Showing papers by "Hydro-Québec published in 1999"
TL;DR: In this article, an extensive mechanical milling was used to make MgH2-Tm (Tm=3d-transition elements Ti, V, Mn, Fe, Ni) nanocomposite powders.
974 citations
TL;DR: In this article, the authors present a systematic study of structural modifications and hydrogen absorption-desorption kinetics of ball-milled magnesium hydride, and they show that after only 2 h of milling, a metastable orthorhombic (γ)-morphological phase is formed.
683 citations
TL;DR: Li4Ti5O12 is a zero-strain insertion material, which was prepared by conventional method and by high energy ball milling (HEBM) of precursor to form nanocrystalline phases as discussed by the authors.
486 citations
TL;DR: In this article, the authors proposed the use of the Gumbel mixed model to analyze the joint probability distribution of correlated flood peaks and volumes, as well as correlated flood volumes and durations.
323 citations
TL;DR: In this paper, the hydrogen storage properties of a new composite MgH2+V prepared by ball milling were presented. But the results were limited to hydrogen desorption at 473 K under vacuum and re-absorbation at room temperature.
321 citations
31 Jul 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the same technique has been extended to the milling of carbides and chlorides and coupled to a lixiviation process to produce new electrocatalysts for polymer electrolyte fuel cells.
Abstract: The paper discusses the application of nanocrystalline alloys as hydrogen storage materials and as electrocatalysts for solid polymer electrolyte fuel cells. After reviewing some of the requirements of metal hydrides for hydrogen fueled vehicles, the paper presents new results on the structure and hydrogen sorption properties of high storage capacity ball-milled magnesium hydride. The great advantages of milling the hydride instead of the pure metals for producing novel nanostructures with high surface area and for improving hydrogen sorption kinetics are presented. In the second part of the paper, the same technique has been extended to the milling of carbides and chlorides and coupled to a lixiviation process to produce new electrocatalysts for polymer electrolyte fuel cells. This new technology offers the possibility of producing nanoparticles with metastable structures whose specific surface area is much larger than that of any nanocrystalline powders made by conventional ball milling techniques. Pt-based nanoparticles were fabricated and tested as anode in fuel cells under pure and CO-contaminated hydrogen feedstreams.
135 citations
TL;DR: The comprehensive aquatic systems model (CASM) was adapted for estimating ecological risks posed by toxic chemicals in rivers, lakes, and reservoirs in Quebec, Canada as discussed by the authors, which provides the capability to estimate the probability of changes in the biomass of multiple populations of primary producers and consumers as a function of the concentration of dissolved chemical contaminant.
119 citations
TL;DR: In this paper, a design approach for power system stabilizing controllers based on parameter optimization of compensators with generalized structures is proposed, which is fully multivariable and remains sufficiently general to apply equally well to a feedback or cascade stabilizer, with any type of input signal or transfer function structure.
Abstract: This paper proposes a design approach for power system stabilizing controllers based on parameter optimization of compensators with generalized structures. It shows that a selective modal performance index is an improved measure of the stabilizing effect of a given design, although its blind minimization can end in a useless local minimum. Adding stability, sensitivity and robustness constraints greatly improve the engineering significance of the resulting design. The development is fully multivariable and remains sufficiently general to apply equally well to a feedback or cascade stabilizer, with any type of input signal or transfer function structure. Three examples are used: a robust PSS design for a single machine-infinite bus system with multiple operating points; multiple PSS coordination for a large system; and a coordinated design of four PSSs for the Kundur's two-area test system. All results show good prospects for the constrained optimization based approach to the design of robust stabilizers.
112 citations
TL;DR: In this article, the direct synthesis of Na3AlH6 and Na2LiH6 by energetic mechanical alloying of stoichiometric mixtures of NaH, LiH and NaAlH4 was investigated.
109 citations
TL;DR: In this article, the authors summarized Hydro-Quebec's current orientation for safeguarding its transmission system after extreme contingencies and described the various automatic measures adopted and, in particular, the RPTC system, one of the main components of the defence plan.
