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This paper reports on the integration of publicly available HTS conductor electromagnetic performance data into a magnetic Finite Element model for determining the critical current distribution along a section of conductor in a spatially fluctuating magnetic field. The simulation results from this model are shown to be in close agreement to experimentally obtained results. Typically monitoring for quench is done by measuring the volt-drop along a section of conductor to be protected and determining when the volt-drop reaches a predetermined level. This work shows that under spatially varying magnetic field conditions, small areas of the voltage monitored section of conductor could have already surpassed the critical current level for that section of conductor and hence stand a high probability of being a site for quench. Under these conditions, it is proposed to use the maximum electric field developed along the conductor as a criterion for determining the critical current. This work points to the need for developing a quench detection technique that can be applied to much smaller sections of conductor, particularly in geometries that are expected to experience the largest variations of magnetic field such as that in a rotating electric machine.

In this work, we demonstrate the potential application of liquid metal galinstan as a means of carrying high currents between two collector electrodes. The room-temperature liquid metal was placed between two electrodes made either of stainless steel (SS) or of copper, where the electrical performance at applied currents as high as 250 A was monitored and found to be highly stable. The surface interaction between galinstan and the collector electrodes in the presence and absence of such high DC currents was also investigated. After 12 h of contact with Cu electrodes, analysis by X-ray diffraction and energy-dispersive X-ray experiments revealed the presence of Ga and Cu as well as evidence of very minor InSn phase separation from liquid galinstan to form a solid alloy. However, after the application of a DC current of 250 A for 12 h, extensive Cu-Ga alloy formation was observed in the form of CuGa2, as well as a more pronounced phase separation of the In and Sn components into islands of InSn. It was found that the slight temperature rise during electrical testing favored alloy formation but was not the origin of the phase separation of the In-Sn components. In contrast, analysis of the SS electrode after 24 h of an applied DC current of 250 A did not reveal any form of alloy formation. This work shows that the electrical performance of liquid metal galinstan is stable upon the application of high DC currents using two different contact materials even though the interaction with the contacts differs. In addition, this provides an interesting pathway that can be explored for alloy production using galinstan and Cu materials under the application of an applied current, which may have other uses apart from high-current-density carriers.

An attractive approach to increasing the output power and bandwidth of converters is through the parallel connection of multiple, subrated converter cells via mutually coupled inductors. Achieving a balanced contribution to the output current by all paralleled converter cells is critical; good reference tracking performance, however, should also be maintained. Since these two control tasks are coupled, tuning of the controller parameters is challenging. This article demonstrates a methodology for decoupling the output current reference tracking control task from the current balancing control. We show that once balancing and tracking controllers are decoupled, the controller parameter tuning can be conducted independently, simplifying design and analysis of controller performance. Experimental results are presented, which validate the proposed methodology, applied to a three-cell, parallel interleaved converter with cyclic cascade coupled inductor filter network, operating at 100 ${\rm V}_{\rm RMS}$ and 9 ${\rm A}_{\rm RMS}$ .

The problem of designing an effective future defense force is quite complex and challenging. One methodology that is often employed in this domain is portfolio optimization, whereby the objective is to select a diverse set of assets that maximize the return on investment. In the defense context, the return on investment is often measured in terms of the capabilities that the investments will provide. While the field of portfolio optimization is well established, applications in the defense sector pose unique challenges not seen in other application domains. However, the literature regarding portfolio optimization for defense applications is rather sparse. To this end, this paper provides a structured review of recent applications and identifies a number of areas that warrant further investigation.

A test facility has been developed in Australia to enable study of the performance of a high temperature superconducting (HTS) synchronous machine under dynamic operating conditions. The test facility will allow exploration of the opportunities and challenges of the use of such machines in maritime applications. This paper presents details of the demonstrator machine, test facility, and initial modeling and test results.

Superconducting rotating machines generate high magnetic fields and for economic application of these machines and to ensure safe and reliable operation accurate assessment of the critical current of the superconductor is required. This paper describes a process to assess the critical current for a HTS synchronous machine with a superconducting rotor using a self-consistent numerical model. The model is used to study the critical current of first generation (1G) Bi-2223 pancake coils under self-field conditions for coil tests as well as within a machine magnetic field under full load conditions. Model results are compared against test measurements on individual HTS pancake coils as well as a double pancake coil in an operating synchronous machine at the Queensland University of Technology (QUT) test facility. Results obtain show that the self-consistent model is fast and accurate in determining the effective critical current of superconductors in such applications. Insights from the modelling assist with the design and optimisation process of the superconducting coils, selection of coil voltage sensing locations to detect the risk of quench and establish safe margins for the superconductor operating current.

Large power systems are normally operated with their neutral points directly earthed. At a major generating or switching station, this results in the provision of a large earth grid buried in the ground. The design of earthing systems requires a worst case approach. There is a possibility of heavy currents flowing into the earth grid from the overhead earth wires through the tower during a line conductor fault and from lightning strikes. The flow of earth current during a fault or lightning conditions results in a rise of earth grid potential with respect to a physically remote earth point, which can lead to unsafe conditions under some conditions for personnel and connected electrical plant. This paper aims to investigate the potential of adding novel coatings to the conventional copper earth grid conductors to enhance overall conductivity and diminish corrosion. This contributes to lowering the rise of earth grid potential. Graphene-coated copper performance as an earth grid conductor is evaluated with staged low voltage fault and the corrosion behavior in both a destructive and nondestructive environment. A comparison of the simulation software packages CDEGS and CST is also carried out using lightning strike conditions.

New substation automation applications, such as sampled value (SV) process buses and synchrophasors, require a sampling accuracy of 1 mu s or better. The Precision Time Protocol (PTP), IEEE Std. 1588, achieves this level of performance and integrates well into Ethernet-based substation networks. This paper takes a systematic approach to the performance evaluation of commercially available PTP devices (grandmaster, slave, transparent, and boundary clocks) from a variety of manufacturers. The "error budget" is set by the performance requirements of each application. The "expenditure" of this error budget by each component is valuable information for a system designer. The component information is used to design a synchronization system that meets the overall functional requirements. The quantitative performance data presented show that this testing is effective and informative. Results from testing PTP performance in the presence of SV process bus traffic demonstrate the benefit of a "bottom-up" component testing approach combined with "top-down" system verification tests. A test method that uses a precision Ethernet capture card, rather than dedicated PTP test sets, to determine the correction field error of transparent clocks is presented. This test is particularly relevant for highly loaded Ethernet networks with stringent timing requirements. The methods presented can be used for development purposes by manufacturers or by system integrators for acceptance testing. An SV process bus was used as the test application for the systematic approach described in this paper. The test approach was applied, components were selected, and the system performance was verified to meet the application's requirements. Systematic testing, as presented in this paper, is applicable to a range of industries that use, rather than develop, PTP for time transfer. Refereed/Peer-reviewed

We have successfully grown graphene film on the surface of cylindrical copper conductors by chemical vapour deposition. The quality and number of graphene layers have been investigated using Raman spectroscopy, Raman mapping and scanning electron microscopy, as a function of methane gas flow rate and of growth temperature. Transmission electron microscopy analysis has been performed to verify the number of graphene layers, confirming the results obtained by Raman spectroscopy. The results open up the possibility of using graphene as an anticorrosion coating for copper cables and earth grids.

High temperature superconductor (HTS) material can be used for the implementation of high-speed low-heat conduction data links to transport digital data from 4 K superconductor integrated circuits to higher-temperature parts of computing systems. In this work, we present a conceptual design of energy efficient interface and results in fabricating such HTS leads. Initial calculations have shown that the microstrip line cable geometry for typical materials employed in production of HTS thin films can be a two-layered film for which the two layers of about 10 cm long are separated by an insulation layer with as low permittivity as possible. With this architecture in mind, the pulsed laser deposition process has been designed in a 45 cm diameter vacuum chamber to incorporate an oscillating sample holder with homogeneous substrate heating up to 900°C, while the laser plume is fixed. This design has allowed us to produce 200 nm to 500 nm thick, 7 cm to 10 cm long YBa2Cu3O7 thin films with the homogeneous critical temperature (Tc) of about 90 K. The critical current density (Jc) of the short samples obtained from the long sample is of (2 ± 1) × 1010 A/m2. Lines of 3-100 μm wide have been successfully patterned along the length of the samples in order to directly measure the Tc and Jc values over the entire length of the samples, as well as to attempt the structuring of multichannel data lead prototype.

