An efficient two dimensional T-A formulation based approach is proposed to calculate the electromagnetic characteristics of tape stacks and coils made of second generation high temperature superconductors. In the approach, a thin strip approximation of the superconductor is used in which the superconducting layer is modeled as a 1-dimensional domain. The formulation is mainly based on the calculation of the current vector potential T in the superconductor layer and the calculation of the magnetic vector potential A in the whole space, which are coupled together in the model. Compared with previous T-based models, the proposed model is innovative in terms of magnetic vector potential A solving, which is achieved by using the differential method, instead of the integral method. To validate the T-A formulation model, it is used to simulate racetrack coils made of second generation high temperature superconducting (2G HTS) tape, and the results are compared with the experimentally obtained data on the AC loss. The results show that the T-A formulation is accurate and efficient in calculating 2G HTS coils, including magnetic field distribution, current density distribution, and AC loss. Finally, the proposed model is used for simulating a 2000 turn coil to demonstrate its effectiveness and efficiency in simulating large-scale 2G HTS coils.

High temperature superconducting (HTS) tri-axial CORC cable has been a potential candidate for the transmission line used in an all-electric aircraft because of its advantages such as compactness, high power density and reduced usage of HTS tapes. A tri-axial CORC HTS cable (10 MW, 3 kV/2 kA) is being developed in University of Bath in cooperating with Airbus. AC/DC converters, generators and motors will induce harmonic currents in the power system of a hybrid electrical aircraft. It may considerably affect the AC loss of the transmission cable, which is one of the key factors determining the efficiency of the cable. This paper studies the transport AC losses of this tri-axial CORC cable and the influence of harmonic current on the losses. A finite element method (FEM) model has been developed based on T-A formulation to analyze the dynamic electromagnetic behavior of this tri-axial CORC cable. Analyses are performed under rated load with & without harmonic currents. Results show that the transport AC loss has a significant non-uniform distribution among three phases even under a three-phase balanced load. A small harmonic current (less than 10 %) can considerably increase the AC loss of the tri-axial cable (up to 40 %).

Low-inductance solenoidal coils, which usually refer to the nonintersecting type and the braid type, have already been employed to build superconducting fault current limiters because of their fast recovery and low inductance characteristics. However, despite their usage there is still no systematical simulation work concerning the AC loss characteristics of the coils built with 2G high temperature superconducting tapes perhaps because of their complicated structure. In this paper, a new method is proposed to simulate both types of coils with 2D axisymmetric models solved by H formulation. Following the simulation work, AC losses of both types of low inductance solenoidal coils are compared numerically and experimentally, which verify that the model works well in simulating non-inductive coils. Finally, simulation works show that pitch has significant impact to AC loss of both types of coils and the inter-layer separation has different impact to the AC loss of braid type of coil in case of different applied currents. The model provides an effective tool for the design optimisation of SFCLs built with non-inductive solenoidal coils.

This paper details the key outputs of the UK's first feasibility study of implementing the High Temperature Superconducting (HTS) cables in electricity distribution networks to solve capacity issues. This project is mainly aimed to study the technical and economic aspects of using superconducting cables and comparing them with the existing approaches, to determine whether a demonstration project of the superconducting solution is feasible. The University of Bath in collaboration with Western Power Distribution (WPD) has conducted this study, considering a previous capacity issue in WPD's network using both conventional and superconducting solutions.The first part of the study investigated the different aspects (installation procedures, power capacity, capital and operational costs etc.) of superconducting cables, comparing them with conventional cables. This identified the unique benefit of the high power density of HTS cables which could allow the usage of a Low Voltage (LV) Superconducting cable in place of a High Voltage (HV) conventional cable. In the second part of the study, a 132kV site in WPD's network that required reinforcement has been chosen for performing the feasibility study.As part of this study, a detailed Cost Benefit Analysis (CBA) was conducted, comparing the superconducting solution with the conventional solution. The outputs from the Present Value (PV) analysis, that has been carried out as part of the CBA are discussed. The results of the CBA power system studies performed are presented, evaluating the impact that each solution has on the network power flows, losses and fault levels. Finally, based on the outputs from the CBA and future projections in the costs of superconducting cables, recommendations were made for the usage of superconducting cables in UK electricity distribution networks to solve network capacity issues. 

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