally Stimulated with Depolarization Currents (TSDC), using 120 KV of polarization voltage in samples as received, annealed at 90 kV and 120°Cup to 672 hours. Measured internal charge of cable C4 at least doubles that of cables C2 and C3. The interfacial phenomenon has been studied by Infrared spectroscopy measurements Attenuated total reflectance (ATR) that show chemical components that migrate, spread, and transport from the external semiconductor layer to the cross-linked polyethene isolation during the thermic treatment of the cable. The PEA measurements using 120 kV/mm electric field showed the formation and propagation of space charge packet from SC to isolation. These results are coherent with TSDC measurements that also show differences in the areas under the curve of current as a function of temperature for each cable type C2, C3and C4. This is a result of the amount of charge accumulated. To sum up, combination of PEA, TSDC and ATR measurements is a useful tool in understanding charge relaxation processes and XLPE cable performance.
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Oleksyuk, I. V. "Aging of Cross-Linked Polyethylene Insulation Cable Lines." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 64, no. 2 (April 9, 2021): 121–29. http://dx.doi.org/10.21122/1029-7448-2021-64-2-121-129.
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Abstract. Preference is given to cable lines with cross-linked polyethylene insulation in electrical networks with a nominal voltage of 10 kV during reconstruction of existing and construction of new industrial enterprises. The standard service life of such cables is at least 30 years (subject to the conditions of storage, transportation, installation and operation), and the actual one is determined by the technical condition of the cable. The service life of a cable line depends on the state of its insulation, the aging of which occurs under the influence of several factors. Conventionally, all factors influencing one or another degree on the cable insulation resource can be divided into thermal, electromagnetic, climatic, mechanical and operational. The most significant reason for the insulation aging is high temperature, which accelerates the reaction of thermo-oxidative destruction, during which high-molecular polymer compounds decompose. In fact, cables are operated at temperatures below the long-term permissible values, and, therefore, the aging of the insulation is slower, and the actual service life will be longer than the standard. At present, condition of the insulation is monitored with the use of high voltage tests related to destructive testing methods. When designing and operating cable lines, it is necessary to estimate the duration of the actual service life under various operating conditions. In theory, there are several expressions for calculating the service life of a cable line when exposed to temperature, humidity, electric field and aggressive environments, but all of them are not applicable in practice due to the presence of a large number of coefficients whose values are unknown. The paper presents an analytical expression obtained for determining the service life of power electric cables, taking into account the aging of the insulation under the influence of temperature and electric field.
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Liu, Shili, Wei Wei, Tao Liu, Zhaoyu Hui, Yuhua Hang, Huan Zheng, Changyou Suo, and Zhonghua Li. "Conductivity Characterization of Insulation and Its Effects on the Calculation of the Electric Field Distribution in HVDC Cables." Mathematical Problems in Engineering 2021 (February 17, 2021): 1–13. http://dx.doi.org/10.1155/2021/6647731.
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The calculation of an electric field distribution provides the basis for the structural design of the insulation, and an accurate characterization of conductivity as a function of temperature and electric field forms an important basis for the simulation of the electric field distribution in HVDC (high-voltage direct current) cables. However, the conductivity functions that describe the insulating materials used for HVDC cables in different studies are different, and very little has been reported regarding how to choose the most accurate function. In this work, the conductivity of insulating materials used for HVDC cables is characterized, and the effects of the conductivity characterization on the simulation of the electric field in HVDC cables are studied. First, eight common conductivity functions are compared qualitatively. Then, the conductivities of XLPE for different temperatures and electric fields are measured, and a data fitting technique is used to analyze the coincidence degree between different functions and the test results. Finally, the steady-state electric field distributions of HVDC cables for different temperature gradients are simulated in COMSOL Multiphysics. The results show that the sum of the square of the relative errors of the fitting when using the original functions is larger than that achieved when using the logarithmic form of the functions. The deviations in the electric field caused by taking the logarithm of different functions are smaller.
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Drost, Dan, Taunya Ernst, and Brent Black. "Soil Heating and Secondary Plant Covers Influence Growth and Yield of Winter High Tunnel Spinach." HortScience 52, no. 9 (September 2017): 1251–58. http://dx.doi.org/10.21273/hortsci12142-17.
