HTS Power Research Articles

Разработка ВТСП кабельных линий для систем вывода мощности от источников генерации и протяженных линий передачи энергии

The article discusses general approaches to the development of HTS cable lines for long energy transmission lines and power output systems from generation sources, as part of a new technological structure of the energy industry. The use of the superconductivity effect makes it possible to achieve power transmission levels of 0.5-2.0 GVA or more without significantly increasing weight and size characteristics while simultaneously reducing energy losses. The results of theoretical estimates are presented, showing the possibility of reducing energy losses to a level of no more than 3% of the transmitted power and creating HTS power transmission lines up to 100 km long. It is shown that the accumulated experience makes it possible to start implementing pilot projects using superconducting cable lines, however, such developments will require taking into account many factors, including infrastructural technical and economic aspects.

Cryogenic Electrical Tree Characteristics of Epoxy Resin for HTS Power Equipment under DC/Impulse Superimposed Voltage

Cryogenic Electrical Tree Characteristics of Epoxy Resin for HTS Power Equipment under DC/Impulse Superimposed Voltage

Operating Reliability of In-grid HTS Power Cables Based on Electromagnetic–Thermal–Hydraulic Analysis

Operating Reliability of In-grid HTS Power Cables Based on Electromagnetic–Thermal–Hydraulic Analysis

Novel Electrical Insulation Coatings for HTS Cables

To develop epoxy based electrical insulation for HTS power cable and other device applications, the suitability of two cryogenic rated commercial epoxies, (MASTERBOND EP29-LPSP and EP37-3FLFAO) were evaluated. Characterization of their electrical breakdown characteristics, mechanical strength, and the interfacial shear strength of the interface with HTS tapes were conducted at room temperature and 77 K. The epoxy materials are ductile at cryogenic temperatures to support their use as electrical insulation of HTS power devices.

Development of a Tape Winding Mechanism for HTS Power Cables

Manufacturing of HTS power cables requires winding the HTS tapes helically around a former. These HTS tapes are costly, and delicate and require sophisticated winding machinery which is expensive. In this paper, an in-house economic mechanism for converting a conventional lathe machine to a Tape Winding Mechanism (TWM) is discussed in detail. In addition to the developed prototype, the technical issues and challenges encountered during the development of TWM are listed. The developed TWM was instrumental in successfully winding 10 HTS tapes simultaneously around a tin-coated braided copper former of 19 mm diameter with a pitch length of 210 mm for a continuous length of 5 m HTS cable. The recommendation of modifying any existing cable winding machine to TWM is also discussed.

Gas-Cooled Peltier Current Leads for Compact HTS Devices

As is known, heat losses through current leads essentially determine the economic efficiency of the superconducting systems. Much attention is paid to the design of optimal current leads, but the Wiedemann-Franz law physically limits the benefits of the standard approach. An innovative way to further reduce heat inflow is to use current leads equipped with Peltier thermoelectric elements. These elements are installed in series in the power circuit. Therefore, when the transport current passes through the Peltier element, the thermoelectric effect counteracts the heat flow caused by the temperature gradient in the current lead. Another advantage of this design is that when the circuit is de-energized, the heat loss is reduced due to the low thermal conductivity of the Peltier element. In addition to the theoretical works devoted to the Peltier current leads (PCLs), many experiments confirmed a decrease in heat loss by about 30%. Moreover, PCLs were installed on 500- and 1000-meter HTS power transmission lines in Ishikari (Hokkaido, Japan). An advanced approach involves cooling the current-carrying parts with evaporating nitrogen, which should improve the performance of PCLs. In this work, an experiment on testing gas-cooled PCLs was carried out for the first time. A 30% additional reduction in heat inflow was achieved. At the same time, the dependence of the specific heat loss on the current became flatter, which means an expansion of the range of operating current. In the experiment, the vented gas passed through copper pipes used as conductors. In the future, to increase the efficiency of the gas-cooled PCLs, we plan to improve the heat transfer between the gas flow and the conductor using surface ribbing.

Optimization of a Three-Phase Coaxial 10 kV/1.5 kA HTS Power Cable for Balancing 3-Phase Current Distribution

With the increasing power load of urban power grid, the upgrading of conventional cable is facing with the problem of space resource shortage. Three-phase coaxial high temperature superconducting cable has the advantages of compact structure, low loss, and nearly 2/3 reduction in the consumption of HTS tape, which provides a new prospective solution for urban expansion. However, due to the different radius of each phase of the three-phase coaxial HTS cable, the symmetry of electromagnetic parameters of each phase are affected, resulting in the imbalance of the three-phase current, which will reduce the transmission efficiency. Based on the multi-loop method, we establish the differential equation of three-phase coaxial superconducting cable in this paper, by calculating the parameters of three-phase inductance and capacitance by a numerical method, and obtain the instantaneous variation rule of voltage and current in the three-phase coaxial HTS cable. We propose a novel two-section Particle Swarm Optimization to solve the problem of three-phase current imbalance in HTS cable. The algorithm divides the C-phase conductor and the copper shield layer into two segments with the same radius but different pitches and twist directions, which increases the variable by one-half. By changing the pitches and winding directions, considering the thickness of the insulation, optimization of current distribution of three-phase coaxial HTS cable is achieved. Finally, we designed a 10 kV/1.5 kA three-phase coaxial HTS cable. The results show that the current imbalance ratio of the superconducting cable is reduced from 41% to 1% after the two-section Particle Swarm Optimization. The mathematical model and the imbalance optimization algorithm of three-phase coaxial HTS cable both are verified. The optimization results provide important reference for the structural design and experimental research of three-phase coaxial HTS cable for urban power grid.