Temperature-stable, high-permittivity (high-dielectric constant) ceramics are used as resonators for microwave telecommunications. Research and development in this area is aimed at increasing the dielectric constant (in order to reduce component size) while maintaining very high quality factor (low dielectric loss). This present work is a synchrotron X-ray powder diffraction study of high quality factor, high permittivity ceramics of the Ti(Al)O2 and (1−x)Ca2/5Sm2/5TiO3–xLi1/2Sm1/2TiO3 families. The synchrotron powder diffraction was used to investigate doping of Al onto the Ti site in Ti(Al)O2. It was found that the lattice parameters in Ti(Al)O2 are not affected by the Al doping. Although this null result does not give any evidence for substitution of Al on the Ti site, it does not exclude the possibility that a small proportion of the Al ions do substitute for Ti in Ti(Al)O2. In (1−x)Ca2/5Sm2/5TiO3–xLi1/2Sm1/2TiO3 the variation of lattice parameters and crystal structure versus x, and the possibility of substitution of Li onto the Ti site were investigated. Single phase samples with the orthorhombic CaTiO3 perovskite structure were obtained for 0.20

This paper presents optimization and testing processes for the deployment of batteries in rural networks. The injection of real power in the single wire earth return (SWER) networks offers advantages of reduced voltage drop and increased loadability. This paper shows how the sizing and location of battery systems can be designed and how the battery system for control of voltage can be tested. The optimal size and location of batteries is found through discrete particle swarm optimization (DPSO). It is seen that each kVA of batteries increases loadability of SWER network by 2kVA. The testing of such a smart battery system has been accomplished through use of a real timer hardware-in-the-loop simulator (OPAL-RT) interfaced to the full battery system.

Major generating or switching stations are normally operated with their neutral points directly earthed (usually an earth grid is buried in the earth). Metallic structures in the yard of generating or switching station, are electrically connected to the earth grid. The dimensions of earth grids are usually up to some hundreds of meters on a side. The design of earthing systems requires a worst-case approach. It ensures that a conductor forming the grid will not fail thermally or mechanically in the worst case of maximum fault current persisting for a fault of maximum duration. Over the life time of the electrical substation and its associated earth grid (30–50 years), it is important to maintain safety. Therefore before installing an earth grid its design is assessed according to the earth grid installation standards. In this paper safety criteria assessment of a design is evaluated with both IEEE-80 and IEC- 60479. In addition, a new method for determining the earth grid's installation depth has been proposed. It is based upon the soil model of particular substation instead of installing it in 0.5 meters depth for any substation.

Pure (0 0 l )-textured CeO 2 buffer layers were deposited on single crystal r -plane Al 2 O 3 (1–102) substrate by a hybrid process which was combined with magnetron sputtering for the seed layer and metal–organic deposition for the subsequent layer. Strongly c -axis oriented YBCO films were deposited on the CeO 2 buffered r -cut Al 2 O 3 (1–102) substrates. Atomic force microscope and scanning electronic microscopy results show that the prepared buffers and YBCO films are relatively dense and smooth. The critical current of the YBCO films exceeds 1.5 MA/cm 2 at 77 K with the superconducting transition temperature of 90 K. The surface resistivity is as below as 14 μΩ at 1 GHz frequency. The results demonstrate that the hybrid route is a very promising method to prepare YBCO films for microwave application, which can combine the sputtering advantage for preparing of highly c -axis oriented CeO 2 buffer layers and the advantages of metal–organic deposition with rapid processing, low cost and easy preparation of large-area YBCO films.

Advanced substation applications, such as synchrophasors and IEC 61850-9-2 sampled value process buses, depend upon highly accurate synchronizing signals for correct operation. The IEEE 1588 Precision Timing Protocol (PTP) is the recommended means of providing precise timing for future substations. This paper presents a quantitative assessment of PTP reliability using fault tree analysis. Two network topologies are proposed that use grandmaster clocks with dual network connections and take advantage of the best master clock algorithm (BMCA) from IEEE 1588. The cross-connected grandmaster topology doubles reliability, and the addition of a shared third grandmaster gives a nine-fold improvement over duplicated grandmasters. The performance of BMCA mediated handover of the grandmaster role during contingencies in the timing system was evaluated experimentally. The 1 mu s performance requirement of sampled values and synchrophasors are met, even during network or GPS antenna outages. Slave clocks are shown to synchronize to the backup grandmaster in response to degraded performance or loss of the main grandmaster. Slave disturbances are less than 350 ns provided the grandmaster reference clocks are not offset from one another. A clear understanding of PTP reliability and the factors that affect availability will encourage the adoption of PTP for substation time synchronization. Refereed/Peer-reviewed

The IEC 61850 family of standards for substation communication systems was released in the early 2000s and includes IEC 61850-8-1 and IEC 61850-9-2 that enable Ethernet to be used for process-level connections between transmission substation switchyards and control rooms. This paper presents an investigation of process bus protection performance, since the inservice behavior of multifunction process buses is largely unknown. An experimental approach was adopted that used a Real Time Digital Simulator and "live" substation automation devices. The effect of sampling synchronization error and network traffic on transformer differential protection performance was assessed and compared to conventional hard-wired connections. Ethernet was used for all sampled value measurements, circuit breaker tripping, transformer tap-changer position reports, and precision time protocol synchronization of sampled value merging unit sampling. Test results showed that the protection relay under investigation operated correctly with process bus network traffic approaching 100% capacity. The protection system was not adversely affected by synchronizing errors significantly larger than the standards permit, suggesting that these requirements may be overly conservative. This "closed loop" approach, using substation automation hardware, validated the operation of protection relays under extreme conditions. Digital connections using a single shared Ethernet network outperformed conventional hard-wired solutions. Refereed/Peer-reviewed

Process bus networks are the next stage in the evolution of substation design, bringing digital technology to the high-voltage switchyard. Benefits of process buses include facilitating the use of nonconventional instrument transformers, improved disturbance recording and phasor measurement, and the removal of costly, and potentially hazardous, copper cabling from substation switchyards and control rooms. This paper examines the role a process bus plays in an IEC 61850-based substation automation system. Measurements taken from a process bus substation are used to develop an understanding of the network characteristics of "whole of substation" process buses. The concept of "coherent transmission" is presented, and the impact of this on Ethernet switches is examined. Experiments based on substation observations are used to investigate in detail the behavior of Ethernet switches with sampled value traffic. Test methods that can be used to assess the adequacy of a network are proposed, and examples of the application and interpretation of these tests are provided. Once sampled value frames are queued by an Ethernet switch, the additional delay incurred by subsequent switches is minimal, and this allows their use in switchyards to further reduce communications cabling, without significantly impacting operation. The performance and reliability of a process bus network operating close to the theoretical maximum number of digital sampling units (merging units or electronic instrument transformers) was investigated with networking equipment from several vendors and has been demonstrated to be acceptable. Refereed/Peer-reviewed

New substation technology, such as nonconventional instrument transformers, and a need to reduce design and construction costs are driving the adoption of Ethernet-based digital process bus networks for high-voltage substations. Protection and control applications can share a process bus, making more efficient use of the network infrastructure. This paper classifies and defines performance requirements for the protocols used in a process bus on the basis of application. These include Generic Object Oriented Substation Event, Simple Network Management Protocol, and Sampled Values (SVs). A method, based on the Multiple Spanning Tree Protocol (MSTP) and virtual local area networks, is presented that separates management and monitoring traffic from the rest of the process bus. A quantitative investigation of the interaction between various protocols used in a process bus is described. These tests also validate the effectiveness of the MSTP-based traffic segregation method. While this paper focuses on a substation automation network, the results are applicable to other real-time industrial networks that implement multiple protocols. High-volume SV data and time-critical circuit breaker tripping commands do not interact on a full-duplex switched Ethernet network, even under very high network load conditions. This enables an efficient digital network to replace a large number of conventional analog connections between control rooms and high-voltage switchyards. Refereed/Peer-reviewed