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High tunnel (HT) winter production may be limited by extreme low air temperatures, suboptimal soil temperatures, large diurnal temperature changes, and short daylengths and associated low light conditions. To determine the productivity of spinach in extreme climates, HT production trials were conducted in the fall (October to December) and winter (January to March) of 2010–12 at the Greenville Research Farm in Logan, UT (lat. 41 N. elevation 1455 m). Soil heating (±) using electric cables and secondary covers (fabric rowcovers and plastic low tunnels) were evaluated to determine combined effects on fall and winter spinach production. Soil heating significantly increased yield in all cover treatments in the Fall 2010 (F2010) trial when spinach was planted in November, but had little to no effect on plant productivity in the other three trials (more appropriate planting dates) even though it did increase soil temperature marginally. The addition of secondary covers significantly increased plant biomass and leaf area when compared with the uncovered control. Excluding the F2011 trial when spinach was planted earlier under more favorable temperature and light conditions, the use of low tunnels resulted in significantly higher spinach yields (biomass and leaf area) than when grown under fabric rowcover. In the fall, relative growth rates (RGRs) decreased exponentially regardless of whether the soil was heated or not heated or if a secondary cover was used. This response was because of the seasonal decline in light levels and temperatures. In the winter production cycle, spinach relative growth without covers was similar or increased as climatic conditions improved. For plants grown under fabric or plastic rowcovers, RGR remained more constant or decreased during the production cycle. Increased yields were possible with secondary covers as air temperatures increase more quickly in the morning, maintained optimal temperatures longer each day (higher growing degree hours), and retained trapped heat later into the evening. Statistical interaction between heating cables and secondary covers were rarely observed. Fall and winter HT spinach production increases when further protection with secondary plant covers is provided; however, supplemental soil heating is not necessary.
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Jörgens, Christoph, and Markus Clemens. "Thermal breakdown in high voltage direct current cable insulations due to space charges." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 37, no. 5 (September 3, 2018): 1689–97. http://dx.doi.org/10.1108/compel-12-2017-0531.
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Purpose In high voltage direct current (HVDC), power cables heat is generated inside the conductor and the insulation during operation. A higher amount of the generated heat in comparison to the dissipated one, results in a possible thermal breakdown. The accumulation of space charges inside the insulation results in an electric field that contributes to the geometric electric field, which comes from the applied voltage. The total electric field decreases in the vicinity of the conductor, while it increases near the sheath, causing a possible change of the breakdown voltage. Design/methodology/approach Here, the thermal breakdown is studied, also incorporating the presence of space charges. For a developed electro-thermal HVDC cable model, at different temperatures, the breakdown voltage is computed through numerical simulations. Findings The simulation results show a dependence of the breakdown voltage on the temperature at the location of the sheath. The results also show only limited influence of the space charges on the breakdown voltage. Research limitations/implications The study is restricted to one-dimensional problems, using radial symmetry of the cable, and does not include any aging or long-term effect of space charges. Such aging effect can locally increase the electric field, resulting in a reduced breakdown voltage. Originality/value A comparison of the breakdown voltage with and without space charges is novel. The chosen approach allows for the first time to assess the influence of space charges and field inversion on the thermal breakdown.
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Zapf, Martin, Tobias Blenk, Ann-Catrin Müller, Hermann Pengg, Ivana Mladenovic, and Christian Weindl. "Lifetime Assessment of PILC Cables with Regard to Thermal Aging Based on a Medium Voltage Distribution Network Benchmark and Representative Load Scenarios in the Course of the Expansion of Distributed Energy Resources." Energies 14, no. 2 (January 18, 2021): 494. http://dx.doi.org/10.3390/en14020494.
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The decentralized feed-ins from distributed energy resources (DER) represent a significant change in the manner in which the power grid is used. If this leads to high loads on electrical equipment, its aging can be accelerated. This applies in particular with regard to the thermal aging of older generations of power cables, namely paper insulated lead covered (PILC) cables. This type of power cable can still be found frequently in medium voltage (MV) networks. If aging of these cables is significantly accelerated in the presence of DER, distribution system operators (DSO) could face unplanned premature cable failures and a high replacement demand and costs. Therefore, this paper investigates the thermal aging of PILC cables in a MV distribution network benchmark for different load scenarios, using standardized load profiles and representative expansion scenarios for wind power and photovoltaics plants in particularly affected network areas in Germany. A main objective of this paper is to present a methodology for estimating the thermal degradation of PILC cables. An approach is used to draw simplified conclusions from the loading of cables to their conductor or insulation temperature. For this purpose, mainly Joule losses are considered. In addition, thermal time constants are used for the heating and cooling processes. Based on the insulation temperature, thermal aging is determined using the Arrhenius law or the Montsinger rule. However, it is important to note that there is an urgent need for research on reference data in this area. For this reason, the results of the lifetime estimation presented in this paper should only be considered as an approximation if the selected reference data from the literature for the aging model are actually applicable. The lifetime assessment is performed for a highly utilized line segment of the network benchmark. Accordingly, extreme values are examined. Different operational control strategies of DSO to limit cable utilization are investigated. The results show that the expansion of DER can lead to a short but high cable utilization, although the average utilization does not increase or increases only slightly. This can lead to significantly lower cable lifetimes. The possible influence of these temporarily high loads is shown by comparing the resulting cable lifetime with previous situations without DER. It is also shown that DSO could already reduce excessive aging of PILC cables by preventing overloads in a few hours of a year. In addition to these specific results, general findings on the network load due to the influence of DER are obtained, which are of interest for congestion management.
