Showing papers by "Hydro-Québec published in 1973"

Mechanism of Surface Charging of High-Voltage Insulators in Vacuum

Abstract: In vacuum, the surface of insulators becomes electrically charged when subjected to high-voltage stresses. The charging mechanism is described. A model simulating the charging shows that the surface charge densities are proportional to the applied voltage and depend on the secondary electron emission of the dielectric surface. It is also time dependent. Surface charges are shown to explain many results obtained in studies of insulator surface breakdown.

The Dielectric Properties of Silicone Fluids

Abstract: The dielectric properties of polydimethylsiloxane fluids have been investigated under dc and ac fields as a function of field, frequency, temperature, and water content. The results of the ac studies have shown that the dielectric constant and dielectric loss of the fluid exhibit several transitions as a function of temperature at low temperatures. These transitions correlate reasonably well with structural changes in the fluid. The dielectric loss is also thermally activated and decreases rapidly with increasing frequency at ambient temperature. It is also weakly dependent on the applied field and the relative humidity. The dc properties exhibit a strong dependence of the conductivity on relative humidity. However, the dependence of the conductivity on the applied field is a complex one, and changes from an ohmic behavior at low fields, to a region of saturation at intermediate fields, and finally to an "ionization" region at high fields. The polydimethylsiloxane fluid also exhibits a reversal in the direction of the discharge current above a certain field, which is reminiscent of the electret effect observed in some polymeric solids. A tentative theoretical discussion of these properties is presented.

Polymerization of benzene in a capacitively coupled RF plasma

Abstract: The influence of various parameters on the polymerization reaction of benzene in a capacitively coupled rf plasma has been investigated, with particular emphasis on coatings structure and quality. Molecular weight distribution studies by gel permeation chromatography indicate that the degree of polymerization is mainly influenced by pressure and power. A two-stage mechanism of polymer formation is proposed on the basis of experimental data: oligomers or polymers are first formed in the gas phase and then diffuse to the electrodes and reactor walls, where they may undergo an emulsiontype polymerization. Sputtering and pyrolysis effects are suggested to explain the additional observations on the lowest-and highest-pressure films.

A Method of Calculating the RI from HVDC Converter Stations

Abstract: Radio Interference ( RI), generated due to the periodic switching of the valves, is an important factor in the design of HVDC converter stations. A method is developed in this paper for calculating the RI level of any given converter station layout. The method consists basically of determining the equivalent circuit for the valve turn-on transients, analyzing the currents as a function of frequency in all elements of the circuit, and finally calculating the RI around the station using the currents obtained above together with data on the physical layout of the station.

The Calculation of Transient Voltage Distribution in a High Voltage DC Thyristor Valve

Abstract: A method of calculating impulse and switching surge overvoltages in a high voltage dc thyristor valve as well as a computer program to perform the calculation, is presented. The effects of valve parameters and stray capacitances on the overvoltages are shown through results of calculations for a representative thyristor valve. The results are supported by measurements performed on a 150 kV thyristor valve.

The thyristor valve in HVDC transmission

Abstract: The application of thyristor valves rather than mercury-arc valves for rectification in high-voltage dc transmission systems has increased Schemes in service include Eel River in New Brunswick, Canada, the Gotland extension in Sweden, and the Sakuma extension in Japan Basic circuits, design, construction, and operation methods are discussed for the use of thyristor valves in HVDC transmission (MCW)

Precipitation in liquid-quenched Al-base Ag alloys

Abstract: Al-base Ag alloys have been quenched from the liquid state and aged at temperatures within the metastable miscibility gap. It is found that in the liquid-quenched condition the alloys contain a solute cluster size-distribution which is considerably narrower than that obtained by normal bulk-quenching. Indeed, liquid-quenching is far more effective than fast bulk-quenching in minimizing clustering. Electrical resistivity, wide-angle and smallangle X-ray techniques and transmission electron microscopy have been used to study the evolution of the decomposition products on ageing the liquid-quenched alloys.

Multi-frequency tuned h.v. synthetic circuit for testing circuit breakers

Abstract: The present invention relates to a high voltage generator used for the synthetic testing of high voltage circuit interrupters, and more particularly for a testing circuit of the current injection type, and capable of providing successively an injection currevent wave-form and a transient recovery voltage wave-form. This generator comprises an injection branch providing the injection current wave-form and a regulating branch providing the transient recovery voltage wave-form. The injection branch is formed by at least two groups of elements, each composed of a capacitance, an inductance and a spark-gap in series and forming a unit, this unit being tuned to the same frequency as the other units but not identical to said units and connected in series with the other units forming said injection branch, and each of the units producing the same injection current wave-form by charging its capacitor to a voltage not necessarily the same as that to which the other capacitors are charged. The regulating branch consists of at least two groups of elements, each composed of at least a capacitance and forming a unit, each of the units capable of producing a different transient recovery wave of one or more frequencies. Also, a method for simulating the voltage required in the synthetic testing of interrupters is disclosed.

A study of iron in gold–iron alloys

Abstract: Gold–iron alloys (composition range 20 to 50 at% Fe) have been examined magnetically. In the as-quenched condition the value of the saturation magnetization appears to saturate at about 3.0 μB per iron atom if all the magnetic forces are attributed solely to the iron atoms. This high value for the number of Bohr magneton is discussed in terms of the nature of the iron in solution. The isothermal decomposition of one of the alloys, Au–38 at% Fe. was followed by the measurement of magnetic properties and by transmission electron microscope observations. The saturation magnetization decreased with ageing time to the expected equilibrium value. The apparent inverse dependence of the coercive force on temperature is interpreted as a magnetic short-circuit effect. Transmission electron microscopy reveals the heterogeneousprecipitation of a second phase in the form of platelets.

Valve Damping Circuit Design for HVDC Systems

Abstract: This paper presents a method of calculating the recovery overvoltages in a HVDC circuit and the optimization of the damping circuit by selecting the lowest value of the damping circuit capacitance and the resistance which together satisfactorily limit the recovery voltage. Furthermore, a new method is developed for exact calculation of the losses in the damping circuit using a hybrid computer. The effect of the bridge operation (commutating and delay angles) and damping circuit parameters on the losses are analyzed using numerical examples. Finally, a method for designing the valve damping circuit is presented.

Microwave Curing of Synthetic Rubbers

Abstract: It is shown that the microwave absorption characteristics of compounds based on a given polymer can be controlled by incorporating suitable compounding ingredients, even if the polymer itself absorbs microwave energy only weakly. On the basis of ten different application-oriented compound formulations it is shown that the quality of microwave-cured rubber is comparable to that of conventionally vulcanized material. Correlations between dielectric measurements at microwave frequencies and curing tests show that the suitability of a given material for microwave curing can be determined from knowledge of the dielectric loss factor and its temperature variation. Finally, various advantages of the slow-wave structure apparatus used in this study are pointed out.

Method and apparatus for determining geodesic measurements by helicopter

Abstract: The present invention concerns a method for determining the geographical characteristics of a number of points of a terrain, and to an apparatus particularly adapted to carry out this method. The system comprises a laser beam transmitter placed on ground at a point to be defined, which beam is detected by means of an airborne device constituted of convergent or divergent lens and mirrors disposed so as to permit the pilot of a helicopter to visualize the beam. This system permits the accurate positioning of the helicopter above the point to be defined. The different angles and distances are obtained by means of instruments, such as a tellurometer and a theodolite placed at a known point of the terrain. However, to obtain the differences in level between the helicopter and the point to be defined, a transmitter-receiver of infrared beams capable of transmitting through a mirror a vertical beam which is reflected by a reflecting plate mounted under the helicopter is provided.

Prevention of Recovery Overvoltages on High Voltage Testing Transformers

Abstract: During flashover tests with ac voltages, both the transformer and the test object may be subjected to excessively high overvoltages. If the recovery overvoltages occur during the negative half cycle, as is generally the case, external flashovers may not necessarily take place and the resultant high stress can damage the internal insulation of the transformer or the test object. The danger of the recovery overvoltage is even more pronounced in extra high voltage tests where several transformer units are cascaded to provide the required test voltage levels.

Interpretation of some aspects of catalytic oxidation of ammonia and propylene by semiconducting oxides in terms of volcano-shaped plots

Abstract: It has been shown that the activity spectrum of oxides towards oxidation of ammonia, when plotted against the heats of atomisation per equivalent (i.e. values of the average bond energies) of oxides, gives volcano-shaped plots. The significance of these correlations has been interpreted in terms of Sabalier-Balandin ideas of heterogeneous catalysis. The mechanistic significance of these volcano correlations has also been discussed qualitatively.An attempt has also been made here to show some correlative trends between the oxidation activity of oxides for the oxidation of propylene and their acrolein formation selectivity, based on the data of Germain and Perez.

Transient Response of a Floor Net Used as Ground Return in High Voltage Test Areas

Abstract: As the test voltage level increases, it becomes more and more difficult to protect the control and measuring cables from the disturbances generated during the tests. To cope with this problem, new high voltage laboratories are nowadays equiped with a copper floor net used as ground return. This paper presents a theoretical analysis of the transient response of such a ground return system. The calculated performances compare favorably with experimental results obtained with the ground return system of the high voltage laboratory at IREQ, and can apply to the selection of the proper ground return system in new high voltage test areas.

Real roots of algebraic equations by hybrid computer simulation

Abstract: The known methods for solving algebraic equations may be classified in two broad categories: 1) those using numerical techniques and hence a digital com puter, and 2) those using simulation techniques which may be implemented on an analog or hybrid computer.

Prediction of performance of induction-motor/synchronous-generator combination

Abstract: The paper describes a digital simulation of an induction-motor/synchronous-generator combination, directly in phase quantities. The equations are developed in phase rather than as d. q quantities, and a digital-computer program is described for their solution. Predictions of the current, voltage and torque transients following a variety of switching operations of a 5.6 kW motor to a 15 kVA generator are shown to compare closely with experimentally obtained results.

Insulation resistance measurements at low frequencies

Abstract: The insulation resistance of oil-impregnated-paper sheets has been determined as a function of temperature, dc field application time and test frequency in the range from 1.0 down to 0.01 Hz. The results have shown that if the true dc insulation resistance is to be derived from the low frequency ac measurements, low frequency test data well below 0.01 Hz is required.

Wind utilization in remote regions: An economic study

Abstract: A wind driven generator was considered as a supplement to a diesel group, for the purpose of economizing fuel when wind power is available. A specific location on Hudson's Bay, Povognituk, was selected. Technical and economic data available for a wind machine of 10-kilowatt nominal capacity and available wind data for that region were used for the study. After subtracting the yearly wind machine costs from savings in fuel costs, a net savings of $1400 per year is realized. These values are approximate, but are though to be highly conservative.

Electrical conduction in carbon loaded polyethylene

Abstract: It is well known that the addition of conducting particles such as “carbon black” can substantially increase the electrical conductivity of various insulating materials. 1–3 At relatively high carbon loading the conductivity undergoes large increases, presumably when the random packing of the particles leads to infinite conducting chains.4 This report deals with the conduction properties of 3% carbon loaded polyethylene where the basic insulating characteristics of the host material are unaltered, except that uniformly distributed conducting centers may give rise to slightly higher levels of conduction.