Conventional Copper Cables Research Articles

Synergizing intelligent signal processing with wavelength-division multiplexing for enhanced efficiency and speed in photonic network communications

Abstract The explosive growth of worldwide mobile data traffic seeks innovations in communication technology to cater to the mounting need for rapid connectivity, high-capacity connections. The mainstreaming of 5G technologies for communication is a dramatic step towards meeting the aforementioned goals, with the ability for reshaping IoT (Internet of things), D2D (device-to-Device) communications, and the smart grids. This work conveys an in-depth study of the fundamental innovations that underlie 5G, including full-duplex distribution, huge multiple-input-multiple-output, ultra-dense connections, the phenomenon of beamforming and millimeter-wave approaches. A special emphasis is focused on the integration of photonic technologies, or microwave photonics, which serves as a critical multidisciplinary study topic. Optical fibers, with their tremendous bandwidth and capacity, have been determined as the best medium for backhaul and fronthaul amenities, outpacing conventional copper cables to accommodate tiny cells and next-generation networks. The synergy between optical and wireless access technologies is analyzed with the emphasis on the central role of wavelength-division multiplexing (WDM) for improving network efficiency and speed. The investigation additionally explores the possibility of intelligent signal processing methods combined with WDM to optimize photonic network communications. The mingling of these technologies anticipates producing unrivaled levels of performance, rupturing the path for an additional intelligent, interconnected era.

Ultra-low electrical loss superconducting cables for railway transportation: Technical, economic, and environmental analysis

Carbon emission from various transportations is one of the major factors towards global warming. With the increasing energy demand from railway transportation, the conventional copper cables with high electric currents and considerable amounts of resistances are facing challenges, e.g., electric loss and heat. This article proposed a novel ultra-low electrical loss hybrid-energy transmission scheme. A real cable sample was fabricated, and the experiment proved the high-current carrying capability. A cable model was built to study the loss and electromagnetic behaviours by different optimization strategies. A general design guideline was established to help those non-experts to easily design their own hybrid-energy superconducting cables. The technical, economic, and environmental analysis was performed for a 1.5 kV/10 kA superconducting cable to transmit hybrid energy in a railway traction system. Results showed that reducing losses by the proposed method can efficiently reduce annual operating costs, e.g., the loss from 0.9 W/m to 0.46 W/m, the annual operating cost from 16, 644, 000 CNY to 8,935,000 CNY and the annual CO2 emissions form 2518 ton to 1090 ton. Overall, the optimization successfully improved the cable performance, and the analysis validated the technical feasibility and economic/environmental benefits of the novel hybrid-energy transmission system to be used into railway systems.

A novel combo‐transmission system of cold energy and electricity for aluminium profile production: Using liquid nitrogen and superconductor technologies

AbstractAluminium production needs the most energy‐intensive technologies among all the metal processing sectors. During the process of aluminium profile extrusion, the whole production line needs bulk electricity, and the mold inside the extrusion equipment needs robust cold energy for rapid cooling of the metal surface. This paper presents a new combo‐transmission that can simultaneously deliver cold energy together with electricity to the aluminium profile extrusion line. Thanks to the superiority of virtually zero loss and compact size, the powerful superconducting cable is used to replace the conventional copper cable. The entire superconducting cable assembly is fully installed into a cryogenic pipeline and cooled by liquid nitrogen at 77 K. In addition to keeping a favourable cryogenic environment for the superconducting cable, liquid nitrogen can also provide a large amount of cold energy for cooling the metal surface. For a typical 100 MN aluminium extrusion production line, the design and optimization of 10 kA class superconducting cable with the pipeline cooling system for aluminium production are presented in detail. The simulation results and comparisons show that the total energy loss of superconducting transmission is about 46% of conventional copper cable, and the energy saved in a year can be up to about 240.6 MWh. Moreover, the net profit increases almost linearly along with the increases of the extrusion speed when the liquid nitrogen cooling is applied to the 100 MN production line. For the case of 23% increase in extrusion speed, the net profit can be up to 1.48 M$ in a year. Overall, the novel design, technical evaluation, and economic analysis of the combo‐transmission system (cold energy + electricity) can provide a promising solution for future high‐dense aluminium production sectors.