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Bardalen, Eivind, Bjørnar Karlsen, Helge Malmbekk, Muhammed Nadeem Akram, and Per Ohlckers. "Evaluation of InGaAs/InP photodiode for high-speed operation at 4 K." International Journal of Metrology and Quality Engineering 9 (2018): 13. http://dx.doi.org/10.1051/ijmqe/2018015.
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An optically controlled high-speed current source located at 4 K is likely to improve the performance of pulse-driven Josephson junction arrays. A custom photodiode module with an Albis PDCS24L InGaAs/InP PIN photodiode is investigated in order to determine the suitability at 4 K. The DC and frequency response were tested at room temperature and at temperatures down to 4 K. For continuous wave optical input, photocurrents above 15 mA were produced at both room temperature and 4 K. I–V measurements show that the threshold voltage increased from 0.5 V at room temperature to 0.8 V at 4 K. The transmission coefficient S21 of the optoelectronic system, including cables and modulated laser source, was measured using a vector network analyzer. Up to 14 GHz, the results showed that the frequency response at 4 K was not degraded compared to room temperature. At room temperature, reverse bias voltages of up to 3 V was required for the highest bandwidth, while at 4 K, the photodiode was operated at nearly full speed even at 0 V reverse bias.
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Roy, Sree Shankhachur, Prasad Potluri, Simon Canfer, and George Ellwood. "Braiding ultrathin layer for insulation of superconducting Rutherford cables." Journal of Industrial Textiles 48, no. 5 (July 26, 2016): 827–47. http://dx.doi.org/10.1177/1528083716661204.
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Over-braiding of superconducting Rutherford cable was used for the composite insulation in this research. Braiding was a suitable alternative to fabric tape winding for achieving ultrathin insulation with required electrical breakdown voltage. A brief overview of the superconducting magnets, their application and requirements of insulation has been covered in order to bridge the literature gap between braiding and the superconducting magnet field of studies. Organic size coating on the fibre leaves carbon residue during high temperature treatment of the cables and hence glass fibre was desized before braiding. Braiding difficulties with desized glass fibre and possibility of braiding using compatible size coating have been discussed. The requirement of ultrathin braided layer was achieved with sufficient surface coverage with a suitable braid angle and fibre. As part of the study, braid cover factor variation on the surface of the cable was investigated and it was discussed using image analysis.
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Kucheriava, I. M. "PARTICULARITIES OF MAGNETIC FIELD SHIELDING FOR UNDERGROUND CABLE LINE BY COMPOSITE FILL-UP SOIL WITH MAGNETIC PROPERTIES." Praci Institutu elektrodinamiki Nacionalanoi akademii nauk Ukraini 2021, no. 58 (May 19, 2021): 14–22. http://dx.doi.org/10.15407/publishing2021.58.014.
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The computations of the magnetic field generated by high-voltage (330 kV) underground power cable line with special fill-up soil having different dimensions (bulk) are carried out by the two- and three-dimensional computer models. The supplementary soil above the cables is the composite material with effective magnetic properties and serves as a magnetic shield. The computer results obtained by 2D and 3D models are compared. The efficiency of magnetic field shielding depending on the magnetic permeability, width, and height of the fill-up soil is studied. As revealed, there is the optimal small soil height for the best magnetic field mitigation on the top of the ground directly over the cable line. In addition, the width of the magnetic soil has an appreciable effect on shielding efficiency. The shielding of underground single-circuit three-phase power cable lines is efficient only when using the magnetic fill-up soil (or ordinary external screen made of magnetic materials) with enough small height. References 14, figures 7.
