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Electrical Engineers, Proceedings of the Institution of

Issue 7 • Date July 1974

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Displaying Results 1 - 25 of 54
  • Dipole-mode propagation in hollow tubular waveguides

    Page(s): 537 - 540
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (593 KB)  

    Guided dipole-mode propagation is best known in its role as a surface wave supported by a dielectric rod isolated in space. A development of that arrangement consists in the provision of an outer coaxial surface satisfying the boundary conditions at a finite radius. The field is found to take the form of a dual-dipole mode comprising a counterpart field on the inside of the outer surface. A further step eliminates the inner surface altogether and allows the same basic mode to propagate within a hollow tubular structure. The requirements are investigated and some experimental results are given. View full abstract»

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  • Pulse response of interconnections in silicon integrated circuits

    Page(s): 541 - 547
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    A direct computation method is derived for analysis of metal-insulator-silicon microstrip structures and yields results in good correspondence with experimental work. This is extended to predict the performance of integrated-circuit interconnection geometries. High-resistivity silicon, despite the higher series loss, gives rise to faster lines, and there is a `critical resistivity¿ dependent on line geometry and silicon-chip area below which poor performance will be obtained owing to skin effect in the substrate restricting return current flow entirely to the bulk silicon. View full abstract»

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  • Initial time-varying flow in the smooth-bore magnetron

    Page(s): 548 - 550
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    A computer program has been written to study the flow pattern at the switching on of a 2-dimensional smooth-bore magnetron. Time-variation and multistream flow are allowed. The results suggest that a simple single-stream flow cannot be established, but that either a double-stream or a multistream flow is established. View full abstract»

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  • Computer-controlled queuing system with switching network and general service times

    Page(s): 551 - 554
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (443 KB)  

    The paper presents a detailed study of a computer-controlled queuing system with a Poisson distribution input, first-come first-served queue discipline, single server with general service times and switching network through which the establishment of connection between customer in the queue and the idle server is subject to blocking. A generating function for the probability of queue size and a necessary and sufficient condition for the existence of statistical equilibrium for the queue size are obtained. Also, the Laplace-Stieltjes transform of waiting-time distribution is presented. Finally, the average queue size and the average waiting time are reported. View full abstract»

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  • Class of linear binary codes

    Page(s): 555 - 558
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (398 KB)  

    A class of algebraic linear codes is introduced in which the parity-check matrix of the code is constructed by using a subset of the Abelian group of Walsh functions. These codes meet the Helgert and Stinaff upper bounds on minimum Hamming distance, and all the codes of this class are easily decodable by a one-step majority-logic algorithm. View full abstract»

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  • Translation of a circuit matrix into the incidence matrix of a network

    Page(s): 559 - 560
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (251 KB)  

    A 2-stage pseudo-Boolean programming scheme is constructed to find all the networks, the circuits of which are determined by a given circuit matrix. An illuminating example is given. View full abstract»

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  • Different forms of the Hilbert transform as applied to digital filters and sequences

    Page(s): 561 - 567
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (678 KB)  

    The paper presents two aspects of the Hilbert transform; first, a unified survey and treatment of the different forms of the Hilbert transform which arise in the study of digital signal processing systems when considering: (a) the frequency-domain relations between the real and imaginary components of the network function of a linear stable digital filter whose impulse response is causal, and (b) the determination of analytic signals associated with periodic waveforms or sequences specified in the time domain. The continuous forms of the Hilbert transform are developed as special cases of the corresponding discrete cases. Secondly, a comparison of two finiteimpulse response (f.i.r.) digital filters for realising the discrete Hilbert transform is made. View full abstract»

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  • Iterative synthesis of low-sensitivity RC earthed networks

    Page(s): 568 - 572
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (621 KB)  

    The possibility of using digital computers and the existence of very convenient technological procedures for constructing RC earthed networks makes it very interesting to have methods available that are capable of taking full advantage of these possibilities. The method proposed in the paper represents an attempt to do this. It is based on an iterative procedure, which directly synthesises an assigned function as the transfer function of a modular RC network. View full abstract»

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  • Numerical methods for antenna problems

    Page(s): 573 - 582
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1508 KB)  

    An account is given of some of the integral equations that can be devised for an antenna on whose surface the tangential electric intensity is prescribed. Some of the problems that can arise in numerical work from the formulation of the integral equations and their possible lack of uniqueness are described. Numerical methods of tackling integral equations are given, together with a survey of their advantages and disadvantages from the point of view of electromagnetism. Whip antennas merit separate consideration because of their special structure. There are also a few remarks on modelling surfaces by wire grids. The differing requirements of pulse and harmonic excitation are compared. Finally, the problems of error analysis are briefly mentioned. View full abstract»

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  • Subjective quality of television pictures impaired by short-delay echo

    Page(s): 583 - 593
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1664 KB)  

    Quality-grading tests have been made on the effect of an undistorted echo of positive or negative polarity and with delay in the range 200¿1300 ns, in a 625-line monochrome television system. The results apply also to the effect on the luminance component of a colour signal. It was found simplest to express echo magnitude in terms of the magnitude of signal plus echo. A logistic relationship between mean picture-quality grading and logarithmic echo magnitude then applies, and the shape of the curve is independent of delay. A mathematical model is described to represent the complete relationships between picture quality, and echo delay and magnitude. Summarised results are given in terms of mark points of subjective impairment. The (signal + echo)/echo ratio at the 1-imp mark point, or midopinion condition, varies from 9 dB at 200 ns to 20 dB at 1300 ns for positive echo and 1 dB to 16 dB for negative echo. At the ¿-imp mark point, the variation is from 14 dB to 25 dB for positive echo and 7 dB to 22 dB for negative echo. View full abstract»

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  • Subjective assessment of flicker in visual-telephone pictures

    Page(s): 594 - 600
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1162 KB)  

    Subjective tests have been made of the effect of the 100 Hz modulation, caused by 50 Hz lighting, on the pictures displayed by two visual telephone systems of equal bandwidth and line frequency, but differing picture frequencies. In a 50 fields/s 319-line system the flicker due to the modulation is normally at a rate of less than one per second and much less objectionable than the inherent flicker of the picture at field rate. In a 60 fields/s 267-line system the modulation flicker is at a rate of about 20 per second and can be much more objectionable than the inherent flicker at field rate. A comparison-type subjective test showed that the two systems were judged to be of equal overall quality for typical pictures of highlight luminance 500 cd/m2 with 2.1% modulation; when the highlight luminance was reduced to 200 cd/m2, equality, was achieved with 1.3% modulation. A quality-grading test with the 60 fields/s 267-line system indicated that, for typical pictures, subjective impairments of 1 imp and 1/8 imp are obtained with 10.3% and 1.6% modulation, respectively, for either value of highlight luminance. View full abstract»

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  • Power-system model for large frequency disturbances

    Page(s): 601 - 608
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (929 KB)  

    The paper describes a mathematical model for studying power-system frequency control. The model provides the basis for economical calculation of frequency transients of up to ten minutes' duration, enabling problems associated with the dynamic balance of generation and load to be studied. The use of test results to establish confidence in the model is described. An account is given of two recent applications: a study of pumpedstorage-plant dynamic-response requirements, and a study of the application of load-shedding relays. View full abstract»

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  • Estimation of maximum demand on a British electricity-board system. Forecast periods of 1-3 years

    Page(s): 609 - 615
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (770 KB)  

    The paper is concerned with the forecasting of maxium demand (m.d.) on an area board (or Central Electricity Generating Board Region) system where forecast periods of 1-3 years are important for planning the amount of, and the timing of, capital expenditure. A causal model is sought that gives a good fit to the historical data of recorded m.d. and a satisfactory performance in prediction. The primary parameters in the causal model were found to be the gross domestic product (g.d.p.), temperature and load factor. The system maximum demand (m.d.) is forecast for average-cold-spell (a.c.s.) conditions with variances due to: (a) standard deviation (s.d.) of model estimating errors (b) s.d. of the National Institute estimating errors for g.d.p. (c) s.d. of departure of temperature for a.c.s. conditions The mathematical formulation of the problem enables an estimate to be given, with a precise probability, of a given load being exceeded under any assumed set of adverse conditions. The principle that the system m.d. can be estimated from a limited number of parameters can be judged by the performance and precision of the model. The model gives a very good fit to historical data. The standard error (s.e.) is of the order of 0.6% of recorded m.d. The parameters were shown to be well chosen by their high mathematical significance, and the performance of the model in the 1973 prediction was consistent with its performance on the historical data. Confidence in the performance of the model, in prediction, was strengthened by a retrospective examination of the predictive performance of the chosen model when based on earlier data. View full abstract»

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  • Analysis of ferro-oscillations in power systems

    Page(s): 616 - 622
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    The paper presents an analysis of ferro-oscillations in capacitor voltage transformers and series-compensated e.h.v. lines. The dual-input describing function is adopted to show the regions of existence and the influence of system parameters on such oscillations. A complete analytical method suitable for digital computation has been developed for determining the amplitudes of these oscillations. View full abstract»

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  • Stability analysis of power systems using Lie series and pattern-recognition techniques

    Page(s): 623 - 629
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (825 KB)  

    This paper concerns the estimation of stability domains for transient stability problems in power systems. Lieseries methods are used for generating a solution to Zubov's partial differential equation and pattern recognition algorithms are applied to obtain the boundary defining a region of stability. Critical clearing times for representative problems are obtained using the analytical expression for the stability boundary, and these values are verified by observing the nature of the swing curves obtained by numerical integration. View full abstract»

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  • Newton-Raphson algorithm for 3-phase load flow

    Page(s): 630 - 638
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (969 KB)  

    One of the problems encountered in power-systems operation is the generation of unbalanced voltages and currents in the presence of long transmission lines with few or no transpositions, including possible unbalances arising in source and load conditions, or indeed any items of plant such as shunt and series reactors. To improve or investigate these unbalance effects in any detail, a 3-phase-load-flow solution that allows representation of all possible unbalances as they exist in the power-systems network without making any assumptions is essential. Consequently, a working Newton-Raphson algorithm is presented, which forms the basis of a computer program developed for the specific purpose of solving the 3-phase-load-flow problem. An indication of program facilities is given, together with sample results for illustration. View full abstract»

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  • Diakoptics in node-to-datum analysis. An approach from linear graph theory

    Page(s): 639 - 644
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    The diakoptic equation and techniques are derived in a simple manner using only the basic electrical laws, simple linear-graph theory and elementary matrix algebra. A technique is presented for dealing with multiple coupling between elements in the links and main network. View full abstract»

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  • Availability of generating units operated discontinuously

    Page(s): 645 - 646
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (266 KB)  

    Some of the important aspects for reliability assessment of power systems are outlined to quantify a desired security level. This quantification eliminates subjective guesswork, and enables efficient prediction of future operating conditions.This requires simple and computationally efficient models. A realistically efficient availability model of a generator unit operated in a 5-state discontinuous cycle is presented. Typical work schedules and transition rates have been analysed. This showed that the work schedule significantly affected the meanoutage probability, and the random-transition rates greatly affected the periodic fluctuations between minimum and maximum-outage probabilities. View full abstract»

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  • Induced field-system transients in synchronous generators having unidirectional forms of excitation supply

    Page(s): 647 - 652
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (706 KB)  

    Synchronous-generator excitation supply systems that are based on a.c. exciters operating in conjunction with rectifiers, as is now widely the practice, give rise to particular modes of generator operation that do not occur when d.c. exciters are used. In the case of a d.c. exciter, the field current can reverse, if it is required so to change by stator operating conditions, whereas an a.c. exciter and a rectifier system provide an essentially unidirectional form of supply. A preclusion of field-current reversals by the rectifiers introduces a constraint into the interaction between the rotor and stator circuits of the generator for which the excitation system provides a supply. For a wide range of generator operating conditions, the constraint is inactive, and so no adverse effects arise, but credible circumstances can combine to cause the constraint to become active. When this is the case, the transition of the constraint from inactive to active is accompanied by a pulse of induced voltage in the field system. The paper reports a study of field-system overvoltages that might be generated in this way for the particular conditions encountered in synchronising. A mathematical model suitable for use in computer studies in this area of applied analysis in power systems is summarised, and the validity of the model is checked by comparing computer study results with those available from fullscale tests on a 120 MW turbogenerator unit. Numerous synchronising studies have been based on this model, and representative results from them are collected together in the paper, together with the synchronising conditions that can give rise to overvoltages. When synchronising is achieved within the close limits typical of British practice, the hazard of induced field voltages of substantial magnitude should be avoided altogether, but the continuously recurring nature of synchronising generator units with a parent system suggests a general study of the conditions. It is a general stu- dy of this kind to which the paper is devoted. View full abstract»

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  • Calculation of magnetic fields in the end regions of turbogenerators

    Page(s): 653 - 656
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (559 KB)  

    To solve the Poisson equations for the vector potential within the end region of a turboalternator, a method based on eigenfunction expansions is proposed. Use of this method allows the effects of the shaft, outer casing and rotor endbell to be approximately represented. In addition, the effects of the stator and rotor core ends can be incorporated by means of the introduction of an airgap current, in the usual way. The stator and rotor end windings are modelled in a fairly detailed manner. View full abstract»

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  • Residual unbalance in symmetrised windings

    Page(s): 657 - 662
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    Polyphase symmetrisation is a new geometrical process for obtaining balanced fractional-slot (irregularly distributed) windings. Practical polyphase windings cannot always comply exactly with the ideal geometry. The paper shows how to calculate the very small residual unbalance, where any exists, with particular reference to 2-speed p.a.m. windings. View full abstract»

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  • Steady-state stability criterion for induction motors

    Page(s): 663 - 667
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    The instability of induction motors has been widely observed when operating on variable-frequency supplies, particularly on light loads at low speeds. This phenomenon is analysed for steady-state conditions using the single-phase equivalent circuit of the motor and considering a stable system to have constant-power balance. The analysis confirms the low frequency, low-slip instability and predicts a high-slip limit of stable operation. These limits are both confirmed by measurements on a motor/inverter drive. The amplitude and frequency of oscillations are not investigated. View full abstract»

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  • Transient voltages generated by inductive switching in control circuits

    Page(s): 668 - 676
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1195 KB)  

    In certain control applications a common d.c. supply is used for both electronic and electromechanical equipment. In this situation semiconductor devices may be subjected to transient voltages generated by the operation of mechanical switches in inductive circuits. This paper describes the factors involved in the generation of such transients and methods for predicting their time duration are proposed. The circuit interruption process is described in terms of either stable or unstable arc switching and the limiting factors for these two conditions are discussed. It is shown that when unstable arc switching occurs short-duration voltage spikes appear across the common power supply and, by implication, across all parallel-connected equipment. Reasonable correlation is shown to exist between predicted and measured transient-voltage time durations and the analytical models proposed could be used as a theoretical basis for transient-voltage specifications. View full abstract»

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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

Full Aims & Scope