Fiber Bragg grating (FBG) temperature sensors are now re-garded as a relatively mature sensing technology for tempera-ture measurement in ambient conditions, and may offer poten-tial as a cryogenic temperature sensor for quench detection. In this work, the temperature response of three different coated FBG sensors from 77 K to 293 K was studied; bare (silica) FBG, acrylic coated, and polyimide coated FBG sensors. For compar-ison measurements were repeated with sensors from two FBG suppliers. The measured temperature response was then com-pared and contrasted with the predicted sensor response. In or-der to assess the sensor sensitivity, repeatability and any hyste-resis, these sensors were then subjected to repeated cool-down / warm-up cycles (77 $\times$ 293 K). Finally, the measurement of quench induced temperature change in an epoxy potted HTS coil was simulated through fabrication of bare FBG sensor embed-ded in a 10 mmμ2 mmν4 mm epoxy block. The effect of epoxy resin impregnation on the temperature response characteristics was analyzed by comparing the sensor response characteristics before and after immersion. From these results, we propose the most cost-effective and practical FBG type for HTS coil quench detection.

Flux diverters (FDs) are used in High Temperature Superconducting (HTS) transformers for AC loss reduction and flux optimization. In this paper, a 2D axial symmetric superconducting winding model is proposed and two designs of flux diverters are applied to the windings. A homogenization approach is used to analyze the windings with large turn numbers. The key parameters including the number, width, height and the spatial positions of the FDs are adjusted for AC loss and magnetic flux analysis. The means of obtaining optimum designs of the FDs is provided and can be used to develop new winding designs with FDs, which contributes to better electromagnetic performance and higher efficiency of HTS transformers.

Smart meters (SMs) are key components of the smart grid (SG) which gather electricity usage data from residences and businesses. Home area networks (HANs) are used to support two-way communications between SMs and devices within a building such as appliances. This can be implemented using power line communications (PLCs) via home wiring topologies. In this paper, a bottom-up approach is designed and a HAN-PLC channel model is obtained for a split-phase power system which includes branch circuits, an electric panel with circuit breakers and bars, a secondary transformer and the wiring of neighboring residences. A cell division (CD) method is proposed to construct the channel model. Furthermore, arc fault circuit interrupter (AFCI) and ground fault circuit interrupter (GFCI) circuit breaker models are developed. Several HAN-PLC channels are presented and compared with those obtained using existing models.

High temperature superconducting (HTS) is a key technology for next generation high-speed railway systems, which guarantees high current and highly efficient traction power supplies. HTS devices can reduce system weight and thus improve loads of vehicles. In high-speed maglev trains, HTS windings wound by second-generation HTS tapes play an important role in suspension and traction. However, in complex ferromagnetic environments, the performance of windings is notably influenced by the varying magnetic fields. In this paper, a new maglev platform is designed and comprised of a winding of six racetrack HTS coils, an E-shaped iron core and a magnetic guide rail. The air core structure of the winding is modeled and tested and the electromagnetic characteristics are analyzed for three dimensional finite element analysis of the platform. An A formulation is used to calculate magnetic vectors A and infer magnetic flux densities and current densities for the structures. After the winding is installed on the iron core and the magnetic guide rail is suspended above the iron core, the air gap between the iron core and the rail is varied from 0 mm to 20 mm in models and experiments. The magnetic fields, critical currents and losses of the winding in the cases of the air core and the iron core conditions are used for analysis. The comparison between the air core and the iron core conditions confirms the reliability of the proposed models. This study provides a means for the analysis of complex superconducting maglev systems.

Second generation (2G) high temperature superconducting (HTS) current leads can be applied in power systems of high speed railway vehicles and determine the performances of the systems. In this paper, five HTS current leads consist of 12 turns of HTS tapes are presented and meet a current carrying capacity requirement of 860 A. The leads are designed with single stack, triangular, quadrilateral, hexagonal, and dodecagonal structures. Finite element method (FEM) is used to build 3D current lead models. Further, magnetic vector potential A is used to calculate electromagnetic fields for analysis. The current distribution, magnetic field distribution and losses of the current leads are obtained and the influence of the structures are investigated, which provide means for optimization designs of HTS current leads for high current applications. Experiments and modeling results of a 24 turn dodecagonal current lead are compared, which proves the effectiveness of this method.

High-temperature superconductor (HTS) has found its way into both ac and dc transmission; yet HTS technology was not specially designed for either transmission type. Now critical current of HTS in dc circumstance is defined, while research on ac current-carrying capability of HTS is still scarce. A new critical current criterion of the ac condition should be established for further studies. In the paper, different dc critical current measurement methods were applied to analyze ac critical current. The E-I curves were obtained by the four-probe method and the frequency ranges from 30 to 540 Hz. The ac current carrying capacity of the superconductors is discussed and analyzed by the RMS method, virtual n value method, and the loss concept method. A criterion of ac critical current was proposed. The RMS method and the virtual n value method are no longer applicable in broad frequency band. While the loss concept method is still applied to explain the theory of critical current which varies with frequency; therefore, an ac critical current calculation method is obtained and the calculative equation at different frequencies is established.