High temperature superconducting magnetic energy storage systems (HTS SMES) have attracted significant attention for fast response and ensure a reliable power supply. However, the current carrying capacity of single superconducting tape often meets limitation for the large scale HTS SMES applied in the power grid. Therefore, a high temperature superconducting composite cable with inner helical cooling tunnel and kA class current carrying ability is proposed for SMES magnet by using REBCO tape. The critical current characteristics of this internal cooling composite cable are analyzed considering the influence of anisotropy in magnetic field. A 100 m length, high temperature composite cable is manufactured in China Electric Power Research Institute (CEPRI). The critical current experimental system with a 3 kA DC current power source and a high-precision Digital Data Acquisition system have been set up to investigate the current carrying ability of a straight and a bending demo composite cable in LN2. The results show that critical current of HTS composite cable consisted of 4 REBCO tapes can achieve 780 A at 77 K self-field and the experimental I-V curve of each REBCO tape in the composite cable is not uniform because of the influence of anisotropy. When the HTS composite cable is bent, its critical current is about 90% of the straight HTS composite cable. Therefore, the design method and the proposed experimental system are proved to be effective as well.

High-current high temperature superconducting (HTS) cables have been developed for use in HTS power devices. This paper presented the structures of HTS cables, including Conductor on Round Core (CORC) cable, Twisted Stacked-tape Conductor (TSTC) cable, and Double coaxial cable. Subsequently, three-dimensional finite element method numerical models were built to analyze the electromagnetic characteristics of the cables, and the critical current of the cables is about 380 Ampere @77 K, self-field. Using the T-A formulation, the numerical model assumed a sheet approximation for conductors, which shortened computational time. The T-A formulation were verified by experiments on a superconducting tape. Then HTS cables with different configurations were made, as functions of different transport current and background magnetic field, and different pitches of Double Coaxial Cable inner conducting layer. According to the results, the ac losses of Double coaxial cable and CORC cable decreased 40% than the TSTC cable with different transport current, and the Double coaxial cable ac loss decreased 20% than the CORC cable when background magnetic field was in the range of 20-60 mT. Conclusions obtained from this study will be helpful for understanding the ac loss properties of HTS cables and useful in design of HTS power devices (such as HTS transformer), using HTS cables.

Superconducting fault current limiter (SFCL) can reduce the capacity of the circuit breaker and lower the cost of line construction, it becomes more and more popular for the application in a high-voltage transmission line. A novel superconducting fault current limiter with bias magnetic flux is proposed by using a reactor with symmetrical double split copper windings and a non-inductive YBCO magnet which is in series to one branch winding. The models of the non-inductive superconducting element and the reactor are established based on MATLAB/SIMULINK. The performance is analyzed through the simulation of a prototype SFCL. The response speed, overvoltage and overcurrent characteristics considering the influence of different fault current are compared and the robustness of the SFCL in a power system are discussed. The simulation results validate the effectiveness of the flux coupling SFCL.

The Superconducting Magnet Energy Storage (SMES) will be more and more popular in the electric power system in the near future. A toroidal SMES magnet with large capacity is a tendency for SMES because it has great energy density and low stray field. Firstly, a toroidal HTS-SMES magnet model is built to obtain the maximum value of the perpendicular magnetic field by the finite element method (FEM), and then the storage energy is calculated. Secondly, the operating current Iop=1kA and internal radius Ri=150mm keep unchangeable to research the relationship for the storage energy E, the number of double pancake coil (DPC) n wound by 150m YBCO tapes and the distance from the element coil center to the toroidal magnet center R. Finally, a 3 MJ toroidal HTS-SMES magnet is designed using the characteristic analysis results and its distribution of magnetic induction intensity and stray field are discussed in detail.

An MJ-class superconducting magnetic energy storage (SMES) system has a wide range of potential applications in electric power systems. The composite high-temperature superconducting HTS conductor, which has the advantages of carrying large critical currents and withstanding high magnetic fields, is suitable for winding an MJ-class magnet coil. However, the Lorentz force of an HTS wire is so large that its induced mechanical stresses should be examined to ensure that the magnet is in good condition. By means of the equivalent material properties method and the sequential coupling method, this paper studies the mechanical properties of a three MJ toroidal SMES magnet wound by a compositeHTSconductor. Based on the electromagnetic-structural coupling analysis, the Von-Mises stress, the radial stress, and the hoop stress of amagnet coil are calculated and employed to validate the stability of the MJ-class toroidal SMES magnet.

The high-temperature superconducting magnet energy storage (HTS-SMES) system can increase the operation temperature range to 20~77K which is dramatically beneficial to the cost of refrigeration.Energy storage magnet is considered as one of the most important components in HTS-SMES system and its electromagnetic optimization design is the fundamental issue in the design of a HTS-SMES magnet.The toroial configuration of SEMS is applied in this paper due to its great energy density and low stray field.And the REBCO coated conductor is used to wind the toroidal HTS-SMES magnet.Based on the magneto-circuit coupling analysis method, an electromagnetic optimization design method for a toroidal HTS-SMES magnet using Matlab and COMSOL is proposed.The distribution of magnetic induction intensity and the stray field of the toroidal HTS-SMES magnet in the operating condition are calculated.And the configuration of the toroidal HTS-SMES magnet is obtained to achieve the maximum storage energy with a given temperature and a fixed length for REBCO tapes.The results indicate that there is little difference in the storage energy in spite of the changes in the number of element coils.Besides, the storage energy increase at first, and then decrease with the increase in the number of element coils.The storage energy can be visibly increased after optimizing by the proposed method which have a great effect on seeking structure parameters of the toroidal HTS-SMES magnet to maximize the storage energy.