Showing papers by "Hydro-Québec published in 2001"

Wide-area measurement based stabilizing control of large power systems-a decentralized/hierarchical approach

Abstract: The aim of this paper is to assess the capability of the emerging synchronized phasor measurement technology in improving the overall stability of the Hydro-Quebec transmission system through supplementary modulation of voltage regulators. Following a thorough singular value and eigenvalue analysis of the system dynamic interactions, five control sites consisting of four generators and one synchronous condenser are chosen to implement new power system stabilizers with a supplementary input from remote phasor measuring units, geographically spread over nine electrically coherent areas. Since the remote feedback loops are built on top of an existing decentralized control system, this design approach results in a decentralized/hierarchical control architecture with significant advantages in terms of reliability and operational flexibility. A systematic control and measurement pairing yielded four dominant natural loops, each associated with a significant open-loop inter-area oscillatory mode at 0.06, 0.4, 0.7 and 0.95 Hz respectively. These PSSs have a speed sensitive local loop operating in the usual way, and a wide-area measurement based global loop which involves a single differential frequency signal between two suitably selected areas. The tuning and coordination technique for these advanced multiple input signals PSSs is described. Their impacts on the system is assessed using both small-signal analysis and nonlinear simulations in a transient stability program. Wide-area stabilizing controllers have a significant potential in improving the dynamic performance of the Hydro-Quebec's existing power system.

Mechanically alloyed metal hydride systems

Abstract: Mechanosynthesis of metal hydrides is a new field in which important progress has been reported. In this paper, we present recent developments in mechanosynthesis of magnesium-based hydrides for storage applications. The effect of intense milling on magnesium and magnesium hydrides is presented. The influence of various additives on hydrogen-sorption properties is discussed with special emphasis on nanocomposite MgH2+5 at. % V, where hydrogen-storage characteristics, cycling properties and the mechanism of hydrogen desorption are presented. The production of novel nanocrystalline porous structures by mechanical alloying followed by a leaching technique is discussed. Hot ball-milling, as a new method for rapid synthesis of alloys, is also presented. Finally, two other methods of production of metal hydrides are discussed. One is reactive milling where metal hydrides are synthesized by mechanical alloying under hydrogen pressure, while the other is milling elemental hydrides to produce complex hydrides.

Characterization of a Ballard MK5-E Proton Exchange Membrane Fuel Cell Stack

Abstract: We present the results of an experimental investigation of the energy balance of a Ballard MK5-E proton exchange membrane fuel cell (PEMFC) stack. We have investigated the transient phenomena that occur during PEMFC stack warm-up, under load switching, and when the PEMFC stack is connected to a DC/AC inverter. A simple and convenient model describing the polarization curve as a function of the temperature is presented and validated by our experimental data. We also present experimental results on the increase PEMFC stack performance as a function of the current density for different oxygen concentrations of the oxidant gas.

Hydrogen desorption mechanism in MgH 2 -Nb nanocomposites

Abstract: In situ time-resolved x-ray scattering measurements of hydrogen desorption in MgH{sub 2}-Nb nanocomposites using synchrotron radiation are presented. Results show that niobium acts like a catalyst for hydrogen absorption and desorption. It is found that hydrogen desorption involves the formation of a short-lived metastable niobium-hydride phase which acts as a gateway through which hydrogen released from MgH{sub 2} is flowing. The desorption kinetics of this system is revealed through temporal profiles showing the lifetimes of the different phases involved.

Modeling and simulation of a distribution STATCOM using Simulink's Power System Blockset

Abstract: This paper presents a study on the modeling of a STATCOM (Static Synchronous Compensator) used for reactive power compensation on a distribution network. The power circuits of the D-STATCOM and the distribution network are modeled by specific blocks from the Power System Blockset while the control system is modeled by Simulink blocks. Static and dynamic performance of a /spl plusmn/3 MVar D-STATCOM on a 25-kV network is evaluated. An "average modeling" approach is proposed to simplify the PWM inverter operation and to accelerate the simulation for control parameters adjusting purpose. Simulation performance obtained with both modeling approaches are presented and compared.

Introductory remarks on nanodielectrics

Abstract: There is today the neologism "nanotechnology" around which much effervescence is consolidating. This scientific wave is complex in nature with multiple ramifications: The domain extends widely including in fact old and newer concepts. At this point of time, a focused perspective revealing the status and incidences of the domain on new materials, especially dielectrics and their insulating possibilities, is desirable. Thus, a personalized overview is given here, offering finally a tentative definition of "nanodielectrics".

Triggering and guiding high-voltage large-scale leader discharges with sub-joule ultrashort laser pulses

Abstract: The triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration (3–7 m rod-plane air gap). By focusing the laser close to the positive rod electrode it has been possible, with a 400 mJ pulse, to trigger and guide leaders over distances of 3 m, to lower the leader inception voltage by 50%, and to increase the leader velocity by a factor of 10. The dynamics of the breakdown discharges with and without the laser pulse have been analyzed by means of a streak camera and of electric field and current probes. Numerical simulations have successfully reproduced many of the experimental results obtained with and without the presence of the laser plasma channel.

LI4TI5O12, LI (4-α) ZαTI5O12, OR LI4ZβTI (5-β)O12 PARTICLES, METHODS FOR OBTAINING SAME AND USE AS ELECTROCHEMICAL GENERATORS

Abstract: The invention concerns a method for synthesising Li4Ti5O12, Li4ZβTi (5-β)O12, OR Li (4-α) ZαTi5O12 particles preferably having spinel structure, wherein: β is greater than 0 and not more than 0.5 (preferably having spinel structure); α represents a number greater than zero and not more than 0.33, Z representing a source of at least a metal selected among the group consisting of Mg, Nb, Al, Zr, Ni, Co. Said particles coated with carbon exhibit particularly interesting electrochemical properties as anode and/or cathode component of electrochemical generators.

Time-Varying Contingency Screening for Dynamic Security Assessment Using Intelligent-Systems Techniques

Abstract: A time-frequency-based approach for contingency severity ranking and rapid stability assessment is described. The aim is to classify correctly all single or multiple contingencies that may result in loss of voltage or frequency stability in the first 20 s following the last disturbing action. We start by selecting a number of strategic monitoring buses where the phasor measurement units are located to capture representative voltage magnitudes and angles during detailed time-domain simulations, which cover special protection systems and on-load tap changers. The short-time Fourier transform is then dynamically applied to the responses for extracting selected decision features as the simulation time evolves. It is shown that frequency-domain features such as the peak spectral density of the angle, frequency, and their dot product evaluated over the grid areas are reliable time-varying stability indicators that can form the basis of an entirely secure classification system able to respond within 2 to 3 s after the last event in the contingency. This allows early termination of about 60% of permanently stable simulations. Fuzzy logic and neural networks are used together to make initial decisions, which are then mixed by voting in order to improve the assessment reliability and security at the expense of a reduced yield. The proposed DSA scheme is successfully tested with 1027 contingencies from two widely differing test systems: a 67-bus fictitious system and a 783-bus system in actual use at Hydro-Quebec's operations planning department.

Pulsed laser deposition of nanostructured tin oxide films for gas sensing applications

Abstract: Pulsed laser deposition (PLD) technique has been successfully used to not only deposit nanostructured tin dioxide (SnO 2 ) thin films, on alumina substrates, but also to concomitantly achieve their in-situ doping by Pt metal catalyst. The deposition of PLD SnO 2 films was investigated at a substrate deposition temperature of 300°C under both vacuum and an oxygen background pressure of 150 mTorr. While the crystalline structure and the composition of the PLD SnO 2 films were systematically determined by means of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, respectively, their morphology and nanostructure were investigated by scanning and transmission electron microscopies (SEM and TEM, respectively). The PLD films deposited under oxygen consist of polycrystalline pure SnO 2 phase, are stoechiometric and exhibit a columnar growth morphology with an apparent inter-columnar porosity. In contrast, those deposited under vacuum consist of a mixture of both a-SnO and poly-SnO 2 phases. TEM observations have revealed that the SnO 2 columns (of few 10 s nm diameter) that constitute the films are, in turn, composed of almost spherical nanograins. On the other hand, the newly developed in-situ doping approach has been shown not only to provide uniform Pt-doping all through the film thickness, but also to be effective in fabricating high-performance gas sensors. A Pt-doping level of ∼2 at.% was identified as the optimal concentration that leads to the highest sensitivity at an operating temperature of the sensors as low as 200°C. The sensing performances of the developed SnO 2 sensors for detecting CO in synthetic air background, over the (10–500 ppm) CO concentration range, are presented.

In situ micro-Raman spectroscopy to investigate pitting corrosion product of 1024 mild steel in phosphate and bicarbonate solutions containing chloride and sulfate ions

Abstract: The nature of the corrosion products generated by localized attack on 1024 mild steel have been investigated in the presence of chloride and/or sulfate ions in bicarbonate and phosphate aqueous solutions. A spectroelectrochemical cell was used for in situ measurements of the Raman spectra of the corrosion products generated during pitting. These products were identified as the so-called green rust compounds. The assignment of the hydroxyl groups in green rust is confirmed by isotopic substitution. The composition of the green rust generated in bicarbonate or phosphate solution containing chloride and/or sulfate ions has been determined. A correlation between the green rust composition and the electrochemical behaviour after the initiation of pitting has been noted and discussed.

Study of the activation process of Mg-based hydrogen storage materials modified by graphite and other carbonaceous compounds

Abstract: A nanocomposite (Mg–V)nano made of 90 wt% Mg and 10 wt% V was prepared by high-energy ball-milling during 40 h. The activation characteristics of (Mg–V)nano are rather poor, the hydrogen content [H] reaching 4 wt% after more than 100 h (t4wt%) following the initial exposure of the material to H2. Adding 9 wt% graphite to (Mg–V)nano and resuming the milling operation for 30 min leads to the formation of (Mg–V)nano /G, which exhibits a t4wt% value of only 10 min. The addition of more than 9 wt% graphite to (Mg–V)nano does not lead to any significant reduction of the t4wt% value. However, extending the milling period with graphite over 30 min leads to a steady increase in t4wt% and, thus, to a deterioration of the activation characteristics. Comparison of the behavior of graphite with other C-based compounds revealed that perylene (C20H12) and pentacene (C22H14), which are made of linked benzene rings, and thus have a 2D structure similar to that of the graphene sheet, are as effective as graphite in improving the activation characteristics of (Mg–V)nano. A structural investigation of (Mg–V)nano /G as a function of the milling time through both C 1s core-level x-ray photoelectron spectroscopy and C K edge x-ray absorption near-edge spectroscopy has shown that the integrity of graphite is progressively lost as the milling period is extended over 30 min. On the basis of these results, it is hypothesized that the adsorption of graphene layer on freshly created Mg surfaces and the formation of highly reactive C species during milling prevents the re-formation of the surface oxide layer responsible for the poor activation characteristics of untreated (Mg–V)nano

Comparative analysis of IEEE 112-B and IEC 34-2 efficiency testing standards using stray load losses in low voltage three-phase, cage induction motors

Abstract: Since 1998, 817 motor efficiency test data sets, in the 1-500 hp (0.75-375 kW) range have been collected from several sources in different countries around the world, for 50 and 60 Hz. The test data include the motor efficiency using the IEC 34-2 and IEEE 112-B test standards, and the quantification of the stray load losses (SLLs), using the IEEE 112-B method. In 125 cases, the test data include the efficiency computed with both methods. The aim of this paper was the quantification of the discrepancy between the two mentioned standards, and to establish an approximate method to allow the comparison between motors tested with the two standards. Based on the significant number of collected motor data sets, it was concluded that, when compared to the IEEE 112-B standard, the IEC 34-2 standard is less accurate, and gives typically higher efficiency values, mainly because of the SLLs estimation procedure. The IEEE 112-B SLLs computed values are typically higher than the IEC SLLs predefined values, on average of 1.0 and 0.8 percentage points for 50-Hz and 60-Hz motors, respectively. Also, the average SLLs values vary slightly with the motor power. Using efficiency measurements made with both standards on the same motors, it was possible to confirm that the SLLs are the main reason for the observed discrepancy in the efficiency values. The results of the analysis carried out in this paper offer the possibility of comparing the efficiency of motors tested under the IEC 34-2 standard with motors tested with IEEE 112-B, leading to a choice of the most cost-effective option. This paper also provides a key contribution to the ongoing revision of the IEC 34-2 standard.

A Combined Directional and Faulted Phase Selector Element Based on Incremental Quantities

Abstract: In this paper, differential incremental or superimposed voltage and current quantities are used in order to determine directionality of a fault in a network. It is shown that this can be accomplished by performing three scalar products between three voltage and current phasor pairs. The relative levels of these same three scalar products can be furthermore used to identify the faulted phases. While, in ultra-high-speed directional comparison relays, superimposed voltage and current had to be treated in the time domain in order to get speed. In this paper, all computations are done in the frequency domain.

Power flow management in an electric power grid

Abstract: Power flow management is achieved in an electrical power transmission network using serial impedance modulation distributed throughout the transmission lines of the network. Switching units are mounted to insulated portions of transmission line towers in proximity to phase lines for modulating power flowing in at least one phase line conductor of at least one bundle conductor phase line in an electric power transmission line at a plurality of segments in the network. Power flow is managed in at the segments by changing the series impedance of the line by controlling the switching units. Enhanced insulation between phase line conductors is added. The power flow in a plurality of electric power lines of the network is analyzed, a desired change in impedance for the electric power lines is determined, and at least some of the switching units are controlled to implement the desired change in impedance.

Method for rapidly carrying out a hydrogenation of a hydrogen storage material

Abstract: Disclosed is a method for rapidly carrying out a hydrogenation of a material capable of absorbing hydrogen. It was discovered that when a powder of a material capable of absorbing hydrogen is ground under a hydrogen pressure, not at room temperature but at a higher temperature (about 300°C in the case of magnesium) and in the presence of a hydrogenation activator such as graphite and optionally a catalyst, it is possible to transform completely the powder of this material into a hydride. Such a transformation is achieved in a period of time less than 1 hour whereas the known methods call for periods of time as much as 10 times longer. This is an unexpected result which gives rise to a considerable reduction in the cost of manufacture of an hydride, particularly MgH2.

Remotely operated vehicle for inspection and intervention of a live line

Abstract: A vehicle for use on a live line. The vehicle is provided with three coplanar traction wheels mounted on a frame and spaced along a first longitudinal axis parallel to the live line and above therefrom. The vehicle is also provided with two movable coplanar pressure wheels mounted on the frame and spaced along a second longitudinal axis parallel to the line and below therefrom. The vehicle has a driving motor mounted on the frame, for driving the traction wheels. The motor has a source of energy, such as batteries. The vehicle has a pressure mechanism mounted on the frame and coupled to the pressure wheels, for maintaining the line squeezed between the traction wheels and the pressure wheels. The vehicle has a control mechanism coupled to the motor for controlling the motor. Thereby, in use, the vehicle is moved along the line. The vehicle can also be provided with a de-icing tool. The de-icing tool has a collar with two parts opening and closing around the line. The collar supports several blades concentrically spaced apart from each other and forming an open cone in a forward moving direction of the vehicle.

Remote-operated trolley for inspection and intervention for a live electrical power grid in operation and ice removing equipment

Abstract: The invention concerns a trolley designed to be used on a live power line. The trolley is equipped with three coplanar traction wheels spaced apart along a first longitudinal axis parallel to the live power line and thereabove. The trolley is also equipped with two coplanar pressure wheels spaced apart along a second longitudinal axis parallel to the line and thereabove. The trolley further comprises a traction motor for powering the traction wheels. Finally, the trolley includes a pressure system for maintaining the line pressed between the pressure wheels and the traction wheels, and a control system for controlling the motor. Said trolley has enhanced tractive power. Thus in operation, the trolley is driven along the line whatever the dimension thereof and/or climatic conditions. The invention also concerns a ice removing equipment mounted on the trolley for use on the live power line. The ice removing equipment comprises a clamp band adapted to be opened and closed around the live power line. The clamp band bears blades concentrically spaced and arranged to form a cone opening in the forward moving direction of the trolley.

Simultaneous determination of dissolved gases and moisture in mineral insulating oils by static headspace gas chromatography with helium photoionization pulsed discharge detection.

Abstract: This paper presents the development of a static headspace capillary gas chromatographic method (HS-GC) for simultaneously determining dissolved gases (H2, O2, N2, CO, CO2, CH4, C2H6, C2H4, C2H2, C3H8) and moisture from a unique 15-mL mineral oil sample. A headspace sampler device is used to equilibrate the sample species in a two-phase system under controlled temperature and agitation conditions. A portion of the equilibrated species is then automatically split-injected into two chromatographic channels mounted on the same GC for their separation. The hydrocarbons and the lighter gases are separated on the first channel by a GS-Q column coupled with a MolSieve 5-A column via a bypass valve, while the moisture is separated on the second channel using a Stabilwax column. The analytes are detected by using two universal pulsed-discharge helium ionization detectors (PDHID). The performance of the method was established using equilibrated vials containing known amounts of gas mixture, water, and blank oil. The...

Influence of thermal cycling on the cable-joint interfacial pressure

Abstract: Cable joints are generally known to be the weak points of underground distribution lines. One of the most common failure modes of premolded cable joints is linked to the occurrence of dielectric breakdown at the interface. Many parameters may influence the dielectric strength of a cable-joint interface: surface roughness, the presence of dielectric grease, and the length of the interface to name a few. Nevertheless, interfacial pressure is known to be a key factor that sets the cable-joint interfacial breakdown strength. AC dielectric breakdown strength is proportional to interfacial pressure up to a threshold pressure. A high interfacial pressure leads to good dielectric breakdown strength whereas a lower pressure leads to a poor long-term performance. Interfacial pressure decreases with the number of thermal cycles. Moreover, partial discharge (PD) monitoring during thermal cycles with thermal gradients in the insulation, following IEEE 404 standard protocol, did reveal a maximum PD intensity at the end of the temperature decrease for each cycle. This could be linked to a decrease in the interfacial pressure. We study the behavior of interfacial pressure when a cable-joint assembly is thermally cycled and identify the worse case for cycles at 75, 90 and 130/spl deg/C with thermal gradients in the bulk of the insulation. The cycling protocol is based on existing IEEE 404 standard for cable joints for use with extruded dielectric cable rated 5-138 kV.

Mechanically Alloyed Nanocrystalline Hydrogen Storage Materials

Abstract: Mechanical alloying and mechanical grinding have been used to synthesize or treat AB, AB 2 , and AB 5 type alloys and Mg-based hydrogen storage materials A nanocrystalline or an amorphous structure was obtained after milling, depending on the system and its composition The structure and the hydrogen storage properties of various nanocrystalline alloys were investigated It was found that the activation and kinetics of hydrogen absorption/desorption were improved However, a severe loss of storage capacity was observed in the AB, AB 2 and AB 5 systems, but not much in Mg-based systems The storage capacity can be recovered by thermal annealing at elevated temperatures A preliminary explanation is given for the change of absorption/desorption kinetics and storage capacity