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1887

Proceedings of the Institution of Electrical Engineers

Volume 121, Issue 12, December 1974

Volumes & issues:

Volume 121, Issue 12

December 1974

Generation-recombination noise of junction-gate field-effect transistors
Design of m.t.i. filters with staggered p.r.f.: a pole-zero approach
Analytic theory of the IMPATT diode and its application to calculations of oscillator locking characteristics
  • Author(s): A.L. Cullen  and  J.R. Forrest
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1467 –1474
  • DOI:  10.1049/piee.1974.0308
  • Type: Article
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  • p. 1467 –1474 (8)
    The paper describes an analytic theory of the IMPATT diode, based on the well known Read model. The inclusion of finite avalanche pulse width and space-charge effects in the treatment yields a relatively simple theory that compares well with a computer simulation such as that of Scharfetter and Gummel, or the University College London full-simulation program. The use of such diode admittance calculations in the prediction of oscillator locking characteristics is described. The circuit of a reflection-type locked oscillator is analysed for steady-state conditions and stability limits. After allocation of practical parameter values to the theory, the resulting predicted variation of locked output power with frequency shows good agreement with experimental measurements on a low-power X band IMPATT oscillator.
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Analysis of skewing in amplitude distributions of filtered m sequences
New families of error-correcting codes generated by modification of other linear binary block codes
  • Author(s): Abdullah A. Hashim
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1480 –1485
  • DOI:  10.1049/piee.1974.0310
  • Type: Article
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  • p. 1480 –1485 (6)
    Two procedures for modifying linear block error-correction codes are proposed. The first is based on the deletion of x rows and y columns from the parity-check matrix of a given (n, k) code, in such a way that the minimum Hamming distance of the resulting (n−y, k+x−y) code remains equal to that of the original. It is shown that if x is unity, then y may be as low asthe minimum Hamming distance of the (n, n−k) dual of the original (n, k) code. This procedure of deleting rows and columns when applied to the known linear binary block code yields a family of codes, some of which have better rates than those of the best previously known codes of identical Hamming distance and the same number of paritycheck digits. 17 examples of such new codes are derived and included in the paper. It is also shown that apart from appropriate slight modification, the coding and decoding algorithms for this family of modified codes are similar to those of the original code. The second proposed procedure of code modification entails lengthening the original (n, k) linear block code by annexing k′ message digits. If the original code is capable of correcting t random errors or less, then the resulting modified (n+k′,k+k′) code has a rate higher than that of the original (n, k) code. Moreover, its error-correcting capability is such that it will correct t random errors or less if at least one of these occurs in the block of k message digits and s random errors or less, where 1≤s<t, if none of the errors occur in any of the k message digits. Five examples of such codes are given.
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Principles of a permanent-magnet axial-field d.c. machine
Sources of harmonic currents in slip-ring induction motors
Determination of synchronous-machine parameters allowing for unequal mutual inductances
Invertor-fed synchronous motors with induced excitation
  • Author(s): B.J. Chalmers ; A.L. Mohamadein ; A.C. Williamson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1505 –1512
  • DOI:  10.1049/piee.1974.0314
  • Type: Article
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  • p. 1505 –1512 (8)
    Invertor-fed brushless synchronous motors are described, in which the harmonic content of typical invertor-supply waveforms is utilised to produce rotor excitation in wound rotors with shaft-mounted diodes. Particular attention is paid to a 3-phase star-connected rotor, connected to two diodes, and a salient-pole rotor with a single diode. Approximate analyses of synchronous performance are presented which provide a clear understanding of the special modes of operation of these systems, and results of full digital simulations are shown to be in excellent agreement with measured performance characteristics. Practical developments are reported which demonstrate the influence of design features, including saturation and skew, and which typify the high levels of performance attained with these motors.
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Simulation of a synchronous generator connected via a delta—star transformer
  • Author(s): M.D. Barber  and  M. Giannini
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1513 –1521
  • DOI:  10.1049/piee.1974.0315
  • Type: Article
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  • p. 1513 –1521 (9)
    A mathematical model of a 3-phase synchronous machine, connected to the infinite bus through a delta—star transformer and a transmission line, is given. Symmetric and asymmetric faults on the low-voltage side and on the high-voltage side of the transformer are analysed by using 3-phase variables. Since the simulation is in terms of the direct-phase quantities, the digital-program solution can very easily simulate simultaneous fault conditions as well as sequential faults on either side of the power transformer. By applying proper constraint conditions, the model can be readily used to include symmetric and asymmetric faults for an unloaded alternator, and power-frequency transients following the closure of the generator circuit breaker. The validity of the analysis developed is examined by comparing the digital results with the theoretical results for 3-phase faults on a generator on open circuit, and with a number of experimental results. Versatility is demonstrated by the range of experimental results considered and by further studies.
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Dynamic performance of field-regulated synchronous machines
  • Author(s): E. Fishwick ; B.W. Hogg ; D.P. Sen Gupta
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1522 –1528
  • DOI:  10.1049/piee.1974.0316
  • Type: Article
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  • p. 1522 –1528 (7)
    The paper analyses the influence of various types of field regulators on the dynamic performance of synchronous generators. Both conventional and dual-excitation generators are considered, with basic controls provided by voltage and angle regulators, which may have proportionate and derivative feedback. In the case of dual-excitation machines, both bus-rotor-angle and terminal-rotor-angle signals are employed in the quadrature-axis regulator.Stability is initially defined by computed regulation curves, and additional information is then obtained by calculating the variations of the synchronising- and damping-torque coefficients (Ts and TD) with regulator gain. These graphs are superimposed on the regulation curves, to show how Ts and TD determine the dynamic stability of the machine, and to illustrate the underlying reasons for stability.
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Brushless cascade alternator
  • Author(s): A.R.W. Broadway ; B.J. Cook ; P.W. Neal
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1529 –1535
  • DOI:  10.1049/piee.1974.0317
  • Type: Article
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  • p. 1529 –1535 (7)
    A brushless a.c. generator is described which has a mode of operation similar to two wound-rotor induction machines connected in cascade. This cascade machine, which has previously been considered for application as a motor, has single stator and rotor windings in a conventional induction-machine frame. The machine is one of inherently high pole number. As an alternator, therefore, it is suitable for the generation of medium- to high-frequency supplies. The direct excitation current and the alternating output current flow in its one stator winding. Its cylindrical rotor iswound with an extremely simple short-circuited polyphase winding. Since no brushes, slip rings or rotating diodes are needed, the machine may be driven reliably at high speeds.A theoretical treatment is developed which takes account of magnetic saturation both in the steady state and in the transient state. Design and performance details of a prototype 400 Hz, 3000 rev/min., 3-phase machine are also included.
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Examination of the axial flux in stator cores with particular reference to turbogenerators
  • Author(s): D. Howe  and  P. Hammond
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1536 –1542
  • DOI:  10.1049/piee.1974.0318
  • Type: Article
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  • p. 1536 –1542 (7)
    The distribution of axial flux in stator cores has been examined by numerical and experimental techniques. It has been found possible to consider separately the tooth region and the core back. In the tooth region, the axial flux is caused by the airgap fringing flux. In the core back, it is caused by the main core flux and the magnetomotive force of the winding overhang. The effect of slits in the teeth has been studied and also the effect of radial cooling ducts. The effect of butted joints between the core segments has also been considered. It has been found that axial flux is a very local phenomenon which cannot be eliminated, but which can be reduced by careful design of those regions where it is likely to be troublesome.
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Phase-variable primary-system modelling and solution methods in dynamic-response assessments of high-speed protection
  • Author(s): W.D. Humpage ; K.P. Wong ; L.Y.S. Au ; H.E. Zollezi
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1543 –1550
  • DOI:  10.1049/piee.1974.0319
  • Type: Article
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  • p. 1543 –1550 (8)
    Dynamic-response evaluations of high-speed primary-protection systems are assuming an increasing importance as protection measuring times are progressively reduced, and these require very considerable detail of representation, not only for protection systems, but for the primary transducers from which they operate, and for the section of the primary system protected. Within this composite simulation, it is the latter area, that of the primary system for which the protection system under investigation provides coverage, to which the paper is devoted. In particular, the paper develops a phase-variable analysis scheme for synchronous generation in a form that allows it to be used directly in conjunction with electromagnetic transient analysis for the network system interconnecting generation. This provides a rational and unified scheme of analysis which combines fast-solution properties with considerable flexibility in application.
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Probabilistic analysis of power flows
  • Author(s): R.N. Allan ; B. Borkowska ; C.H. Grigg
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1551 –1556
  • DOI:  10.1049/piee.1974.0320
  • Type: Article
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  • p. 1551 –1556 (6)
    The paper describes and examines a technique which permits the power-flow problem in a power system to be analysed probabilistically instead of using normal deterministic methods. All the nodal loads and generation are defined as random variables and the power flow in each line is computed in terms of a probability density function. The expected values and standard deviation of each power flow are also calculated, and, in addition, the overall balance of power in the system is determined in terms of a density function. The purpose of this analysis is to account for the errors and statistical variations known to exist in the operation and planning of systems within one solution. This enables the power-flow problem to be treated objectively and allows quantitative assessment of reliability and security. The paper compares the results obtained probabilistically with those that would be obtained deterministically, and shows the much wider range of information gained in this type of analysis.
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Distance relay performance as affected by capacitor voltage transformers
  • Author(s): M.A. Hughes
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1557 –1566
  • DOI:  10.1049/piee.1974.0321
  • Type: Article
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  • p. 1557 –1566 (10)
    A 3-phase capacitor-voltage-transformer simulation is described which, when used in conjunction with a conventional artificial transmission line, allows complete relaying schemes to be tested. The accuracy of the simulation is confirmed by comparison of its response with that of a full-scale capacitor voltage transformer. Conjunctive distance-relay/capacitor-voltage-transformer tests are reported showing that transient errors degrade relay performance in speed and stability. Various methods for providing a more faithful voltage signal to supply the relay circuits are discussed.
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Direct digital closed-loop control of h.v. d.c. convertors
  • Author(s): J. Arrillaga  and  D.G. Baldwin
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1567 –1571
  • DOI:  10.1049/piee.1974.0322
  • Type: Article
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  • p. 1567 –1571 (5)
    As an alternative to present analogue-based control schemes, the basic design characteristics and dynamic performance of a newly proposed direct digital control are described. Tests are carried out in a specially designed scaled-down model provided with the necessary monitoring facilities for direct digital control. Special emphasis is given to the performance of relatively weak a.c. systems, and therefore the model includes suitable representation of the system parameters and of the filters normally used. It is shown that the implementation of equidistant-firing control by means of digital feedback loops provides fast recoveries from convertor and line disturbances.
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Numerical technique for computing surges in multiphase power systems with nonlinear lumped elements
  • Author(s): S.C. Tripathy  and  M. Yusuf Khan
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1572 –1574
  • DOI:  10.1049/piee.1974.0323
  • Type: Article
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  • p. 1572 –1574 (3)
    A numerical technique for computing switching transients in multiphase nonlinear systems is presented. The nonlinear terminal characteristics of the lumped parameters have been considered in totality without approximating them as piecewise linear characteristics It has been shown that a fast, stable and accurate algorithm results from using Bergeron's method of characteristics for distributed parameter lines and a semi-implicit Runge—Kutta method for solution of the differential equations which describe the dynamics of linear/nonlinear lumped parameters.
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Costs of electricity-supply interruptions to industrial consumers
Digital simulation of distance-relay comparators and their response to primary-system d.c. transients
  • Author(s): D.A. Bradley ; C.B. Gray ; D. O'Kelly
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1577 –1578
  • DOI:  10.1049/piee.1974.0325
  • Type: Article
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  • p. 1577 –1578 (2)
    Digital computer models of a selection of 2-input phaseand amplitude-comparator distance relays, generating mho and offset-mho characteristics in the steady state, are described and evaluated under transient conditions, necessitating interpretation of the criteria of operation in instantaneous terms. The primary system is simply represented by sinusoidal-voltage source and lumped impedances, comparator representation includes consideration of finite sensitivity and the provision of self polarisation. Dynamic performance is presented in the form of contoured distance-to-fault/system-impedance-ratio curves.
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Analysis of circuits containing components with cores of ferromagnetic material
  • Author(s): A. Wright  and  S. Carneiro
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1579 –1581
  • DOI:  10.1049/piee.1974.0326
  • Type: Article
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  • p. 1579 –1581 (3)
    Examinations of ferromagnetic behaviour under conditions likely on power systems show that eddy currents may be allowed for by including an appropriate linear resistor in mathematical models. They also show that hysteresis paths depend on the previous history of a core but are hardly affected by the time derivative of the flux. Current-transformer studies are described to illustrate a computational method in which discrete points on a number of hysteresis paths are specified. An extrapolation technique is used, and consideration is given to points at which flux reversals occur. It is shown that highly-accurate representation may be achieved.
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Variable-characteristic generalised techniques for distance protection: Double-circuit-application studies
  • Author(s): A.T. Johns  and  A.A. El-Alaily
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1582 –1584
  • DOI:  10.1049/piee.1974.0327
  • Type: Article
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  • p. 1582 –1584 (3)
    A previous paper outlined the principles of a new method for dynamically varying the shape of polarised quadrilateral relay characteristics for the protection of e.h.v. transmission lines. The present paper extends these methods to the protection of double-circuit lines. Consideration is given to the compensation of earth-fault relays, and it is shown that compensation schemes which ignore the effect of mutual coupling between circuits are desirable. Digital-computer application studies of a typical double-circuit 400kV transmission line of earthed construction indicate that, from the point of view of accuracy and fault coverage, there is little advantage in the use of variable devices in zone 1. However, they enable a greater proportion of the protected feeder to be covered with minimum fault-detection time. Emphasis is placed on the response of relays connected to healthy conductors, and the possibility of avoiding unwanted tripping emerges. A high degree of immunity to maloperation during heavy-circuit loading and power swings is achieved.
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Application of fuzzy algorithms for control of simple dynamic plant
Gapped solenoid as a means of producing a highly uniform magnetic field over an extended volume
Model of emitting sites and erosion on nonrefractory arc cathodes with relatively thick oxide films
  • Author(s): A.E. Guile
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1594 –1598
  • DOI:  10.1049/piee.1974.0330
  • Type: Article
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  • p. 1594 –1598 (5)
    A model is proposed for the mechanisms by which multiple emitting sites are formed and material is lost from a nonrefractory arc cathode with an oxide layer more than about 10−8 m thick, when an arc is rotated magnetically over its surface for long times. Using measured copper cathode erosion rates and scanning-electron-microscope photographs of the size and number of craters on cathode arcing surfaces, results have been obtained which seem to support the model. Average lifetimes of emitting sites have been estimated to be considerably greater than those on cathodes with very thin oxide films. The model suggests that it is important to keep the oxide layer from becoming too thick, to obtain low cathod erosion rates.
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Time dependence of loss tangent in impregnated polypropylene capacitors
Phonopore and phonoplex F.D.M.telegraph systems used on railways in the late 19th century
  • Author(s): D.G. Tucker
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1603 –1608
  • DOI:  10.1049/piee.1974.0332
  • Type: Article
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  • p. 1603 –1608 (6)
    The phonopore and the phonoplex were both systems introduced in 1885 for providing additional telegraph channels (or, alternatively, in the phonopore system, a telephone channel) in the frequency range above that of the ordinary d.c. or Morse channels. The phonopore, developed by Charles Langdon-Davies in England, used a special kind of coupling transformer/condenser, which is here analysed but shown to have had few useful special properties, and used a ‘harmonic’ telegraph channel, i.e. a keyed oscillatory signal. Edison's phonoplex used, for the highpass channel, signals derived from the transients produced by an induction coil. Both systems were made commercially, and had a certain success on railways. The Phonopore Syndicate (later Company) had an interesting but not successful history, here partially unravelled; from 1893, its managing director was C.E. Spagnoletti, F.R.S., Past-President of the Society of Telegraph Engineers, and newly-retired telegraph superintendent of the Great Western Railway. Although the company had, by 1895, raised around £100 000 of capital, it was in that year effectively purchased by the New Phonopore Telephone Co. for £2000. The new company continued in existence, with an issued capital reaching no more than about £8000, until it was purchased for £175 in 1916 by the Phonopore Construction Co., which finally ceased operations soon after 1920.
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