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1887

Proceedings of the Institution of Electrical Engineers

Volume 111, Issue 4, April 1964

Volumes & issues:

Volume 111, Issue 4

April 1964

Theory of loaded scatterers
  • Author(s): Roger F. Harrington
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 617 –623
  • DOI:  10.1049/piee.1964.0111
  • Type: Article
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  • p. 617 –623 (7)
    A general formulation is given for the problem of electromagnetic scattering by an object having N terminal pairs (or ports) to which N loads or an N-port network is connected. The theory is applicable to back scattering and bistatic scattering, reciprocal and nonreciprocal media, near-field and far-field scattering and passive and active loads. The representation is made in terms of both open-circuit impedance parameters and short-circuit admittance parameters. Variational formulas for all parameters are given. Specialisation to the case of planewave scattering is made. Relationships between scattering parameters and commonly defined antenna parameters are given. Several examples of applications of the theory are included.
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Mersey and North Wales Electronics Section: Chairman's address. Research on electric breakdown in liquids
Approximate solution of the H plane right-angled corner in overmoded rectangular waveguide, operating in the H10 mode
Dispersion and impedance of dielectric-supported ring-and-bar slow-wave circuits
Thermoelectric cooling applied to the absolute measurement of microwave power
  • Author(s): Alan G. Heaton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 642 –646
  • DOI:  10.1049/piee.1964.0115
  • Type: Article
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  • p. 642 –646 (5)
    The development of efficient thermoelectric semiconductors such as p and n type bismuth telluride has given rise to a variety of applications of thermoelectric cooling in the field of instrumentation.3,4This paper is concerned with the application of thermoelectric cooling to a load in which the heat produced, by the microwave power absorbed, is balanced by the heat extracted thermoelectrically. By this means the load may be maintained at the temperature of its surroundings, in which case extraneous heat transfer is reduced to zero. A restriction is applied to the temperature drop across the thermoelements used, and it is shown that the cooling power required to balance the microwave power may then be evaluated from the Peltier coefficient and two values of direct current.A simple form of waveguide termination is described to which distributed cooling is applied. It is concluded that the type of waveguide load required, to approach the inherent accuracy of the method, will be closely approached as the wavelength decreases into the millimetre band.
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Time-compression-multiplex transmission
  • Author(s): J.E. Flood  and  D.I. Urquhart-Pullen
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 647 –668
  • DOI:  10.1049/piee.1964.0116
  • Type: Article
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  • p. 647 –668 (22)
    In time-compression multiplex (t.c.m.) transmission, the signals of the channels are scanned and the samples are stored before being transmitted at high speed. In this way, the signals of a large number of channels can be sent over a single transmission path. Methods of time-compression multiplexing that are described include the use of a cathode-ray storage tube, a delay-line store and a gated-capacitor store. The function of the store is to change the order in which the samples of the channels occur in time. In the transmitted waveform, samples are arranged in groups. Each group comprises consecutive samples from a single channel and is separated by a short interval from the next group containing samples of another channel.It is shown that t.c.m. transmission requires less bandwidth than time-division multiplex transmission. As the time of storage is increased, the bandwidth required for t.c.m. decreases towards that for frequency-division multiplexing (f.d.m.). For storage times of the order of 10ms, the bandwidth needed for t.c.m. is little greater than that needed for f.d.m.It is shown that bandwidth limitation introduces attenuation distortion and a form of interference that is called grouping noise. However, this noise can be practically eliminated by transmitting redundant ‘guard’ samples before and after the group of signal samples of each channel. Another source of noise is store-switching noise. This can be eliminated by interweaving the scanning sequences of the stores.The feasibility of t.c.m. transmission was demonstrated by experiments on model systems using gated-capacitor stores. The development of practical t.c.m. systems depends on the availability of suitable stores. It appears that the cathode-ray storage tube may ultimately be the solution, but currently available tubes are inadequate.
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Gated capacitor store for t.c.m. transmission
  • Author(s): J.E. Flood  and  D.I. Urquhart-Pullen
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 669 –674
  • DOI:  10.1049/piee.1964.0117
  • Type: Article
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  • p. 669 –674 (6)
    In time-compression multiplex (t.c.m.) transmission, the signals of the channels are scanned and the samples are stored before being transmitted at high speed. A store that can be used in t.c.m. systems is described in the paper. Each channel sample is stored as charge on a capacitor. These capacitors are connected to common input and output leads through diode gates.A theoretical analysis is made of the operation of the store. It is shown that its frequency response is adversely affected by residual charges left by previous samples. These can be removed by using erase pulses. The theory was confirmed by experiments on a model store with 32 storage elements per channel. The leakage current of the diodes used was found to limit the noise performance of the store.
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Time-assignment speech interpolation in time-compression-multiplex transmission
  • Author(s): J.E. Flood  and  D.I. Urquhart-Pullen
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 675 –683
  • DOI:  10.1049/piee.1964.0118
  • Type: Article
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  • p. 675 –683 (9)