Development of Supervisory Control and Data Acquisition System for India’s First High Temperature Superconducting Cable Testing

High Temperature Superconductor (HTS) based power cable is a technological marvel which can transmit bulk power over large distances without any joule heating as compared to a conventional copper cable, owing to its zero DC resistance in superconducting state. However, to maintain this superconducting state, the cable must be at a temperature below its critical temperature under self-field. Commonly used HTS material includes BSCCO (Tc = 110 K) and YBCO (Tc = 93 K) and thus, requires cryogenic liquid nitrogen (77 K) for attaining superconductivity. Further, the voltage drops across the various joints such as joint box and current leads in the termination unit must be monitored to ensure optimal operation of the cable. This demands for sophisticated instrumentation operating under extreme low cryogenic temperatures for safe operation, performance monitoring, cryogenic measurements, and control of the HTS power cable cryogenic process. This paper presents the instrumentation scheme followed for testing India’s first 6-meter HTS power cable. The instrumentation scheme involves housing of the various temperature sensors and location of voltage tapping, current measurement, cryogen flow measurements, operation of control valves, operation and measurement of high vacuum system, stray field measurement, insulation resistance measurement and dielectric measurements for cable are the important parameters for the successful operation of HTS power cable. To perform data logging NI-DAQ and LabVIEW software was used to develop in-house Supervisory Control and Data Acquisition (SCADA) system. This paper discusses intrinsic aspects of complete instrumentation and developed SCADA system for HTS power cable.

Preliminary Design of a Superconducting LVDC Power Cable for Tokamak Application

Tokamak device requires a very high current power supply from the local power distribution sources to the targeted magnets such as toroidal field (TF) coils and poloidal field (PF) coils. This paper presents a preliminary design of a 30-m/1-kV/10-kA low voltage direct current (LVDC) superconducting cable for the potential in Tokamak applications. The outer diameter of the DC cable is 122.41 mm, and the pressure drop of liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) in the inner and outer channels is about 6.59 kPa. The flow velocity of inner and outer LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> channels are 0.5 m/s and 0.25 m/s, respectively. The temperature rise of the entire cable was designed to be less than 5 K, which enhances the electricity supply safety and reliability. These preliminary design lays some technical bases for achieving high current and low loss power transmission. The designing results show that the LVDC superconducting cable has significant potentials for Tokamak applications compared with conventional copper cables.

Liquefied natural gas (LNG) and DC electric power transfer system by cryogenic pipe of superconducting DC power transmission (SCDC)

We propose a hybrid energy transmission pipeline that combines the liquefied natural gas (LNG) cryogenic pipelines and superconducting direct current (DC) electrical power transmission cable system (SCDC). The system design is based on experimental data from the SCDC Ishikari project in Japan and related laboratory experiments. The particular structure of the hybrid cryogenic pipe connects the thermal radiation shield of the pipe that contains the DC high temperature superconducting (HTS) electrical cable to the LNG pipe and significantly reduces the heat leak into the SCDC pipe. Because the specific heat of LNG is higher than that of liquid nitrogen and the LNG transfer rate is quite high, the thermal loss of the SCDC cable becomes only 1/100 that of present-day conventional copper cables, far below the factor 1/10 reduction achievable by a stand-alone SCDC transmission lines. The LNG temperature rises by less than 2 K over a 100 km transport distance, which is negligible in actual use. LNG also saves significantly on pumping power compared to a natural gas pipeline. To liquefy the LNG at cryogenic temperature from natural gas at ambient temperature requires a large refrigerator that consumes enormous power. The gas pipeline, however, needs a compressor to produce high-pressure gas, which also consumes a massive amount of power. Due to these considerations, the proposed hybrid system is a viable design for the long-distance joint transportation of LNG and electricity.

Design of Wireless Power Transfer System for Charging of Electronic Gadgets

Wireless charging of gadgets is one of the new emerging technologies in the world at present moment. The most common method used is wireless power transfer is by using the method of inductive coupling. Wireless power transfer is one of the simplest and inexpensive ways of charging as it eliminates the use of conventional copper cables and current carrying wires. The inductive coupling technique is used since currently it is the easiest method of wireless power transfer because of high efficiency and large amount of the energy transferred. Its versatility and range of applications the power transferred will be used to charge a battery with the aid of additional circuitry. This research work focuses on the study of wireless power transfer for the purpose of transferring energy at maximum efficiency within a small range or in the near field region. The motivation to this proposed design model is contact less mobile device charging about 5cm-100cm distance range, which can be used to charge the mobile electronic devices like mobile phones, laptops, smart phones wirelessly. This proposed design is very helpful in the pandemic situation to charge electronic gadgets contactless as well wirelessly in the hospitals, public transports like metro stations, educational institutions, and in office communication systems.

