Resistive-type Superconducting Fault Current Limiter (RSFCL) and Its Application in Power Systems

With the rapid increase in electrical loads, a considerable percentage of global power systems have been stretched to their designed capacity, leading to a sharp rise in the fault current. High fault current levels have severe impact on power systems. They can increase the likelihood of overcurrent damage, which may destroy electrical facilities or even cause system blackout. The resistive-type superconducting fault current limiter (RSFCL) is a device that can help to mitigate the increasing level of fault currents. It can also contribute to the performance, stability and efficiency of electricity grids. In order to promote the RSFCL more effectively, it is essential to study the device itself and conduct simulations regarding the performance and applicability from the system point of view. Chapter 1 and Chapter 2 of this thesis introduced fundamentals of superconductivity and RSFCLs, respectively. In Chapter 3, a power system model was built, and the transient analysis of short-circuit currents was given. Then, the operating principle of RSFCL was explained, and a step-resistance RSFCL model was introduced. To validate the current limiting performance of the SFCL module, wind farm protection schemes were studied under various fault scenarios. After thorough analysis it was concluded that the optimal allocating strategy of SFCLs was the installation of one SFCL at the integrating point of the system model. Chapter 4 presented a comprehensive study on the performance and optimal allocation strategy of RSFCLs. The two power system models used in this chapter were built based on the UK network standard. To assess the impact of incorporating SC material properties on the performance of SFCLs, three different models were compared throughout the study. Although computing time can be reduced when step-resistance and exponential equation models were used, such simplifications led to strong overestimations of the SFCL performance and resulted in wrong conclusion of optimal installing strategies. For both power system models, the simultaneous use of three SFCLs was the best protection strategy in terms of the performance, economic efficiency and reliability of the overall grids. To draw this conclusion, all the potential combinations of two, three, four, and five SFCLs were studied under a wide number of fault scenarios and measuring strategies. In Chapter 5, a series of experiments were performed to study the magnetic field-angular dependence of the critical current of different commercial YBCO samples. We selected ten 2G-HTS tapes with broad differences in width, fabrication process, and laminar structure. The obtained I_c (B,θ) characteristics of HTS samples were applied in the simulation of RSFCLs, showing unneglectable effect on the first peak limiting performance during faults. This study is helpful to the design and simulation of RSFCLs and other HTS applications which require superconducting wires operating inside magnetic fields. In Chapter 6, we presented a High Frequency (HF) AC-assisted quench study of the YBCO conductor. The differences in quench processes triggered by HF AC field were recorded and studied. We found that AC signals of 10 kHz can trigger quench of the HTS tape. Also, the device proved to be effective at guaranteeing uniform quench of the sample. After then, we placed the experimental device in a magnet, to study whether the quench process can be accelerated by external DC magnetic field. It was found that the DC field can reduce the quench time, but its performance was dependent on the amplitude of transport current and the characteristics of HF AC signals. In addition, the angle between the DC magnetic field and the tape surface showed a huge impact on the quench time. Finally, a comprehensive field-angular dependence study about the quench time of the YBCO sample was conducted, revealing the same pattern as J_c (θ,B) dependence of the tape, but with a greater anisotropy. To summarize, this technique showed outstanding performance regarding quench acceleration and tape protection, and therefore has huge potential to be applied in RSFCLs.China Scholarship Counci

Laboratory directed research and development. FY 1995 progress report

This document presents an overview of Laboratory Directed Research and Development Programs at Los Alamos. The nine technical disciplines in which research is described include materials, engineering and base technologies, plasma, fluids, and particle beams, chemistry, mathematics and computational science, atmic and molecular physics, geoscience, space science, and astrophysics, nuclear and particle physics, and biosciences. Brief descriptions are provided in the above programs

Study on the Mechanisms and Prediction Methods of Arcing Contact Erosion of High-voltage SF6 Circuit Breaker

High-voltage SF6 circuit breaker (SF6 HVCB) is a key equipment in the power transmission system for breaking the fault current and protecting the safe and stable operation of the power grid. In the process of current breaking, the arcing contacts will be eroded subjecting to the heat of the arc, which will seriously affect the capability of breaking current and the electrical lifetime of the HVCB, and further endanger the safe and stable operation of the power grid. The investigation of the erosion mechanisms and prediction methods of arcing contacts erosion of HVCB can advance the theory of contacts erosion, improve the accuracy of massloss prediction of the arcing contacts to provide reference for the condition maintenance of the equipment. This thesis takes the SF6 HVCB as the research object and strives to lay a theoretical foundation for the development of monitoring system of arcing contacts erosion. Based on a 245kV/40kA live tank SF6 HVCB, an arcing contact erosion experimental platform is built using a noval fiber-optic sensor system. The use of optical approaches effectively avoids electromagnetic interference in a practical scenario. Using the combination of high-speed camera and multiple reflective mirrors, the macroscopic behavior of the arc is observed, which provides important reference for the install location of sensors. By using a noval fiber-optic sensor system, combined with photodiode and high-speed spectrometer, the trajectory and time-varying spectra of the arc roots on the arc contact surface are monitored synchronously, offering abundant experimental data for further investigation of massloss prediction algorithm of arcing contacts erosion. Using the spatial domain chromatic method to predict the massloss of arcing contacts, the prediction accuracy is improved by 31.0% compared to the existing widely used arc energy accumulation method. The macroscopic behavior of the arc in the SF6 HVCB and its effects on arcing contact erosion are studied. Using high-speed photography technology, the shape of the arc column, the spatial distribution of metal vapor of the arc column, and the mobility of the arc root on the contact surface are observed. The effects of the shape of the arc column and the mobility of the arc root on the erosion process are interpreted. Using the spatial domain chromatic method, the trajectory of the arc root on the contact surface is measured. The mobility of the arc root at different current levels is studied and a method for the massloss prediction of the arcing contacts at relative low currents is proposed. A prediction method of massloss of arcing contacts based on chromatic analysis of arc spectra is proposed. Through the analysis of chromatic spectral data both in the wavelength domain and time domain, a series of chromatic parameters representing the erosion characteristics of the arcing contacts are obtained, and the contacts erosion modes at various current amplitudes are identified. Furthermore, the chromatic parameters which are closely related to the arc contact ablation are selected. In combination with the linear regression algorithm, the prediction method for massloss of the arcing contacts at relative high currents is explored, the accuracy of massloss prediction has been improved by 39.1% comparing with using the square of current. A 3D thermal model of arcing contact erosion considering the movement of the arc root and the structure of the copper-tungsten material is proposed. The temperature, mass loss rate, and change of contact surface geometry are simulated and compared with the experimental data and the simulation results of a fixed arc root model. The influence of the root movement on the erosion process is further verified and explained. The simulated results of massloss of arcing contacts are obtained

Particle Physics Reference Library

This third open access volume of the handbook series deals with accelerator physics, design, technology and operations, as well as with beam optics, dynamics and diagnostics. A joint CERN-Springer initiative, the “Particle Physics Reference Library” provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A,B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open acces