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Milani, G., A. Galanti, C. Cardelli, F. Milani, and A. Cardelli. "COMBINED NUMERICAL, FINITE ELEMENT AND EXPERIMENTAL-OPTIMIZATION APPROACH IN THE PRODUCTION PROCESS OF MEDIUM-VOLTAGE, RUBBER-INSULATED ELECTRIC CABLES VULCANIZED WITH STEAM WATER. PART 1: DSC AND RHEOMETER EXPERIMENTAL RESULTS." Rubber Chemistry and Technology 88, no. 3 (September 1, 2015): 482–501. http://dx.doi.org/10.5254/rct.15.85971.
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ABSTRACT The standard industrial process to produce medium-voltage electric cables based on EPDM consists of cross-linking by peroxides with high-temperature steam (pressurized water vapor). Suboptimal material cross-linking is usually due to a decrease of the temperature along the vulcanization pipe. Temperature variations are connected to variations in steam pressure into pipe system. A combined numerical and experimental approach to optimize the production process of medium-voltage, rubber-insulated electric cables vulcanized with steam water is presented. The numerical part of this process is based on the use of finite elements and an optimization genetic algorithm (GA) and will be presented in Part 2. In Part 1, attention focuses on the experimental investigation. In particular, the final cross-linking degree is experimentally obtained by means of differential scanning calorimetry (DSC) determination of nondecomposed peroxide from the external layer to the core of the cable insulation. The final task is to minimize the difference between numerically predicted and experimentally determined cross-linking degree using a steam-temperature profile along the pipe to explain the variations. A preliminary evaluation of kinetic-reaction constants of rubber cured with peroxides is provided with the support of a comprehensive experimental investigation of the curing process by means of standard rheometer characterizations done at different curing temperatures. An existing mathematical, kinetic model is applied to the experimentally determined rheometer curves, allowing the determination of partial-reaction kinetic constants used in the finite-element computations.
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Zhu, Lewei, Boxue Du, Hongna Li, and Kai Hou. "Effect of Polycyclic Compounds Fillers on Electrical Treeing Characteristics in XLPE with DC-Impulse Voltage." Energies 12, no. 14 (July 18, 2019): 2767. http://dx.doi.org/10.3390/en12142767.
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Electrical tree is an important factor in the threat of the safety of cross-linked polyethylene (XLPE) insulation, eventually leading to the electrical failure of cables. Polycyclic compounds have the potential to suppress electrical treeing growth. In this paper, three types of polycyclic compounds, 2-hydroxy-2-phenylacetophenone, 4-phenylbenzophenone, and 4,4′-difluorobenzophenone are added into XLPE, denoted by A, B, and C. Electrical treeing characteristics are researched with DC-impulse voltage at 30, 60, and 90 °C, and the trap distribution and carrier mobility are characterized. It has been found that although three types of polycyclic compounds can all suppress the electrical tree propagation at different voltages and temperatures, the suppression effect of these polycyclic compounds with the same DC-impulse polarity is worse than with the opposite polarity. As the temperature increases, the suppression effect becomes weak. The energy level and deep trap density are the largest in XLPE-A composite, leading to a decrease in the charge transportation and resulting in the suppression of electrical treeing growth. Experimental results reveal that the polycyclic compound A has great application prospects in high voltage direct current (HVDC) cables.
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Nguyen, Dung. "THE INFLUENCE OF POLYPROPYLENE LAMINATED PAPER ON THE BREAKDOWN STRENGTH OF INSULATION FOR HIGH TEMPERATURE SUPERCONDUCTING CABLE." Vietnam Journal of Science and Technology 58, no. 1 (February 21, 2020): 46. http://dx.doi.org/10.15625/2525-2518/58/1/14387.
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Polypropylene Laminated Paper (PPLP) and Kraft paper has been used as ac power insulation for conventional cable as well as high temperature superconducting (HTS) cable because of its prominent insulating characteristics. However, research on the use of PPLP/Kraft insulation for HTS cables are thinly scattered. In this paper, the effect of PPLP on the breakdown strength of PPLP/Kraft multi-layer sample impregnated with liquid nitrogen (LN2) under ac and impulse applied voltage was studied. In addition, the breakdown strength characteristics of PPLP and Kraft samples were also investigated in order to determine breakdown strength characteristics of PPLP/Kraft insulation directly. It was found from the experimental data that the breakdown strength increases as the component ratio of PPLP in the PPLP/Kraft sample increases and is slightly affected by the inserting position of PPLP but in impulse case, the breakdown strength strongly depends on the number of PPLP and the relative position of PPLP.