Flow cryogenic supply systems for HTS power systems

Operation principles of cryogenic supply systems for power HTS systems have been examined. Two flow cryogenic supply systems have been described. These cryogenic supply systems have been created in MAI and utilized to ensure the operation of HTS power devices (power cables, electric motors, and generators, transformers, etc.).

Non-flow cryogenic supply systems for HTS power systems

Operation principles of cryogenic supply systems for power HTS systems have been examined. Two non-flow (autonomous) cryogenic supply systems have been described. Gas circuit of cryorefrigerator uses neon, rather than helium, what makes it possible to decrease several-fold the number of compression stages in compressors and losses of working fluid in the circuit when leakage occurs. The use of turbomachines and gas bearings allows for substantially increasing an overhaul period of cryorefrigerator (over 30 000 h).

The Feasibility Design Study and Cold Test of the First Model of HTS Cable With the Longitudinal Magnetic Field Effect

Since the 1970’s the effect of the increase of the critical current of superconductors in the longitudinal external magnetic field has been known. The critical current density of a Nb-Ti wire at low longitudinal magnetic fields demonstrated several times the larger value compared with that in a transverse magnetic field. The same phenomenon has been observed for 2G HTS tapes. It is natural to try to use this phenomenon to increase the critical current in DC HTS power cables. In this paper, we present the analysis of feasibility to use the longitudinal magnetic field effect to increase critical currents in practical HTS power cables. The experimental model of the HTS DC cable has been developed, produced, and tested in liquid nitrogen. The increase of the critical current observed when the longitudinal magnetic field generated. This increase coincides with the calculations.

Numerical Studies on Two-Phase Flow of Liquid Nitrogen to Cool HTS Power Cables

Liquid nitrogen is the foremost coolant when it comes to cooling HTS power devices due to its abundance and since it is more economical than other cryogens. Sub-cooled LN2 is preferred over saturated LN2 as it ofers substantial advantages in terms of performance. However, in the cases where it is not possible to cool HTS power cables using sub-cooled LN2, saturated LN2 is the only option. Additionally, even when sub-cooled LN2 is used for long length cables, the heat-in-leaks along with other core losses result in rise in temperature and an unavoidable two-phase fow afects the cooling characteristics of the cryogen. This paper deals with the modeling and numerical analysis of a two-phase fow through an HTS power cable cryostat to understand the temperature profle, the pressure drop per unit length, and required pumping power for circulation of cryogen.

Feasibility study of capacitance based quench detection technique for HTS power transmission cables

2nd Generation High Temperature Superconducting (2G HTS) tapes are replacing the conventional Low Temperature Superconducting (LTS) wires in various felds of applied superconductivity, especially in the power transmission applications. Transients in the electrical grid can result in the loss of superconductivity leading to thermal runaway. This phenomenon is known as quench. To avoid catastrophic consequences, timely detection of quench is imperative. However, the HTS materials possess a low Normal Zone Propagation Velocity (NZPV) compared to LTS materials during quench. This property combined with a low electromagnetic shielding makes the conventional voltage tap detection technique unreliable for HTS power transmission cables. A capacitance based quench detection technique is proposed and its feasibility is studied. A variation in the permittivity of the cryogenic fuid and the dielectric can be observed in association with the heat generation during faults. This can be refected as the variation in the measured capacitance between cryostat and cable former. In this study, this capacitance is computed using the FEM model of HTS cable operating at various temperatures along with diferent vapour liquid ratios of cryogen. The results of this work can be extended into experiments for quench detection in HTS power transmission cables.

Effect of magnetic fields due to electric currents in an HTS power cable and estimation of stress

Effect of magnetic fields due to electric currents in an HTS power cable and estimation of stress

Optimization and Cold Test of a Triaxial 2G HTS Power Cable With High Current Capacity

Triaxial HTS AC power cables, that incorporates three HTS phases wound around a single core within a single cable is considering the optimal solution for low and medium voltages. Such a design permits to save expensive HTS conductor and to increase the power density transmitted. It is difficult to increase the transmission capacity of a triaxial cable by increasing its operating voltage and therefore, insulation thickness between phases. The other way is to increase the operation current by using a multilayer structure in each phase of the triaxial cable. This task demands a complicated optimization analysis and a precise manufacturing technology. Following our previous studies, we developed and tested the triaxial cable prototype with two layers per phase made of ReBCO wire. The optimal parameters of the cable (twist pitch, diameters of phases, etc.) have been determined using the numerical simulation methods developed. DC and AC tests of the cable has been performed. In the result, the feasibility to provide a uniform current distribution in a triaxial cable, each phase of which consists of two layers, has been demonstrated. With the outer diameter of ∼24 mm only, this is the most compact triaxial HTS power cable manufactured and tested up to date with currents up to 4 kA per phase. The anticipated power transfer with three phases of this cable can be as large as ∼34 MW.

A Simplified 2D Modeling Method for Electromagnetic Analysis of HTS Power Transmission Cable Spiraled With Coated Conductors

A two-dimensional (2D) modeling method, which takes helical structure of superconducting layers in HTS cables into consideration, is proposed to analyze electromagnetic properties of HTS power transmission cable. The model is characterized by E-J power law and H-formulation, and is successfully implemented by finite element software. We first expound the principle of using 2D model to simulate 3D structure of a HTS cable. Then, the modeling process is given. In order to verify the validity of the method, a 3D model was established as the control group, and the current distribution and AC loss were compared. The influence of the 3D structure parameters of the cable has been investigated, including the pitch of superconducting layers and the gap width between HTS tapes.

Review of the design, production and tests of compact AC HTS power cables

Review of the design, production and tests of compact AC HTS power cables

An Investigation into the Characteristics of a Novel Rotatable Pantograph Catenary System for High-Speed Trains

High speed trains receive traction electrical energy from a high-voltage catenary via a pantograph catenary system (PCS). As the velocity of trains increases, the traditional PCSs face significant challenges, such as strong aero resistance under high-speed conditions, severe electrochemical corrosion caused by poor contact between the pantograph strip and the catenary, harmful wear both on the pantograph strip and the contact wire produced by high-speed sliding friction between them, etc. The effectiveness and reliability of the PCS has a direct impact on the performance and safety of the HTS power supply. In order to alleviate some of these bottleneck effects related to the operation of the currently used PCSs, especially under high-speed conditions, this paper proposes a novel configuration where rotatable pantograph rollers replace the currently used pantograph strips. As the sliding friction is now replaced by rotating friction, this has numerous benefits, such as less friction heat, better heat dispersion and improved catenary-tracking performance. Moreover, should the whole system be modularized, it could adapt to different levels of traction power through adjusting the number of rollers.

Experimental and Numerical Study of Quench Propagation Characteristics of Different Epoxy Impregnated REBCO Coated Conductors

REBCO coated conductors are very promising for various HTS power applications. However, a detailed knowledge about their quench characteristics is crucial for developing effective quench detection methods. This article experimentally and numerically analyzed the quench propagation characteristics of REBCO coated conductors impregnated with different epoxy. The quench parameters, including minimum quench energy (MQE), voltage profiles, and normal zone propagation velocities, obtained from the experimental results are validated by numerical model. The experimental phenomenon can be further described by the numerical model. The analysis shows that higher thermal conductivity of epoxy increase the MQE of the epoxy impregnated conductor, indicating that maintaining a relatively high thermal conductivity of epoxy is helpful to decrease the quench damage of the epoxy impregnated conductor.

Effect of Transverse Compressive Loading on the Quench Characteristics of Epoxy-Impregnated REBCO-Coated Conductor

REBCO-coated conductor is widely used in various HTS power applications. The HTS coils for power applications are generally impregnated with epoxy resin to enhance their mechanical stability, and the coil conductors would be subjected to transverse compressive loading in these applications. Although the effect of various operating conditions on the quench characteristics of REBCO-coated conductor have been investigated, the effects of compressive stress on quench characteristics of epoxy-impregnated REBCO-coated conductor has rarely been reported. This study examined the effects of transverse compressive loading on the minimum quench energy (MQE) and normal zone propagation velocities (NZPV) of epoxy-impregnated REBCO-coated conductor. The critical current of the conductor shows little degradation when transverse compressive stress is applied up to 80 MPa. Under the same compressive stress, the MQE decreases but the NZPV increases with the transport current. For fixed transport current, compressive stress increases the thermal contact conductance between conductor and epoxy which allows the heater energy of the conductor dissipating faster towards the surrounding epoxy, resulting in the increase of MQE and decrease of NZPV when increasing transverse compressive stress. The results indicate that higher compressive stress is helpful to decrease the quench damage of the conductor.

Principal analysis of hybrid power systems with HTS electrical machines

The hybrid power systems (HPS) for transport application are currently under consideration. It causes with ecological and fuel efficiency aspects. The successful solving the problems of enhancing the specific output power parameter, fuel efficiency and diminishing weight of such systems focus on a use the cryogenic cooling and cryogenic fuel as a source of on-board energy. The article is devoted to the analysis and comparison of HPS of different design. The comparison is provided for HPS with different fuel (diesel oil, kerosene, petroleum, liquid natural gas, and liquid hydrogen). The analysis of application in HPS of different types of conventional and HTS electrical machines illustrates the advantage of the latter. The prospective of application of cryogenic power electronics is considered like advanced for HPS. Besides the article provides specific parameters of the HPS with HTS generator, motor, cryogenic electronics and HTS power cable at different cooling