Coaxial HTS Research Articles

Numerical Analysis on Three-phase Coaxial HTS Cable With Copper Protective Layers

Numerical Analysis on Three-phase Coaxial HTS Cable With Copper Protective Layers

Study on AC Losses and Influencing Factors of Three-Phase Coaxial HTS Cable Under Harmonic Current

Study on AC Losses and Influencing Factors of Three-Phase Coaxial HTS Cable Under Harmonic Current

Influence of the Relative Position of Conductors Constituting Each Phase on the AC Loss in a Three-Phase Coaxial HTS Cable

Influence of the Relative Position of Conductors Constituting Each Phase on the AC Loss in a Three-Phase Coaxial HTS Cable

Optimization of a Three-Phase Coaxial 10 kV/1.5 kA HTS Power Cable for Balancing 3-Phase Current Distribution

With the increasing power load of urban power grid, the upgrading of conventional cable is facing with the problem of space resource shortage. Three-phase coaxial high temperature superconducting cable has the advantages of compact structure, low loss, and nearly 2/3 reduction in the consumption of HTS tape, which provides a new prospective solution for urban expansion. However, due to the different radius of each phase of the three-phase coaxial HTS cable, the symmetry of electromagnetic parameters of each phase are affected, resulting in the imbalance of the three-phase current, which will reduce the transmission efficiency. Based on the multi-loop method, we establish the differential equation of three-phase coaxial superconducting cable in this paper, by calculating the parameters of three-phase inductance and capacitance by a numerical method, and obtain the instantaneous variation rule of voltage and current in the three-phase coaxial HTS cable. We propose a novel two-section Particle Swarm Optimization to solve the problem of three-phase current imbalance in HTS cable. The algorithm divides the C-phase conductor and the copper shield layer into two segments with the same radius but different pitches and twist directions, which increases the variable by one-half. By changing the pitches and winding directions, considering the thickness of the insulation, optimization of current distribution of three-phase coaxial HTS cable is achieved. Finally, we designed a 10 kV/1.5 kA three-phase coaxial HTS cable. The results show that the current imbalance ratio of the superconducting cable is reduced from 41% to 1% after the two-section Particle Swarm Optimization. The mathematical model and the imbalance optimization algorithm of three-phase coaxial HTS cable both are verified. The optimization results provide important reference for the structural design and experimental research of three-phase coaxial HTS cable for urban power grid.

Compact 2G HTS power cable: new cold tests results

In Russian Scientific R&D Cable Institute we continue studies to develop as compact as possible 2G HTS power cables for electric power systems. Compact cables should have minimized diameter compared to other co-axial HTS cables developed before. Recently we developed the cable prototype with four HTS layers in the core and two layers in the shield. Numerical optimization of compact cables has been used together with manufacturing technology to produce small diameter cables with uniform current distribution. The first cold test of the compact cable demonstrated that we were able to control the homogeneous current distributions in a compact cable with the inner diameter of the core ~10 mm and the outer diameter of the shield ~20 mm. In this work we present more test results of this cable, including, mechanical test and high voltage tests. New test results demonstrated very high parameters of the compact cable developed. The compact cables perspectives for electric systems are discussed.

Insulation design of ±10kV bipolar coaxial HTS DC cable

The high-temperature superconducting cable has low loss and high current-carrying density, and has extensive research prospects in power system transmission. In recent years, the advantages of DC transmission over long distances have become more and more obvious, and superconducting DC transmission has also become a research hotspot. Bipolar coaxial DC cable has a good economy, compact structure, and greater transmission power density, but also requires higher insulation, so the insulation design is particularly important. In this paper, a 10 kV / 6000 A / 10 m bipolar coaxial superconducting DC cable with a cold insulation structure is considered. In consideration of DC withstand voltage and lightning shock, an insulation design is carried out and a type test is performed. The test results meet the cable insulation requirements.

Cold test and numerical analysis of the compact 2G HTS power cable

The R&D project is underway in the Russian Cable Institute to reduce mass and dimensions of HTS cables for such applications as electrical aircrafts or ship propulsion systems. Such compact cables should have minimized diameter compared to other co-axial HTS cables developed before. Recently we developed and tested the compact cable prototype with three layers in the core and two layers in the shield. As continuation of this project we developed the new cable prototype with four HTS layers in the core and two layers in the shield. Narrower 2G HTS tape with 3 mm width has been used for this cable. Numerical optimization of the cable with analysis of manufacturing errors influence on current distribution has been performed. The method to produce small diameter cable with uniform current distribution has been suggested. The cold test of the compact cable manufactured has been performed at the Russian Cable Institute test facility. We demonstrated that we can control the homogeneous current distributions in a compact cable with the inner diameter of the core ~10 mm and the outer diameter of the shield ~20 mm. AC loss measurements in the compact cable demonstrated that they are close to those in previously tested HTS 2G cables with larger diameters.

Simulation Analysis and Experimental Tests of a Small-Scale Flux-Coupling Type Superconducting Fault Current Limiter

Superconducting fault current limiter (SFCL) is able to efficiently solve the short-circuit problems occurred in the modern power system. In this paper, the simulation analysis and experimental tests of a small-scale flux-coupling type SFCL (FC-SFCL) are carried out. In regard to the developed 400 V/20 A small-scale prototype of the FC-SFCL, it is composed of two coaxial HTS windings carrying current in reverse directions, two metal oxide varistors, and a controlled switch. The parameter design of the FC-SFCL prototype is presented. Based on the simulations, the design scheme's effectiveness can be confirmed from the higher current-limiting ratio, and the SFCL has lower average ac losses under normal condition. The experimental results are in accord with the simulation ones, and the current-limiting characteristics of the FC-SFCL can be well verified.

Modeling of Second Generation HTS Cables for Grid Fault Analysis Applied to Power System Simulation

HTS power cable systems are an emerging technology aimed at competing with XLPE cable systems. Knowledge on the thermal operating conditions of HTS power devices is needed to estimate their availability when connected to a power system, because the HTS material must remain below its critical temperature to transport current. In this work, a simple finite difference method is used to assess the temperature distribution at certain cross-section of a second-generation coaxial HTS cable. This method has been implemented in MATLAB and its proper functioning has been verified with the software package FLUX. This method is a tool to establish temperature distributions among HTS cable layers under normal operating conditions. Additionally, the aim of this work is to serve as basis for future simulations including heat generation changes within the cable layers typically caused by grid fault events.

Quench-induced partial discharge characteristics of HTS cables

This paper discusses the partial discharge (PD) characteristics of HTS cables under quench condition, where the thermal stress due to quench would be transiently superposed on the electric field stress under the operating voltage of HTS cables. Such electrical insulation characteristics under thermal/electrical combined stress can be referred to as the "quench-induced PD characteristics" of HTS cables, which should be taken into account for the reliable insulation design of HTS cables. Experimental results using coaxial HTS cable samples revealed that the quench-induced PD could be generated, even under the intrinsic or static PD inception voltage (PDIVsta) without the quench. The criteria of the thermal/electrical combined stress level for quench-induced PD inception were quantified for different LN2 pressures and fault durations under sub-cooled condition.