An Assessment of PIER Electric Grid Research 2003-2014 White Paper

This white paper describes the circumstances in California around the turn of the 21st century that led the California Energy Commission (CEC) to direct additional Public Interest Energy Research funds to address critical electric grid issues, especially those arising from integrating high penetrations of variable renewable generation with the electric grid. It contains an assessment of the beneficial science and technology advances of the resultant portfolio of electric grid research projects administered under the direction of the CEC by a competitively selected contractor, the University of California’s California Institute for Energy and the Environment, from 2003-2014

Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Experimental Characterization and Manufacture of Polymer Nanocomposite Dielectric Coatings for High-Temperature Superconductor Applications

Increased implementation of high-temperature superconducting (HTS) power transmission has the potential to revolutionize the efficiency of electrical grids and help unlock a fully electric transportation infrastructure. Realizing the benefits of HTS systems has been impeded by a lack of available dielectric insulation materials that can 1) withstand the extreme cryogenic operating environment of superconductors and 2) demonstrate low temperature processing that is compatible with existing superconductor manufacturing methods. Solving this problem necessitates a high-performance dielectric material with multifunctional properties specifically suited for operation in HTS systems. A polyamide and silicon dioxide (PA/SiO2) nanocomposite material with exceptional thermal stability has been developed as a solid dielectric coating solution. This study conducts mechanical, thermomechanical, and dielectric characterization efforts that explore multi-scale material property relationships in the nanocomposite to optimize it for this application. Additionally, an experimental manufacturing system is developed to provide a transition to large-scale processing of the nanocomposite coating material. The results of these efforts demonstrate a viable option to solve the material challenges impeding wider implementation of HTS power transmission and chart a path forward for the development of manufactured nanocomposite dielectrics

Fault management in networks incorporating Superconducting Cables (SCs) using Artificial Intelligence (AI) techniques.