A proposal for a lightweight, large current superconducting cable for aviation

More Electric Aircraft (MEA) is one of the most important subjects for designing the next generation of aircraft. Since we cannot ground the electric power systems of a flying aircraft and the air insulation voltage is lower at high altitude, a low voltage, direct current (DC) aircraft electrical system is preferable for a MEA. Since the current must be high to supply high power, we consider high temperature superconducting (HTS) technology because it handles large currents well. We propose a new HTS cable in this paper. The cable uses a stacked conductor, with oppositely directed current in each HTS tape, a structure that has already been shown to be feasible for low voltage cables. It enhances the critical current compared to a single tape conductor, especially for Bi2223 tape. In order to avoid a current imbalance in the stacked conductor, we use the current lead resistance rather than a Roebel conductor design. Then the critical current remains high, and this is confirmed by measurements. The cryogenic pipe will be made of magnesium-lithium alloy, one of the lightest metals available at the present time. We estimate the weight-to-current ratio per unit length to be less than 0.5 kg/A/km at the liquid nitrogen operational temperature of 77 K, lighter than conventional copper cable. If instead we use liquid hydrogen at 20 K, we expect a value less than 0.1 kg/A/km, which is one of the lowest presently achievable values and satisfies the requirements for MEA.

Investigation of HTS cable impact on turbo‐electric aircraft performance

With significant interest in the use of high-temperature superconducting (HTS) components in electric aircraft, there is a need for novel modelling techniques that allow architecture-level studies of the electrical systems including HTS components. In this study, a simple electric network architecture, as proposed in the literature has been considered, which includes generators, dynamic propulsion load and cables. This electric network has been modelled considering conventional technology and using HTS cables by replacing the conventional copper cables, to evaluate the variations in the network performance. The network performance has been studied for the dynamically varying propulsion load, which is nearly equivalent to the aircraft load over the entire flight duration. Following this, electric faults have been applied at various locations, and the impact of HTS cables on the network fault levels has been evaluated. The fault current levels are compared using both conventional and HTS cables, due to the fault current limiting properties of the HTS cables, they are observed to offer lowered fault current values.

Study of wireless power transmission

Wireless charging of gadgets is one of the new emerging technologies in the world at the moment. The most common method used at the moment is wireless power transfer by inductive coupling. Wireless power transfer is one of the simplest and inexpensive ways of charging as it eliminate the use of conventional copper cables and current carrying wires. In this paper, write up, a methodology and principle of operation are devised for wireless power transfer through inductive coupling, and a feasible design is modeled accordingly. The inductive coupling technique is used since currently, it is the easiest method of wireless power transfer because of high efficiency and large amount of the energy transferred. In this paper, results of experiments done to check wireless working is shown. Also to further show its versatility and range of applications the power transferred is used to charge a battery with the aid of additional circuitry. We also study the effect of placing hurdles between the transmitter and receiver so as to establish if it is an alternative in the medical industry for charging pace makers etc. This research work focuses on the study of wireless power transfer for the purpose of transferring energy at maximum efficiency within a small range or in the near field region.

Technical and Economical Evaluation of DC High-Temperature Superconductor Solutions for the Grid Connection of Offshore Wind Parks

The connection system of offshore wind parks with the onshore power grid can have a crucial impact on the overall energy yield. The possible (ac and dc) connection systems for offshore wind parks are investigated in detail and compared both in terms of cost and losses. Both conventional copper (Cu) cables and high-temperature superconductor (HTS) cables are considered in the case of dc systems. An offshore wind park with a 360-MW peak power capacity in a 50-km distance from the shore is considered as within this case study. The comparison between the connection systems is carried out in terms of overall energy loss in a full year. The economical comparison is also discussed in detail. It is shown that a hybrid (HTS and Cu) medium-voltage dc connection system with a two-stage dc collector grid followed by an HTS high-voltage dc transmission at ±150 kV offers reduced losses and is cost competitive with respect to ac connection systems based on today's quotation of HTS material. In the near future, as soon as the foreseen reduction in the cost of HTS material is achieved, a full-HTS dc connection system can become the most cost-attractive solution.

English

The major objective of this project is to build up a device for wireless power transfer (WPT). Wireless power transfer can make an extraordinary change in the field of the electrical engineering which eliminates the use of conventional copper cables and current carrying wires. WPT is based on strong coupling between electromagnetic resonant objects to transfer energy wirelessly between them. The tuned magnetic fields generated by the primary coil can be arranged to interact vigorously with matched secondary windings in distant equipment but far more weakly with any surrounding objects or materials such as radio signals or biological tissues. But for very long distances, microwave transmission is used for the effective transfer of power.

AC Loss of Ripple Current in Superconducting DC Power Transmission Cable

As a method of largely reducing the transmission loss in the electric power grid, superconducting direct current (DC) power transmission cable has been investigated. Using superconducting DC power transmission cables, large amounts of current and energy can be transferred compared to conventional copper cables. In this case, an alternating current (AC) is converted to DC and superposed AC which is known as ripple current, and the energy loss by the ripple current is generated. Therefore it is desired to estimate the energy loss density for the case of DC current and superposed AC current for a design of DC transmission cable system. In this study, the hysteresis loss for DC current of 2 kA rectified from 60Hz alternating current is calculated using the Bean model, and coupling loss was also estimated. The diameter of the cable was 40mm. The ripple currents generated by multi-pulse rectifiers, 6-pulse, 12-pulse, and 24-pulse were considered. It is found that the total AC loss including the hysteresis loss and the coupling loss is considerably smaller than the supposed heat loss of 0.5W/m which is obtained with a newly developed cable.

Electrical and thermal characterization of a novel high pressure gas cooled DC power cable

High-temperature superconductors (HTS) allow power cables of substantially higher current density than conventional copper or aluminum cables. This is important for applications where a low mass and a low volume are critical such as naval, aeronautical and space applications. The novel type of cable under consideration is cooled by gaseous Helium at elevated pressure. Helium is known for having poor electric breakdown strength; therefore the dielectric capabilities of this type of cable must be tested under conditions similar to the envisaged operation. In order to study the dielectric performance we have designed and built a novel high pressure cryostat rated at 2.17MPa which has been used for testing model cables of lengths of up to 1m. The cryostat is an open system where the gas is not re-circulated. This allows maintaining a high purity of the gas. The target temperature range is between 40K and 70K. This substantially increases the critical current density of the HTS compared to 77K, which is the typical temperature of cables cooled by liquid Nitrogen. The cryostat presented allows for adjusting the temperature and keeping it constant for the time necessary to run a complete dielectric characterization test. We give a detailed description of the cryostat. Measurements of partial discharge inception voltages as well as the temperature distribution along the model cables as a function of time are presented. Tests showed that the thermal insulation characteristics of this cryostat were sufficient for the dielectric tests of up to 1h duration. The partial discharge inception voltage (PDIV) of the high voltage bushing was about 16kV. These values are well within our design requirements.

Balanced three‐phase distribution experiment of a triaxial HTS cable

AbstractHigh Temperature Superconducting (HTS) cables have been studied because of their low loss and compactness compared with conventional copper cables. Three‐phase cables are usually composed of three single‐phase coaxial cables. Recently, triaxial cables, composed of three concentric phases, have been intensively developed, because they have advantages such as reduced amount of HTS tape, small leakage fields, and small heat loss in leaks, compared with three single‐phase cables. However, there is an inherent imbalance in the three‐phase currents in the triaxial cable due to differences in the radii of the three‐phase current layers. The imbalance of currents causes additional losses and large leakage field in the cable, and also degrades the electric power quality. Therefore, we propose a new model, a triaxial cable composed of two longitudinal sections with different twist pitches to obtain the solutions of the balanced three‐phase currents and the homogeneous current distribution in each phase of the triaxial cable. We derive a general equation satisfying both the balanced three‐phase currents and homogeneous current distribution, as functions of the winding pitches, and finally apply it to the simplest cable. We fabricated and tested a 1‐m HTS cable in order to verify that the proposed theory can satisfy the balanced distribution. The results demonstrate the validity of the theory. We also investigated the current distributions along a long triaxial cable considering the capacitances between the layers in the triaxial cable. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(2): 51–58, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10283

AC Loss of a Multi-Layer per Phase Tri-Axial HTS Cable with Balanced Current Distribution

Recently, high-temperature superconductor (HTS) cables have been widely studied because of their compactness and high power capacity compared to conventional copper cables. In HTS cables, AC loss is an important issue since large losses reduce the efficiency of the power line. Among HTS cables, tri-axial cable is under intensive investigation recently, since it has a smaller amount of HTS tapes, small leakage fields and small heat loss in leak when compared with the three single-phase cables. For realizing high current capacity, more than one layer is required for each phase; therefore AC loss of the multi-layer tri-axial HTS cable should be carefully examined. In the tri-axial cable, different phase currents produce the out-of-phase magnetic fields on the other phase layers. In case of multi-layer arrangement, net magnetic fields on layer surfaces may exceed the penetration field of the HTS tape. Therefore in this paper, we analyze the AC loss of a tri-axial HTS cable which is composed of two layers per phase. Here, we treat the tri-axial cable which consists of two different longitudinal segments and thus satisfies balanced phase and homogeneous current distribution condition by controlling twist pitch and length of separate segments.

