Graduate School of Engineering, The University of Tokyo, Japan1
Graduate School of Frontier Sciences, The University of Tokyo, Japan2
A resistive type SFCL using REBCO tapes has shown high potential in limiting fault currents rapidly and improving the power system reliability [1]. REBCO coils are the key component of such SFCL. They are usually wound in solenoid type, pancake type, etc. with inductance or without inductance like a helical bifilar coil. Current distribution deviation in the tape’s width direction of a REBCO coil is observed because of the magnetic field generated by itself. Therefore, it is necessary to study the current distribution deviation in different coil types, and the influence of this deviation together with the local JC degradation on the hot-spot phenomenon under overcurrent.
In this paper, we have developed a 3D electromagnetic and thermal field coupled FEM analysis model to study the transient characteristics of an SFCL REBCO coil immersed in liquid nitrogen. A thin-plate approximation and coordinate transformation (from Cartesian coordinates system to orthogonal curvilinear coordinate system) is utilized to conduct the electromagnetic analysis of REBCO coils in 2D calculation space which have 3D structures. The governing electromagnetic equation is given by ∇×(ρ∇×T)=-∂B/dt (T: current vector potential; ρ: electric resistivity; B: magnetic flux density), where T is defined by J=∇×T (J: current density). In thermal analysis, the 3D structure of REBCO coil is modeled and the temperature rise is calculated under the condition of Joule heating, heat conduction, heat transfer, and cooling characteristics of liquid nitrogen [2]. With this analysis model, we have studied the difference in current distribution deviation between REBCO coils with inductance and without inductance during the rise of the current. Furthermore, we investigated the influence of the current distribution deviation and the local JC degradation on the hot-spot phenomenon under overcurrent.
References
[1] H. S. Ruiz, X. Zhang, and T. A. Coombs, “Resistive-Type Superconducting Fault Current Limiters: Concepts, Materials, and Numerical Modeling,” IEEE Transactions on Applied Superconductivity, vol. 25, no. 3, pp. 1–5, Jun. 2015
[2] K. Qian, T. Shiratani, Y. Terao, and H. Ohsaki, “Three-Dimensional Thermal Analysis of an SFCL REBCO Coil Immersed in Liquid Nitrogen,” J. Phys.: Conf. Ser., vol. 1054, no. 1, p. 012078, 2018
Keywords: superconducting fault current limiter, finite element method, coated conductor, 3D electromagnetic and thermal analysis