This letter presents a technique to assess the overall network performance of sampled value process buses based on IEC 61850-9-2 using measurements from a single location in the network. The method is based upon the use of Ethernet cards with externally synchronized time stamping, and characteristics of the process bus protocol. The application and utility of the method is demonstrated by measuring latency introduced by Ethernet switches. Network latency can be measured from a single set of captures, rather than comparing source and destination captures. Absolute latency measures will greatly assist the design testing, commissioning and maintenance of these critical data networks. Refereed/Peer-reviewed

Many substation applications require accurate time-stamping. The performance of systems such as Network Time Protocol (NTP), IRIG-B and one pulse per second (1-PPS) have been sufficient to date. However, new applications, including IEC 61850-9-2 process bus and phasor measurement, require accuracy of one microsecond or better. Furthermore, process bus applications are taking time synchronisation out into high voltage switchyards where cable lengths may have an impact on timing accuracy. IEEE Std 1588, Precision Time Protocol (PTP), is the means preferred by the smart grid standardisation roadmaps (from both the IEC and US National Institute of Standards and Technology) of achieving this higher level of performance, and integrates well into Ethernet based substation automation systems. Significant benefits of PTP include automatic path length compensation, support for redundant time sources and the cabling efficiency of a shared network. This paper benchmarks the performance of established IRIG-B and 1-PPS synchronisation methods over a range of path lengths representative of a transmission substation. The performance of PTP using the same distribution system is then evaluated and compared to the existing methods to determine if the performance justifies the additional complexity. Experimental results show that a PTP timing system maintains the synchronising performance of 1-PPS and IRIG-B timing systems, when using the same fibre optic cables, and further meets the needs of process buses in large substations Refereed/Peer-reviewed

We report continuing investigations into practical applications of the AC Josephson effect as the basis for a voltage-tunable radio-frequency oscillator. We have previously demonstrated experimentally that useful power levels (10 s of nW) and linewidths of a few kHz can be achieved in the heterodyne output from a high-temperature-superconducting resistive SQUID (HTS-RSQUID) operating in the frequency range 1-50 MHz. Those results were achieved with 2-junction R-SQUIDs incorporating current-biased shunt resistors of a few micro-ohms. We have now modified the fabrication procedures, and adjusted the shunt resistors and bias current values so that higher frequencies can be achieved. The Josephson junctions are of step-edge type, rather than the bi-crystal type used in our earlier work. The step-edge technique permits much more flexibility in the geometrical lay-out and utilizes the more cost-effective single-crystal MgO substrates. In the present paper, we report numerical simulations and experimental measurements on these devices in the frequency range up to 2 GHz.

Yttrium barium copper oxide (YBCO) film was synthesized by a metal-organic deposition (MOD) process with fluorine-free Y and Cu precursor. The precursor solution with Sm addition enabled further improvement of the thickness and uniformity of precursor films. The calcination and firing processes were studied, and the precursor film was successfully converted to dense and uniform YBCO film on LaAlO3 (LAO) substrate after annealing in a wet Ar and O2 atmosphere. The measured critical current density (J c) value was about 80 A/cm-w (2.66 MA/cm2). The trifluoroacetate (TFA) reduced MOD process has the advantage that it has a larger tolerance for variations in the gas flow rate and path. The results on a Sm-YBCO film deposited on LAO with a CeO2 buffer layer fabricated by MOD are also presented.

Highly c -axis orientated YBa 2 Cu 3 O 7– x films were prepared on LaAlO 3 single crystal substrates via metal–organic deposition using trifluoroacetates using ethanol as solvent instead of the toxic methanol. The onset transition temperature is 91 K and the critical current density under self field is over 1 MA/cm 2 at 77 K, which indicates ethanol can be used as solvent for high-quality YBCO films using TFA–MOD.

A high-temperature superconducting (HTS) Josephson heterodyne oscillator based on step-edge junction technology has recently been developed (Du et al 2008 Appl. Phys. Lett. 93 033507, Macfarlane et al 2009 IEEE Trans. Appl. Supercond. 19 920). In this work, the implementation and characterization of such a heterodyne oscillator on a compact pulse-tube cryocooler (PTC) are presented. The rf performance of the oscillator cooled by the cryocooler is compared to that of the same device when cooled in the quiet gas phase of a liquid helium Dewar. Any measurable influence of additional electromagnetic noise and mechanical vibration of the cryocooler on the oscillator performance is assessed by measuring the linewidth broadening of the heterodyne oscillation. The cryocooled oscillator demonstrated excellent performance and negligible excess noise was observed when operating the PTC.

Single-phase Ba(Cd1/3Ta2/3)O-3 powder was produced using conventional solid state reaction methods. Ba(Cd1/3Ta2/3)O-3 ceramics with 2 wt % ZnO as sintering additive sintered at 1550 degreesC exhibited a dielectric constant of similar to32 and loss tangent of 5x10(-5) at 2 GHz. X-ray diffraction and thermogravimetric measurements were used to characterize the structural and thermodynamic properties of the material. Ab initio electronic structure calculations were used to give insight into the unusual properties of Ba(Cd1/3Ta2/3)O-3, as well as a similar and more widely used material Ba(Zn1/3Ta2/3)O-3. While both compounds have a hexagonal Bravais lattice, the P321 space group of Ba(Cd1/3Ta2/3)O-3 is reduced from P (3) under bar m1 of Ba(Zn1/3Ta2/3)O-3 as a result of a distortion of oxygen away from the symmetric position between the Ta and Cd ions. Both of the compounds have a conduction band minimum and valence band maximum composed of mostly weakly itinerant Ta 5d and Zn 3d/Cd 4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and is suggested to play an important role in producing materials with a high dielectric constant and low microwave loss. (C) 2005 American Institute of Physics.

SUMMARY Four patients, age 25 to 30 years, with bronchial or mediastinal venous obstruction due to chronic fibrous mediastinitis are reported. Fibrous mediastinal lesions with various degrees of calcification were so extensive, obliterating anatomical planes, that pulmonary resections were technically impossible or considered unwise. Clinical and laboratory findings with uniform gross and microscopic appearance of these intrathoracic lesions, in our opinion, has given us a sufficient basis to make a diagnosis of chronic fibrous mediastinitis due to histoplasmosis. Morphologically typical organisms of histoplasma capsulatum were demonstrated in the caseous material from a granulomatous lymph node in one patient and organisms highly suggestive of such a fungus disease were found in another. Multiple mediastinal biopsies from the other two patients were not conclusively diagnostic in that no lymph node demonstrating such early collagenous replacement of necrotic foci was encountered although the typical hyalinized fibrous and calcific tissue was in abundance. Discussion points are presented dispelling the past opinions that severe chronic mediastinitis and associated superior vena caval obstruction may be the result of a tuberculous process.

The solitary circumscribed pulmonary nodule seems to have become the hunting ground of the thoracic surgeon in recent years. Report after report has affirmed that primary resectable pulmonary malignancy may present itself in this form (Fig. 1). 1-24 There is thus a good argument for removing all solitary pulmonary nodules. The argument runs as follows. Primary lung cancer has been seen in patients as young as 21 years of age. Furthermore, patients with nonmalignant nodules, including tuberculosis and other infections, are very seldom made worse by surgery. It is important to both physician and patient to know the cause of the lesion, not only from the standpoint of further treatment but also from that of prognosis. 25-29 In short, tissue diagnosis permits a reliable prognosis and usually sound therapy. The situation was becoming reasonably clarified until May, 1956, when Holin and associates presented at the annual meeting of the American