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Čiegis, Raimondas, Gerda Jankevičiūtė, and Natalija Tumanov. "ON EFFICIENT NUMERICAL ALGORITHMS FOR SIMULATION OF HIGH POWER ELECTRICAL CABLES." Mathematical Modelling and Analysis 20, no. 6 (November 23, 2015): 701–14. http://dx.doi.org/10.3846/13926292.2015.1108250.
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The new virtual modelling tool is constructed, which is used for optimal design of power transmission lines and cables. The construction of such lines should meet the latest power transmission network technical and economical requirements. The solver is is based on classical and modified mathematical models describing main heat conduction processes: diffusion, convection and radiation in various materials and environments. In basic heat conduction equation, we take into account a linear dependence of the resistance on temperature. Multi-physic and multi-scale models are required to simulate industrial cases of power transmission lines. The velocity of convective transport of the heat in air regions is simulated by solving a coupled thermo-convection problem including the heat conduction problem and the standard Navier-Stokes model of the heat flow in air. Another multi-physic model is used to describe changes of material heat conduction coefficients in soil due to influence of heating. This process is described by by solving a simplified mass balance equation for flows in porous media. The multi-scale and homogenization analysis is required to to formulate simple and accurate mathematical describing heat conduction process is metal region which consists of a bundle of tightly coupled metal wires. The FVM is used to solve the obtained systems of differential equations. Discretization of the domain is done by applying “aCute” mesh generator, which is a modification of the well-known Triangle mesh generator. The discrete schemes are implemented by using the OpenFOAM tool.
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Riches, S. T., C. Warn, K. Cannon, G. Rickard, L. Stoica, and C. Johnston. "Design and Assembly of High Temperature Distributed Aero-engine Control System Demonstrator." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2014, HITEC (January 1, 2014): 000285–90. http://dx.doi.org/10.4071/hitec-tha12.
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This paper covers the development of a distributed high temperature electronics demonstrator for integration with sensor elements to provide digital outputs that can be used by the FADEC (Full Authority Digital Electronic Control) system or the EHMS (Engine Health Monitoring System) on an aircraft engine. This distributed electronics demonstrator eliminates the need for the FADEC or EHMS to process the sensor signal, which will assist in making the overall system more accurate and efficient in processing only digital signals. This will offer weight savings in cables, harnesses and connector pin reduction. The design concept was to take the output from several on-engine sensors, carry out the signal conditioning, multiplexing, analogue to digital conversion and data transmission through a serial data bus. The unit has to meet the environmental requirements of DO-160 with the need to operate at 200°C, with short term operation at temperatures up to 250°C. The work undertaken has been to design an ASIC based on 1.0μm Silicon on Insulator (SOI) device technology incorporating sensor signal conditioning electronics for sensors including resistance temperature probes, strain gauges, thermocouples, torque and frequency inputs. The ASIC contains analogue multiplexers, temperature stable voltage band-gap reference and bias circuits, ADC, BIST, core logic, DIN inputs and two parallel ARINC 429 serial databuses. The ASIC was tested and showed to be functional up to a maximum temperature of 275°C. The ASIC has been integrated with other high temperature components including voltage regulators, a crystal oscillator, precision resistors, silicon capacitors within a hermetic hybrid package. The hybrid circuit has been assembled within a stainless steel enclosure with high temperature connectors. The high temperature electronics demonstrator has been shown to operate from −40°C to +250°C. This work has been carried out under the EU Clean Sky HIGHTECS project with the Project being led by Turbomeca (Fr) and carried out by GE Aviation Systems (UK), GE Research – Munich (D) and Oxford University (UK).
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Benabed, F., and Tahar Seghier. "Dielectric Properties and Relaxation Behavior of High Density Polyethylene (HDPE)." Applied Mechanics and Materials 799-800 (October 2015): 1319–24. http://dx.doi.org/10.4028/www.scientific.net/amm.799-800.1319.
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The method of dielectric spectroscopy is an instrument of choice for the diagnosis of insulation used in high voltage and also to assess the quality of the insulation of HV equipment such as transformers, cables, capacitors, etc...This method allows to estimating the state and the quality of the insulation using the dielectric response of the frequency range. In this article, we have presented results of dielectric studies in high-density polyethylene (HDPE) by means of dielectric relaxation spectroscopy (DRS) in frequency range 10-2 - 106 Hz and temperature between-60 and 60 °C, we will invest this method to measure the dielectric properties and evaluate the performance of this insulator witch has always been chosen as a model polymer material because it is the simplest polymer with respect to its chemical structure and is used in a wide range of applications in daily life.
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Park, Ji Sun, Young Sun Kim, Hyun-Jung Jung, Daseul Park, Jee Young Yoo, Jin Ho Nam, and Yoon Jin Kim. "Polyethylene/Graphene Nanoplatelet Nanocomposite-Based Insulating Materials for Effective Reduction of Space Charge Accumulation in High-Voltage Direct-Current Cables." Journal of Nanomaterials 2019 (March 24, 2019): 1–11. http://dx.doi.org/10.1155/2019/9035297.
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We have demonstrated a straightforward hydrophobic surface modification of graphene nanoplatelets (GNPs) through a defect-healing process to fabricate well-dispersed insulating low-density polyethylene (LDPE)/GNP nanocomposites and have confirmed their effective suppression of space charge accumulation. Without any organic modifiers, GNPs containing oxygen-based functional groups at the edges were successfully reduced at optimal high-temperature defect-healing condition and modified to have hydrophobic surface properties similar to those of the LDPE matrix. The degree of dispersion and the reproducibility of the mechanically melt-mixed LDPE/GNP nanocomposites were immediately analyzed by thickness-normalized optical absorption measurement. In the LDPE matrix, below the percolation threshold concentration, well-dispersed GNP fillers effectively acted as trapping sites under high electric fields, resulting in the successful suppression of packet-like space charge accumulation (field enhancement factor=1.04 @ 0.1 wt% LDPE/GNP nanocomposite).
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Oh, Dong-Hun, Ho-Seung Kim, and Bang-Wook Lee. "A Novel Diagnosis Method for Void Defects in HVDC Mass-Impregnated PPLP Cable Based on Partial Discharge Measurement." Energies 14, no. 8 (April 7, 2021): 2052. http://dx.doi.org/10.3390/en14082052.
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Mass Impregnated PPLP cable, which is applied to various high-voltage direct current (HVDC) projects due to its excellent dielectric and temperature properties, has a problem wherein voids are formed inside the butt-gap due to cavitation. However, there has been no previous research into technology for void defect identification and insulation diagnosis on HVDC MI-PPLP cables. In this paper, to propose an insulation diagnosis method for void defects in HVDC MI-PPLP cable, the direct current (DC) void discharge patterns were analyzed according to the specimen temperature and the magnitude of applied voltage using the pulse sequence analysis method. In addition, to confirm the pre-symptoms of dielectric breakdown in MI-PPLP cable due to DC void discharge, partial discharge patterns were analyzed continuously until dielectric breakdown occurred. From the experimental results, DC void discharge patterns of the same shape were obtained regardless of the specimen temperature and the magnitude of applied voltage. In addition, it was confirmed that new insulation aging patterns were generated as electrical and thermal aging occurred due to the continuous DC void discharge. Therefore, it is demonstrated that identification and insulation diagnosis of void defects in HVDC MI-PPLP cable is possible through the obtained DC void discharge and insulation aging patterns.
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Gangadhara Rao, MVBB, and D. N. Singh. "A generalized relationship to estimate thermal resistivity of soils." Canadian Geotechnical Journal 36, no. 4 (November 22, 1999): 767–73. http://dx.doi.org/10.1139/t99-037.
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Soil thermal resistivity plays an important role in the design and laying of high-voltage buried power cables, oil and gas pipelines, nuclear waste disposal facilities, ground-modification techniques employing heating and freezing, etc. For these situations, it is important to estimate the resistance offered by the soil mass in dissipating the heat generated. Several investigators have tried to develop mathematical and theoretical models to estimate soil thermal resistivity. However, these models are not always capable of predicting thermal resistivity of soils. This is mainly due to the fact that thermal resistivity of soil is a complex phenomenon that depends upon various parameters, viz. type of the soil, particle-size distribution, compaction characteristics, etc. As such, none of the relationships available in the literature are suitable for estimating the thermal resistivity of all soils. This paper deals with the details of fabrication of a "laboratory thermal probe" which has been used to evaluate thermal resistivity of various soils. A relationship has been proposed to estimate thermal resistivity of soils depending upon the moulding moisture content and density of the soils.Key words: thermal resistivity, laboratory thermal probe, black cotton soil, fly ash, sands, silty sand.
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Zhou, Yifan, Wei Wang, and Tailong Guo. "Space Charge Accumulation Characteristics in HVDC Cable under Temperature Gradient." Energies 13, no. 21 (October 24, 2020): 5571. http://dx.doi.org/10.3390/en13215571.
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One of the main issues that affect the development of high-voltage direct-current (HVDC) cable insulation is the accumulation of space charge. The load operation of an HVDC cable leads to the formation of a radially distributed temperature gradient (TG) across the insulation. In this study, the space charge accumulation in a cross-linked polyethylene (XLPE) cable is measured under a DC electric field and TG using the pulsed electro-acoustic (PEA) method, and the effect of the TG on the space charge behavior is investigated. In addition, the bipolar charge transport (BCT) model and the conductivity model based on an improved cylindrical geometry are used to simulate the charge behavior in the HVDC XLPE cable under TG, and the experimental and simulated results are compared. The results show that the higher temperature of the cable conductor promotes the accumulation of homocharge near the side of high temperature. Additionally, with the increase of the TG, not only does more heterocharge accumulates adjacent to the side of low temperature, but more space charge also extends into the bulk of the cable insulation. More attention should be paid to the conductor shield layer and the insulation shield layer in HVDC cables. Moreover, the BCT model can more accurately describe the experimental results than the conductivity model.
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Bumgarner, Natalie R., Mark A. Bennett, Peter P. Ling, Robert W. Mullen, and Matthew D. Kleinhenz. "Active and Passive Zonal Heating Creates Distinct Microclimates and Influences Spring- and Fall-time Lettuce Growth in Ohio." HortTechnology 22, no. 2 (April 2012): 228–36. http://dx.doi.org/10.21273/horttech.22.2.228.
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Low and high tunnels and root-zone heating systems are proven tools in horticultural production. However, impacts of their individual and combined application on crop yield, composition, and microclimates are under-reported. We set out to enhance the record of management strategy effects on abiotic environmental conditions and cropping variables in open field and high-tunnel settings. In each setting, raised bed plots were subsurface heated (underlain by electric heating cables), aerial covered (0.8-mil, clear, vented, low tunnels), subsurface heated and aerial covered, or unheated and uncovered (control). The study was repeated four times in spring and fall seasons across 3 years in Wooster, OH. Red-leaved romaine lettuce (Lactuca sativa ‘Outredgeous’ and ‘Flagship’) was direct seeded in all plots in early October and late March and harvested after ≈4 weeks. Subsurface and aerial temperatures were monitored throughout the experiments. Here, we report primarily on treatment effects on crop microclimate conditions, including temperature and light, and related cropping variables. Subsurface and aerial temperatures varied consistently with plot microenvironment management. Relative to control plots, variability in shoot- and root-zone temperatures generally increased and decreased, respectively, with the addition of low tunnels and electric heating cables, regardless of setting. Still, the relative influence of aerial and soil temperature on crop biomass appeared to differ by setting; aerial temperature correlated most strongly with yield in the high tunnel, while the combination of aerial and root-zone temperature correlated most strongly with yield in the field. Growing degree day accumulation was least in control plots. And, the highest thermal energy to plant biomass conversion efficiency was recorded in the high tunnel. Comparing study-wide and historical climatic data collected in Wooster and other locations in the region suggests that results reported here may hold over a larger area and longer time frame in Wooster, OH.
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Jiang, Kaihua, Lin Du, Yubo Wang, and Jianwei Li. "A Smart Overvoltage Monitoring and Hierarchical Pattern Recognizing System for Power Grid with HTS Cables." Electronics 8, no. 10 (October 20, 2019): 1194. http://dx.doi.org/10.3390/electronics8101194.
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As one part of the power system, high-temperature superconducting (HTS) cables may be subject to various system faults, such as overvoltage. When overvoltage occurs, HTS cables may quench and the resistance of HTS tapes will increase rapidly, which will result in reduction of transmission capacity, increase of power loss and even electrical insulation breakdown. To protect the operation safety of power system, the level of overvoltage should be investigated in the system. This paper proposes a non-contact variable frequency sampling and hierarchical pattern recognizing system for overvoltage. Lightning and internal overvoltage signals are captured by specially designed non-contact voltage sensors. The sensors are installed at the grounding tap of transformer bushings and the cross arm of transmission towers. A variable sampling technique is employed to solve the conflict between sampling speed and storage capacity. A hierarchical pattern recognizing system is proposed to subdivide each overvoltage into specific types. Seven common overvoltages are discussed and analyzed. Wavelet theory and S-transform singular value decomposition (SVD) theory are adopted to extract the feature parameters of different overvoltages. Particle swarm optimization is employed to maintain a high classification rate and improve the initial set of the support vector machine (SVM) used as recognition algorithm. Field-acquired overvoltage data from an 110 kV substation validate the effectiveness of the proposed recognition system.
