Peng Ju

Bio: Peng Ju is an academic researcher. The author has contributed to research in topics: Electrical conductor & Ultimate tensile strength. The author has an hindex of 2, co-authored 3 publications receiving 41 citations.

Investigation on Critical Current Properties of Quasi-Isotropic Strand Made From Coated Conductors

Abstract: The high-temperature superconducting (HTS) strand, with high current capacity and a round or square cross section, is expected to have widely potential applications in current leads and superconducting power devices since it is easily insulated to avoid point charging. This paper describes a quasi-isotropic strand made from coated conductors. The magnetic field distribution and critical current characteristic of the strand in self-field are simulated by the finite-element method and tested in liquid nitrogen. The result indicates that this strand has high current-carrying capacity. The critical currents in different external magnetic fields and various orientations were measured. It is verified by the experiments that the strand has isotropic characteristics in low magnetic field and weak anisotropy in higher field. The potential of the strands with high engineering current density makes them also suitable for high-field magnets and high-voltage power applications, while maintaining flexibility.

Quench Behavior of Isotropic Strand Made From Coated Conductors With Overcurrent at Power Frequency

Abstract: This paper presents the quench behavior of isotropic strands made from second-generation (2G) coated conductors (CCs) subjected to overcurrent at power frequency and liquid nitrogen, in order to evaluate their prospects for power applications. The isotropic strands with high current capacity, consisting of CCs in parallel, were prepared by putting them into different metal sheaths using industrial soldering techniques and drawing as well as extrusion processes. Current over the critical current was supplied to the sample strands, with a duration of 700 ms, at 77 K. Profiles of the voltage, current, and temperature in the sample strand were recorded during the pulsing overcurrent test. Based on the U(t) and I(t) curves, the resistance of sample strands and phase angle between voltage and current were also obtained. After each pulsing current, the critical current and n-values of the sample strands were retested. The results show that quench characteristics of the sample strands with different sheaths are very different from each other. Additionally, the sample strand fabricated by stainless-steel sheath has stronger current-limited ability than the copper or aluminum sheaths.

Research on Ice-Melting Efficiency of OPGW with Aluminum Nitride

Abstract: Ice accident on transmission lines influences the safe operation of power grid. Preventing ice disaster is one of the key technologies for the construction of power network. Ground wire ice-melting technology is of great significance in conventional technology. Based on the layer stranded structure of Optical Fiber Composite Overhead Ground Wire (OPGW), a twisted bifilar wire fabricated by insulated wire is used as a heater for AC de-icing of ground wire. In order to enhance the heat transfer rate and shorten the ice-melting time as well as reduce the heat loss and improve ice melting efficiency, aluminum nitride, a semiconductor with high thermal conductivity, is used to fill in the gap among the conductor. An equivalent thermal circuit is established to calculate the de-icing efficiency of OPGW with aluminum nitride. With the samples of ice melting conductors, the ice melting time is analyzed based on de-icing conditions. It is confirmed that the ice melting efficiency of OPGW can be feasibly improved by filling the aluminum nitride.

High-Current HTS Cables: Status and Actual Development

Abstract: Second-generation high-temperature superconductors (HTS) REBCO are promising for high-field application due to the excellent $j_{c}(B)$ performance at low temperatures and for power transmission at liquid nitrogen temperature. For power transmission with HTS, the formation of high-current HTS cables from single HTS tapes is desirable for cable currents of several 10 kA up to more than 100 kA. On the other hand, to avoid high inductances, which would cause high-voltage problems in case of quench or fast shutdown, high-current HTS cables are needed for larger high-field magnets, too, typically operated at 4.5 K or lower. In the last years, several HTS cable designs have been proposed, such as twisted stacked cable, CORC cable, and Roebel cable. This talk will give an overview of such proposals and highlight actual developments in HTS cable design and REBCO tape optimization, e.g., for highest field. In addition, an optimization of round TSTC strand will be introduced, which is designed for simple fabrication in long lengths for versatile use either for the production of cables to be used at high fields or for power transmission.

High temperature superconducting cables and their performance against short circuit faults: current development, challenges, solutions, and future trends

Abstract: Along with advancements in superconducting technology, especially in high-temperature superconductors (HTSs), the use of these materials in power system applications is gaining outstanding attention. Due to the lower weight, capability of carrying higher currents, and the lower loss characteristic of HTS cables, compared to conventional counterparts, they are among the most focused large-scale applications of superconductors in power systems and transportation units. In near future, these cables will be installed as key elements not only in power systems but also in cryo-electrified transportation units, that take advantage of both cryogenics and superconducting technology simultaneously, e.g., hydrogen-powered aircraft. Given the sensitivity of the reliable and continuous performance of HTS cables, any failures, caused by faults, could be catastrophic, if they are not designed appropriately. Thus, fault analysis of superconducting cables is crucial for ensuring their safety, reliability, and stability, and also for characterising the behaviour of HTS cables under fault currents at the design stage. Many investigations have been conducted on the fault characterisation and analysis of HTS cables in the last few years. This paper aims to provide a topical review on all of these conducted studies, and will discuss the current challenges of HTS cables and after that current developments of fault behaviour of HTS cables will be presented, and then we will discuss the future trends and future challenges of superconducting cables regarding their fault performance.

AC Loss Analysis on a Quasi-Isotropic Strand Stacked by 2G Wires by Numerical Simulation in Cryogenic Temperature

Abstract: This paper mainly presents an ac loss numerical study of quasi-isotropic strands fabricated by second generation wires in cryogenic temperatures of 4.2 and 77 K. In order to estimate the ac losses accurately, a scaling relation of critical current density depending on the magnetic field and magnetic field angle with wire is adopted in the model. AC loss contributions, including hysteresis and eddy current losses, are estimated in detail at 5-Hz magnetic field with amplitude range from 0.1 to 7 T. At low fields and 4.2 K temperature, hysteresis losses of quasi-isotropic strands are less than the eddy current losses (which mainly comes from the copper sheath), this situation is very different from the 77 K. Effects of the magnetic field frequency and orientation with a strand on ac losses are also particularly analyzed under different magnetic fields. The numerical results are helpful for overall understanding on ac loss characteristics of quasi-isotropic strands and are also useful for their applications in high magnetic field at low temperatures.

Simulations of Bending and Twisting Mechanical Characteristics of a Cable Strand Made of REBCO Conductors at Cryogenic Temperatures

Abstract: High-temperature superconducting (HTS) materials, especially REBCO coated conductors (CCs), are promising for the application of high field magnets, current leads, and power devices. However, the current capacity is limited for a single CC. In recent years, several prototypes of cable, conductor, and strand were proposed and demonstrated in order to increase current capacity. Except for the high current capacity, the mechanical property is other one of the important factors in practical applications. This paper numerically analyzed the mechanical characteristics of a quasi-isotropic strand composed of four substrands by stacking ReBCO CCs in parallel, which mainly include dependencies of bending radii and twisting pitches on critical currents. The strain distributions of the strand in bending and twisting as well as combination of bending with twisting were calculated by the simulation method. The results are useful in application of high field and large-scale magnet and current lead in low temperature.