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1887

Proceedings of the Institution of Electrical Engineers

Volume 118, Issue 10, October 1971

Volumes & issues:

Volume 118, Issue 10

October 1971

Application of incoherent-scatter data to communication
  • Author(s): G.N. Taylor
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1319 –1322
  • DOI:  10.1049/piee.1971.0247
  • Type: Article
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  • p. 1319 –1322 (4)
    The application of a very sensitive radar system to the observation of signals incoherently scattered in the ionosphere is briefly described. This technique can give more detailed information about height and time variations of bottom-side electron-density profiles than any other method, besides measuring several further parameters of the plasma. Electron-density profiles of the day-time lower Eregion, and of the whole of the night-time Eregion, allow much more reliable estimates than hitherto to be made of nondeviative h.f. absorption, and of the reflection heights of m.f. and l.f. waves. The morphology of the ‘valley’ in the profile between the E and Fregions can be investigated; also the ability to measure details of profile changes during ionospheric disturbances should allow the accompanying deterioration in h.f. propagation conditions to be understood. Incoherent-scatter measurements give unique opportunities of making independent calibrations of statellite instruments in orbit, and of measuring plasma movements induced by neutral aid winds. An empirical law relating the temperature and density of the electrons has been discovered; this will help in predicting the changes in density which should occur when additonal heat energy is deposited in the ionosphere during disturbances.
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Use of flayer theory in ionospheric predictions
Theory of cylindrical antennas with arbitrary impedance loading
Analysis of multicomponent wavefields
Factors influencing conversion efficiency in gaseous-plasma harmonic generators working at microwave frequencies
  • Author(s): J.R. Riley
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1339 –1344
  • DOI:  10.1049/piee.1971.0251
  • Type: Article
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  • p. 1339 –1344 (6)
    This paper describes a novel application of the field-gradient theory of plasma microwave harmonic generation, proposed by Krenz and Kino, to the case of a positive column placed through a rectangular waveguide. The distribution of 2nd-harmonic power between the TE01 and TE11 waveguide modes has been examined experimentally and found to be in agreement with qualitative predictions made from the gradient model. An inverse-cubic depence between the 2nd-harmonic-conversion efficiency and electron-collision frequency, predicted by Krens, has also been observed. A metal probe plaved against the column, with the intention of introducing severe microwave-field gradients in the plasma resonace at the fundamental frequency, a best overall conversion of about 25% was produced for an input power of 500mW at 2.42 GHz. At higher power levels, the plasma electron density appropriate for fundamental resonance could not be sustained, and the conversion effiency fell. Experiments using 9.6 and 35GHz fundamental signals gave best conversion efficiencies to the second harmonic of only 2.5 % and about 0.01%, respectively. It is concluded that the gradient model provides a satisfactory description of 2nd-harmonic generation in gaseous plasmas, but that devices based on this model do not operate efficiently at high power levels or at high microwave frequencies.
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Relative-phase measurement at Q band
V.L.F. propagation parameters derived from observations of sunrise and sunset phenomena
  • Author(s): S.F. Mahmoud  and  J.C. Beal
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1351 –1357
  • DOI:  10.1049/piee.1971.0253
  • Type: Article
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  • p. 1351 –1357 (7)
    Received v.l.f. signals during sunrise and sunset times over the propagation path are used to deduce information about the attenuation coefficients and phase velocities of the day and night waveguide modes, as well as the conversion factors between these modes at the day/night transition. Unlike any previous method used to obtain modal propagation constants, the present method does not need a mobile receiver, since it directly makes use of the moving secondary source formed by the mode conversion that takes place at the shadow line, or transition. A two-night-modes/two-day-modes model is discussed in detail. It is seen that it has a wider range of validity, with regard to both the path length and the frequency, than both the two-night-modes/one-day-mode model suggested by Crombie in 1964, and the one-night-mode/two-daymodes model used for the early part of the sunrise period by Kaiser.
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Binary nonconsecutive one code for time-tag data compression
Perception efficiency for radio and television displays
Parametric graphical computer display system using analogue storage
  • Author(s): D.J. Woollons ; H.B. Kendler ; R.L. Grimsdale
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1363 –1372
  • DOI:  10.1049/piee.1971.0256
  • Type: Article
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  • p. 1363 –1372 (10)
    A cathode-ray-tube graphical display system for use as a digital-computer output terminal has been developed The display employs analogue function-generation circuits to produce line drawings composed of straight-line and curved-line segments which are specified by parameters transferred from the computer in analogue form. To maintain a flicker-free image, while also imposing a minimal demand on the computer to which it is connected, the display incorporates an analogue memory composed of capacitors and field-effect-transistor switches. The displayed image may then be refreshed at the required rate by cyclically reading the line and curve control parameters from this memory. The computer need only access the memory to insert fresh data to be displayed or, infrequently, to refresh the stored information. The paper includes discussions of the specification of the overall display system, of the design of the analogue storage system and of two methods used to produce the required picture segments for display. Some results obtained with the display connected online to a small digital computer are shown.
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Computer-controlled queuing systems with feedback
  • Author(s): W.-C. Chan  and  W.-K. Chung
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1373 –1377
  • DOI:  10.1049/piee.1971.0257
  • Type: Article
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  • p. 1373 –1377 (5)
    A generalised approach is presented for the study of a computer-controlled queuing system with general input, ‘first-come-first-served’ queue discipline and multiple servers with feedback for either exponential servers or constant service times. Two generating functions for the state probabilities of the system corresponding to the two different types of service times are derived. Further, necessary and sufficient conditions for the existence of statistical equilibrium of the computer-controlled queuing system are obtained from the generating functions. The results obtained here generalise many results previously obtained by other workers.
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Waiting-time distribution in computer-controlled queuing system
  • Author(s): W.-K. Chung  and  W.-C. Chan
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1378 –1382
  • DOI:  10.1049/piee.1971.0258
  • Type: Article
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  • p. 1378 –1382 (5)
    The paper presents two formulas for the determination of the waiting-time distribution in a computer-controlled queuing system with Poisson input, multiple-exponential servers and first-come-first-served queue discipline. The formulas obtained are expressed in terms of the stationary-state probabilities of the computer-controlled queuing system. One of the formulas is derived by means of the formula of total proability and the other is derived by the use of the theory of Markov chains. It is shown that, by virtue of a limiting process, the first formula obtained in the paper yields the waiting-time distribution in the conventional queuing system without computer control. Furthermore, application of the two formulas for the determination of waiting-time distribution is illustrated by an example.
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Corrigendum: Use and design of 4-wire telephone trunk concentrators
Method of using redundancy in very large computer stores
  • Author(s): J.G. Axford  and  A.R. Fiske
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1383 –1392
  • DOI:  10.1049/piee.1971.0260
  • Type: Article
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  • p. 1383 –1392 (10)
    The organisation of a very large random-access computer store which uses redundancy in the form of error-correcting codes is described. The improvements in manufacturing yield which can be achieved by means of such redundancy are emphasised in the form of examples. However, with typical basic store sizes in the capacity range 107−108 bits, some of the most significant improvements in manufacturing yield are achieved by programmed assembly which makes use of the ease of testability of such redundant systems. The conclusion is that widespread use of the proposed technique of design and manufacture can result in significant savings, both to designer and customer.
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Techniques for the measurement of source and drain series resistance in m.o.s. transistors
Simple estimators for error probability in simulation studies of digital communication systems
Thermal insulation for energy storage
  • Author(s): D.J. Dickson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1399 –1407
  • DOI:  10.1049/piee.1971.0263
  • Type: Article
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  • p. 1399 –1407 (9)
    Efficient thermal-energy storage requires effective thermal insulation. From a consideration of the possible heat-transfer modes, the requirements for a thermal barrier can be deduced. In a good conventional thermal insulation, most of the heat transfer takes place by conduction through the gas (air) in the insulation voids, the conductivity of the ‘still’ gas representing the limiting performance of such a material. It follows that a better performance can be obtained only by reducing this gas-conducted heat by having voids smaller than the molecular mean-free path (‘microporous’), by replacing the air by a low-conductivity gas or by partially evacuating the insulation.
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Space harmonics in unified electrical-machine theory
  • Author(s): J.L. Willems
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1408 –1412
  • DOI:  10.1049/piee.1971.0264
  • Type: Article
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  • p. 1408 –1412 (5)
    The paper deals with the applicability of unified machine theory to electrical machines where space harmonics can not be neglected. It is shown that there exists cases where a linear transformation can de determined to transform the set of time-depended linear differential equations for a machine at constant speed into a set of linear time-invariant differential equations, even if space harmonics are taken into considertation. A criterion for applicability is presented that involves the number of phases, the number of harmonics and the order of the harmonics that have to be considered.
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Performance of d.c. linear machines based on an assessment of flux distributions
  • Author(s): C.W. Green  and  R.J.A. Paul
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1413 –1420
  • DOI:  10.1049/piee.1971.0265
  • Type: Article
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  • p. 1413 –1420 (8)
    An analytical study is described of the magnetic-field system in a d.c. linear motor. The equations derived are solved by numerical techniques based on a finite-difference approximation. A modification of existing methods is adopted to deal with heterogeneous regions of permeability. The computed flux profiles are shown to compare favourably with experimental results obtained on a 2-pole machine, including the effects of armature reaction. The results are used in tahe derivation of the developed force and dynamic characteristics of a loaded machine, and the theoretical results are again shown to agree closely with experimental results.
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Design of microalternator for power-system-stability investigations
  • Author(s): T.J. Hammons  and  A.J. Parsons
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1421 –1441
  • DOI:  10.1049/piee.1971.0266
  • Type: Article
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  • p. 1421 –1441 (21)
    The paper describes the design of a microalternator in which negative-resistance devices are employed to obtain representative constants of the model's rotor circuits. Dimensional scaling in assessing the parameters of model alternators is reviewed. Methods of calculating the model's principal constants from design data are outlined for a machine of salient-pole-rotor construction. Core and short-circuit losses are examined, and the choice of design criteria is discussed. Test results for a machine of salient-pole construction are given which compare very favourably with the constants derived from design considerations. Attention is also given to the special facilities which are provided by the time-constant regulator and other associated auxiliary equipment.
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Comparisons of synchronous-machine models in the study of the transient behaviour of electrical power systems
  • Author(s): T.J. Hammons  and  D.J. Winning
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1442 –1458
  • DOI:  10.1049/piee.1971.0267
  • Type: Article
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  • p. 1442 –1458 (17)
    Methods of modelling power systems in the study of the system transient behaviour are reviewed. Six machine models of varying complexity are developed from the fundamental machine equations. Factors in the form of the machine equations, which critically influence the economy of solution, are identified, The relationship between the machine and system equations is examined in relation to the digital solution of multimachine problems, and generalised methods of solution of the equations are outlined. Comparisons are made between results obtained from the range of machine models and those obtained from full-scale fault-throwing tests on the public supply system. In one case, a single machine connected to a system of high capacity is modelled, while, in the second example, two 60 MW machines connected to a large mulrimachine system is modelled. Both non-pole-slipping and pole-slipping tests for the case of the 2-machine system are examined, in which a machine marginally remained in synchronism and marginally lost synchronism, respectively. It is shown that models in which subtransient phenomena are simulated, but in which some transformer voltages in the stator equations, together with subtrasient saliency, are neglected, provide an adequate and economical model for system disturbances, including those in which the machine may fall from synchronism.
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Synchronous-machine sudden 3-phase short-circuit. Analysis by norton's, constant-flux-linkage and thévenin's theorems
  • Author(s): S.K. Goswami
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1459 –1466
  • DOI:  10.1049/piee.1971.0268
  • Type: Article
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  • p. 1459 –1466 (8)
    The paper presents a new technique of analysis. Equivalent circuits, which normally omit altogether the asymmetrical and 2nd-harmonic armature-current components, are made to give the complete solution including the said components by applying theorems which are well known for their simplifying effect. In the first alternative, Norton's theorem is used to replace the 3-phase armature-voltage source by equivalent current sources on the direct and quadrature axes. The appropriate axis loads presented by the rest of the machine are connected to the current sources. Thus, appropriately energised equivalent circuits are obtained which give the complete solution. In the second alternative, the ‘effective’ 2-axis armature-voltage source, for short-circuit conditions, is determined by the constant-flux-linkage theorem. Then, by Thévenin's theorem, the appropriately energised equivalent circuits are obtained which again give the complete solution.
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Transient stability of power systems containing both synchronous and induction machines
  • Author(s): S.S. Kalsi  and  B. Adkins
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1467 –1474
  • DOI:  10.1049/piee.1971.0269
  • Type: Article
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  • p. 1467 –1474 (8)
    A method is described of calculating the effect of large induction motors on the transient performance of a multimachine power system under fault conditions. The representation of an induction motor is similar to that used for synchronous machines, and is therefore suitable for describing composite systems. The method is based on Park's equations and, unlike earlier methods, allows for the ‘deep-bar effect’ usually present in large cage induction motors. The most accurate result is obtained by using the full set of equations, but more approximate methods using simplified equations are considered. The method is verified by tests on model machines connected by impedances representing transmission lines. Preliminary tests were made on a simple system comprising an induction motor connected to an infinite busbar through an impedance, and were followed by tests on a composite system containing a synchronous machine and an induction motor connected in parallel parts of the system. The results slow that good results are obtained with the accurate calculation which, however, requires a large amount of computer time, but that any approximation introduces considerable error.
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Discussion on “Starting methods for generator/motor units employed in pumped-storage stations” and “Investigation into damping-torque coefficients and stability of a 2-synchronous-machine system employed in synchronous starting”
Design and parameters affecting the surface stress of overhead-power-line conductor systems
  • Author(s): R.N. Allan  and  J.E.J. Cottrill
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1486 –1492
  • DOI:  10.1049/piee.1971.0271
  • Type: Article
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  • p. 1486 –1492 (7)
    To prevent undue radio interference and energy loss from overhead conductors, the permissible operating stress must be minimised. Therefore, the design of such conductors was investigated theoretically using a conformal transformation proposed by Timascheff. First, the effect of the design parameters, that is, the subconductor diameter, subconductor spacing, number of subconductors and phase spacing on the maximum surface stress, was considered. This showed that the surface stress decreases as the subconductor diameter, number of subconductors and phase spacing is increased. It also showed that there is an optimum subconductor spacing at which the surface stress is a minimum. Secondly, an equation defining the optimum subconductor spacing was determined. From this equation, it was found that the optimum spacing is affected by all the other parameters, and that subconductor spacings close to the optimum can be justified economically. Finally, the general design of conductor systems was discussed, and possible conductors for a 765kV system were computed using optimum spacings. This showed that the total conductor material is considerably reduced and that the overall diameter of the bundle remains unchanged with an increasing number of subconductors. A suggested computational method for determining possible conductor systems was also described.
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Design for a superconducting a.c. power cable
  • Author(s): E.C. Rogers ; R.J. Slaughter ; D.A. Swift
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1493 –1500
  • DOI:  10.1049/piee.1971.0272
  • Type: Article
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  • p. 1493 –1500 (8)
    The paper describes a design study for a 750 MVA 33 kV superconducting a.c. power cable. Conductor and dielectric design, thermal insulation and refrigeration and methods of construction and installation are all considered. Niobium is the chosen conductor material, and a triple coaxial construction the chosen conductor geometry. The capital costs of the systems considered are estimated to be rather more than twice that of the equivalent 275kV conventional oil-filled cables. The running costs are about the same as that of the conventional equivalent, but represent only a small proportion of the total cost. Problems which need further study and development work, and whose solution could lead to significant design improvements and cost reductions, are: (a) protection of the conductors against current overload, (b) thermal contraction and (c) dielectric design. It is concluded that, though superconducting cables are unlikely to be economical at the power level considered in the study, they may find application in the multi-GVA region.
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Corrigendum: Influence of conductor designs and operating temperature on the economics of overhead lines
Full-wave rectifier with constant-current load
Design of digital controllers for randomly disturbed systems
  • Author(s): D.W. Clarke  and  R. Hastings-James
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1503 –1506
  • DOI:  10.1049/piee.1971.0275
  • Type: Article
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  • p. 1503 –1506 (4)
    The paper presents a method of designing digital controllers for randomly disturbed single-input/single-output linear systems with time delay which minimise the cost function E{y2t+k+λu2t}. The process and noise models used are those obtained from current identification programs, and the control law developed has significant advantages over standard minimum-variance designs. (a) There is no difficulty with nonminimum-phase systems. (b) For processes with constraints on control effort, a marked improvement in the resultant output variance can be achieved. (c) There is a flexibility in the design to deal with cases where the closed-loop performance becomes unsatisfactory because of parameter drift or other causes. A typical example of the design procedure is given, and a comparison between the new control law and a minimum-variance law is made.
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Determination of the least order of transfer-function matrices
Nonlinear analysis of a 1st-order thyristor-bridge control system. Use of difference equations and transition mapping
  • Author(s): J.O. Flower  and  P.A. Hazell
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1511 –1516
  • DOI:  10.1049/piee.1971.0277
  • Type: Article
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  • p. 1511 –1516 (6)
    By considering the solution of the differential equation governing the current delivered, via a thyristor bridge, to a series R-L load, an exact nonlinear difference equation relating the current at consecutive firing instants is established. The behaviour of the system, both statically and dynamically, is thereby examined and use is made of transition-mapping concepts. Perturbational analysis is performed to linearise the equation and it is demonstrated that the system can be considered as a discrete controller with proportional and derivative control having a varying time constant. Computer simulation and experimental results are presented as evidence of the validity of the developed models.
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Numerical inversion of the Laplace transform using generalised Laguerre polynomials
Characteristics of impulse breakdown of standard rod gaps under controlled-atmosphere conditions
  • Author(s): J.E. Matthews  and  R. Saint-Arnaud
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1524 –1527
  • DOI:  10.1049/piee.1971.0279
  • Type: Article
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  • p. 1524 –1527 (4)
    The effect of humidity, polarity and irradiation on the 1/50μs impulse voltage breakdown and time lag of standard rod gaps has been determined for a range of spacings from 5cm to 30cm and a range of humidities from 1g/m3 to 24g/m3. An anomalous condition is reported for a 5cm unirradiated gap under positive impulses in which the slope of the humidity characteristic is opposite to that normally obtained. It is shown that, although the time lag is independent of humidity, the probability of breakdown in the sigmoid region is not independent of humidity.
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Prebreakdown phenomena in standard rod gaps subjected to impulse voltages
  • Author(s): J.E. Matthews  and  R. Saint-Arnaud
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 10, p. 1528 –1534
  • DOI:  10.1049/piee.1971.0280
  • Type: Article
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  • p. 1528 –1534 (7)
    The prebreakdown phenomena of impulse corona, corona propagation and leader propagation in the standard rod gap in air have been studied for spacings of up to 30 cm. The variations occurring in the measured quantities of corona-current amplitude, time of occurrence, corona-propagation time, corona speed, number and length of steps in the leaders, leader-propagation time and leader speed are correlated to the variations in the conditions of gap length, applied voltage, humidity and irradiation. The results of the prebreakdown phenomena have been shown to explain the characteristics of impulse breakdown of the rod gap.
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