Showing papers on "Electric power published in 1991"

FACTS-flexible AC transmission system

Abstract: For economic reasons most if not all of the worlds electric power supply are widely interconnected, involving interconnections inside utilities own territories which extend to inter-utility interconnections and then to inter-regionals. The author describes how with this in mind, the Electric Power Research Institute representing the collaborative R&D arm of the US utilities, has put forward a concept, a vision of the future based on silicon science, called flexible AC transmission system (FACTS). While some of the relevant technology i.e., static VAR compensation is already in wide use, the FACTS concept has brought to the table a tremendous potential for thyristor based controllers which will surely revolutionize the power system. >

Real-time pricing of reactive power: theory and case study results

Abstract: An analysis is made of real-time pricing policies of reactive power using a modification of the OPF (optimal power flow) model. The theory of real-time pricing of reactive power is presented, followed by a case study illustrating the magnitudes and ranges that real-time prices of reactive power might take on under different circumstances. The efficiency implications of real-time pricing of reactive power are compared with traditional power factor penalties. It is concluded that real-time pricing of reactive power should develop simultaneously with that of active power for maximum economic efficiency and smooth operation of the electricity marketplace. >

A new approach to the definition of power components in three-phase systems under nonsinusoidal conditions

Abstract: A method has been proposed for the definition of active and nonactive power components in three-phase systems under nonsinusoidal conditions. The method is more attractive than others since it is not a mere extension of methods employed in single-phase systems, but comes from the application of a quite powerful and synthetic mathematical tool specifically studied for the representation of three-wire three-phase systems in any possible condition: the Park transformation and the Park vectors. It is proven that the application of this method leads to the definition of two quantities, the real and the imaginary power, that are measurable in a quite simpler way than those proposed by other theories. The two satisfy all properties typical of the electrical power and are directly related, under sinusoidal and balanced conditions, to the active and reactive powers. It is shown how this method fits with other proposed methods that can be regarded in terms of this more general theory. >

A fault location technique for rural distribution feeders

Abstract: This work presents a digital fault location technique for rural distribution feeders, using the voltage and current data at a single location. Rural distribution feeders include single-phase, two-phase, and three-phase laterals off a main three-phase primary distribution feeder. The fault location scheme presented here attempts to account for the multiphase laterals, the unbalanced conditions, and the unsymmetrical nature of distribution feeders by continually updating voltage and current vectors at set locations within the system. The updated voltage and current vectors are the estimates of the 60-Hz phasor quantities obtained using a recursive optimal estimation algorithm. The distance to the fault is then estimated using a method based on the apparent impedance approach and the updated voltage and current vectors. Another consideration is the ability to determine the fault location on a lateral. A simulation of an actual rural distribution feeder using the Electromagnetic Transients Program (EMTP) is used to test the approach. >

Contactless power delivery system for mining applications

Abstract: The ability to transfer large amounts of electrical power (up to 1 MW) to a moving load has traditionally used means that are unreliable, inefficient, and potentially unsafe. These include sliding or rolling metal contacts, sliding carbon brushes, and trailing cables. More recently, flat inductively coupled coils have been used to help mitigate these problems. Except for the inductively coupled coils, these techniques have not been developed with the capabilities of power electronics in mind. This paper presents the first conceptual description of a power delivery system design unifying power electronics and a coaxial-winding transformer for devices that require a contactless connection and/or relative motion while delivering large amounts of power. The transformer's unique characteristics and how they might be used to advantage in combination with power electronics are emphasized. Potential applications are flexible power distribution, material handling, electric vehicle boost, and battery opportunity recharge. Test results of a small scale prototype are presented and verify these initial concepts.

Battery enhanced power generation for mobile X-ray machine

Abstract: A mobile X-ray machine utilizes batteries to provide electrical power to produce high-voltage necessary to generate X-rays during a X-ray exposure. A battery charger circuit is used to supplement the battery during the X-ray exposure and charges the batteries during non-exposure periods. By using batteries to power the X-ray generating device, the X-ray machine is capable of being operated from 110 volt AC power sources permitting the machine to be mobile due to its ability of being operated from ordinary house current.

An approach to assess the performance of utility-interactive wind electric conversion systems

Abstract: A probabilistic approach based on the convolution technique is presented to assess the performance of utility-interactive wind electric conversion systems supplying tools. The wind regime is modeled using a Weibull distribution. Expressions are developed to obtain the duration curve for the power injected into the utility grid. The energy injected into the grid and drawn from it to supply the load during the study period can be calculated from this duration curve. The load model employed enables the study period to range from one year to one particular hour-of-day, thus allowing the inclusion of the time-value of energy as appropriate in economic assessments. >

Dynamics and stability of wind and diesel turbine generators with superconducting magnetic energy storage unit on an isolated power system

Abstract: Dynamic system analysis is carried out on an isolated electric power system consisting of a diesel generator and a wind-turbine generator. The 150 kW wind turbine is operated in parallel with a diesel generator to serve an average load of 350 kW. A comprehensive digital computer model of the interconnected power system including the diesel and wind-power dynamics with a superconducting magnetic energy storage (SMES) unit is developed. Time-domain solutions are used to study the performance of the power system and control logic. Based on a linear model of the system, it is shown that changes in control-system settings could be made to improve damping and optimization of gain parameters and stability studies are done using the Lyapunov technique and eigenvalue analysis. The effect of introducing the SMES unit for improvement of stability and system dynamic response is studied. >

Battery charging and monitoring system

Abstract: This invention relates to the use of rechargeable batteries for supply of electrical power. Devices are provided which are highly efficient and which provide accurate and reliable control and indications, while using a small number of component parts and being otherwise readily and economically manufacturable. Devices of the invention are compact and such that they can be readily included, if desired, as integral parts of battery packs such as those used for supplying power to lap-computers and other types of portable equipment.

Iontophoretic delivery device

Abstract: An electrically powered iontophoretic delivery device is provided. The device includes a pair of electrode assemblies (41, 43) and a source of electrical power (30) connected thereto. Circuit means (60) are provided including an activation circuit (62) and a power generating circuit (70). Before use, neither the power generating circuit (70) nor the activation circuit (62) draw current from the power source (30). When the device is placed on the body (50) and electrical contact is established between the two electrode assemblies (41, 43), the activation circuit (62) is closed causing the power generating circuit (70) to be activated, thereby activating the device. The circuit means (60) improves the shelf-life of the device by minimizing current drain from the battery (30) before use.

Ensuring electrical power supply in motor vehicle - grouping electrical appliances according to their importance for safety of vehicle

Abstract: Vehicle electric loads are positised into at least three groups, namely, those essential to vehicle operation, those which definitely improve safe operationand other loads. The loads important for safe operation are further subdivided. A charge - state signal is derived from the battery and a number of threshold levels generated. The loads of the last group are turned off first to allow power reduction, at the first threshold, and this process continues down to the lowest threshold. The load reduction is effected by timewise switching of the loads, e.g. chopping with varying switch-on time. ADVANTAGE - Greatest possible ease of travel.

Pressure-jet and ducted fan hybrid electric car

Abstract: A hybrid electric vehicle (10) capable of ground travel and air travel is described. The vehicle provides for movement over the ground by wheel motors (20) mounted at each of four ground engaging wheels (14 and 16). The wheel motors are supplied with electric power by a battery pack (24) or an electric generator (32) powered by a combustion engine (22). The combustion engine is also geared to vertically oriented ducted fans (40) and a horizontally oriented ducted fan or propeller (76) for providing the vehicle with the capability of travel through the air. Pressure jets (62), supplied with compressed air from a compressor (66) driven by the combustion engine, augment the lift of the ducted fans and provide steering for the vehicle. The vehicle can also be provided with photo-electric cells (82) for supplying a portion of the electric power for the vehicle.

Dual-input infinite-speed integral motor and transmission device.

Abstract: A combination electric motor and transmission unit (1) device has two inputs (2, 3) and a rotational mechanical output (10) at least one of the inputs being of electrical power, to a corresponding integral combination of an electric motor means with a transmission means. The directions of rotation and the rotational speeds of the two inputs can be controlled to provide the mechanical output at any desired rotational speed with peak power output, depending on the controls, thus providing an ideal infinite speed device. The device employs a novel arrangement of a differential unit (24, 42, 41) or a planetary gear unit (27, 36, 46). The combined motor and transmission device is lightweight, requires a small number of moving parts, and is useful in vehicles powered by electricity, including for regenerative braking. Another embodiment of the drive device is useful for a flywheel for peak power supplementation and also regeneration.

