Showing papers by "Hydro-Québec published in 2007"

Intelligent-Based Approach to Islanding Detection in Distributed Generation

Abstract: This paper introduces a new intelligent-based approach for detecting islanding in distributed generation (DG). This approach utilizes and combines various system parameter indices in order to secure the detection of islanding for any possible network topology, penetration level and operating condition of the DG under study. Hence, every parameter index displays characteristics for a given set of events. The proposed technique uses the data-mining technology to extract information from the large data sets of these indices after they are screened off-line via massive event analyses using network simulations. The technique is tested on a typical DG with multiple distributed resources and the results indicate that this technique can successfully detect islanding operations. In addition, this technique can also overcome the problem of setting the detection thresholds inherent in the existing techniques by optimizing their settings

Mechanism of the Fe3+ Reduction at Low Temperature for LiFePO4 Synthesis from a Polymeric Additive

Abstract: Comparison is made between the use of either a carbon powder or a polymer additive to the precursors in the synthesis of LiFePO4 from the Fe(III) compound FePO4(H2O)2 and Li2CO3. The evolution of the structural properties and phase purity with temperature and time have been monitored at all length scales by X-ray diffraction, Fourier transformed infrared spectroscopy, and magnetic susceptibility. The reactor temperature was decreased to 300 °C to investigate the early stages of the reaction. Formation of crystalline LiFePO4 begins in the range 300−400 °C only if the polymer is used as the carbonaceous additive. This LiFePO4 formation is made possible by the reduction of Fe(III) species by gases such as H2 or gaseous hydrocarbons evolved during the calcination of the polymer. Moreover, decomposition of the polymer results in a carbonaceous deposit on the surface of the LiFePO4 particles. An Li3Fe2(PO4)3 impurity found after sintering at 400 °C for 4 h was greatly reduced after sintering at 400 °C for 24 h,...

Automatic Segmentation of Large Power Systems Into Fuzzy Coherent Areas for Dynamic Vulnerability Assessment

Abstract: This paper proposes a technique for partitioning a large power system into a number of coherent electric areas for possible application to dynamic vulnerability assessment. The coherency concept and a fuzzy clustering algorithm grouping of buses are combined to achieve this goal. The clusters are obtained by selecting representative buses from the data set in such a way that the total fuzzy dissimilarity within each cluster is minimized. The initialization problem of the conventional fuzzy c-means algorithm, which usually leads to multiple solutions, is suitably tackled by incorporating the maximum-dissimilarity based sequential phasor measurement unit (PMU) placement technique. Results of bus grouping for two test systems of three and nine areas demonstrate the potential of the approach. It is observed that such an approach to bus grouping results in a PMU configuration with minimum number of devices and fast data aggregation for a wide-area measurement system.

Identification of a chemical indicator of the rupture of 1,4-β-glycosidic bonds of cellulose in an oil-impregnated insulating paper system

Abstract: In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded (TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with 2-furfuraldehyde, which is the current reference in the domain.

Predicting river water temperatures using stochastic models : case study of the Moisie River (Québec, Canada)

Abstract: Successful applications of stochastic models for simulating and predicting daily stream temperature have been reported in the literature. These stochastic models have been generally tested on small rivers and have used only air temperature as an exogenous variable. This study investigates the stochastic modelling of daily mean stream water temperatures on the Moisie River, a relatively large unregulated river located in Quebec, Canada. The objective of the study is to compare different stochastic approaches previously used on small streams to relate mean daily water temperatures to air temperatures and streamflow indices. Various stochastic approaches are used to model the water temperature residuals, representing short-term variations, which were obtained by subtracting the seasonal components from water temperature time-series. The first three models, a multiple regression, a second-order autoregressive model, and a Box and Jenkins model, used only lagged air temperature residuals as exogenous variables. The root-mean-square error (RMSE) for these models varied between 0·53 and 1·70 °C and the second-order autoregressive model provided the best results. A statistical methodology using best subsets regression is proposed to model the combined effect of discharge and air temperature on stream temperatures. Various streamflow indices were considered as additional independent variables, and models with different number of variables were tested. The results indicated that the best model included relative change in flow as the most important streamflow index. The RMSE for this model was of the order of 0·51 °C, which shows a small improvement over the first three models that did not include streamflow indices. The ridge regression was applied to this model to alleviate the potential statistical inadequacies associated with multicollinearity. The amplitude and sign of the ridge regression coefficients seem to be more in agreement with prior expectations (e.g. positive correlation between water temperature residuals of different lags) and make more physical sense. Copyright © 2006 John Wiley & Sons, Ltd.

Recursion-based multiple changepoint detection in multiple linear regression and application to river streamflows

Abstract: [1] A large number of models in hydrology and climate sciences rely on multiple linear regression to explain the link between key variables. The relationship in the physical world may experiment sudden changes because of climatic, environmental, or anthropogenic perturbations. To deal with this issue, a Bayesian method of multiple changepoint detection in multiple linear regression is proposed in this paper. It is an adaptation of the recursion-based multiple changepoint method of Fearnhead (2005, 2006) to the classical multiple linear model. A new class of priors for the parameters of the multiple linear model is introduced, and useful formulas are derived that permit straightforward computation of the posterior distribution of the changepoints. The proposed method is numerically efficient and does not involve time consuming Monte-Carlo Markov Chain simulation as opposed to other Bayesian changepoint methods. It allows fast and straightforward simulation of the probability of each possible number of changepoints as well as the posterior probability distribution of each changepoint conditional on the number of changes. The approach is validated on simulated data sets and then compared to the methodology of Seidou et al. (2006) on two practical problems, as follows: (1) the changepoint detection in the multiple linear relationship between mean basin scale precipitation at different periods of the year and the summer-autumn flood peaks of the Broadback River located in Northern Quebec, Canada; and (b) the detection of trend variations in the streamflows of the Ogoki River located in the province of Ontario, Canada.

Nanoscopic scale studies of LiFePO4 as cathode material in lithium-ion batteries for HEV application

Abstract: We present a review of the structural properties of LiFePO4. Depending on the mode of preparation, different impurities can poison this material. These impurities are identified and a quantitative estimate of their concentrations is deduced from the combination of X-ray diffraction analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and magnetic measurements. An optimized preparation provides samples with carbon-coated particles free of any impurity phase, insuring structural stability and electrochemical performance that justify the use of this material as a cathode element a new generation of lithium secondary batteries.

Multilayer material, method for making same and use as electrode

Abstract: A multilayer material includes a solid substrate and at least two superimposed solid layers containing particles of an electrochemically active material, the first solid layer adhering to the solid substrate and the second solid layer adhering to the first solid layer. The multilayer material has a constant thickness of upper layer not less than 95% and a depth of penetration of the second layer into the first layer which is less than 10% of the thickness of the first layer, and enables as electrode constituent, generators having a low risk of overload degradation to be prepared.

Catalytic activity and performance of LSM cathode materials in single chamber SOFC

Abstract: The catalytic activity of symmetrical LSM (La0.8Sr0.2MnO3) cells operated under single chamber solid oxide fuel cell (SC-SOFC) conditions was investigated for methane-to-oxygen ratios Rin between 1 and 2. The oxidation reactions over electrodes sintered at 1100 °C (LSM1100) and 1200 °C (LSM1200) were studied, and the effect of any combustion was followed through electrochemical impedance spectroscopy (EIS). The activity of the LSM1100 electrode increases with temperature. Above 700 °C, the conversion of the oxygen species may exceed 30%. As a consequence, oxygen depletion is occurring and a low frequency semicircle in the EIS spectra becomes predominant. An increase of the sintering temperature to 1200 °C leads to a decrease in the catalytic activity. A LSM1100 electrode deposited on a Julich half-cell proves to reach better performance at 600 °C than at 700 °C. On such complete cells, however, the catalytic combustion becomes much more complex than on a LSM cathode alone. We are thus proposing a comprehensive parameter, Rout, that is summarizing the processes inside the single chamber reactor.

Modelling of DEMO core plasma consistent with SOL/divertor simulations for long-pulse scenarios with impurity seeding

Abstract: The integrated core-pedestal-SOL model is applied to the simulation of a typical DEMO operation. Impurity seeding is used to reduce the power load on the divertor to acceptable levels. The influence on long-pulse operation of impurity seeding with various impurities is investigated. DEMO operation at acceptable peak power loads and long-pulse lengths is demonstrated.

Cumulative effects assessments at Hydro-Québec: what have we learned?

Abstract: Twelve cumulative effects assessments (CEAs) have been conducted at Hydro-Quebec since 1999. This article explains how they have evolved in a seven-step approach. It also describes the problems encountered and solutions found for each of these steps. Hydro-Quebec's CEAs focus on historical and regional perspectives, including a detailed past baseline description. However, there is no specific methodology proposed for significance determination, and possibly no need for it. CEAs provide a broader view that is found useful to assess impacts sometimes not properly tackled at the project level, but the question of how the promoter should conduct follow-up and mitigation efforts in the context of cumulative effects is still open. CEA must be a separate section of an impact assessment with its own methodology, spatial and temporal scales. Only certain environmental components should be examined. A well-documented past baseline condition is essential. Future effects can rarely be predicted over a ten-year period...

Coplanar Electrodes Design for a Single-Chamber SOFC Assessment of the Operating Parameters

Abstract: Solid-oxide fuel cells (SOFC) made of conventional materials with coplanar interdigitated electrodes located on the same side of the electrolyte have been fabricated and tested in a uniform mixture of methane and air in order to evaluate the influence of various operating parameters on cell performances. Anode thickness of several hundred micrometers is required to reach good cell stability. Also, the relative positioning of the electrodes in regard to the gas flow should be optimized as the gas composition is modified after passage over the anode. This aspect is particularly important with stacked cells, due to the modification of the gas composition in the upstream portion of the stack. Enhanced performances of the single-side cell were obtained by decreasing the width of the electrodes and their spacing, which both have the effect of reducing the ohmic loss. Following this approach, performances of 40 mW cm -2 were recorded at 800°C using electrodes of 0.5 X 8 mm separated by a gap of 0.2 mm.

An Experimental Evaluation of the Temperature Gradient in Solid Oxide Fuel Cells

Abstract: The use of solid oxide fuel cells SOFCs 1,2 as efficient energyconverter devices rests on their high working temperature. These ceramic fuel cells generally operate between 800 and 1000°C, although a major research effort is put forward to reduce their operation below 800°C for reducing manufacturing costs and improving cell lifetime. Depending on the selected range of temperature, a SOFC system would allow for either cogeneration or bottoming cycle, which add significantly to the overall power-generation efficiency. The high operating temperature of SOFC affords, in principle, for the direct use of hydrocarbon fuels by means of their catalytic conversion to carbon monoxide and hydrogen. The most economical way to convert these fuels is to proceed through direct internal reforming DIR, as it is observed in tubular or planar designs, or through catalytic partial oxidation CPOX, which is at the basis of the functioning of single-chamber SOFC SC-SOFC. However, both DIR and CPOX may lead to high temperature variations along the fuel cell. In the case of direct reforming of methane, a significant cooling at the inlet of the fuel cell is expected due to the fast kinetics of the endothermic reforming reaction, especially over conventional Ni– yttria-stabilized zirconia YSZ cermet. 3 It then aggravates the tem

Multilayer material based on active lithium, method of preparation and applications in electrochemical generators

Abstract: A method for preparing a multilayer material based on active lithium, by depositing a film of active lithium on a protective layer at a sufficient speed so that substantially no oxidation of the lithium occurs, and/or during a sufficient time for the adhesion of the lithium to develop after contact with the protective layer. The multilayer material, when incorporated in an electrochemical battery as an anode, has excellent impedance stability and no formation of dendrites during the cycling. Batteries where the anode is the multilayer material are particularly efficient in terms of their coulomb efficiency.

A 100-MW Variable Frequency Transformer (VFT) on the Hydro-Québec TransÉnergie Network - The Behavior during Disturbance

Abstract: The Langlois project is the world's first application of the "variable frequency transformer" (VFT) technology, which was successfully commissioned on the Hydro-Quebec TransEnergie (HQTE) system in the spring of 2004. The VFT consists of a rotary transformer, for continuously controllable phase shift, together with a drive system and control that adjust the angle and speed of the rotary transformer to regulate the power flow through the VFT. The VFT system provides a means to control power flow between asynchronous grids. This paper show's how the VFT reacts to grid disturbances by showing curves of real events like single phase to ground faults, three phase faults, islanding, how its natural reaction helps weak networks by comparing the results of a simulation of the network with and without the VFT.

Surface preparation of natural graphite and the effect of impurities on grinding and the particle distribution

Abstract: The present invention relates to the physical or chemical specific purification of natural mineral graphite This purification is preferably applied to the surface of natural graphite in order to allow the formation of a passivation film during the first electrical discharge or the insertion of lithium in the graphite when the latter is used in a lithium-ion cell The grinding to a small size before purification allows the optimization of the distribution of the particles, resulting in a more uniform electrode This grinding is carried out in the presence of the natural impurities of the graphite that play the role of a micro-abrasive and result in a hardness of the graphite that increases its mechanical properties

Synthesis method for carbon material based on LiMPO4

Abstract: Method of synthesis for a material made of particles having a core and a coating and/or being connected to each other by carbon cross-linking, the core of these particles containing at least one compound of formula Li x M 1-y M′ y (XO 4 ) n , in which x, y and n are numbers such as 0≦x≦2, 0≦y≦0.6 and 1≦n≦1.5, M is a transition metal, M′ is an element with fixed valency, and the synthesis is carried out by reaction and bringing into equilibrium the mixture of precursors, with a reducing gaseous atmosphere, in such a way as to bring the transition metal or metals to the desired valency level, the synthesis being carried out in the presence of a source of carbon called carbon conductor, which is subjected to pyrolysis. The materials obtained have excellent electrical conductivity, as well as very improved chemical activity.