Investigation on AC loss of a high temperature superconducting tri-axial cable depending on twist pitches

High temperature superconductor (HTS) cables have been intensively studied because they are more compact compared with conventional copper cables. Since it is strongly expected that the HTS cables replace conventional power lines, some HTS cables are designed, manufactured, installed in power grids and tested to demonstrate full time operation. Recently, a tri-axial cable composed of three concentric phases has been developed, because of its reduced amount of HTS tapes, small leakage field and low heat loss when compared with single phase and co-axial HTS cables. The layers inside the tri-axial cable are subject to azimuthal fields applied from inner layers and axial fields applied from outer layers with different phase from their transport currents. These out-of-phase magnetic fields should be calculated under the condition of the three phase-balanced distribution of the tri-axial cable, and thereby AC losses should be evaluated. In this paper, the AC loss in the tri-axial HTS cable consisting of one layer per phase is theoretically treated for simplicity. The AC losses in the cable are calculated as functions of the twist pitches of HTS tapes. It is found that the AC losses rapidly decrease with increasing twist pitch.

Balanced Three-Phase Distributions of Tri-Axial Cable for Transmission Line

High Temperature Superconducting (HTS) cables have been intensively developed because of low loss and compactness, compared with conventional copper cables. A tri-axial cable composed of three concentric phases has been studied, because it has advantages such as reduced amount of HTS tapes and low heat-in-leak, compared with the three single-phase cables. However, there is an inherent imbalance in the three-phase distribution in the tri-axial cable due to differences in radii of the three-phase layers. We proposed a theory to obtain the balanced three-phase distribution for the tri-axial cable by treating two longitudinal cable sections together and adjusting all twist pitches. We derived a generalized formula as functions of winding pitches satisfying the balanced distribution. We designed and fabricated a short HTS tri-axial cable composed of 1 layer/phase to verify the proposed theory. The test results demonstrated that the theory is right for an equivalent impedance circuit model. The theory should be applied to the unbalanced three phase distributions caused by fabrication errors and inherent imbalance of capacitances in the tri-axial cable. We calculate the unbalanced three phase currents and voltages in steady state, and resolve them into symmetrical components to evaluate an imbalance ratio, which is defined as zero-sequence or negative-sequence to positive-sequence component. It is found that the fabrication errors of twist pitch and radius cause the imbalance ratios less than 1%, and the unbalanced capacitances of the cable of 10 km in length cause imbalance ratios of about 1%.

AC loss in a tri-axial HTS cable with balanced current distribution

High temperature superconductor (HTS) cables have been studied because they are more compact compared to conventional copper cables. In power applications of HTS cable AC loss is significantly important, as it is related with capacity and efficiency of the power line. Recently, a tri-axial cable composed of three concentric phases has been intensively developed, because of their reduced amount of HTS tapes, small leakage field, low heat loss when compared to three coaxial HTS cable. However, it experiences additional losses and large leakage field due to inherent imbalanced currents. Inside the tri-axial cable, each phase is subject to out-of-phase magnetic fields formed by other phase layer currents. Because tapes are twisted on successive layers, axial field by outer layers and azimuthal field by inner layers are produced in a tri-axial HTS cable. Any slab in the cable experiences parallel component of magnetic field on the wide faces of the tapes; induced by currents of all layers. Since the fields on tapes generate magnetization losses, they should be calculated in consideration of the balanced current distribution of the tri-axial cable. In this paper, AC loss in the tri-axial HTS cable consisting of one layer per phase is described, theoretically, where the balanced phase current distribution is satisfied through treating two different cable segments. The average AC losses in the cable are calculated as functions of the segment lengths and the segment twist pitches.

AC losses of a tri-axial superconducting cable with balanced three-phase current distributions

High Temperature Superconducting (HTS) cables have been studied because of low loss and compactness, compared with conventional copper cables. Three-phase cables are usually composed of three single-phase concentric cables. Recently, a tri-axial cable composed of three concentric phases, has been intensively developed, because it has advantages such as reduced amount of HTS tapes, low leakage fields, low heat in leak and compactness, compared with the three single-phase cables. We analyzed the three-phase balanced current distributions in the tri-axial cable as functions of winding pitches of three concentric phase layers. We formulated the general form of AC losses in the case of the transport current and the field in different phase. We analyze AC losses of a tri-axial cable with balanced three-phase current distributions.