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Nguyen, Thai-Thanh, Hak-Man Kim, and Hyung Suk Yang. "Impacts of a LVRT Control Strategy of Offshore Wind Farms on the HTS Power Cable." Energies 13, no. 5 (March 5, 2020): 1194. http://dx.doi.org/10.3390/en13051194.
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High temperature superconducting (HTS) power cables are a potential solution for the grid integration of offshore wind farms since the HTS cable can conduct bulk wind power at low voltage levels. However, the transient current through the HTS cable in cases of low voltage ride through (LVRT) operation has a negative impact on the HTS cable operation due to the quenching phenomenon. This paper analyzes the impact of LVRT control strategies on the HTS cable operation. In addition, a coordinated control of wind turbines for LVRT improvement of an offshore wind farm is proposed. The feasibility of the HTS cable application for the grid connection of offshore wind farms is also discussed in this study. The proposed controller is designed for the wind turbine generator based on a type-4 permanent magnet synchronous generator. In the proposed controller, the transient current through the HTS cable is reduced by regulating the machine side power during fault conditions. The feasibility of the proposed controller is validated in the PSCAD/EMTDC program (Manitoba Hydro International Ltd., Winnipeg, Manitoba, Canada, version 4.2.1). The effects of transient current on the cable temperatures and resistances are analyzed in this study. Simulation results show that the proposed control strategy could reduce the transient current and temperature rise of the HTS cable.
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Qin, Runzhi, Yanxia Du, Zitao Jiang, Xiuyun Wang, Anqing Fu, and Yi Lu. "Corrosion Behavior of X80 Pipe Steel under HVDC Interference in Sandy Soil." Metals 8, no. 10 (October 10, 2018): 809. http://dx.doi.org/10.3390/met8100809.
Full textAbstract:
With the development of high voltage direct current (HVDC) systems, some pipelines have been badly interfered. The corrosion mechanism of pipelines has not been clearly clarified. In this work, laboratory experiments were designed to study the corrosion behavior of X80 steel under HVDC interference in sandy soil. The corrosion rates were related to the change in direct current (DC) density, which experienced three stages in the interference process. As soon as high DC interference voltage was applied to the working electrode, the current density increased sharply to a peak value in a few seconds. It then decreased rapidly to a steady value over dozens of seconds. Finally, it remained steady for the remaining time. With the measurement of local soil properties, the change in DC density was attributed to the local soil temperature increment, the water content decrement, and the substantial growth in the soil spread resistance. Moreover, the parameters contribute to the corrosion reaction during the interference process. The corrosion products were characterized at different times of interference via Raman spectroscopy. Lepidocrocite was produced under high DC density and then transformed to hematite under low DC density. Based on the above, the corrosion model during HVDC interference is proposed.
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Cui, Yingchao, Hongxia Yin, Zhaoliang Xing, Xiangjin Guo, Shiyi Zhao, Yanhui Wei, Guochang Li, Meng Xin, Chuncheng Hao, and Qingquan Lei. "Effect of Ionic Conductors on the Suppression of PTC and Carrier Emission of Semiconductive Composites." Applied Sciences 10, no. 8 (April 23, 2020): 2915. http://dx.doi.org/10.3390/app10082915.
Full textAbstract:
The positive temperature coefficient (PTC) effect of the semiconductive layers of high-voltage direct current (HVDC) cables is a key factor limiting its usage when the temperature exceeds 70 °C. The conductivity of the ionic conductor increases with the increase in temperature. Based on the characteristics of the ionic conductor, the PTC effect of the composite can be weakened by doping the ionic conductor into the semiconductive materials. Thus, in this paper, the PCT effects of electrical resistivity in perovskite La0.6Sr0.4CoO3 (LSC) particle-dispersed semiconductive composites are discussed based on experimental results from scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a semiconductive resistance test device. Semiconductive composites with different LSC contents of 0.5 wt%, 1 wt%, 3 wt%, and 5 wt% were prepared by hot pressing crosslinking. The results show that the PTC effect is weakened due to the addition of LSC. At the same time, the injection of space charge in the insulating sample is characterized by the pulsed electroacoustic method (PEA) and the thermally stimulated current method (TSC), and the results show that when the content of LSC is 1 wt%, the injection of space charge in the insulating layer can be significantly reduced.