Power plant for generation of electrical power and pneumatic pressure

Abstract: A power plant (10) for generating electric power and pneumatic pressure is disclosed which includes an internal combustion engine (20), an electrical generator (24), and a compressor (28) and pneumatic supply tanks (40). Both the electrical generator (24) and the compressor (28) are driven by the engine (20); however, the engine drive is so coupled and controlled that the engine (20) drives the generator (24) as its primary load, and the compressor (28) as its secondary load and apportions the engine power between these units according to need. When the generator (24) uses all the engine power, pneumatic power is supplied by the pneumatic supply tanks (40), permitting a smaller than normal drive engine. A quick start and quick kill mechanism is provided for the engine by using the air supply from the pneumatic supply tanks (40) and an air motor (34), and a time delay shut down relay (110) when no power is being used. Also, the generator (24) can be used as an electric drive motor for the compressor (28) in place of the internal combustion engine (20), where 110 volt ac power is available on the job site.

Electric potential distribution device and an electronic component case incorporating such a device

Abstract: The invention provides a device for distributing electric potentials for supplying a component with electric power, capable of being incorporated in the case in which the component is encapsulated. This device is in the form of a plate comprising conducting planes connected to external power supply potentials. This plate either forms the cover of the case or is placed inside the case above said component. Each of the conducting planes of the device is connected, outside the case, to the power supply potential and, inside the case, at multiple points to the component so as to distribute these potentials to the appropriate inputs/outputs thereof, thus reducing the number of inputs/outputs of the case.

Apparatus and method for providing electrical power in a well

Abstract: A power supply for providing electricity to one or more electrical circuits located downhole in a well comprises a fuel cell adapted to be disposed in the well with the electrical circuit(s). In addition to generating electricity, the fuel cell produces a byproduct liquid, such as water, which can be expelled from the power supply into the well despite substantial pressure, such as hydrostatic pressure, in the well. The fuel cell also generates heat which can be dissipated into the well through the wall of a housing of the power supply. The byproduct liquid can be circulated through the fuel cell to accomplish or assist in this heat dissipation.

Space electric propulsion plasmas

Abstract: Electric thrusters offer the promise of a substantial improvement in performance over that of conventional chemical rockets currently used in space propulsion applications. There are three basically different ways in which electrical power and propellant inputs might be combined to produce thrust: (1) propellant can be heated electrically and then expanded through a nozzle; (2) electromagnetic body forces can be applied to accelerate a plasma to the desired exhaust velocity; or (3) electrostatic body forces can be applied to accelerate charged particles. Electric thrusters are classified in accordance with the mechanism by which they induce thrust as electrothermal, electromagnetic, and electrostatic. The characteristics of plasmas in electric thrusters along these lines are considered. >

Method of and device for protecting electrical power system

Abstract: An electrical power system protection device includes a circuit breaker and a switch connected in series to a power line. The protection device also has a current limiting element connected in parallel to the circuit breaker. When the level of electrical current flowing in the power line, detected by a current detector, has exceeded a predetermined first set level, a first over-current detector delivers immediately a trip command to the circuit breaker. As a consequence, fault current is commutated to the current limiting element so that any drop of voltage in the power line upstream of the circuit breaker is greatly suppressed. When a state in which a predetermined second set level is exceeded by the detected current level is continued beyond a predetermined period, a second over-current detector delivers an off command to the switch, thus protecting the upstream portion of the power line against the fault in this power line. The current level is set to fall within a range which activates a momentary element of an over-current relay of a receiving end breaker of a downstream sub-system connected to the power line. In the event of a failure in the downstream power line, the receiving end breaker is tripped immediately so that the sound portion of the power line is reset to a normal state of operation.

Battery power supply system

Abstract: A battery power supply system for supplying DC electric power to a DC operated apparatus includes an AC/DC adapter for converting AC electric power into DC electric power, a plurality of batteries and a battery charger for charging the plurality of batteries. The battery power supply system includes a plurality of charge lines for connecting the battery charger to the plurality of batteries and a plurality of discharge lines connected to outputs of the plurality of batteries. Switches are provided in each of the plurality of charge lines and discharge lines.

Optimization of multiplant cogeneration system operation including electric and steam networks

Abstract: The problem of optimizing the short-term operation of a multiplant cogeneration system in a large industrial complex is solved. A cogeneration system is defined as a system that simultaneously produces electric power (electricity) and thermal power (steam). The cogeneration system model includes both the electric and thermal systems. The electric system model includes generation and transmission. The thermal system model includes the individual plants, which comprise boilers, turbines, condensers, deaerators, pumps, and storage tanks and the interconnecting steam network. The optimization problem has as its objective the minimization of the overall cost of all fuels and make up water used during the scheduling horizon (1 to 24 h), subject to satisfying a number of constraints on electric and steam systems. A novel solution approach is introduced which is based on coordinated optimization of the electric and thermal systems. A production-grade computer program has been developed and tested for a real industrial complex. >

Antriebsanordnung fuer ein kraftfahrzeug

Abstract: The drive system for a motor vehicle comprises an internal combustion engine (1) with at least one controlling element (29) affecting its power and/or torque and/or rotation speed, controllable by a motor element (27), an electric generator system (3) driven by the engine (1), at least one electric motor (11) powered by the generator system (3) and driving the motor vehicle and an electronic control (19) which controls at least the one motor element (27) and the electric power supplied by the generator system (3) and/or the electric power taken by the electric motor (11) depending on the position of an accelerator pedal (23). The system includes means for detecting the actual value of the rotation speed of the engine (1) and means for detecting an actual value of the power supplied by the generator system (3). The control (19) comprises rotation speed regulators (33), which maintain the actual rotation speed at a predetermined setting, and power regulators (37) which maintain the actual electric power at a predetermined setting. To the control (19) is allocated a data store (31) in which characteristic data for combinations of data for the power setting and data for the rotation speed setting and/or data for regulating the at least one motor element (27) are stored. Both with the generator arrangement (3) and with the engine (1) on overrun, depending on the current from the generator arrangement, the control (19) detects the torque cycle depending on the crankshaft angle and, depending on the rotation speed cycle, diagnoses operating faults and/or the state of the motor.

Power consumption meter for displaying electric power consumed by appliance and the time period of consumption

Abstract: A power meter (10) is provided which can plug into an electric wall socket and it is provided with its own socket (16) for receiving the plug of an electrical appliance. The power meter has means for measuring electric current flow to an electrical appliance and indicates the amount of electrical power consumed by an appliance. In alternative embodiments, the meter is provided as an integral part of an electric wall switch (30) or wall socket (40) or it is built into an electrical appliance (50). In another embodiment, the power meter has a plurality of sockets for receiving the plugs of a number of electrical appliances for separately indicating the power consumption of each appliance.

Docking system for enhancing computer functionality

Abstract: A docking system comprising a first detecting element 13 which detects combination states of a personal computer 2 and a station 1. A second detecting element 14 is provided which detects a separation of the personal computer 2 from the station 1. The docking system also includes a combination holding element for holding a combination state of the personal computer side connector 33 and the station side connector 12. Furthermore, the docking system includes a switching element 32 for switching the personal computer side electric power source 39 to the station side electric power source 18. A third detecting element 34 is provided which detects placement of the personal computer 2 on the station 1. A control unit is provided which has three functions. First, it cuts the personal computer side electric power source 39 after performing backup processing of an execution program under a first set of predetermined conditions. Second, it supplies electric power from the station side electric power source 18 to the personal computer 2 by switching element 32 under a second set of predetermined conditions. Third, it cuts the electric power source under a third set of predetermined conditions. Each set of conditions is determined by the detecting elements.

Nuclear power plant performance study by using neural networks

Abstract: The thermal performance data obtained from the Tennessee Valley Authority (TVA) Sequoyah nuclear power plant show that the heat rate is changing constantly and the plant is probably losing some megawatts of electric power due to variation of the heat rate. It is very difficult to analyze the raw data recorded weekly during the full power operation of the plant because a nuclear power plant is a very complex system with thousands of parameters. The hybrid type of neural network was set up to work as the internal model for prediction of the heat rate. A sensitivity study was then applied to extract information about the key parameters which might strongly affect the plant thermal performance. The preliminary results show that neural networks can be used to analyze plant data and extract some useful information which may be difficult to obtain through traditional analytical models. >

New approach to the design of digital algorithms for electric power measurements

Abstract: Digital algorithms for electric power measurements are represented as 2-D digital finite-impulse-response (FIR) filters applied on voltage and current samples. Based on this approach, a novel technique for algorithm design is developed. The technique provides a convenient way to design new algorithms for measuring the electric power components according to various definitions in both sinusoidal and nonsinusoidal conditions. Several new algorithms are derived by using the proposed design technique. The existing algorithms for power measurements are also derived by using the new approach. The algorithm performance was tested using actual signal recordings. >

Innovation as a social process : Elihu Thomson and the rise of General Electric, 1870-1900

Abstract: List of figures and tables Editors' preface Acknowledgments Abbreviations used in footnotes Introduction 1. The cultivation of a scientific man 2. Learning the craft of invention 3. The Philadelphia partnership, 1879-80 4. Frustration in New Britain, 1880-3 5. Success in Lynn: the Thomson-Houston electric company, 1883-92 6. Maintaining the organization: product development at General Electric, 1892-1900 Epilogue and conclusion Index.