Search

High temperature superconducting (HTS) cable represents a promising solution for fulfilling the power demands of cities with large loads and high density. However, due to their connection to the distribution network, HTS cables are vulnerable to fault currents exceeding ten times their rated current, which poses a serious threat to both the safety of the cable and the operation of the grid. Considering the highly nonlinear nature of superconducting conductivity, this study develops a field–circuit coupling model to investigate the transient characteristics of distribution networks incorporating superconducting cables (DNSC). Firstly, a finite element model based on the two-dimensional H formulation was built to calculate the electrical and thermal parameters of the HTS cable. Subsequently, an equivalent circuit model of the distribution network was employed to estimate the short-circuit currents. Communicating via a co-simulation server, the superconducting cable current and distribution network impedance were updated in each step. Further, based on an actual DNSC system in Shenzhen, China, the highest quenching temperature of the cable and the maximum fault current of busbars were assessed. Finally, by integrating current limiters into the system, the withstand capability of the cable and busbars was determined, which indicates that the improved protection configuration can effectively suppress fault currents and ensure safe operation. Successfully applied to an actual distribution network, the co-simulation model utilizing the field–circuit coupling method addresses the challenges of solving highly nonlinear and time-varying systems, enabling transient analysis and protection research for the integration of superconducting devices into the conventional grid. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) cables have advantages of low loss and large capacity transmission. In order to analyze and protect the HTS cable, especially in the transient process, this paper develops a new method to analyze its thermal properties. Based on the structure parameters and actual working conditions of three-phase coaxial (tri-axial) HTS cable a two-dimensional (2-D) axisymmetric finite element simulation model along the axis was built in COMSOL. By coupling first and then decoupling, the temperature distribution was studied under the conditions of cooling, rated current, cryogenic system failure, local hot spot and short circuit fault. This method solves the problem that non-isothermal flow (nitf) is hard to converge under transient conditions, and has the advantages of simple and accurate. [ABSTRACT FROM AUTHOR]

• A PF model is proposed for thermo-electro-mechanical fracture in flexoelectric solids. • The PF model is validated by studying representative numerical examples. • The multi-physical effects on the fracture behavior can be well characterized. • The PF model can predict complex crack paths in flexoelectric solids. Piezoelectrics working in a temperature varying environment are prone to thermo-electro-mechanical fracture due to their brittle nature. In the meantime, flexoelectricity can greatly influence the fracture behavior of piezoelectrics since large strain gradients exist near the crack tip. In this paper, a novel phase field model is developed to investigate the thermo-electro-mechanical fracture behavior of piezoelectrics with consideration of the flexoelectric effect. In the proposed phase field model, the crack surfaces are assumed to be thermally adiabatic and electrically impermeable. The damage driving force is derived from the Clausius-Duhem inequality where the mechanical part is regarded as the driving force for the crack evolution. The mechanical driving force is decomposed to properly characterize the mixed mode crack propagation behavior. The governing equations of the four-field-problem are derived from the variational principle and solved numerically with the mixed finite element method. The fracture behavior of the flexoelectric solid under combined thermal, electrical and mechanical loads is then investigated by phase field modelling. The numerical results indicate that the proposed phase field model can well characterize the multi-physical effects and predict complex crack propagation trajectories in flexoelectric solids. Besides the mechanical and electrical loads, the thermal effect, the flexoelectric effect and the temperature dependence of the flexoelectric coefficients can all have significant influences on the thermo-electro-mechanical fracture behavior of flexoelectric solids. The present phase field model can thus act as a promising numerical tool to predict the reliability of flexoelectric components working in a temperature varying environment. [ABSTRACT FROM AUTHOR]