Abstract: In recent years, Hydro-Quebec has undertaken a major program to upgrade the reliability of its transmission system. Much effort has focused on increasing the system's ability to withstand extreme contingencies, usually caused by multiple incidents or the successive tripping of transmission lines. In order to counteract such events on its system, Hydro-Quebec has adopted a number of special defensive measures, globally called the "defence plan against extreme contingencies". The goal of this plan, which will be fully operational by 1998, is to detect and confine incidents that exceed the system's strength. This paper summarizes Hydro-Quebec's current orientation for safeguarding its transmission system after extreme contingencies and describes the various automatic measures adopted and, in particular, the RPTC system, one of the main components of the defence plan. The RPTC system will detect multiple line losses directly from fifteen 735 kV substations, include four generation rejection sites and a centralized remote load shedding system.
93 citations
TL;DR: In this paper, the conditions for the onset of streamers in such laser-produced plasmas, both experimentally and through numerical simulations, were studied, demonstrating the importance of the electron density and its gradient on the generation of streamer.
Abstract: In an ongoing program using ultrashort laser pulses to provoke discharges in air over considerable distances at electric fields below breakdown threshold, we have studied the conditions for the onset of streamers in such laser-produced plasmas, both experimentally and through numerical simulations. The results demonstrate the importance of the electron density and of its gradient on the generation of streamers. Also, a significant reduction of the breakdown voltage for a 30 cm plane-plane gap in air was observed with a laser pulse energy of 15 mJ. Finally, a direct comparison of laser-induced breakdown in air and in nitrogen shows the influence of electron attachment to oxygen on the discharge process.
TL;DR: In this article, a linear relationship between the backscattering ratios of a winter image and a snow-free (fall) image, and the snowpack thermal resistance (thermal insulation properties) has been established.
Abstract: In the 1998-1999 winter, the operational feasibility of using RADARSAT SAR data to estimate the spatial distribution of snow water equivalent (SWE) in a large hydroelectric complex managed by Hydro-Quebec (La Grande River watershed) has been successfully demonstrated. This watershed is located in the subarctic climatic region in the north-west of the Quebec province. The vegetation consists of moderately dense to open Black Spruce forests, open lands, burned lands and peat bogs. In the last few years, an original approach well adapted for this region has been developed to estimate the SWE from SAR data (ERS-1, RADARSAT). This approach is based on the fact that the snow cover characteristics influence the underlying soil temperature which influences the dielectric properties of the soil and then the recorded backscattering signal. Then, a linear relationship between the backscattering ratios of a winter image and a snow-free (fall) image, and the snowpack thermal resistance (thermal insulation properties) has been established. Consequently, the algorithm infers the SWE from the estimated thermal resistance and the measured mean density of the snowpack. This algorithm has been implemented within a MapInfo application that has been named EQeau. It allows mapping of the spatial distribution of the estimated SWE at the desired level (pixel, square grid, sub-watershed). During the 1998-1999 winter, EQeau has been used successfully in a pre-operational mode using calibrated Wide beam images (W1) from RADARSAT. The algorithm has given mean estimated SWE values similar to the SWE values derived from Hydro-Quebec snow transects (relative difference between 1% and 13%). Also, the SWE increase measured from January to March 1999 is clearly detected on the maps covering almost 77 000 km 2 . The next steps will be the evaluation of the ScanSAR images and the demonstration of the economical advantages of using RADARSAT data in a hydrological forecasting system.
TL;DR: In this paper, the mechanical alloying technique was used to make nanocrystalline Mg2Ni and Mg1.9Ti0.1Ni powders and their hydrogen storage properties were characterized.
TL;DR: In this article, the authors used high energy ball milling to produce CO tolerant unsupported Pt-Ru based catalysts for the oxidation of hydrogen in polymer electrolyte fuel cells, and obtained a specific area of 38 m2g−1.
