Application of multiple resistive superconducting fault-current limiters for fast fault detection in highly interconnected distribution systems

Superconducting fault-current limiters (SFCLs) offer several benefits for electrical distribution systems, especially with increasing distributed generation and the requirements for better network reliability and efficiency. This paper examines the use of multiple SFCLs in a protection scheme to locate faulted circuits, using an approach which is radically different from typical proposed applications of fault current limitation, and also which does not require communications. The technique, referred to as “current division discrimination” (CDD), is based upon the intrinsic inverse current-time characteristics of resistive SFCLs, which ensures that only the SFCLs closest to a fault operate. CDD is especially suited to meshed networks and particularly when the network topology may change over time. Meshed networks are expensive and complex to protect using conventional methods. Simulation results with multiple SFCLs, using a thermal-electric superconductor model, confirm that CDD operates as expected. Nevertheless, CDD has limitations, which are examined in this paper. The SFCLs must be appropriately rated for the maximum system fault level, although some variation in actual fault level can be tolerated. For correct coordination between SFCLs, each bus must have at least three circuits that can supply fault current, and the SFCLs should have identical current-time characteristics

Analysis of energy dissipation in resistive superconducting fault-current limiters for optimal power system performance

Fault levels in electrical distribution systems are rising due to the increasing presence of distributed generation, and this rising trend is expected to continue in the future. Superconducting fault-current limiters (SFCLs) are a promising solution to this problem. This paper describes the factors that govern the selection of optimal SFCL resistance. The total energy dissipated in an SFCL during a fault is particularly important for estimating the recovery time of the SFCL; the recovery time affects the design, planning, and operation of electrical systems using SFCLs to manage fault levels. Generic equations for energy dissipation are established in terms of fault duration, SFCL resistance, source impedance, source voltage, and fault inception angles. Furthermore, using an analysis that is independent of superconductor material, it is shown that the minimum required volume of superconductors linearly varies with SFCL resistance but, for a given level of fault-current limitation and power rating, is independent of system voltage and superconductor resistivity. Hence, there is a compromise between a shorter recovery time, which is desirable, and the cost of the volume of superconducting material needed for the resistance required to achieve the shorter recovery time

Foreland Magmatism during the Arabia–Eurasia Collision: Pliocene–Quaternary Activity of the Karacadağ Volcanic Complex, SW Turkey

Pliocene to Quaternary magmatism in the Karacadağ Volcanic Complex in SE Turkey occurred in the foreland region of the Arabia–Eurasia collision and can be divided into two phases. The earlier Karacadağ phase formed a north–south-trending volcanic ridge that erupted three groups of lavas. The same range of mantle sources contributed to the younger Ovabağ phase lavas, which were erupted from monogenetic cones to the east of the Karacadağ fissure. As at several other intraplate localities across the northern Arabian Plate this magmatism represents mixtures of melt from shallow, isotopically enriched mantle and from deeper, more depleted mantle. The deep source is similar to the depleted mantle invoked for other northern Arabian intraplate volcanic fields but at Karacadağ this source contained phlogopite. This source could be located in the shallow convecting mantle or may represent a metasomatic layer in the base of the lithosphere. There is no evidence for a contribution from the Afar mantle plume, as has been proposed elsewhere in northern Arabia. Melting during the Karacadağ and Ovabağ phases could have resulted from a combination of upwelling beneath weak or thinned lithosphere and restricted local extension of that weakened lithosphere as it collided with Eurasia. Tension associated with the collision focused magma of the Karacadağ phase into the elongate shield volcano of Mt. Karacadağ. The northern end of the fissure accommodated more extensive differentiation of magma, with isolated cases of crustal contamination, consistent with greater stress in the lithosphere closest to the collision. Most magma batches of the Karacadağ and Ovabağ phases differentiated by fractional crystallization at ∼5 MPa, near the boundary between the upper and lower crust. Magma batches dominated by melt from garnet lherzolite show evidence for restricted amounts of differentiation at ∼22·5 MPa, which is close to the base of the lithospheric mantle

Inter-element fractionation of highly siderophile elements in the Tonga Arc due to flux melting of a depleted source

Highly siderophile element concentrations (HSEs: Os, Ir, Ru, Pt, Pd, and Re) have been determined for a suite of fresh, submarine mafic lavas from the northern Tonga Arc front and the nascent backarc Fonualei Spreading Centre (FSC). Prior melt depletion of the Tongan mantle wedge combined with a high degree of fluid fluxed melting is thought to have produced boninitic magmas at several arc and FSC locations. As such, this arc system provides an opportunity to assess the fluid mobility of HSEs and to investigate the effects of fluid-induced melting and prior melt depletion on HSE behaviour during both mantle melting and magma evolution. Tongan lavas display extreme enrichment of Pt (2.5–32 ng/g) and Pd over Os (0.002–0.6 ng/g), Ir, and Ru, significantly greater than basalts from mid-ocean ridges. Magma evolution increases the degree of fractionation, resulting in the highest recorded Pt/Ru ratios (>300) in arc front samples with MgO <8 wt.%. This increasing fractionation is due to the mild incompatibility of Pt and Pd, and concurrent compatibility of Ru, during sulphide undersaturated magma evolution. However, the fractionation of Pt and Pd from Os, Ir, and Ru is observed in the highest MgO samples, indicating source inheritance. Prior melt depletion of the mantle and elevated oxygen fugacity both increase the likelihood of complete consumption of sulphide in the source during melting, which typically leads to melts with high concentrations of all the HSE. Indeed, modelling indicates that 25% aggregate partial melting of a depleted MORB-mantle source, proposed for the Tonga Arc, will lead to complete base-metal sulphide consumption unless there is considerable addition of S by the slab flux (at least 200 μg/g). Although source enrichment of Pt, Pd, and Re by slab fluids may take place, the fractionation of Pt and Pd from Os, Ir, and Ru can largely be explained by relatively low-temperature, yet high-degree, melting of fluid-fluxed melt-depleted mantle. The high Pt and Pd contents can be produced by the exhaustion of sulphide in the source, while the presence of Ru–Os–(Ir) alloys or sulphides (e.g. laurite) associated with Cr-spinel can explain Os, Ir, and Ru retention in the source residue. Such phases have been documented in fluid-fluxed sub-arc mantle from ophiolites. Osmium isotopes co-vary negatively with Os abundance and thus appear to be dominated by shallow level contamination. The most Os-rich samples, however, have 187Os/188Os ratios (0.126–0.132) which are typical of DMM and MORB, suggesting an indistinguishable flux of radiogenic Os from the slab. The significant fractionation of Pt and Re from Os in arc settings will lead, over time, to elevated 186Os and 187Os which may be relevant to the observed enrichments of these isotopes in some mantle regions. In addition, the differing behaviour of Ru and Ir, and the implication of a mantle source containing Ru-rich microphases, may have consequences for the estimation of the HSE composition of primitive upper mantle

