Method for estimating future markets for high-temperature superconducting power devices

This paper describes a spreadsheet model for estimating the impact of high-temperature superconducting (HTS) power devices on the national electric grid. The distribution of losses in the national grid is carefully traced and those losses that HTS can eliminate are identified. The energy savings achievable by the many sizes of HTS generators, transformers, cables, and motors are then computed and totaled using a spreadsheet analysis. The economic savings are very sensitive to the price (and J/sub e/) of HTS wire, and to the cost of cooling the devices to operating temperature. A market penetration model is used to estimate how fast HTS devices become commercially,successful. The emphasis of the paper is the analytic tool, not the numerical results of one specific case. This entire model is explicitly designed to allow others to enter their own estimated parameters and arrive at their own conclusions.     

Transforming transformers [superconducting windings]

Use of high-temperature superconducting (HTS) windings may soon turn power transformers into compact high-performers on good terms with the environment. The potential for HTS transformers is being examined in major design and hardware development programs by several teams of engineers and scientists worldwide. The team to which the authors belong is led by Waukesha Electric Systems. The Waukesha-led team has conducted a series of reference designs concentrating mostly on a 30-MVA, 138-kV/13.8-kV transformer rating. This rating is representative of a medium power transformer class foreseen as comprising about half of all US power transformer sales in the next two decades. Two of these designed are compared with a 30-MVA conventional oil-filled transformer typical of this class. Each uses a different commercially successful and reliable type of refrigeration. Since reliable operation is paramount, both transformers are designed to have a several-day on-board refrigeration reserve that lets them operate continuously with no interruption of service to customers     

Development of HTS Transformers and a 10 kVA HTS Transformer Prototype Design

With the improvement of high temperature superconductor （HTS） practical performance, research and development concerning the applications of HTS transformers have been progressed actively worldwide. This paper provides a comprehensive summary on various HTS transformers, and studies the design of a single-phase 10 kVA （220V/24V） HTS transformer prototype to verify HTS for practical transformer applications.     

Development status of rotating machines employing superconducting field windings

Superconducting rotating machines have looked promising since multifilamentary niobium-titanium (NbTi) superconductors became available in the mid-1960s. Both dc homopolar and ac synchronous machines were successfully tested from the 1970s to the 1990s. Three different 70-MW generators were recently demonstrated by the SuperGM project in Japan. However, economic considerations with respect to competitive cost combined with the requirement for liquid helium cooling did not make these machines commercially attractive. On the other hand, high-temperature superconductors (HTSs) can operate at much higher temperatures (30-40 K), providing much larger thermal margin and simpler cooling systems. This refrigeration advantage has provided new impetus to the development of such machines for commercial applications. In the last few years, a number of superconducting rotating machines with HTS field windings have been demonstrated and several projects are currently transitioning to advanced development stages. HTS machines with ratings from a few kilowatts to several megawatts have been demonstrated in the United States and Europe. Currently, large high-torque ship propulsion motors, large generator prototypes, and synchronous condensers are under development and are expected to be commercially available in the next few years. Prospects for improved life cycle cost, smaller size, less weight, and higher efficiency benefits are providing incentives for the development of these larger rating HTS machines. This paper reviews the past and recent progress on the worldwide development of industrial-grade superconducting rotating machines utilizing low-temperature superconductor and HTS field windings and provides an outlook on the benefits and opportunities of this new technology.     

Magnetization Loss and Shield Effect in Multi-Stacked Tapes With Various Stacking Configurations

AC loss is one of the major topics in large AC power applications using high temperature superconductor such as power transformers, transmission cables and fault current limiters because it is closely related to operation efficiency. Multi-stacked tape conductors should be used to transport the large current in those power applications. A research of various arrangements of HTS tapes for multi-stacked tapes has been performed to increase the capacity of transport current in HTS power applications. In this paper, we studied magnetization loss and shield effect from several different arrangements of BSCCO tapes such as Face-to-Face type, regular matrix type (m$times$2) and irregular matrix type. The results show that the magnetization loss of the Face-to-Face arrangement was lower than those of the other matrix types for the same stacking numbers. We think that the result was due to the shield effect by demagnetization of adjacent HTS tapes which were located as face to face.     

