Showing papers on "Electrical network published in 1985"

Circuits, Signals, and Systems

Abstract: These twenty lectures have been developed and refined by Professor Siebert during the more than two decades he has been teaching introductory Signals and Systems courses at MIT. The lectures are designed to pursue a variety of goals in parallel: to familiarize students with the properties of a fundamental set of analytical tools; to show how these tools can be applied to help understand many important concepts and devices in modern communication and control engineering practice; to explore some of the mathematical issues behind the powers and limitations of these tools; and to begin the development of the vocabulary and grammar, common images and metaphors, of a general language of signal and system theory.Although broadly organized as a series of lectures, many more topics and examples (as well as a large set of unusual problems and laboratory exercises) are included in the book than would be presented orally. Extensive use is made throughout of knowledge acquired in early courses in elementary electrical and electronic circuits and differential equations.Contents: Review of the "classical" formulation and solution of dynamic equations for simple electrical circuits; The unilateral Laplace transform and its applications; System functions; Poles and zeros; Interconnected systems and feedback; The dynamics of feedback systems; Discrete-time signals and linear difference equations; The unilateral Z-transform and its applications; The unit-sample response and discrete-time convolution; Convolutional representations of continuous-time systems; Impulses and the superposition integral; Frequency-domain methods for general LTI systems; Fourier series; Fourier transforms and Fourier's theorem; Sampling in time and frequency; Filters, real and ideal; Duration, rise-time and bandwidth relationships: The uncertainty principle; Bandpass operations and analog communication systems; Fourier transforms in discrete-time systems; Random Signals; Modern communication systems."Circuits, Signals, and Systems" is included in The MIT Press Series in Electrical Engineering and Computer Science, copublished with McGraw-Hill.

Transmission Network Planning Using Linear Programming

Abstract: In long range transmission planning, where new load growth, new generation sites and perhaps a new voltage level are to be considered, a computer aided method of visualizing new circuits in a network context is needed. The new method presented meets this need by the combined use of a linear (dc) power flow transmission model and a transportation model (also known as a trans-shipment model). The dc transmission model is solved for the facilities network by obeying both of Kirchhoff's laws, flow conservation at each bus and voltage conservation around each loop. The transportation model is solved for the overloads by obeying only the bus flow conservation law while minimizing a cost objective function.

Kalman Filtering Applied to Power System Measurements for Relaying

Abstract: Digital protection algorithms are becoming more complex as the cost of computational equipment continues to decrease. In particular, optimal response digital filters, such as Kalman filters, can be implemented on presently available devices. Optimal filters are not yet extensively applied because they appear complex and engineers have not become familiar with their use. This paper presents the basics of the Kalman filtering technique in power systems terminology and illustrates its use for estimating rotating phasors. Sample designs are presented for voltage and current phasor estimation during system transients. A method for including decaying dc and harmonic frequency components in the filter design is also described and sample results are presented.

Ground fault circuit interrupting system

Abstract: A switching system for interrupting an electrical circuit is described. This switch includes a number of preferred and other embodiments which have this as their goal, but which represents a number of distinctive and novel approaches to solving switching problems in the prior art. By way of example only, these approaches include provision of mounting strap which supports ground terminals while also serving as a magnetic circuitry conduit; a "banger" type arrangement which enables alternate making and breaking of a circuit; and a space-saving method for supporting the arrangement within a device or system able to be installed within a conventional receptacle box.

Modeling the electrical behavior of anatomically complex neurons using a network analysis program: Passive membrane

Abstract: We describe the application of a popular and widely available electrical circuit simulation program called SPICE to modeling the electrical behavior of neurons with passive membrane properties and arbitrarily complex dendritic trees. Transient responses may be calculated at any location in the cell model following current, voltage or conductance perturbations at any point. A numbering method is described for binary trees which is helpful in transforming complex dendritic structures into a coded list of short cylindrical dendritic segments suitable for input to SPICE. Individual segments are modeled as isopotential compartments comprised of a parallel resistor and capacitor, representing the transmembrane impedance, in series with one or two core resistors. Synaptic current is modeled by a current source controlled by the local membrane potential and an "alpha-shaped" voltage, thus simulating a conductance change in series with a driving potential. Extensively branched test cell circuits were constructed which satisfied the equivalent cylinder constraints (Rall 1959). These model neurons were perturbed by independent current sources and by synaptic currents. Responses calculated by SPICE are compared with analytical results. With appropriately chosen model parameters, extremely accurate transient calculations may be obtained. Details of the SPICE circuit elements are presented, along with illustrative examples sufficient to allow implementation of passive nerve cell models on a number of common computers. Methods for modeling excitable membrane are presented in the companion paper (Bunow et al. 1985).

Modular electrical conductor system

Abstract: A modular electrical conductor system for electrical wiring including one or more discrete elongated generally rectilinear track or carrier members and a plurality of modular electrical elements which are selectively connectable with the carrier members to establish a selected electrical circuit, the various carrier members and modular elements having preassembled electrical conductors carried therein such that ends of the conductors are adapted for mating electrical connection while being continually shielded from contact by an installer. The modular electrical elements include modular switch and/or receptacle elements having internal switch means operative to enable selective connection of internal conductors so as to vary circuit configurations to create at least one primary circuit and selective auxiliary circuits, each modular switch and receptacle element defining four quadrant oriented multiple conductor connector sites enabling the switch and receptacle elements to be connected to elongated carrier track members. The various prewire modular circuit components are preferably coded in a manner to enable easy selective connection in various circuit configuration by a person untrained in electrical circuitry.

Wall system with multicircuit electrical system

Abstract: An electrical system for a wall system formed from a plurality of serially connected wall panels. Each panel has at least one electrical terminal mounted thereon, and the terminals are joined by electrical cables or flexible electrical connectors. The electrical system is a seven-conductor system employing three live and three neutral conductors for defining three separate electrical circuits each having a separate neutral. A portable power-tap unit, specifically a receptacle unit, can be plugged into the power block for selective engagement with any one of the three circuits. The power-tap unit has a connector portion which plugs into the power block, which connector portion is defined soley by three contacts. Two of the three contacts, namely the live and neutral contacts, are mounted on a carrier which is slidably supported on the power-tap housing so as to be slidably displaced between three selected positions so that the power-tap can be selectively joined to any one of the three circuits.

Probabilistic load flow considering network outages

Abstract: Many techniques have been proposed to solve the load flow problem probabilistically. The great majority have only accounted for load and generation data uncertainties, and therefore, the network configuration has been considered fixed. So far, the effects of the configuration uncertainties due to the probabilistic nature of the network have not been deeply analysed. The paper presents a new method for obtaining a probabilistic load flow solution when network outages are modelled as a random variable. The proposed technique is applied to a typical power system and the results discussed.

A Method That Combines Internal State Estimation and External Network Modeling

Abstract: A method that combines internal state estimation and external network modeling is developed. The external system is represented by an unreduced load flow model. One state estimation covering both the internal system and the external system is used. The external system operating data on power injections and bus voltages are entered as pseudo-measurements. At each iteration the set of active pseudo- measurements are selected to conform with the specified variables in a load flow program. Because such a set of non-redundant measurements is used, the internal state estimation is not affected by the external system pseudo-measurements. External generation MVAR and controlled bus voltage limits are enforced. A technique is developed to make a pseudo-measurement dormant. Using the dormant-measurement technique, it is possible to maintain the same external system state estimation formulation while the PV-PQ switching takes place from iteration to iteration. The method can easily be implemented by modifying an existing state estimation program. It has been implemented in a fast model-decoupled estimation program. Because of the dormant measurement technique, the constant gain matrix evaluated at flat voltage is used in every iteration. The method has been tested on the IEEE 14- bus, 30-bus, and Brazilian 66-bus systems. Excellent results are obtained. The number of iterations for the method to converge is usually the same as the regular state estimation runs. Thus the method presented here achieves simultaneously the internal state estimation and the external network modeling without adversely affecting the internal state estimation.

Method and apparatus for power-up of unattended computer

Abstract: An electrical circuit is disclosed which provides the capability of starting up an unattended computer or similar device either from a remote location or at a predetermined date and time. The circuit includes an electrical energy storage device which, when a telephone ring signal is detected, initiates start-up of the computer. Alternatively, an interrupt from a date timer may initiate start-up of the computer using the energy storage device. Once start-up of the computer is initiated, its power supply provides the necessary voltage which, in conjunction with a latching transistor, maintains the electrical circuit providing AC power to the power supply and computer and recharges the electrical energy storage device. Finally, an electrical signal to power-down the computer may be initiated either remotely or through software instruction.

Enhancement of the Transient Stability of Integrated AC/DC Systems Using Active and Reactive Power Modulation

Abstract: Active power modulation has been successfully used to improve the dynamic performance of interconnected AC/DC systems. This, however, results in uncoordinated reactive power modulation which, in the case of weak systems, reduces the effectiveness of the method. The paper presents the basic design of a DC link controller which, in the presence of major disturbances in the AC system, modulates the active and reactive power of the converters and improves the transient stability of the integrated system. The proposed control method was tested using dynamic simulation techniques and the results obtained are presented in the paper. These results show that the application of the method, under certain conditions, leads to significant improvement of the transient performance of the interconnected AC/DC system.

Power supply switching circuit

Abstract: A power supply switching circuit is disclosed which provides for automatically switching an electrical circuit load from a main power source to an auxiliary power source, yet maintains the two power sources isolated from each other. The power supply switching circuit is readily integrated with its electrical load to form a monolithic integrated circuit. A pair of MOSFETs provides alternate connections of the load to the respective power sources. The circuit effectively connects the gate and source of the appropriate MOSFET across the available power source and thus assures the maximum turn-on voltage is applied to the MOSFET.

Advanced Scheme for AC Voltage Control at HVDC Converter Terminals

Abstract: A new economic and effective scheme for controlling the ac voltage at the HVDC terminals during both steady state and dynamic conditions is presented By extending the basic characteristics of an HVDC converter, it is possible to affect and modulate the reactive power balance on the ac side Analytical studies as well as digital and simulator results are presented to demonstrate the viability of the proposed ac voltage control strategy to optimize HVDC terminal design and performance for a practical system The economic and technical features of the new scheme are discussed and compared with other ac voltage control techniques such as synchrononous condensers and static VAr compensators

Stabilization of a High Voltage AC-DC Power System I. Evaluation of Control Strategies

Abstract: Various optimal and suboptimal stabilizing signals for a single machine infinite bus system connected through an ACDC link have been investigated. The controls in order of effectiveness of transient control are the linear state regulator control, a quasioptimal proportional control, output regulator controls from terminal voltage and frequency, and frequency and acceleration. From implementation viewpoint the proportional control is preferred. This scheme can also be easily extended to Include the nonlinearities in the system dynamics.

Studies of turn-off effects in power semiconductor devices

Abstract: An analytical model has been developed for analyzing current and voltage transients during high power diode recovery. Using the charge control approach and approximating the excess charge distribution by simple geometrical curves a fast and convenient method for computer analysis is obtained. The model is thoroughly physical and makes use of the proper diode design parameters and the differential equations of the electrical network. There is no need for any experimental fitting parameter. All relevant complicating effects as emitter recombination, nonabrupt pn -junction and reverse current influence on the space-charge layer are considered. Comparisons between calculated and measured recovery behavior under several different conditions show good agreement and prove that the model may serve as a useful tool in device and circuit development including RC-snubber design. Furthermore, the calculated charge distribution varies during the recovery in a physically reasonable manner. Starting from measured recovery transients this model may also be used as a new method for determining the excess charge content in the diode at the beginning of the recovery phase.

Electrical circuit arrangement, which is supplied from a DC voltage source, for supplying a load two-pole network with a direct current which is impressed but can be interrupted or a block-form alternating current which is impressed but can be interrupted, with adjustable limiting of the voltages on the load two-pole network and on the electronic one-way switches which are used

Abstract: Electrical load two-pole networks must be supplied in many applications (for example in the case of electrical welding, spark erosion or the excitation of lasers) with an impressed direct current or alternating current, which would frequently be capable of being pulsed. In order to impress a current, circuit arrangements which have been widespread until now use either a bias resistor, which results in poor efficiency, or an inductor in the output circuit, which severely constrains the pulsing capability. These disadvantages are avoided in the basic arrangement according to the invention, which is shown by way of example in Fig. 4. The current through the load two-pole network (1) is impressed with the aid of an input step-down controller (7). If it is not intended to supply any power to the load two-pole network, the short-circuiting switch (5) must be closed. When the short-circuiting switch is blocked, the voltage on the load two-pole network and on the short-circuiting switch is limited by a buffering network (12). The voltage on the buffering capacitor is regulated at a preferably constant setting by suitably influencing a feedback controller (15). If an invertor is introduced between the output terminals of the circuit arrangement according to Fig. 4 and the load two-pole network, the load two-pole network can be supplied with an impressed, block-form alternating current. In addition, it is possible to design the circuits to be isolated in terms of potential.

Consideration for Implementing Multiterminal DC Systems

Abstract: The established principles of multiterminal dc transmission are applied to the planning needs of practical projects. Without further detailed review of operating techniques, possibilities and contraints that are intended to be useful in the assessment of potential projects are discussed. Reference is made to the plans for certain schemes and the status of dc circuit breakers is reviewed.

Electromagnetic Transients in a Line-Transformer Cascade by a Numerical Laplace Transform Technique

Abstract: The purpose of this work is to present a method for studying electromagnetic transients appearing in a power network consisting of a long transmission line and a transformer connected in cascade. An exact equivalent circuit representation of the system is developed using distributed element analysis in the s-domain. The proposed model assumes distributed inductances and self and mutual capacitances within the transformer windings. In addition, the new model can easily account for various connections of the transformer neutral. The line, which can be of any length, is represented by a single exact two-port network which is derived from distributed parameter theory. The new model yields closed form expressions in the s-domain for the transient potential distributions along the turns of the transformer winding as well as the connecting transmission line.

Validation of Digital Simulation of DC Links - Part II

Abstract: This paper establishes the validity of digital simulation of transients in HVDC-ac power systems. For the digital simulation BPA's EMTP was used. Manitoba Hydro's Nelson River HVDC system comprising two HVDC bipoles, Bipole 1: 1668 MW and Bipole 2: 1000 MW was used for digital simulation test cases. The simulation results were compared with the field tests conducted by Manitoba Hydro.

Noise making mask

Abstract: An over-the-head face mask is provided with a completely self-contained, electrical noise generating system. The noise generator comprises a speaker, a signal generating electrical circuit, a battery or other power supply and wires connecting the electrical components together. In addition, an on/off switch can be provided in the electrical circuit. Light emitting diodes, located as pupils of the fake eyes of the face mask are also connected in the electrical circuit so that they light up when the electrical circuit is closed. The noise generating speaker of the electrical system is located in a protuberance of the face portion of the face mask. Preferably, the protuberance is an integral disguise feature of the face mask and, therefore, the speaker is camouflaged, self-contained and yet capable of transmitting an unmuffled sound. In this manner, the speaker is hidden from view and, yet, is located proximal to the face mask to provide realistic sound or noises apparently emanating from the front of the face mask.

Problems associated with unit commitment in uncertainty

Abstract: This paper is one of a series presented on behalf of the System Operations Subcommittee with the intent of focusing industry attention on current problems faced by electric utility operators.

Techniques for the Steady State Representation of Unbalanced Power Systems: Part I. A Systematic Building Block Approach to Network Modeling

Abstract: The effects of interphase coupling in multiphase power systems become important in the presence of network topology imbalance and unbalanced phase loadings. Currents that flow in the earth can have significant effects on the system's behavior. Both of these effects of imbalance must be accounted for in an accurate model of a multiphase system. A step-by-step procedure for unbalanced power system modeling is presented. The procedure relies upon linear graph theory and produces a multiport model which is a generalization of the well-known bus admittance model. This paper reviews some important results of linear graph theory and gives sufficient detail that the procedure can be followed without extensive use of the references (whose nomenclatures differ). Mutual coupling effects, the effects of neutral and static conductors, the finite conductivity of earth, and various component models are considered. A companion paper describes a procedure for reducing the order of the power system model.

Reliability and economic assessment of generating systems containing wind energy sources

Abstract: There is much interest in using renewable energy sources, such as wind, wave and solar, to generate electrical energy. Unfortunately, such energy sources are intermittent, and, therefore, conventional sources must still be available to meet the demand during quiescent periods. Hence, the reliability and economic assessment of these novel sources cannot be made using standard capacity-replacement-based methods; instead, energyreplacement methods are required. The paper extends the loss-of-energy-expectation method to evaluate the generation reliability including novel energy sources. These results are then used to calculate the economic benefits of such sources. The approach is illustrated using the IEEE reliability test system. Although the paper concentrates on wind energy sources, the technique and approach are applicable to a generation system containing any type of intermittent energy source.

Stability of Converter Control for Multiterminal HVDC Systems

Abstract: The stability analysis of converter control, particularly for multiterminal HVDC systems, is complex and requires a systematic approach. This paper presents a new discrete converter model based on average system quantities and the development of the state space model of the AC/DC system. The linearized, discrete time, state space model of the overall system is derived utilizing the linearized component models and identifying the interconnections between them. Both frequency and time domain techniques are employed for stability investigations. The system model is demonstrated through the stability analysis of some sample systems and the results are validated using digital simulation.

Neuromuscular stimulating apparatus

Abstract: A portable electrical neuromuscular stimulating apparatus is disclosed. The apparatus comprises a plurality of portable electrical stimulation units, with each unit including at least one pair of electrodes adapted to be placed on the body of the patient. Electrical circuit means are provided that operatively interconnect each of the units so that a pulsed electrical energy signal is supplied to each pair of electrodes as desired, whereby a predetermined amount of therapeutic pulsed electrical energy is delivered to the desired muscle.

Wire tap detection device

Abstract: The present invention discloses a device for detecting the presence of an intruder listening device on a telephone or data line. The device comprises an electrical circuit electrically connected to the telephone line for measuring the values, polarity and electrical characteristics of the telephone line. These measured values are then compared with predetermined values for each electrical characteristic which are stored by the electrical circuit. An indicator is activated by the electrical circuit when the measured value varies from its respective predetermined value by more than a predetermined amount. The circuit, which is preferably microprocessor controlled, also includes a signal sweep generator for generating one or more electrical wave forms into the telephone line as well as a receiver which receives and analyzes the reflected signal from the telephone line.

State Estimation for Integrated Multi-Terminal DC/AC Systems

Abstract: In the past few years, many papers have been published on state estimation applied to electric power systems. Different types of algorithms-static, tracking and dynamic-have been proposed aside with a variety of applications: detection and identification of bad data, network configurator, etc. Most of such studies have been carried out for AC systems, although there are some power systems around the world with DC links in operation. Moreover, engineers are now considering DC multiterminal networks as a feasible option. Therefore the state estimation techniques have to be extended to deal with such mixed AC/DC systems. So far, few papers have been published on this matter.

A generalized Benders decomposition approach to reactive source planning in power systems

Abstract: Reactive sources in an electric power system do not consume or generate average power, but alter the phase relationships among system voltages and currents, and hence affect the power flows in the system. This paper deals with the location and sizing of such elements, with the objective of making the system operate satisfactorily if a certain set of contingencies should occur, while keeping investment costs low. This problem is analogous to other facility location problems except that, for a fixed set of location decisions, the relationships among system power flows and voltages are nonlinear.