Titanium stable isotope investigation of magmatic processes on the Earth and Moon

We present titanium stable isotope measurements of terrestrial magmatic samples and lunar mare basalts with the aims of constraining the composition of the lunar and terrestrial mantles and evaluating the potential of Ti stable isotopes for understanding magmatic processes. Relative to the OL–Ti isotope standard, the δ49Ti values of terrestrial samples vary from −0.05 to +0.55‰, whereas those of lunar mare basalts vary from −0.01 to +0.03‰ (the precisions of the double spike Ti isotope measurements are ca. ±0.02‰ at 95% confidence). The Ti stable isotope compositions of differentiated terrestrial magmas define a well-defined positive correlation with SiO2 content, which appears to result from the fractional crystallisation of Ti-bearing oxides with an inferred isotope fractionation factor of View the MathML source. Primitive terrestrial basalts show no resolvable Ti isotope variations and display similar values to mantle-derived samples (peridotite and serpentinites), indicating that partial melting does not fractionate Ti stable isotopes and that the Earth's mantle has a homogeneous δ49Ti composition of +0.005 ± 0.005 (95% c.i., n=29). Eclogites also display similar Ti stable isotope compositions, suggesting that Ti is immobile during dehydration of subducted oceanic lithosphere. Lunar basalts have variable δ49Ti values; low-Ti mare basalts have δ49Ti values similar to that of the bulk silicate Earth (BSE) while high-Ti lunar basalts display small enrichment in the heavy Ti isotopes. This is best interpreted in terms of source heterogeneity resulting from Ti stable isotope fractionation associated with ilmenite–melt equilibrium during the generation of the mantle source of high-Ti lunar mare basalts. The similarity in δ49Ti between terrestrial samples and low-Ti lunar basalts provides strong evidence that the Earth and Moon have identical stable Ti isotope compositions

Generation of the Mt Kinabalu granite by crustal contamination of intraplate magma modelled by Equilibrated Major Element Assimilation with Fractional Crystallisation (EME-AFC)

New geochemical data are presented for the composite units of the Mount Kinabalu granitoid intrusion of Borneo and explore discrimination between crustal- and mantle-derived granitic magmas. The geochemical data demonstrate that the units making up this composite intrusion became more potassic through time. This was accompanied by an evolution of isotope ratios from a continental-affinity towards a slightly more mantle-affinity (87Sr/86Sri ∼0.7078; 143Nd/144Ndi ∼0.51245; 206Pb/204Pbi ∼18.756 for the oldest unit compared to 87Sr/86Sri ∼0.7065, 143Nd/144Ndi ∼0.51250 and 206Pb/204Pbi ∼18.721 for the younger units). Oxygen isotope ratios (calculated whole-rock δ18O of + 6.5–9.3‰) do not show a clear trend with time. The isotopic data indicate that the magma cannot result only from fractional crystallisation of a mantle-derived magma. Alkali metal compositions show that crustal anatexis is also an unsuitable process for genesis of the intrusion. The data indicate that the high-K units were generated by fractional crystallisation of a primary, mafic magma, followed by assimilation of the partially melted sedimentary overburden. We present a new, Equilibrated Major Element – Assimilation with Fractional Crystallisation (EME-AFC) approach for simultaneously modelling the major element, trace element, and radiogenic and oxygen isotope compositions during such magmatic differentiation; addressing the lack of current AFC modelling approaches for felsic, amphibole- or biotite-bearing systems. We propose that Mt Kinabalu was generated through low degree melting of upwelling fertile metasomatised mantle driven by regional crustal extension in the Late Miocene

Persistent northward North Atlantic tropical cyclone track migration over the past five centuries

Accurately predicting future tropical cyclone risk requires understanding the fundamental controls on tropical cyclone dynamics. Here we present an annually-resolved 450-year reconstruction of western Caribbean tropical cyclone activity developed using a new coupled carbon and oxygen isotope ratio technique in an exceptionally well-dated stalagmite from Belize. Western Caribbean tropical cyclone activity peaked at 1650 A.D., coincident with maximum Little Ice Age cooling, and decreased gradually until the end of the record in 1983. Considered with other reconstructions, the new record suggests that the mean track of Cape Verde tropical cyclones shifted gradually north-eastward from the western Caribbean toward the North American east coast over the last 450 years. Since ~1870 A.D., these shifts were largely driven by anthropogenic greenhouse gas and sulphate aerosol emissions. Our results strongly suggest that future emission scenarios will result in more frequent tropical cyclone impacts on the financial and population centres of the northeastern United States

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter