Showing papers by "Hydro-Québec published in 2004"
TL;DR: The modeling of multivariate extreme values using copulas allows us to model the dependence structure independently of the marginal distributions, which is not possible with standard classical methods.
Abstract: [1] This article presents the modeling of multivariate extreme values using copulas. Our approach allows us to model the dependence structure independently of the marginal distributions, which is not possible with standard classical methods. The methodology has been applied on two different problems in hydrology. The first application is concerned with the combined risk in the framework of frequency analysis. Four copulas have been tested on peak flows from the watershed of Peribonka in Quebec, Canada. The second application relates to the joint modeling of peak flows and volumes. Three copulas have been applied to the watershed of the Rimouski River in Quebec, Canada. This approach using copulas is promising since it allows us to take into account a wide range of correlation which can happen in hydrology.
583 citations
TL;DR: A personal view of the nanodielectric field is given in this paper, with a tentative definition of the concept of nanodieslectrics being offered at the end of the paper.
Abstract: The neologism nanotechnology exists today and is attracting a considerable amount of interest and activity. It is complex in nature with multiple ramifications. It has a vast scope and in fact includes older as well as newer concepts. At this point in time, a greater focus on the field status and impact on new materials, especially dielectrics and their insulating properties, would certainly be desirable. A personal view is thus being presented here, with a tentative definition of the concept of nanodielectrics being offered at the end.
174 citations
TL;DR: In this paper, the aging and performance of natural graphite/PEO-based gel electrolyte/LiFePO4 cells are reported, and the gel polymer electrolytes were produced by electron-beam irradiation and then soaked in a liquid electrolyte.
145 citations
TL;DR: In this article, the performance of natural graphite/PEO-based gel electrolyte/LiFePO 4 cells (5.5mm, 4 cm 2 ) was reported.
134 citations
TL;DR: Li4Ti5O12 was prepared by a solid-state reaction of ternary precursor materials TiO2, Li2CO3 and carbon as discussed by the authors, and the particle shape and size of the product were connected to the carbon type used in the synthesis.
107 citations
TL;DR: In this paper, a comparative analysis of hydrophobicity of fluoroalkylsiloxane and alkylsiloxane monolayers is presented, where a simple model considering various self-assembly degrees of organic molecules and various area fractions of air inclusion is used.
95 citations
TL;DR: In this paper, a statistical analysis of meteorological data for icing and ice shedding on overhead power-line conductors was performed, which aimed at establishing shape and statistical parameters of the transfer functions representing the correlations between hourly icing rate and the variations of the following meteorological variables: ambient temperature, hourly number of ice rate meter signals, wind speed and direction, and freezing precipitation rate.
Abstract: Statistical analysis of meteorological data for icing and ice shedding on overhead power-line conductors was performed. The data studied were recorded during the 57 icing events (1659 h), which occurred in the period between February 1998 and January 2000 at the Mont Be/spl acute/lair icing test site in Quebec, Canada. The analysis aims at establishing shape and statistical parameters of the transfer functions representing the correlations between hourly icing rate and the variations of the following meteorological variables: ambient temperature, hourly number of ice-rate meter signals, wind speed and direction, and freezing precipitation rate. Two different regimes of the ice formation process, in-cloud icing, and freezing precipitation icing, are considered for characterizing ice events. The set of fitting regression curves obtained is the statistical base for creating an empirical probabilistic icing, and ice shedding model for studying and forecasting atmospheric-icing loads on overhead power-line conductors.
89 citations
TL;DR: In this article, single-chamber cells of two different types have been operated between 700 and 800°C in various methane-air mixtures, and the anode-supported cells operate in a narrower range of methane air ratios, but offer remarkable maximum specific powers, 360 and 285 mW/cm 2 at 800 and 700°C.
Abstract: Single-chamber cells of two different types have been operated between 700 and 800°C in various methane-air mixtures. These cells are made mostly of conventional materials for solid oxide fuel cells (SOFCs), strontium-doped lanthanum manganite, yttria-stabilized zirconia (YSZ), and Ni-YSZ cermet. One type is electrolyte-supported, while the other represents a state-of-the-art fabrication for anode-supported cells. The anode-supported cells operate in a narrower range of methane-air ratios, but offer remarkable maximum specific powers, 360 and 285 mW/cm 2 at 800 and 700°C, respectively. Some theoretical considerations about the actual operation of these cells are also provided.
88 citations
TL;DR: In this article, the structure and hydrolysis reaction of ball-milled MgH 2 -Ca and mgH2 -CaH 2 mixtures was investigated in function of milling time and component proportion.
80 citations
TL;DR: In this article, Raman spectra of Li4/3+xMe5/3O4 spinels are compared and analyzed on the basis of structural modifications of their lattices upon lithium insertion.
69 citations
TL;DR: In this article, the authors present a real-time AC drive simulator that combines in a single model both the power converter and motor models to simulate the behavior of large DC drives.
Abstract: This paper presents the analysis and validation of a real-time AC drive simulator. Real-time simulation has been used for over a decade in power systems engineering to test controllers thoroughly, efficiently, and safely. The development and testing of large DC drives could benefit from this type of simulation, but real-time power system simulators have modeling restrictions preventing stable and accurate simulation of isolated drives switching at high frequencies. These restrictions can be overcome by combining in a single model both the power converter and motor models. After discussing the salient issues related to the real-time simulation of DC drives, a prototype real-time simulator for drives is described. Its ability to accurately emulate the behavior of large drives is demonstrated through two case studies. A first case study demonstrates the feasibility of simulating a drive of typical complexity in real-time. The second case study demonstrates how the controller for a PWM VSI fed induction motor, switching at 4 kHz, is designed, implemented in a microcontroller and tested in real-time using a simulated inverter, motor and load. Comparisons against results obtained with another simulation tool, which uses extremely accurate variable-step integration algorithms, demonstrates the validity of our approach.
01 Jan 2004
TL;DR: In this paper, the 1989 collapse of the Hydro-Quebec system and the 2001 TranPower system in New Zealand were reviewed. But, the 1989 event was significantly less severe than the 2001 event, which caused plant failures on a system that had no previously considered geomagnetic induced currents a threat to power quality and security of supply.
Abstract: Space weather has long been known to effect electric power systems, these effects can range in scale from the barely noticeable to the catastrophic. This paper reviews two events, one the 1989 collapse of the Hydro-Quebec system which ranks as probably the most significant power system event tracable to geomagnetically induced currents and two, the 2001 event on the Tranpower system in New Zealand, which while significantly less severe did cause plant failures on a system that had no previously considered geomagnetically induced currents a threat to power quality and security of supply
TL;DR: In this article, the authors measured CO2 fluxes at the water-air interface using floating chambers connected to an automated NDIR or a Fourier transform infrared instrument (FTIR).
Abstract: The fluxes of carbon dioxide were determined at the water–air interface using floating chambers connected to an automated nondispersive infrared instrument (NDIR) or a Fourier transform infrared instrument (FTIR). The fluxes were measured in 2002 over 280 sites in Canadian reservoirs, rivers, and natural lakes. Mean measured emissions of CO2 in old Quebec reservoirs (> 10 years) were around 1600 ± 1500 mg CO2/m2/day and around 735 ± 1125 mg CO2/m2/day in natural lakes. In a young Quebec reservoir (5 years old), values were higher, with mean measured emissions around 4400 ± 4000 mg CO2/m2/day. In Manitoba, old reservoirs had mean values around 3350 ± 2725 mg CO2/m2/day and natural lakes values around 1365 ± 2375 mg CO2/m2/day. In British Columbia, mean values were around 250 ± 800 and 500 ± 650 mg CO2/m2/day, respectively, for old reservoirs and natural lakes. Our data suggest that water quality and the input of carbon from terrestrial systems affect CO2 fluxes from waterbodies. Our results also show that reservoirs older than 10 years are comparable to natural lakes or rivers in terms of the water quality or gross CO2 fluxes and that higher emissions in young reservoir would last 6–8 years.
TL;DR: In this paper, structural and electrochemical properties of Li4/3Me5/3O4 (Me Ti, Mn) spinel materials exhibiting nanostructured morphology were reported.
TL;DR: In this article, a method for evaluating the performance of demodulation-based frequency measurement algorithms in the presence of additive interfering sinusoids is presented, where the error induced by a single interfering tone is easily computed using the cascade algorithm's frequency response magnitude.
Abstract: This paper presents a method for evaluating the performance of demodulation-based frequency measurement algorithms in the presence of additive interfering sinusoids. Determination of the performance of amplitude measurement schemes under such conditions is straightforward once the frequency responses of the filters involved in the process are known, since the error induced by a single interfering tone is easily computed using the cascade algorithm's frequency response magnitude. This paper presents a similar method for predicting the worst error of frequency measurement schemes with respect to sinusoidal interference. Once acquainted with the proposed error prediction formula, the only difficulty in designing effective frequency measurement algorithms is the appropriate selection of output filters to achieve the specified performance. The method has been used successfully in designing frequency measurement algorithms currently used in Hydro-Que/spl acute/bec's special protection schemes.
TL;DR: This paper reformulate the original shifting level model to conform to the so-called Hidden Markov Chain models (HMMs), and uses Gibbs sampling in a Bayesian framework for parameter estimation and shows the applicability of the reformulated shiftinglevel model for detection of abrupt regime changes and forecasting of annual streamflow series.
TL;DR: In this article, a single-chamber solid oxide fuel cell (SOFC) experiments have been carried out at temperatures below 900°C with methane-air mixtures with conventional materials like for the cathode and a NiO-yttria-stabilized zirconia (YSZ) cermet for the anode.
Abstract: Single-chamber solid oxide fuel cell (SOFC) experiments have been carried out at temperatures below 900°C with methane-air mixtures. Our study confirms previous results obtained by Hibino and co-workers with conventional materials like for the cathode and a NiO-yttria-stabilized zirconia (YSZ) cermet for the anode. In addition, special attention has been paid both to the gas flow and to the actual operating temperatures. Platinum meshes and wires upon the electrodes would greatly influence their actual operating temperature and they have been systematically avoided for the working cells within this study. © 2004 The Electrochemical Society. All rights reserved.
TL;DR: The study of dolostone of the Lower Silurian Sayabec Formation of the Lac Matapedia syncline, at the western end of the Gaspe Peninsula, sheds new light on porosity development and reservoir potential of the area as mentioned in this paper.
Abstract: The study of dolostone of the Lower Silurian Sayabec Formation of the Lac Matapedia syncline, at the western end of the Gaspe Peninsula, sheds new light on porosity development and reservoir potential of the area. The dolomitized section is close to the Shickshock Sud Fault that cuts the southern limb of the syncline. The dolostone occurs either as a highly brecciated unit or as stratiform replacement of peritidal carbonates at the base of the formation. Residual bitumen is seen in the breccia as well as filling of small secondary vugs and fractures within the stratiform dolostone. The dolostone consists predominantly of replacive matrix dolomite; petrography and oxygen and carbon stable isotope ratios (δ18OVPDB = -6.3 to -7.8‰ and δ13CVPDB = 1.2 to 3.3‰) of the matrix dolomite indicate early burial formation with later recrystallization in the presence of high temperature fluids. Saddle dolomite is found as a pore-filling cement in secondary dissolution pores and fractures. Oxygen stable isotope ratios of the saddle dolomite cement (δ18OVPDB = -14.5 and -15.3‰) indicate precipitation at high temperature. Dull luminescent burial calcite cement follows saddle dolomite. Later dissolution is locally apparent in carbonates as scalloped surfaces covered by finely laminated, bright-very dull luminescent calcites. Petrography and stable isotope ratios of the calcite (δ18OVPDB = -10.1 and -11.2‰ and δ13CVPDB = -2.3 and -6.9‰) suggest precipitation from meteoric waters. Meteoric dissolution and luminescent-zoned calcite cements are related to a Pridolian sea level lowstand. This event provides a first age constraint on the timing of the hydrothermal dolomitization and hydrocarbon charge of the Sayabec Formation along the northern edge of the Gaspe Belt. The Shickshock Sud Fault channelled the hydrothermal fluids, which dolomitized the Sayabec Formation shortly after initial burial. A recent regional seismic program showed compressive structures (duplexes, backthrust, triangle zone) in the Sayabec Formation inferred to have occurred in latest Silurian-Early Devonian that generated structural traps superimposed on the stratigraphic (shaly facies) and diagenetic (tight non-dolomitized limestone) seals. Seismic anomalies ("flat spots") in the Lower Silurian section in eastern Quebec suggest the presence of hydrocarbon-filled reservoirs.
TL;DR: In this article, the feasibility of bipolar membrane electroacidification (BMEA) to fractionate whey proteins and the effect of protein concentration on its performance in comparison with chemical acidification were investigated.
Abstract: Bipolar membrane electroacidification (BMEA) is a technology offering the coupled effect of demineralization and acidification by using the properties of bipolar membranes to dissociate water molecules at their interfaces and of cation exchange membranes (CEM) to demineralize by migration of low molecular weight ionic species. The aim of the present study was to demonstrate the feasability of BMEA to fractionate whey proteins and to study the effect of protein concentration on its performance in comparison with chemical acidification. These results demonstrated the feasability of BMEA for whey protein separation and the influence of the initial protein concentration on the purity and yield of the separated fraction. At 5% whey protein isolate (WPI) initial concentration, this technology allows the separation of 98% pure β-lactoglobulin (β-lg) fraction with a 44.0% recovery yield. At 10% WPI initial concentration, BMEA allows the production of a β-lg-enriched fraction containing 97.3 of β-lg and 2.7% α-lactalbumin (α-la), for a 98% total protein purity.
Patent•
12 Nov 2004TL;DR: In this paper, a motorized bracelet assembly for ultrasonic crack detection in a pipe is presented, which includes a motorised frame adapted for installation around the pipe and a sliding arrangement slideable mounted onto the frame.
Abstract: A motorized bracelet assembly for ultrasonic crack detection in a pipe. The bracelet has a motorized frame adapted for installation around the pipe and a sliding arrangement slideably mounted onto the frame. The sliding arrangement guides a displacement of sensor modules in periphery of the pipe. A first driving device controllably drives the sliding arrangement and thereby displacing the sensor modules in periphery of the pipe at desired operating positions. The bracelet comprises biasing devices for biasing the sensor modules against the pipe and a second driving device for controllably driving the frame along the axial direction of the pipe at a desired operating position.
TL;DR: In this article, the vibrational spectra of nanostructured magnesium hydride were used as a probe for the local structure and the influence of the nanostructure on the potential landscape experienced by the hydrogen.
Abstract: Light-weight magnesium metal can reversibly store up to 7 wt.% hydrogen and is therefore interesting for application as hydrogen storage material. Neutron vibrational spectroscopy has been used to study the interactions of hydrogen atoms with it surroundings. The neutron spectra are compared directly with density functional theory calculations providing detailed insight in structure and dynamics. Dispersion of the vibrational modes has to be taken into account in order to reproduce the data. This study on bulk magnesium hydride will provide a bench mark for similar studies on nanostructured magnesium alloys: these are more promising as hydrogen storage materials because of their significantly faster hydrogen sorption processes. Because of its sensitivity and the compatibility to calculations, the vibrational spectra of these nanostructured compounds can be used as a probe for the local structure and the influence of the nanostructure on the potential landscape experienced by the hydrogen. Parameters can be extracted for MD and Monte Carlo calculations of slower diffusion processes.
TL;DR: In this paper, accelerated aging tests have been carried on stator bars under simultaneous electrical, thermal and mechanical multi-stress conditions, using a simulated three-phase model stator.
Abstract: Accelerated aging tests have been carried on stator bars under simultaneous electrical, thermal and mechanical multi-stress conditions, using a simulated three-phase model stator. Over each thermal load cycle, the partial discharge activity has been found to be a strong function of temperature. Tests at twice rated electrical stress did not result in any bar specimen failures up to a total of 1500 load cycles. However, when the three phase load current was increased above its rated value, current-limited type failures were observed to occur below 1000 load cycles, thereby indicating a marked influence of thermal and mechanical stresses associated with the elevated three phase load current.
TL;DR: In this article, the authors presented a method to modify 5-damped response spectra for sites in eastern North America (ENA) to provide response spectrum for damping values other than 5, based on analysis of typical ENA earthquake ground-motion signals over a range of magnitudes and distances.
Abstract: National seismic hazard maps in Canada and the United States generally provide input ground motions in the form of 2%/50-year response spectra for an assumed 5% of critical damping. This paper presents a practical method to modify 5%-damped response spectra for sites in eastern North America (ENA) to provide response spectra for damping values other than 5%, based on analysis of typical ENA earthquake ground-motion signals over a range of magnitudes and distances.
TL;DR: Evidence is provided that EMF exposure may modify the response of dairy cows to photoperiod and plasma prolactin concentrations found were lower, and the mean plasma PRL concentration was not affected by treatment.
Abstract: Two experiments were conducted to test the hypothesis that electric and magnetic field (EMF) exposure may result in endocrine responses similar to those observed in animals exposed to long days. In the first experiment, 16 lactating, pregnant Holstein cows were assigned to two replicates according to a crossover design with treatment switchback. All animals were confined to wooden metabolic cages and maintained under short day photoperiods (8 h light/16 h dark). Treated animals were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 microT (EMF) for 16 h/day for 4 weeks. In a second, similar experiment, 16 nonlactating, nonpregnant Holstein cows subjected to short days were exposed to EMF, using a similar protocol, for periods corresponding to the duration of one estrous cycle. In the first experiment, circulating MLT concentrations during the light period showed a small numerical decrease during EMF exposure (P < .05). Least-square means for the 8 h light period were 9.9 versus 12.4 pg/ml, SE = 1.3. Melatonin concentrations during the dark period were not affected by the treatment. A similar trend was observed in the second experiment, where MLT concentrations during the light period tended to be lower (8.8 pg/ml vs. 16.3 pg/ml, P < .06) in the EMF exposed group, and no effects were observed during the dark period. Plasma prolactin (PRL) was increased in the EMF exposed group (16.6 vs. 12.7 ng/ml, P < .02) in the first experiment. In the second experiment, the overall PRL concentrations found were lower, and the mean plasma PRL concentration was not affected by treatment. These experiments provide evidence that EMF exposure may modify the response of dairy cows to photoperiod.
TL;DR: Arcing faults on 600/347-V underground cables can cause considerable damage, even explosions, despite the installed protection system as mentioned in this paper, and the protection sometimes appears to be quite slow to operate considering the prospective short circuit.
Abstract: Arcing faults on 600/347-V underground cables can cause considerable damage, even explosions, despite the installed protection system. In fact, the protection sometimes appears to be quite slow to operate considering the prospective short circuit. Laboratory tests provided an opportunity to better characterize these arcing faults and prove that they can be intermittent. They can be quite random in nature, usually comprising periods of conduction lasting one half-cycle separated by periods of nonconduction lasting from a few cycles to several minutes. This type of fault can easily make fuse-type protection ineffective, as other tests proved. The fuse operating time can become even longer, to the extent that explosive gases will form.
TL;DR: A structural and morphological study of nanostructured gold thin films prepared by pulsed laser deposition in the presence of several inert background gases (Ar, He, and N2) and at various pressures (from 10 mTorr to 1 Torr) and target-to-substrate distances (from 1 to 10 cm) is presented in this article.
Abstract: A structural and morphological study of nanostructured gold thin films prepared by pulsed laser deposition in the presence of several inert background gases (Ar, He, and N2) and at various pressures (from 10 mTorr to 1 Torr) and target-to-substrate distances (from 1 to 10 cm) is presented. Structural and morphological analyses were undertaken using semiquantitative x-ray diffraction, scanning tunneling microscopy, and transmission electron microscopy. For each set of deposition conditions, the kinetic energy of the neutral gold species [Au(I)] present in the plasma plume was determined by time-of-flight emission spectroscopy and used to characterize the plasma dynamics. It is shown that all films exhibit a transition from highly [111] oriented to polycrystalline as the Au(I) kinetic energy decreases. The polycrystalline phase ratio is close to 0% for Au(I) kinetic energy larger than approximately 3.0 eV/atom and approximately 86 ± 10% for Au(I) kinetic energy smaller than approximately 0.30 eV/atom, irrespective of the background gas atmosphere. The mean crystallite size of both phases and the mean roughness of the films also follow a unique relation with the Au(I) kinetic energy, independently of the nature of the background gas, and nanocrystalline films with crystallite size as small as 12 nm are obtained for Au(I) kinetic energy smaller than 0.3 eV/atom.
TL;DR: In this article, the discharge behavior of metallic cylinder-dielectric plane gaps in flowing helium was examined under atmospheric pressure at a frequency of 10 kHz as a function of gap length and applied voltage.
Abstract: The discharge behaviour of metallic cylinder-dielectric plane gaps in flowing helium was examined under atmospheric pressure at a frequency of 10 kHz as a function of gap length and applied voltage. The high-voltage electrode consisted of a steel cylinder with a radius of 3.15 mm, with alumina (Al2O3) or glass plates being utilized as low-potential electrodes. The bottom surface of the low-potential electrodes was covered with a thin Al layer (alumina plate) or an ITO layer (glass plate) that formed the grounded counter-electrodes. The electrical and photoemission currents were recorded simultaneously and precisely synchronized with an ultra-high-speed intensified charge coupled device camera for recording the discharge patterns. The experimental results were compared with those derived from a mathematical model on the basis of the continuity equations for electrons, ions and excited particles and the Poisson equation. The influence of surface charge on the dielectric electrodes on the time evolution of the helium discharge was analysed, and the experimental and theoretical vertical (y(t)) and horizontal (x(t)) dimensions of the discharges were determined for different low-potential electrode arrangements. A reasonable agreement was obtained between the measured and calculated y(t) and x(t) values.
10 Jun 2004
TL;DR: In this paper, the authors deal with the conception and the control logic of an undervoltage load shedding scheme aimed at protecting the Hydro-Quebec system against long-term voltage instability.
Abstract: In recent years, Hydro-Quebec has undertaken a major program to upgrade the reliability of its transmission system. Much effort has been focused on increasing the system's ability to withstand extreme contingencies, usually caused by multiple incidents or the successive tripping of transmission lines. This work deals with the conception and the control logic of an undervoltage load shedding scheme aimed at protecting the Hydro-Quebec system against long-term voltage instability. Various results showing the impact of the operation of these automatisms on the system stability are provided in this paper.
Patent•
23 Sep 2004TL;DR: In this article, a method and apparatus for providing a determined position in real-time of an underwater object using a plurality of sensors operating at various sampling rates and for using the determined position to perform inspection tasks inter alia.
Abstract: A method and apparatus is disclosed for providing a determined position in real-time of an underwater object using a plurality of sensors operating at various sampling rates and for using the determined position in real-time in order to perform inspection tasks inter alia.
TL;DR: In this article, an integrated core-pedestal-SOL modeling for ITER was performed using the MMM95 model for energy transport, modified with additional magnetic shear stabilization to produce a pedestal.
Abstract: Integrated core–pedestal–SOL modelling is performed for ITER using the MMM95 model for energy transport, modified with additional magnetic shear stabilization to produce a pedestal. The additional stabilization term is calibrated against experiment. The operating space of ITER predicted by the model with neoclassical accumulation of intrinsic carbon impurity is determined. The relationship to an SOL-based density limit is investigated. A reasonable window for operation, with Q larger than 10 is found.