With the increasing penetration of renewable energy sources, the immense growth in energy demand and the ageing of existing system infrastructure, future power systems have started to face reliability and resiliency challenges. To mitigate these issues, the need for bulk power corridors which enable the effective sharing of the available power capacity, between countries and from remote renewable energy sources, is rendered imperative. In this context, the deployment of multi-layer Superconducting Cables (SCs) with High Temperature Superconducting (HTS) tapes have been considered as a promising solution towards the modernisation of power systems. As opposed to conventional copper cables, SCs are characterised by a plethora of technically-attractive features such as compact structure, higher current-carrying capability, lower losses, higher power transfer at lower operating voltages and over longer distances, and reduced environmental impact. The performance of SCs is mainly determined by the structure of the cable and the electro-magneto-thermal properties of the HTS tapes, accounting for the critical current, critical temperature and critical magnetic field. Particularly, during steady state conditions, HTS tapes operate in superconducting mode, providing tangible benefits to power system operation such as a current-flowing path with approximately zero resistance. However, under certain transient conditions (e.g., electric faults), when the fault current flowing through HTS tapes reaches values higher than the critical current, HTS tapes start to quench. The quenching phenomenon is accompanied by a rapid increase in the equivalent resistance and temperature of SCs, the generation of Joule heating and the subsequent reduction in fault current magnitudes. Consequently, the transition of SCs from superconducting state to resistive state, during transient conditions, introduces many variables in the fault management of such cable technologies. Therefore, in order to exploit the technological advantages offered by SC applications, accommodate their wide-scale deployment within future energy grids, and accelerate their commercialisation, the detailed evaluation of their transient response and the consequent development of reliable fault management solutions are vital prerequisites. On that front, one of the main objectives of this thesis is to provide a detailed fault signature characterisation of AC and DC SCs and develop effective and practically feasible solutions for the fault management of AC and High Voltage Direct Current (HVDC) grids which incorporate SCs. As the fault management (i.e., fault detection, fault location, and protection) of SCs has proven to be a multi-variable problem, considering the complex structure, the unique features of SCs, and the quenching phenomenon, there is a need for advanced methods with immunity to these factors. In this context, the utilisation of Artificial Intelligence (AI) methods can be considered a very promising solution due to their capability to expose hidden patterns and acquire useful insights from the available data. Specifically, data-driven methods exhibit multifarious characteristics which allow them to provide innovative solutions for complex problems. Given their capacity for advanced learning and extensive data analysis, these methods merit thorough investigation for the fault management of SCs. Their inherent potential to adapt and uncover patterns in large datasets presents a compelling rationale for their exploration in enhancing the reliability and performance of superconducting cable systems. Therefore, this thesis proposes the development of novel, data-driven protection schemes which incorporate fault detection and classification elements for AC and multi-terminal HVDC systems with SCs, by exploiting the advantages of the latest trends in AI applications. In particular this thesis utilises cutting-edge developments and innovations in the field of AI, such as deep learning algorithms (i.e., CNN), and state-of-the-art techniques such as the XGBoost model which is a powerful ensemble learning algorithm. The developed schemes have been validated using simulation-based analysis. The obtained results confirm the enhanced sensitivity, speed, and discrimination capability of the developed schemes under various fault conditions and against other transient events, highlighting their superiority over other proposed methods or existing techniques. Furthermore, the generalisation capability of AI-assisted schemes has been verified against many adverse factors such as high values of fault resistance and noisy measurement. To further evaluate the practical feasibility and assess the time performance of the proposed schemes, real-time Software In the Loop (SIL) testing has been utilised. Another very important task for the effective fault management of AC and DC SCs is the estimation of the accurate fault location. Identifying the precise location of faults is crucial for SCs, given their complex structure and the challenging repair process. As such, this thesis proposes the design of a data-driven fault location scheme for AC systems with SCs. The developed scheme utilises pattern recognition techniques, such as image analysis, for feature extraction. It also incorporates AI algorithms in order to formulate the fault location problem as an AI regression problem. It is demonstrated that the scheme can accurately estimate the fault location along the SCs length and ensure increased reliability against a wide range of fault scenarios and noisy measurements. Further comparative analysis with other data-driven schemes validates the superiority of the proposed approach. In the final chapter the thesis summarises the key observations and outlines potential steps for further research in the field of fault management of superconducting-based systems.With