Performance of an HTS Generator Field Coil Under System Fault Conditions

High-temperature superconducting (HTS) coils are generally stable against transient thermal disturbances. Protection against spontaneous quenches is not a main design issue for an HTS coil. However, HTS coils used in many electric devices such as motors, generators, transformers, and current limiters will operate under over-current fault conditions, which may result in a coil quench and thermal runaway. Those electric devices should be able to ride through some grid fault conditions and remain functional. This requires a certain over-current capability of the HTS coils. This paper discusses the over-current requirements from grid faults and the thermal transient responses of a BSCCO coil. It presents the analysis results of the coil subjected to over-current pulses at different operating conditions. The study also investigates the thermal runaway current and its relationship with the over-current pulse     

Magneto-Thermal Modeling of Second-Generation HTS for Resistive Fault Current Limiter Design Purposes

Coated conductors (CCs) are very promising for the design of novel and efficient resistive fault current limiters (FCLs). However, a detailed knowledge about their thermal and electromagnetic behaviors in the presence of over-critical currents is crucial for their improvement. In this context, we performed finite-element magneto-thermal modeling of CCs under over-critical current on several geometries. Accordingly, we have investigated the influence of the physical properties of stabilizer and substrate on the thermal stability to improve the high-temperature superconductor (HTS)-FCL design. All simulations were performed using COMSOL Multiphysics, a commercial finite-element package, which has a built-in coupling between the thermal and electrical equations, allowing us to compute both quantities simultaneously during the solving process. Our results allow us to determine the current threshold to achieve thermal stability of HTS FCLs made with CCs.     

High capacity cable's role in once and future grids

High temperature superconducting (HTS) cables cooled to 77 K are starting to be tested and could soon be carrying a lot more current through the same old underground city pipes. If superconducting transmission cables can be made to work compatibly with other emerging high-temperature superconducting technologies then it may be possible to layout grids in innovative ways and to position generators closer to customers without having to step voltage up and down. Conventional underground cables normally incorporate fluid, such that the use of liquid-nitrogen coolant in superconducting cables is not such a departure as it might at first seem. The main immediate challenge in developing superconducting cables is to acquire operational experience. Only by working with live-networks and with the users of network equipment will it be possible to evaluate compatibility with existing components, system reliability, maintenance and total system costs. Two basic types of superconducting cable designs are emerging. In one the HTS conductor is enclosed in a cryogenic environment, which in turn is covered by conventional room temperature dielectric. In the other, a cryogenic-dielectric design, two concentric HTS conductors are used transmit electricity. These designs are discussed as are superconducting tapes for 77 K operation, cooling and insulation, joints and terminations, and testing parameters     

Electric power applications of superconductivity

The development of superconducting systems for electric power is driven by the promise of improved efficiency, smaller size, and reduced weight as compared to existing technologies and by the possibility of new applications. Superconducting power components can also contribute to improved power quality and increased system reliability. This paper addresses historical developments and technology status of four superconducting power applications: cables, superconducting magnetic energy storage (SMES), fault-current limiters, and transformers. Today, SMES is the only fully functional superconducting system and it has seen only limited use at grid power levels. A few model or demonstration units exist for each of the other three applications. Superconductivity faces several hurdles on the path to widespread use. Perhaps the most important is the need for operating voltages of 100 kV or more. Though progress in this and other areas has been rapid, considerable development is needed before superconducting devices perform reliably in the utility environment. As a result, today, most initial installations are aimed at niche applications and will be installed where space is limited, where power demands are increasing over existing corridors, and/or where initial development costs can be offset by enhanced power grid performance.     

Superconducting materials for large scale applications

Since the 1960s, Nb-Ti (superconducting transition temperature T/sub c/=9 K) and Nb/sub 3/Sn (T/sub c/=18 K) have been the materials of choice for virtually all superconducting magnets. However, the prospects for the future changed dramatically in 1987 with the discovery of layered cuprate superconductors with T/sub c/ values that now extend up to about 135 K. Fabrication of useful conductors out of the cuprates has been difficult, but a first generation of silver-sheathed composite conductors based on (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ (T/sub c//spl sim/110 K) has already been commercialized. Recent progress on a second generation of biaxially aligned coated conductors using the less anisotropic YBa/sub 2/Cu/sub 3/O/sub 7/ structure has been rapid, suggesting that it too might enter service in the near future. The discovery of superconductivity in MgB/sub 2/ below 39 K in 2001 has brought yet another candidate material to the large-scale applications mix. Two distinct markets for superconductor wires exist-the more classical low-temperature magnet applications such as particle accelerators, nuclear magnetic resonance and magnetic resonance imaging magnets, and plasma-containment magnets for fusion power, and the newer and potentially much larger market for electric power equipment, such as motors, generators, synchronous condensers, power transmission cables, transformers, and fault-current limiters for the electric utility grid. We review key properties and recent progress in these materials and assess their prospects for further development and application.     

Low-calorie, high-energy generators and motors

Building on prototype motors and generators incorporating low-temperature superconductors, development of high temperature superconducting (HTS) counterparts is well along in Japan and the United States. In this article, the basic approach and principles of a superconducting AC synchronous generator or motor are described, and then the merits of using HTS field windings in their construction are assessed. Machines employing the early lower-temperature as well as the more recent high-temperature superconductors are discussed next. Finally, an update is provided on worldwide activities on developing a commercial generator and large motor utilizing superconductor windings     

Multiobjective Optimization for HTS Fault-Current Limiters Based on Normalized Simulated Annealing

This paper presents an improved simulated annealing (SA) algorithm for multiobjective optimization, which is a positive approach in the design of high-temperature superconducting (HTS) fault-current limiters (SFCLs).The main goal of this paper is to achieve an effective and feasible approach in the structural design of HTS FCLs by means of multiobjective decision-making techniques, based on normalized SA. The combination of electrical and thermal models of a purpose-designed resistive-type HTS FCL is defined as a component in PSCAD/EMTDC simulations from which the proposed method will be used to optimize the selective parameters of the SFCL. The above requires the need of advanced numerical techniques for simulation studies by PSCAD on a sample distribution system for determining a global optimum HTS FCL, by considering individual parameters and accounting for the constraints, which is the main motivation for initiating this paper.      

Organic outgassing behavior of plastic material and reduction of organic contamination in semiconductor equipment

We developed a low organic contamination (LOC ) electric cable as part of efforts to reduce organic contamination in semiconductor equipment. Our development strategies for LOC cables were obtained from the study of the behavior of outgassing from electric cables and the behavior of adsorption on silicon wafers. Strategy I: Reduce low boiling point organic contaminants from electric cables. Strategy II: Reduce organic contaminants with high adsorption rates on silicon wafers. Developing LOC cable under these two strategies, consequently, the amount of organic contaminants that are outgassed from the developed LOC cable was 1/10 or less of the level that is achieved by conventional cables. When compared with conventional cables, the flame-retardancy and flexibility are comparable. Then, we installed LOC cables in actual semiconductor equipment. The amount of organic contaminants adsorbed on the silicon wafer exposed in the equipment that was installed LOC cable and other low outgas parts were 1/6 lower than the conventional equipment. By using this low-outgassing cable in semiconductor equipment, we succeeded in reducing organic contamination in the equipment.     

光纤总线型煤矿井下电网监控系统的研制

介绍了以可编程逻辑控制器为核心的全光介质的煤矿井下光纤总线和井下工业以太网组成的电网监控系统,主干传输介质采用本质安全的矿用阻燃光缆,井下网络采用光缆或电缆,实现井下变电所、人员、设备、电网运行状况及参数的综合监控,该系统具有电气防爆、抗干扰强、服务半径大、信道容量大等特点,极大改善煤矿安全生产现状。同时该系统电气接口及通信协议规范透明,不依赖于系统提供商,使用国际标准接口,便于与其它系统互联,也可扩展构成全矿井控制系统。     

Superconducting FCL: design and application

Design, parameters, and application areas of a superconducting fault current limiter (FCL) are analyzed on the basis of the requirements of power systems. The comparison of resistive and inductive designs is carried out. An example of the effective application of FCLs in distribution substations is considered and the gain from the FCL installation is discussed. It is shown that an FCL not only limits a fault current but also increases the dynamic stability of the synchronous operation of electric machines. The calculation procedure of the parameters of an inductive FCL for a specific application case is described.     

Design of a linear bulk superconductor magnet synchronous motor for electromagnetic aircraft launch systems

High-temperature superconducting (HTS) material in bulk form is used to design a linear synchronous motor for an electromagnetic aircraft launch system. The motor is designed without an iron core. Stator coils are placed in the air while the permanent magnets used in conventional design of linear permanent magnet synchronous motors are replaced by the HTS bulk magnets. The physical, operational, and equivalent circuit parameters of the linear motor with HTS bulk magnets are compared with those of a linear permanent magnet synchronous motor and linear induction motor designed for the same application. Results show that utilizing superconducting magnets is only superior at temperatures below 40 K.     

Power and energy

The design and manufacture of electric power equipment, the one electrotechnology in which Europe could gain worldwide dominance by the end of the century, is examined. All three power-equipment categories-generation, transmission, and distribution-are involved. Europeans already lead in the production of extra-high-voltage (EHV) circuit breakers, high-voltage, direct-current (HVDC) equipment, and hydroelectric turbines. More recently, they have entered world markets for photovoltaics, nuclear generation equipment and services, combined-cycle generating plants, and energy storage. Currently, a spate of mergers and acquisitions is pushing the larger European companies in the field toward a continental stance. Both ABB (Asea Brown Boveri Ltd.), a giant created by a Swedish-Swiss merger, and Siemens, in Munich, have excellent lines of sulfur-hexafluoride and other EHV circuit breakers. ABB and Siemens are also strong suppliers of large power transformers and turbines     

Superconductivity: an emerging power-dense energy-efficient technology

As the world becomes more "electrified," efficient distribution and use of electrical power becomes increasingly important. Loss of electrical energy due to resistance to current flow translates into wasted energy and wasted economic resources. Superconductivity offers zero (dc) to near zero (ac) resistance to electrical flow; thus, the use of superconducting materials can improve the overall electrical system efficiency while significantly reducing the size and weight of power components and machinery. Although superconductivity was first discovered in 1911, the requirement of an extreme cryogenic environment (near absolute zero temperature) limited its utility. With the discovery in 1986 of a new class of "high-temperature superconductors (HTS)" that operate at substantially higher temperatures (although still cryogenic), remarkable progress has been made in advancing a broader use for superconducting technology. Full-scale demonstrations are now permitting the development of engineering skills required for systems implementation and are quantifying system benefits of this new HTS technology. This article briefly reviews some of the fundamental attributes of superconductivity and discusses how they can benefit our electrical power system. The article then briefly describes some of the ongoing U.S. demonstration projects (transmission lines, transformers, motors/generators, etc.), showing the benefits of superconductivity.     

Design and Comparison of Inductors and Intercell Transformers for Filtering of PWM Inverter Output

This paper presents an original design option dedicated to output-filtered pulsewidth modulation inverters used in uninterruptible power systems, embedded networks, or motor drives operating on long cables. It is based on the coupling of interleaved inverter cells by means of intercell transformers (ICTs) and is characterized by very good dynamic behavior on load transients, which is an important issue in such applications. ICT solutions are compared with the classical interleaved solutions using separate inductors. A specific design method is developed to achieve this comparison based on toroidal core shapes. The results obtained with a 600 V, 7.5 kW inverter show the usefulness of ICT-based designs, especially when nanocrystalline magnetic material is used; high specific power and very good dynamic performances are obtained.     

Analytical model of superconducting to normal transition of bulk high Tc superconductor BSCCO-2212

A comprehensive theoretical expression for the superconducting-to-normal transition of high-temperature superconducting (HTS) materials is derived. The electric field and resistivity of bulk melt-cast processed BSCCO-2212 are derived from the superconducting, flux creep, flux flow, and resistive properties of high critical temperature superconductors (HTS). An asymptotic function is used to model the Bean and Ohmic limits of the E(B,T,J) characteristics. Comparison is made with the experimental results of Elschner et al. The new model may be used in simulating the operation of HTS power equipment, and may be applicable to other HTS materials.