Abstract: High energy ball milling, an industrially amenable technique, has been used to produce CO tolerant unsupported Pt–Ru based catalysts for the oxidation of hydrogen in polymer electrolyte fuel cells. Nanocrystalline Pt0.5–Ru0.5 alloys are easily obtained by ball-milling but their performances as anode catalysts are poor because nanocrystals composing the material aggregate during milling into larger particles. The result is a low specific area material. Improved specific areas were obtained by milling together Pt, Ru and a metal leacheable after the milling step. The best results were obtained by milling Pt, Ru, and Al in a 1:1:8 atomic ratio. After leaching Al, this catalyst (Pt0.5–Ru0.5 (Al4)) displays a specific area of 38 m2g−1. Pt0.5–Ru0.5 (Al4) is a composite catalyst. It consists of two components: (i) small crystallites (∼4 nm) of a Pt–Al solid solution (1–3 Al wt%) of low Ru content, and (ii) larger Ru crystallites. It shows hydrogen oxidation performance and CO tolerance equivalent to those of Pt0.5–Ru0.5 Black from Johnson Matthey, the commercial catalyst which was found to be the most CO tolerant one in this study.
TL;DR: In this paper, a new approach for the statistical identification of synchronous-machine parameters from on-line test data that were recorded on a 202 MVA hydro-generator at Hydro-Quebec's La Grande 3 generating station is presented.
Abstract: This paper presents a new approach for the statistical identification of synchronous-machine parameters from on-line test data that were recorded on a 202 MVA hydro-generator at Hydro-Quebec's La Grande 3 generating station. Data processing is performed to remove harmonics in noise-corrupted measurements. The time-domain parameter identification is carried out by means of our proposed maximum-likelihood estimation method, also called the iteratively reweighted least-squares algorithm. A comparison of the results with the ordinary weighted least-squares estimation, which is equivalent to the maximum-likelihood estimation only when the noise is white, shows the superiority of the proposed method. This procedure appears more convenient than previous schemes for parameter identification of the synchronous-machine linear equivalent-circuits, especially when the noise statistics are poorly known.
TL;DR: In this article, the saturation effects are incorporated in the magnetizing inductance and the stator mutual inductances, taking into account the nonuniform distribution of magnetic saturation within the motor core.
Abstract: This paper proposes a new model for saturated induction motors. The saturation effects are incorporated in the magnetizing inductance and the stator mutual inductances, taking into account the nonuniform distribution of magnetic saturation within the motor core. The proposed model can be used to analyze the manner in which the induction motors interact with the supply network or power source, since it can predict the motor current/voltage harmonics produced by magnetic saturation. Experimental tests show that the proposed model represents with reasonable accuracy (8%) the motor saturation effects at nominal stator voltage as well as for overvoltage operation.
TL;DR: Toroidal mesostructured molybdenum bronzes and blues have been synthesized and the effect of phase changes on the electrical conductivity of these materials is explored in depth.
Abstract: Toroidal mesostructured molybdenum bronzesand blues (shown schematically) have been synthesized. The effect of phase changes on the electrical conductivity of these materials is explored in depth. A unique shape-evolution reaction is also discussed.
TL;DR: Concentrations of Ca, Mg, Cu, Zn, Fe, Mn, Na, P, and K in blood plasma and cerebrospinal fluid were determined and exposure to electric and magnetic fields resulted in decreased concentrations of Mg inBlood plasma and in increased concentrations of Ca and P and decreases concentrations of Fe and Mn in cerebro Spinal fluid.
Abstract: Eight multiparous, nonlactating pregnant Holstein cows (at 198 +/- 35 days of gestation and weighing 608 + 24 kg) and seven nonlactating nonpregnant ovariectomized heifers (weighing 370 + 29 kg) were confined to wooden metabolism crates in an electric and magnetic field chamber. Subarachnoidal catheters were inserted before the activation of the electric and magnetic fields. For 30 days, cows and heifers were continuously exposed in separate trials to electric and magnetic fields (60 Hz, 10 kV/m, and 30 microT). Blood plasma and cerebrospinal fluid samples were collected for 3 consecutive days before the exposure period, the last 3 days of the exposure period, and for 3 days starting 5 days after the exposure period. Concentrations of Ca, Mg, Cu, Zn, Fe, Mn, Na, P, and K in blood plasma and cerebrospinal fluid were determined. Exposure to electric and magnetic fields resulted in decreased concentrations of Mg in blood plasma and in increased concentrations of Ca and P and decreased concentrations of Fe and Mn in cerebrospinal fluid.
TL;DR: In this paper, the performance of Hg-plated-iridium based microelectrode arrays intended to heavy metal trace analysis was evaluated by means of multiple square wave anodic stripping voltammetry (MSWASV).
Patent•
29 Jan 1999TL;DR: In this article, cross-linked sulphonated polymers, optionally perfluorinated, and the method for preparing them were described, and shown to be useful in electrochemical cells, in a chlorine-sodium electrolysis process, as separator in en electrochemical preparation of organic and inorganic compounds, or as catalyst for Diels-Alder additions, Friedel-Craft reactions, aldol condensations, cationic polymerisation, esterification and acetal formation.
Abstract: The invention concerns cross-linked sulphonated polymers, optionally perfluorinated, and the method for preparing them. When they are moulded in the form of membranes, said polymers are useful in electrochemical cells, in a chlorine-sodium electrolysis process, as separator in en electrochemical preparation of organic and inorganic compounds, as separator between an aqueous phase and an organic phase, or as catalyst for Diels-Alder additions, Friedel-Craft reactions, aldol condensations, cationic polymerisation, esterification, and acetal formation.
TL;DR: In this article, the thermal stability of the inductive limiter is investigated as a function of the temperature of the nitrogen bath (67-77 K), where both electromagnetic and thermal behaviour are considered.
Abstract: Since 1992, Hydro-Quebec has been developing prototypes of screened iron core fault current limiters for medium voltage distribution networks. Fault current limiters (FCLs) are amongst the most promising applications of high temperature superconductors. The unique properties of HTS such as high T/sub c/ and high resistivity in the flux flow state make them suitable for a design based on bulk materials. A 100 kVA class inductive study prototype of SFCL built around five commercial Bi-2212 hollow tubes (Hoechst) has been repeatedly tested at /spl sim/600 V RMS in nominal and fault conditions. In particular, the thermal stability has been investigated as a function of the temperature of the nitrogen bath (67-77 K). Simulation of the behaviour of the inductive limiter using differential equations are presented where both electromagnetic and thermal behaviour are considered. Part of this work is done within the joint collaboration between Hydro-Quebec and Siemens.
TL;DR: In this paper, the bulk and surface characteristics of high-energy ball-milling alloys were studied over the whole compositional range, and the structure of the various alloys was determined by X-ray diffraction.
TL;DR: In this paper, an analysis, operating experience and simulations of a large power system are used to demonstrate that active load modulation can improve the system's dynamic performance to a large extent, with just a fraction of the base load available for control.
Abstract: Analyses, operating experience and simulations of a large power system are used to demonstrate that active-load modulation can improve the system's dynamic performance to a large extent, with just a fraction of the base load available for control. At a time when the cost effectiveness of FACTS devices for damping interarea oscillations is constantly being questioned, it is natural to look to active-load modulation as a potential alternative method of insuring grid reliability. In developing the case, it was found that continuously modulating load stabilizers need to be fed with global signals for full efficiency. Although more difficult to design, implementation of a discontinuous control scheme shows good prospects, especially with regard to decentralization and robustness against communication delays.
TL;DR: In this paper, the authors provide an analysis of the components of V, and identify parameters and processes that arc involved in the effect of V on electroosmotic dewatering of clays, suspensions and fines.
Abstract: In the electroosmotic dewatering (EOD) of clays, suspensions and fines, a continuous or interrupted DC voltage, V, is applied between the anode and the cathode. In the previous literature on this subject the components of V have not been completely clarified. Following a brief outline of the EOD that emphasizes the central role of the electrochemical double layer, we provide an analysis of the components of V, Three case are distinguished (1)Threshold voltage V-n, for initiating the EOD and its connection to the so-called open-circuit voltage; (2)EOD at very low voltages viz. around IV; (3)EOD at very high rates for prolonged times where electrodes such as A𝓁 can form barrier oxides and some “caking” is also observed near the a node, This attempt to define the components of V under different conditions of EOD is aimed to identify parameters and processes that arc involved in the effect of V on EOD; RT for example, it is generally not recognized that —pH can form a significant part of V F under so...
TL;DR: Two dihydrophenazine derivatives bearing either 2-hydroxypropyl or ethyl substituents on both N atoms, have been tested in liquid and polymer electrolyte lithium cells as discussed by the authors.
TL;DR: In this article, the voltammetric behavior of methylmercury at Nafion ® coated glassy carbon electrodes is examined, showing that cyclic voltammograms recorded at coated electrodes show a dramatic increase of peak currents with respect to bare electrodes, this effect being more evident in perchlorate supporting electrolytes rather than in chloride containing media.
TL;DR: In this article, the effect of the Hg charge on the electroanalytical performance (net peak current, peak potential and peak width) of the metal trace sensors has been systematically studied by using square wave anodic stripping voltammetry (SWASV).
Abstract: Mercury-electroplated-Ir microelectrode array based sensors have been developed; their electroanalytical performance is investigated for the simultaneous detection of ultratraces of Pb, Cd and Zn. Two Ir microelectrode array geometries were used, namely: (i) an array of 1089 microelectrodes of 3-μm diameter and (ii) an array of 1764 microelectrodes of 6-μm diameter. Prior to the Hg electroplating, the arrays were systematically characterized by means of cyclic voltammetry at various scan rates ranging from 5 to 500 mV s−1 and found to exhibit a steady-state voltammetric behavior. The effect of the Hg charge (over a range as wide as 0.05–40 mC) on the electroanalytical performance (net peak current, peak potential and peak width) of the metal trace sensors has been systematically studied by using square wave anodic stripping voltammetry (SWASV). It is clearly shown that the net peak current not only depends on the magnitude of Hg charge, but also presents a maximum value for an optimum Hg charge. Optimum Hg charges of 4 and 15 mC were identified for the 3- and 6-μm diameter Ir microelectrodes, respectively. At the optimum Hg charges, calibration plots demonstrated good linearity for the three metal traces over a concentration range as wide as (100 ppt–1 ppm). By increasing the preconcentration time from 5 to 20 min, it is shown that the detection limit of metal ultratraces can be decreased from 100 to 20 ppt.
TL;DR: In this paper, an attempt is made to summarize the salient experimental observations on electroosmotic dewatering (EOD), as reported extensively but diffusely in the previous literature.
Abstract: An attempt is made to summarize the salient experimental observations on electroosmotic dewatering (EOD), as reported extensively but diffusely in the previous literature. The effects of the following factors on EOD have been examined: voltage; current magnitude and type (i.e.; interrupted or continuous DC); salts; acids; flocculants; clay types; electrode materials etc. This whole range of experimental data has been encapsulated as thirteen factual observations. The possible theoretical interpretation of each of the thirteen observations is proposed either by developing suitable arguments here or by referring to our previous theoretical papers on the subject
TL;DR: The use of polypropylene fibers up to 0.5% by the volume of the shotcrete did not affect significantly the compressive strength, and the fiber-reinforced shotcrete incorporating both fly ash and silica fume bonded well to the base concrete.
Abstract: This paper describes the materials used, mixture proportions, mixing and shotcreting operation, and properties of the fresh and hardened polypropylene fiber-reinforced shotcrete incorporating silica fume and high volumes of fly ash. The polypropylene fiber-reinforced high-volume fly ash shotcrete produced had satisfactory workability, mechanical properties, and resistance to freezing and thawing cycling. The shotcrete containing silica fume had negligible rebound compared with that without silica fume. The incorporation of fly ash and silica fume improved the workability of the fresh shotcrete, and this resulted in lower operating pressure for the shotcreting. The use of polypropylene fibers up to 0.5% by the volume of the shotcrete did not affect significantly the compressive strength, and the shotcrete incorporating both fly ash and silica fume bonded well to the base concrete. The fiber-reinforced shotcrete showed satisfactory performance after 300 cycles of freezing and thawing with a durability factor greater than 80, even though the air contents were relatively low and the spacing factor was relatively high.