the increasing penetration of renewable energy sources, the immense growth in energy demand and the ageing of existing system infrastructure, future power systems have started to face reliability and resiliency challenges. To mitigate these issues, the need for bulk power corridors which enable the effective sharing of the available power capacity, between countries and from remote renewable energy sources, is rendered imperative. In this context, the deployment of multi-layer Superconducting Cables (SCs) with High Temperature Superconducting (HTS) tapes have been considered as a promising solution towards the modernisation of power systems. As opposed to conventional copper cables, SCs are characterised by a plethora of technically-attractive features such as compact structure, higher current-carrying capability, lower losses, higher power transfer at lower operating voltages and over longer distances, and reduced environmental impact. The performance of SCs is mainly determined by the structure of the cable and the electro-magneto-thermal properties of the HTS tapes, accounting for the critical current, critical temperature and critical magnetic field. Particularly, during steady state conditions, HTS tapes operate in superconducting mode, providing tangible benefits to power system operation such as a current-flowing path with approximately zero resistance. However, under certain transient conditions (e.g., electric faults), when the fault current flowing through HTS tapes reaches values higher than the critical current, HTS tapes start to quench. The quenching phenomenon is accompanied by a rapid increase in the equivalent resistance and temperature of SCs, the generation of Joule heating and the subsequent reduction in fault current magnitudes. Consequently, the transition of SCs from superconducting state to resistive state, during transient conditions, introduces many variables in the fault management of such cable technologies. Therefore, in order to exploit the technological advantages offered by SC applications, accommodate their wide-scale deployment within future energy grids, and accelerate their commercialisation, the detailed evaluation of their transient response and the consequent development of reliable fault management solutions are vital prerequisites. On that front, one of the main objectives of this thesis is to provide a detailed fault signature characterisation of AC and DC SCs and develop effective and practically feasible solutions for the fault management of AC and High Voltage Direct Current (HVDC) grids which incorporate SCs. As the fault management (i.e., fault detection, fault location, and protection) of SCs has proven to be a multi-variable problem, considering the complex structure, the unique features of SCs, and the quenching phenomenon, there is a need for advanced methods with immunity to these factors. In this context, the utilisation of Artificial Intelligence (AI) methods can be considered a very promising solution due to their capability to expose hidden patterns and acquire useful insights from the available data. Specifically, data-driven methods exhibit multifarious characteristics which allow them to provide innovative solutions for complex problems. Given their capacity for advanced learning and extensive data analysis, these methods merit thorough investigation for the fault management of SCs. Their inherent potential to adapt and uncover patterns in large datasets presents a compelling rationale for their exploration in enhancing the reliability and performance of superconducting cable systems. Therefore, this thesis proposes the development of novel, data-driven protection schemes which incorporate fault detection and classification elements for AC and multi-terminal HVDC systems with SCs, by exploiting the advantages of the latest trends in AI applications. In particular this thesis utilises cutting-edge developments and innovations in the field of AI, such as deep learning algorithms (i.e., CNN), and state-of-the-art techniques such as the XGBoost model which is a powerful ensemble learning algorithm. The developed schemes have been validated using simulation-based analysis. The obtained results confirm the enhanced sensitivity, speed, and discrimination capability of the developed schemes under various fault conditions and against other transient events, highlighting their superiority over other proposed methods or existing techniques. Furthermore, the generalisation capability of AI-assisted schemes has been verified against many adverse factors such as high values of fault resistance and noisy measurement. To further evaluate the practical feasibility and assess the time performance of the proposed schemes, real-time Software In the Loop (SIL) testing has been utilised. Another very important task for the effective fault management of AC and DC SCs is the estimation of the accurate fault location. Identifying the precise location of faults is crucial for SCs, given their complex structure and the challenging repair process. As such, this thesis proposes the design of a data-driven fault location scheme for AC systems with SCs. The developed scheme utilises pattern recognition techniques, such as image analysis, for feature extraction. It also incorporates AI algorithms in order to formulate the fault location problem as an AI regression problem. It is demonstrated that the scheme can accurately estimate the fault location along the SCs length and ensure increased reliability against a wide range of fault scenarios and noisy measurements. Further comparative analysis with other data-driven schemes validates the superiority of the proposed approach. In the final chapter the thesis summarises the key observations and outlines potential steps for further research in the field of fault management of superconducting-based systems

A Review of Structural Health Monitoring Techniques as Applied to Composite Structures.

Structural Health Monitoring (SHM) is the process of collecting, interpreting, and analysing data from structures in order to determine its health status and the remaining life span. Composite materials have been extensively use in recent years in several industries with the aim at reducing the total weight of structures while improving their mechanical properties. However, composite materials are prone to develop damage when subjected to low to medium impacts (ie 1 – 10 m/s and 11 – 30 m/s respectively). Hence, the need to use SHM techniques to detect damage at the incipient initiation in composite materials is of high importance. Despite the availability of several SHM methods for the damage identification in composite structures, no single technique has proven suitable for all circumstances. Therefore, this paper offers some updated guidelines for the users of composites on some of the recent advances in SHM applied to composite structures; also, most of the studies reported in the literature seem to have concentrated on the flat composite plates and reinforced with synthetic fibre. There are relatively fewer stories on other structural configurations such as single or double curve structures and hybridised composites reinforced with natural and synthetic fibres as regards SHM

자기 공명 응용기기를 위한 고온 초전도 자석의 차폐 전류 해석 및 완화

학위논문(박사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2022. 8. 한승용.초전도 자석은 다량의 전류가 흐를 수 있는 한편 발열 손실이 거의 발생하지 않는다는 매력적인 특성을 바탕으로 강한 자석에 대한 엄청난 가능성을 가지고 있다. 그들은 실제로 고성능 및 대용량 응용기기를 위한 전자석에 대하여 혁신적인 기술을 가능하게 했다. 그 중에서도 초전도 자석은 상전도 자석 보다 높은 자기장 강도와 균일성을 제공함으로써 핵자기공명 및 자기공명영상 응용기기에 핵심적인 역할을 수행해 왔다. 지난 몇 년 동안, 저온 초전도 자석은 핵자기공명 및 자기공명 응용기기를 개발하는 데 있어 실로 핵심적인 역할을 했다. 그러나 핵자기공명 및 자기공명영상용 저온 초전도 자석의 최대 자기장 강도의 실질적인 한계에 도달했다. 따라서 고온 초전도 자석은 자기공명 응용기기, 즉 핵자기공명 및 자기공명영상 응용기기에서 저온 초전도 자석의 핵심 역할을 대체하기 위해 긍정적으로 검토되고 있으며 그 이유는 고온 초전도 선재는 저온 초전도 선재 대비 높은 자기장 환경에서 보다 우수한 전류 통전 용량을 가지고 있는 것으로 확인되었기 때문이다. 핵자기공명 및 자기공명영상 응용기기용 고온 초전도 자석을 개발하는 데 있어 중요한 과제는 차폐 전류 및 그 결과적 영향, 즉 차폐 전류 유도 자기장과 차폐 전류 유도 응력이다. 이와 관련하여, 차폐 전류로 인한 고 자기장 고온 초전도 자석의 전자기 및 기계적 고장에 대한 여러 연구가 보고되었다. 차폐 전류 유도 자기장은 공간 자기장 균일성 및 시간 자기장 안정성 측면에서 고온 초전도 자석의 자기 성능을 저하시킨다. 차폐 전류 유도 응력은 자석 작동에서 기계적 안정성을 저하시킨다. 이에 따라 고온 초전도 자석 분야에서는 수치 해석을 통한 차폐 전류의 심층적인 이해와 차폐 전류 및 그에 따른 영향을 완화하기 위한 실용적 기술이 시급한 상황이다. 본 논문에서는 자기공명 응용기기를 위한 고온 초전도 자석의 차폐 전류 문제를 다루는 것을 목표로 한다. 차폐 전류 특성을 모사 할 수 있는 수치 해석 방법이 부족하고 차폐 전류를 실질적으로 완화할 수 있는 실용적 기법이 부족한 것을 현재의 고온 초전도 자석 기술의 문제로 정의한다. 그런 다음 수치 해석과 실질적 기술의 두 가지 측면에서 두 가지 해결책이 제공된다. 각 해결책은 실험 연구를 통해 입증된다. 두가지 해결책에 대한 자세한 설명은 다음과 같다. 첫째, 차폐 전류와 그에 따른 영향을 모사하기 위해 수치 해석 방법을 연구한다. 차폐 전류 유도 효과를 설명하기 위해 여러 해석 방법이 개발된다. 예를 들어, 불균일한 전류 밀도, 고온 초전도 코일의 비선형 유도 전압, 공간 및 시간 자기장 거동 및 과도한 기계적 스트레스에 대한 해석 방법이 개발된다. 그런 다음 고온 초전도 핵자기공명 자석에 대한 분석 연구를 수행하여 차폐 전류와 그 영향을 설명함에 있어 제안된 수치 해석 방법의 유효성을 입증한다. 핵자기공명 응용기기을 위한 3~T 및 9.4~T 전 고온 초전도 자석이 분석 연구에 채택된다. 수치 해석의 계산 결과는 전압, 공간 자기장, 공간 자기장 균일성, 시간 자기장 안정성 및 자석 작동의 기계적 안정성 측면에서 측정된 결과와 비교된다. 그 결과 계산과 측정 결과 사이에 양호한 일치성이 확인되었다. 결론적으로, 비교 결과는 제안된 수치 해석 방법의 사용이 고온 초전도 자석의 차폐 전류에 의해 유도되는 비선형 전자기 거동을 설명하는 데 유효함을 시사한다. 둘째, 고온 초전도 코일의 차폐 전류를 완화하기 위한 실용적인 솔루션으로 최적 설계된 맞춤형 전기 히터를 제안한다. 해당 기술의 핵심 개념은 고온 초전도 코일의 온도 구배를 최적화하는 것이다. 완화 메커니즘은 선별전류의 특성에 따라 임계전류의 크기에 따라 달라지게 되는데 열지우개는 최적의 온도제어로 고온 초전도 코일 내 개별 권선의 임계전류의 크기를 의도적으로 낮추는 것을 목표로 한다. 고온 초전도 코일과 최적 설계된 전기 히터를 포함하는 초전도 모듈은 전도 냉각 설비에서 설계, 제작 및 실험 된다. 본 실험 연구를 통해 히터의 활성화로 인한 차폐 전류 유도 자기장 감소가 포착되었으며, 이는 차폐 전류가 완화됨을 의미한다. 실험 결과는 최적 설계된 전기히터를 사용하여 차폐 전류를 실질적으로 억제할 수 있는지 그 타당성을 검증한다. 비선형 수치 분석 방법으로 실험 후 분석을 수행한다. 그 결과, 온도 구배와 차폐 전류 유도 자기장 감소 측면에서 분석과 측정 결과 간의 양호한 일치성이 확인되었다. 결론적으로, 본 논문은 핵자기공명 및 자기공명이미지 용 저온 초전도 자석의 유망한 대안인 고온 초전도 자석의 문제점을 정의하고 수치해석 및 실용기법 측면에서 솔루션을 제공한다. 수치 및 실험 연구는 솔루션의 유효성을 확인한다. 이 논문의 주요 기여는 다음과 같이 요약된다. 첫째, 수치 해석 방법은 차폐 전류를 ``정확하게" 설명하기 위해 제안 및 시연되며 이 연구를 통해 선택된 차폐 전류 문제를 수치 방식으로 해결할 수 있을 것으로 기대 한다. 둘째, 열지우개는 고온 초전도 코일의 차폐 전류를 ``실질적으로" 완화하기 위해 제안 및 시연되었으며, 이 연구를 통해 실용적인 방식으로 차폐 전류 문제를 해결할 수 있을 것으로 기대한다. 이 해결책들을 통해 수치 해석 방법과 실용적인 기술의 부족으로 인한 차폐 전류 문제를 해결 할 수 있을 것이다. 따라서 나는 이 논문이 더 높은 자기장 강도와 균일성을 탐구하는 길을 열어줄 것이라고 믿는다. 마지막으로, 이 논문이 차세대 핵자기공명 및 자기공명영상 응용기기를 위한 고자기장 고온 초전도 자석의 새로운 지평을 열 수 있기를 바란다.Superconductor magnets hold immense promises for strong magnets based on the fascinating nature that high current can flow with negligible Joule-heating loss dissipation. They have indeed enabled a disruptive technology in high-field and large-power applications. Among the applications, superconductor magnets have played an essential role in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) applications by providing higher magnetic field intensity and uniformity---it is well-known that higher fields created by superconductor magnets can guarantee the higher performance of NMR and MRI applications. In the past years, low-temperature superconductor (LTS) magnets have played a key role in developing NMR and MRI applications. However, the practical limit of the maximum field intensity of LTS magnets has reached for NMR and MRI. Hence, recently, high-temperature superconductor (HTS) magnets have been positively reviewed to substitute the key role of LTS in magnetic resonance (MR) applications, i.e., NMR and MRI---it is identified that HTS conductors have a superior current-carrying capacity in high fields compared to their LTS counterparts. Significant challenges in developing HTS magnets for NMR and MRI applications are detrimental effects caused by screening current: e.g., screening current-induced field (SCF) and screening current-induced stress (SCS). Multiple studies of electromagnetic and mechanical failures of high field HTS magnets due to screening current have been reported. SCF degrades the magnetic performances of an HTS magnet in terms of spatial magnetic field uniformity and temporal magnetic field stability. SCS degrades mechanical stability in the magnet operation. Accordingly, an in-depth understanding of screening current with numerical simulation and a practical technique to mitigate screening current and its consequential effects are urgently required in the HTS magnet discipline. In this thesis, I thus aim to resolve selected screening current issues of detrimental effects on HTS magnets for MR applications. The lack of numerical simulation methods to explain screening current and the lack of practical techniques to mitigate screening current are defined as problems of the current HTS magnet technology. Then, two solutions are provided in the two aspects of numerical simulation and practical technique; each solution is demonstrated with experimental studies. The detailed descriptions for the two solutions are as follows. Numerical simulation methods are studied to elucidate screening current and its consequential effects. As a result, multiple simulation methods are developed to explain screening current-induced effects: e.g., non-uniform current density, nonlinear inductive voltage behaviors, spatial and temporal magnetic field behaviors, and excessive mechanical stress distribution. Then, numerical studies of HTS NMR magnets analysis are performed to demonstrate the validity of the proposed simulation methods for describing screening current and its detrimental effects. In this study, 3~T and 9.4 T all-HTS magnets for NMR applications are adopted. Calculation results from nonlinear numerical simulation are compared to measured ones in terms of voltages, spatial magnetic fields, spatial field uniformity, temporal field stability, and mechanical stability in the magnet operation. Good agreements between calculation and measurement results are confirmed. Conclusively, comparison results suggest that the use of proposed numerical simulation methods may be valid in describing nonlinear electromagnetic behaviors induced by screening current in an HTS magnet. A customized electric heater named ``Thermal Eraser" is discussed as a practical solution to mitigate detrimental effects caused by screening current. The key concept of Thermal Eraser is the optimal temperature control to degrade spatially distributed critical current. In detail, the mitigation mechanism is implemented by the nature of screening current depending on the critical current's magnitude. Here, Thermal Eraser intentionally lowers the magnitude of critical currents of individual windings in an HTS coil by the optimal temperature control. A superconducting module, including an HTS coil and a Thermal Eraser, is designed, constructed, and tested in a conduction cooling facility. With this experimental study, SCF reduction is captured due to activation of the Thermal Eraser, which implies screening current is mitigated. The test results validate the feasibility of using the Thermal Eraser in mitigating screening current. A post-experiment analysis is performed with the numerical analysis methods. As a result, good agreements between calculation and measurement results are confirmed in terms of temperature gradient and SCF reduction. In conclusion, this thesis defines issues of HTS magnet, which is a promising alternative to LTS magnet for NMR and MRI, and provides solutions in the aspect of numerical simulation methods and a practical mitigation technique. Numerical and experimental studies confirm the validity of the solutions. The key contributions of this thesis are summarized as follows. First, numerical simulation methods are proposed and demonstrated to ``precisely'' describe screening current, and they can address the selected screening current issues in a numerical way. Second, Thermal Eraser is proposed and demonstrated to ``substantially'' mitigate screening current in an HTS coil, and it can address the issues in a practical way. With the solutions, screening current issues caused by the lack of numerical simulation methods and practical techniques could be resolved. Therefore, I believe this thesis would pave the way to explore higher field intensity and uniformity. Finally, I hope this thesis opens a new horizon of high field HTS magnets for the next-generation NMR and MRI applications.1 Introduction 1 1.1 Research Motivation 2 1.1.1 High field HTS magnet for the next generation NMR and MRI 2 1.1.2 Key issues of high field HTS magnet: screening current 9 1.2 Research Object 12 1.2.1 Review of fundamental superconductivity and MR physics 13 1.2.2 Numerical methods to simulate screening current 14 1.2.3 Optimal temperature control to mitigate screening current 15 1.3 Thesis structure 16 2 Theoretical Background 18 2.1 Fundamental Physics of Superconductors 18 2.2 The Basics of Spin Physics and Magnetic Resonance 29 3 Numerical Methods to Simulate Screening Current and Its Detrimental Effects on HTS Magnet 41 3.1 Non-uniform Current Distribution Simulation Method 41 3.1.1 H formulation of Maxwell's equations for governing equation 43 3.1.2 The domain homogenization technique for integral contraint 45 3.2 Current and Voltage Behavior Simulation Method 47 3.2.1 Lumped-circuit model 48 3.2.2 Distributed-circuit model 49 3.3 Nonlinear Inductance Variation Simulation Method 52 3.3.1 Garrett's method and energy method 52 3.3.2 Modified inductance calculation methods 54 3.4 Spatial Harmonic Coefficients Simulation Method 63 3.4.1 Legendre expansion to describe spatial magnetic fields 64 3.4.2 "Segmentation" method to consider non-uniform current density 67 3.5 Mechanical Stress Distribution Simulation Method 75 3.5.1 Analytic formula-based method to analyze stress distribution 76 3.5.2 Finite element method to simulate stress distribution 80 4 Analysis Results of HTS NMR Magnets to Demonstrate Numerical Simulation Methods of Screening Current 83 4.1 Introduction to the Project of a 400 MHz 1H NMR Application Development using a 9.4 T All-HTS Magnet 83 4.2 Analysis Results of a 3 T All-HTS NMR Demo Magnet 84 4.3 Analysis Results of a 9.4 T All-HTS NMR Magnet 91 4.3.1 Key parameters of the 9.4 T HTS NMR magnet 91 4.3.2 Numerical simulation results 98 4.3.3 Comparison between simulation and measurement results 113 5 A Customized Heater to Mitigate Screening Current in HTS Coil by Optimal Temperature Control 125 5.1 Key Concept: Optimal Control of Critical Current with a Customized Heater named "Thermal Eraser" 125 5.2 Experimental Study to Validate the Feasibility of "Thermal Eraser" in Mitigating Screening Current 128 5.2.1 Design and simulation results 128 5.2.2 Construction and instrumentation results 132 5.2.3 Operation and evaluation results 135 6 Conclusion 141 Abstract (In Korean) 162박

1994 NASA-HU American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program

Since 1964, the National Aeronautics and Space Administration (NASA) has supported a program of summer faculty fellowships for engineering and science educators. In a series of collaborations between NASA research and development centers and nearby universities, engineering faculty members spend 10 weeks working with professional peers on research. The Summer Faculty Program Committee of the American Society for Engineering Education supervises the programs. Objectives: (1) To further the professional knowledge of qualified engineering and science faculty members; (2) To stimulate and exchange ideas between participants and NASA; (3) To enrich and refresh the research and teaching activities of participants' institutions; (4) To contribute to the research objectives of the NASA center

Protection of Future Electricity Systems

The electrical energy industry is undergoing dramatic changes: massive deployment of renewables, increasing share of DC networks at transmission and distribution levels, and at the same time, a continuing reduction in conventional synchronous generation, all contribute to a situation where a variety of technical and economic challenges emerge. As the society’s reliance on electrical power continues to increase as a result of international decarbonisation commitments, the need for secure and uninterrupted delivery of electrical energy to all customers has never been greater. Power system protection plays an important enabling role in future decarbonized energy systems. This book includes ten papers covering a wide range of topics related to protection system problems and solutions, such as adaptive protection, protection of HVDC and LVDC systems, unconventional or enhanced protection methods, protection of superconducting transmission cables, and high voltage lightning protection. This volume has been edited by Adam Dyśko, Senior Lecturer at the University of Strathclyde, UK, and Dimitrios Tzelepis, Research Fellow at the University of Strathclyde

Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors