Showing papers by "Hydro-Québec published in 1992"

Motor vehicle drive system for a motor vehicle having an electric motor system, and a method of operating said drive system

Abstract: The motor vehicle drive system is for a motor vehicle having an electric motor system, an actuating system, an accelerator system, a mode selector and a battery. The drive system comprises a power supply bus having an output for supplying the electric motor system; a battery connector for connection to the battery, the connector having a power output for supplying the power supply bus; a controller system having inputs respectively for connection to the components of the vehicle so that it can monitor their status; a power converter system connected to the power supply bus of the controller system, and to the motor system for supplying it; a combustion motor electric power supply having an input connected to the controller system, and an output for producing current; a first power converter having an input connected to the power supply, and an output for supplying the power supply bus, the controller system being connected to the power converter so that it is monitored and controlled by the controller system, whereby the controller system monitors and controls operation of the electric motor system and, when auxiliary electric power is needed on the power supply bus, the controller system activates operation of the combustion power supply.

On the spark to pseudoglow and glow transition mechanism and discharge detectability

Abstract: The transition mechanism for spark to pseudoglow and glow discharge is examined and the attending question of discharge detectability in an electrical apparatus is considered. The effect of gap spacing or cavity diameter and overvoltage is discussed in terms of experimental observations and theoretical calculations using a two-dimensional mathematical model. >

Investigation of the effect of repetitive voltage surges on epoxy insulation

Abstract: The aging of epoxy electrical insulation by unipolar, repetitive voltage surges has been investigated to determine whether such surges can precipitate premature failure of high-voltage motor windings and gas insulated switchgear spacers. A full factorial statistical test was devised and performed on 180 pure epoxy insulation specimens to examine the effect of voltage magnitude, polarity, and surge repetition rate on the life of unfilled epoxy specimens containing a needle-plane electrode geometry. All factors and interactions were determined to have a significant effect on the life, and life prediction equations were estimated. Increasing the voltage magnitude or repetition rate, decreased or increased the life, respectively. Aging was found to occur at as low a stress as 2 MV/cm. Gradual aging of the epoxy does occur under repetitive voltage surges. Based on a realistic number of surges with typical voltage amplitudes which can normally occur from vacuum switchgear during service, gradual deterioration of the epoxy turn insulation in motor stator windings is possible in some situations. Situations where surge aging may occur are identified. >

A frequency-domain maximum likelihood estimation of synchronous machine high-order models using SSFR test data

Abstract: The authors propose a numerical scheme for processing noisy signals originating from standstill frequency response (SSFR) tests on synchronous machines. Instead of using a univariate nonlinear least-squares procedure to fit only the weighted sum of magnitude responses, they minimize a multivariate prediction error criterion based on the determinant of the residuals covariance matrix. The algorithm pertains to a large class of prediction error methods and results in a multiresponse nonlinear regression procedure related to the maximum likelihood viewpoint when the residuals distribution is Gaussian. To demonstrate the efficiency of the proposed scheme, the implementation was tested using noisy simulated data, based on the Rockport model 3.3. It is shown, using actual data from the Nanticoke turbogenerator, dating back to the EPRI-project RP-9997-2 (1980), that the frequency-domain maximum likelihood approach can be effective for direct estimation of generalized circuits with up to five equivalent windings per axis, providing satisfactory predictions of both magnitude and phase as far as the 16th harmonic. >

Electrical aging and electroluminescence in epoxy under repetitive voltage surges

Abstract: An extensive statistical accelerated aging experiment, involving a total of 180 unfilled type epoxy specimens, has been conducted to determine the number of voltage surges required to initiate electrical trees under various magnitudes, surge repetition rates, and polarity conditions. The specimens were tested one at a time according to a full factorial experimental design. During many of the aging tests, the electroluminescence (EL) from the epoxy specimens was monitored. Conventional Weibull analysis techniques were used to investigate the experimental results. The analysis showed that life decreased with increasing applied voltage and was longer for negative polarity surges. As the surge repetition rate increased, the number of surges to initiate a tree increased. A modified inverse power model, with a voltage power law constant similar to that found in AC aging was determined to be appropriate. No correlation was observed between either the trend in EL over time or the total amount of EL and the number of surges required to initiate a tree. >

Expert systems in transmission planning

Abstract: The state of the field of expert systems and knowledge engineering in transmission planning is reviewed. A detailed analysis of the goals, definition, requirements and methodology of transmission planning is presented. Potential benefits of knowledge-based applications in transmission planning are reviewed. This is followed by a thorough review of the area broken down into subareas or important related topics. The conclusions offer a number of suggestions for possible future research and development. Finally, a detailed bibliography divided into subareas is presented. >

Effect of oil viscosity on transformer loading capability at low ambient temperatures

Abstract: The applicability of the ANSI loading guide for power transformers is limited to ambient temperatures above 0 degrees C because the thermal model does not account for variations in the oil viscosity and winding resistance. A practical calculation method based on the bottom-oil temperature and the surface temperature at the top of the cooling duct has been developed. Results indicate that the proposed thermal model could provide a sound basis for calculating the overload capacity for ambient temperatures below 0 degrees C or for severe overloads of short duration. >

Alternatives for blocking direct current in AC system neutrals at the Radisson/LG2 complex

Abstract: The authors document the development of alternative approaches to the design and application of blocking devices placed between transformer neutrals and the substation ground. System constraints on the impedance and overvoltage limitation of the neutral blocking device (NBD) are covered. Three alternative NBD schemes are developed and optimized. System performance of the NBD is discussed, as are the practical implementation considerations for this unconventional equipment application. Although the focus is on the NBD requirements of Hydro-Quebec's Radisson/LG2 complex, the fundamental information is applicable to any situation where DC must be blocked from a power transformer neutral in a system designed for effectively grounded operation. >

EMTP TACS-FORTRAN interface development for digital controls modeling

Abstract: A FORTRAN interface to be used with TACS (transient analysis of control systems) in EMTP (electromagnetic transient program) has been developed at Hydro-Quebec to allow the use of FORTRAN language for simulating digital controls for power system components such as static compensators, DC transmission, and relays. The interface has been designed without any time delay between TACS and the FORTRAN subroutines and allows users to benefit from the flexibility of FORTRAN language to ease the task of modeling digital controls. The property of task cyclicity in digital controls can be exploited to reduce the CPU time of each EMTP run. The authors present details of the interface and provide results confirming its advantages for simulation of digital controls within EMTP. >

Electrode erosion in plasma torches

Abstract: Cathode erosion rates are reported (or copper electrodes in a simulated plasma torch operating at atmospheric pressure. The are current was 100A (or most experiments; the magnetic field used to move the arc varied between 0.001 and 0.15 T. Different plasma gases were used (Ar, He, air, N2, CO, and mixtures of the noble gases with O2, N2, CO, CH4, Cl2, and H2S) at flow rates varying between 0.2 and 20 liters/min. Different criteria (arc velocity, arc attachment residence time, arc current density) were used to analyze the erosion results.

Ice Accretion On Energized Line Insulators

Abstract: A laboratory study of ice accretion from supercooled droplets on energized insulators was investigated. Wet ice, which is associated with the highest probability of flashover, was produced at temperatures of _12°C and _7°C with water droplets of 50 and 80 11m and liquid water contents of 4.4 and 6.8 g.m-3. Wind velocity and the conductivity of freezing water played important roles in the uniformity and roughness of ice accreted, respectively. It was also found that the mean power fed to the insulators by conduction current and corona discharges was about 40% of heat power liberated by the freezing process during wet ice accretion.

Stimulated Raman scattering: Action evolution and particle trapping via Euler–Vlasov fluid simulation

Abstract: The Manley–Rowe action relations and trapped‐electron orbit theory have been applied to the problem of stimulated Raman scattering (SRS) in the forward direction, as simulated by an Euler–Vlasov fluid (EVF) code in periodic geometry. After a slight initial delay, the Vlasov results agree well with three‐oscillator theory (but with damping larger than the Landau linear value). The action sum of the pump and the scattered SRS wave was well conserved, while the action loss between the pump and plasma wave was shown to be well accounted for in detail by examining the electron energy for electrons above the lower trapping boundary (separatrix) in x‐px phase space. However, unlike the three‐oscillator model, the action sum of the pump and plasma wave was observed to actually increase for a short time because of retrieval of apparently lost action from the trapped‐electron effect in regenerating the plasma wave. Thus the utility was clearly demonstrated of using action conservation to separate the effects of three‐wave interaction from those due to nonlinear particle–wave interaction. The EVF code also shows clearly the fine details of layering and folding seen in x‐px phase space due to electron trapping, detrapping, and retrapping. [These details would have been invisible in the usual particle‐in‐cell (PIC) code because of graininess at low phase space densities.]

A static compensator model for the EMTP

Abstract: A static voltampere-reactive (VAr) compensator (SVC) model based on nodal analysis, is presented. The model is integrated in the electromagnetic transients program (EMTP) with minimal interface error and by taking into account initialization. The model is basically a generic compensator using thyristor controlled reactors. The models are modular to represent adequately compensators of different designs while being detailed enough for predicting possible harmonic interactions between the AC system and the SVC. Typical applications on the Hydro-Quebec system are described. >

Manhole explosions due to arcing faults on underground secondary distribution cables in ducts

Abstract: Arcing faults on low-voltage insulated conductors are widely considered to be self-extinguishing and consequently not very hazardous to people or property. Nevertheless, a number of arcing faults recently occurred on Hydro-Quebec's underground secondary 120/240 V and 347/600 V systems and caused manhole explosions in downtown Montreal. To trace the probable cause, a series of staged tests was performed in IREQ's high-power laboratory. The results obtained proved that in wet, dirty ducts an arcing fault can take the form of an interrupted arc which is difficult if not impossible for common overcurrent protection systems to detect. Any such fault that has a long duration produces a significant amount of gaseous by-products which escape to the ends of the duct where they can ignite or form explosive concentrations. >

Process for the preparation of collectors-electrodes for the thin film cell, collectors-electrodes assemblies and cells obtained

Abstract: Metallization by deposit under vacuum of metal on a face of a support film of synthetic resin at a thickness of 0.005 to 0.1 micron, followed by the electrochemical deposit of an additional metallic layer, whose thickness is between 0.1 and 4 microns. A coating of an electrode of a generator is then applied on the surface of the collector thus prepared. The assembly is characterized by the adhesion of its components and its facility of mechanized handling during the steps of assembling the complete generator.

Effect of pressure and length on interfacial breakdown between two dielectric surfaces

Abstract: The phenomenon of interfacial AC breakdown is considered Two pieces of EPDM (ethylene-propylene diene monomer) rubber were pressed together and a special jig was conceived to provoke arcing along the interface The voltage at which breakdown occurred was measured and its dependence on interfacial length and pressure established In the absence of silicone grease at the interface, breakdown voltage showed a linear dependence on pressure With silicone grease, breakdown values were consistently higher and reached a plateau at higher pressures The dependence on length was similar to what is observed for bulk dielectrics While the dielectric strength curve for a silicone-greased interface decreased with length, the one with a dry interface, although it followed the same general behavior, exhibited an unexplained dip at around 4 mm >

Current collectors for safe electrochemical generators, process of preparation and generators obtained thereby

Abstract: Self-protecting current collector, with lateral collection an insulating plastic support film having a thickness between about 1 and 30 microns, and a conductive metallic coating, of a thickness lower than about 10 microns, adhering to at least one face of the insulating support film, compatible with the corresponding material of the electrode of the generator, and wherein its conductive surface is divided into a plurality of adjacent distinct areas, each area being electrically insulated by means of non-conductive borders except for at least one conductive bridge of small cross-section connected to a lateral common conductive margin enabling a lateral collection of the entire distinct areas; the nature and electrical resistance of the conductive bridges enabling on the one hand, passage of currents corresponding to maximum currents provided for each of the individual collection areas of the generator to be produced, and limiting on the other hand, in case of an accidental short-circuit inside an area, the maximum current received by this area originating from the entire areas of the generator.

Lanthanum Phosphate‐Bonded Composite Nickel‐Rhodium Electrodes for Alkaline Water Electrolysis

Abstract: Nickel-powder electrodes bonded with a polymer of lanthanum phosphate were prepared and tested for their performance in water electrolysis of KOH aqueous solutions. Disintegration of the phosphate-bonded electrodes made with spiky filamentary nickel particles is strongly reduced at open circuit potential with LaPO4 rather than AlPO4 as the binding material, but the electrocatalytic performance toward hydrogen evolution is practically the same for both materials.

Plasma torch for the treatment of gases and/or particles and for the deposition of particles onto a substrate

Abstract: A plasma torch for the treatment of gases of particles, or for the deposition of particles onto a substrate, which has two concentrical electrodes coaxially mounted onto a support. The gases or particles to be treated or deposited are injected through an injection passage that is coaxial with the central electrode and opens centrally into an outlet nozzle so as to inject the gases or particles centrally and coaxially within the center of the flame torch without unduly affecting the characteristics of the plasma. In use, the central electrode extends well downstream of the peripheral electrode, whereby the electric arc may not block the injection passage. Moreover, a magnetic field is generated externally to the electrodes in the direction parallel to the annular passage defined between the electrodes in order to rotate the electric arc within the passage and thus reduces the erosion of the electrodes while ensuring better heating of the plasma gas.

Process of immobilizing ashes by vitrification thereof in a plasma reactor

Abstract: Disclosed is a process for immobilizing ashes by vitrification thereof in a plasma arc reactor, which is very efficient to treat ashes and any other pulverulent residues containing toxic leachable components that may be a source of pollution. The process makes use of a plasma reactor of the falling film type, in which an axial transferred or non-transferred arc melts and treats a load tangentially injected or otherwise blown in a cyclonic manner in a sleeve while this load falls down by gravity along the wall of the sleeve and accumulates at the bottom of the reactor in the form of a liquid bath. The load that is fed into the reactor consists of the ashes exclusively if they contain a sufficient amount of silica to make them self-vitrifying, or of a mixture of ashes with silica or another glass-forming agent. The temperature of the bath of glass that accumulates at the bottom of the reactor is controlled in a very precise and adequate manner to reduce as much as possible the formation of fumes and the risk of evaporation. The glass that is so obtained may be removed in a continuous manner from the bottom of the reactor, or poured out of the same at regular interval.

Retractable shutter for continuously covering the pit of a movable vehicle lift post

Abstract: A retractable shutter for continuously covering the pit of a movable vehicle lift post which along with a fixed lift post is used to elevate vehicles of various lengths comprises two series of articulated panels positioned on one side and the other of the movable lift post at floor level in order to completely cover the pit opening. The articulated panels are horizontally guided at the opening level by horizontal guide rails mounted on the longitudinal walls of the pit and, at each end of the pit, by arcuate guide rails which then extend downwards in order to accommodate the excess of articulated panels depending on the relative position of the movable lift post along the pit. Therefore, when the movable lift post is displaced horizontally in the pit, it causes the two series of articulated panels to displace therewith, some panels emerging from the pit at one of its extremities, whereas other panels retract therein at its other extremity. Consequently, the shutter continuously covers the opening defined by the pit for every position of the movable lift post therein. The articulated panels engage the guide rails by way of carrying axials which also act as articulations between each pair of successive panels.

Effect of pressure and temperature on interfacial breakdown between two dielectric surfaces

Abstract: Breakdown experiments were performed on slices of EPDM rubber pressed one against the other. To achieve this, an experimental jig was designed so as to induce breakdown between the two slices, longitudinally along their interface. Effects of interfacial pressure and of the presence of silicone grease at the interface are taken into account. Breakdown voltages are given for AC measurements. The authors illustrate how deformations, due to high-temperature operation, can occur in a cable joint. A relationship is also established between this deformation and the joint interfacial pressure, which in turns affects the interfacial dielectric strength. It is concluded that the dielectric strength of an EPDM/EPDM interface is greatly affected by the interfacial pressure. Moreover, the presence of silicone grease both improves (at low pressure) and limits, even if the interfacial pressure is increased (above 50 kPa), the dielectric strength of EPDM/EPDM interfaces. >

The growth of oxide platelets on nickel in pure oxygen. I. Morphology and oxidation kinetics

Abstract: A very specific oxide morphology consisting in rounded oxide platelets a few microns in diameter has been obtained on pure nickel. The main experimental factors in the achievement of such a controlled morphology have been thoroughly investigated. Platelets are produced in the temperature range from 600 to 850°C and for oxidation times varying from a hundred hours to a very few minutes. Platelets could not be grown on very pure nickel. Scanning electron microscopy has been used extensively, and the corresponding observations are reported in the first part of this study together with thermogravimetric results.

Effect of air admixture in helium on the rate of the breakdown current rise

Abstract: The influence of dry air admixtures on the breakdown mechanism of helium in small gap separations was investigated using plane parallel stainless-steel electrodes enclosed within a Pyrex chamber. The experiments, carried out using different admixtures of air, shown that the time constant of the rate of breakdown current rise is a linear function of the product of the overvoltage across the gap and the partial pressure of the admixture. An empirical formula is derived to express this linear relationship. The rate of the breakdown current rise is calculated, using a quantitative model of the breakdown process; although these values somewhat exceed the experimental ones, the theoretical and experimental values are found to converge when measurements are performed at a slightly elevated relative partial air pressure of 3*10/sup -4/. >

Field experience with a digital relay for synchronous generators

Abstract: The authors provide the specifications and characteristics of a digital relay for synchronous generators that performs seven protection functions. They also present preliminary performance results, following installation on one of the units at the Carillon generating station in the Hydro-Quebec power system. During a period of four months, although no fault was recorded in the unit, the relay watchdog system and self-monitoring routines functioned flawlessly. The prototype provides the basis for a new standard protection system for Hydro-Quebec's future and existing generating stations. >

Susceptibility and magnetization characterization of bulk high Tcsuperconductors: scaling length and critical current densities

Abstract: Low field DC and AC susceptibility (swept temperature) and magnetization (swept field) are routinely used to characterize bulk samples of high Tc superconducting materials More information can be obtained by extending these techniques, for example, by adding a DC offset field in the AC susceptibility measurements and by making magnetization measurements for several different cycles of the applied field The relationships between the critical current and its scaling length are developed with respect to these experimental techniques

Interfacial breakdown phenomena between two EPDM surfaces

Abstract: The phenomenon of interfacial AC and DC breakdown is the subject of this paper. Two pieces of EPDM rubber were pressed together and a special jig was conceived so as to provoke arcing along the interface. The voltage at which breakdown occurred was measured and its dependence on the type of voltage (AC or DC), the interfacial pressure (0 to 100 kPa range) and on the presence of silicone grease was established. In the absence of silicone grease at the interface, DC breakdown voltages were two times greater than those for AC and both showed a linear dependence on pressure. With silicone grease, both AC and DC breakdown values were consistently higher; in the case of AC, values reached a plateau at higher pressures whereas for DC, values showed a slow linear increase with pressure. >