    In time-compression multiplex (t.c.m.) transmission, the signals of the channels are scanned and the samples are stored before being transmitted at high speed. In this way, the signals of a large number of channels can be sent over a single transmission path. The number of telephone channels that can be transmitted can be at least doubled by the process called time-assignment speech interpolation (t.a.s.i.). This exploits the fact that, on average, each channel in a multiplex telephone system is transmitting speech for less than half the time.The addition of t.a.s.i. facilities to a t.c.m. system is relatively simple because the main t.a.s.i. requirement (switching of all speech signals) already exists as an inherent part of any t.c.m. system. Furthermore, the extra information which has to be transmitted (the channel identification information) can be incorporated in the standard t.c.m. signal with very little change in the bandwidth requirements.The simplest t.a.s.i. systems favour the lower-numbered channels, so that, in the event of more channels being active than there are transmission slots available, the same higher-numbered channels are always ‘frozen out’. In order to overcome this difficulty, a queue-control system is necessary. It can be made to balance the overload conditions such that the queuing channels always accept the back of the queue in time rotation. A queue controller for a t.c.m.-t.a.s.i. system consists of a logical array of conventional binary stores, gates and shift registers.
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Discussion on “Time-compression-multiplex transmission”, “Gated capacitor store for t.c.m. transmission” and “Time-assignment speech interpolation in time-compression-multiplex transmission”
Analysis of the relative information rates in digital systems using case coding
Magnetic-tape head for frequency-spectrum determination
Transmission systems for trunk and junction circuits
  • Author(s): R.H. Franklin
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 700 –712
  • DOI:  10.1049/piee.1964.0122
  • Type: Article
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  • p. 700 –712 (13)
    In the telecommunication transmission field the word ‘system’ has been widely used for many years when referring in a collective sense to the equipment forming a communication path, usually of multichannel type. The purpose of the paper is to present a broad survey of the systems commonly used in trunk and junction networks, in particular, those in use and being developed in the United Kingdom. Transmission paths, or links, and terminal translating equipment, together with its associated carrier-generation equipment, are treated in separate sections of the paper for convenience of description.Trunk and junction networks, however, rarely consist of multichannel systems alone. For example, in the United Kingdom, as in most other countries, individual audio circuits form a large part of the network; programme and television channels have also to be accommodated. Information regarding equipment for the provision of these facilities is therefore included in the paper.
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Local networks
  • Author(s): E.W. Anderson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 713 –726
  • DOI:  10.1049/piee.1964.0123
  • Type: Article
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  • p. 713 –726 (14)
    The local network is briefly described and three problems are posed: establishing an acceptable standard of performance, providing local planning engineers with a sound basis for economic calculation, and determining the quantity of plant to be provided. The standard local telephone circuit is described, and methods of assessment of the transmission performance are referred to. This leads to the methods of determination of line planning limits for design purposes in the local network. The basic principles of engineering economic cost comparisons at present used in the Post Office are described. Methods of forecasting growth and of providing a flexible system to meet fluctuations in the demand for telephones are described.A brief section on the more efficient use of the network at audio frequencies is included, and the paper concludes with consideration of the use of the network at carrier frequencies. Various uses, e.g. subscribers' carrier, wired-broadcast services, data collection and alarm concentration, are mentioned. The transmission properties of the existing local network at carrier frequencies are given and conclusions drawn as to the limitations on its use for various methods of working. A final Section deals with the possible future use of the network at carrier frequencies.
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Overall survey of transmission-performance planning
  • Author(s): H. Williams
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 727 –743
  • DOI:  10.1049/piee.1964.0124
  • Type: Article
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  • p. 727 –743 (17)
    Communication-network planning is a complex process involving a number of interrelated factors among which transmission performance is of major importance. In the paper, detailed consideration is given to the various aspects of transmission performance in relation to speech, telegraph, programme and television channels.Under the auspices of the international consultative organisations (CCITT and CCIR) much study has been devoted to the subject of performance planning. The rapidly increasing length and complexity of modern communication channels have intensified this study in recent years. Several of the major recommendations of the CCITT and CCIR are enumerated and discussed in the paper.Transmission-performance assessment, particularly of speech channels, is a fundamental factor in determining transmission performance limits. The paper includes brief information on assessment studies.The provisions of the new United Kingdom national transmission plan and of the proposed new CCITT switching and transmission plan for worldwide telephony circuits are defined and discussed in some detail.
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Technical aspects of the design of communication-satellite systems
  • Author(s): W.J. Bray
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 744 –758
  • DOI:  10.1049/piee.1964.0125
  • Type: Article
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  • p. 744 –758 (15)
    The paper surveys some of the technical problems involved in the design of communication-satellite systems providing substantially worldwide coverage for the transmission of multichannel telephony and television signals.Factors affecting the choice of orbit and type of satellite are discussed, and it is concluded that attitude-stabilised, station-keeping satellites in medium-altitude circular orbits represent a desirable design objective.The operational and performance requirements for multichannel telephony and television are considered in the light of the findings of the international Radio Consultative Committee at its Xth Plenary Assembly (Geneva, 1963).Technical factors, such as the choice of frequency and modulation method, are discussed, with particular reference to the problem of providing multistation access to satellites. The limitations on satellite and terrestrial radio-relay system transmitter power imposed by the need to share the same frequency bands are examined, and the advantages of using preferred radio-frequency channelling arrangements by both systems are discussed.Finally, an outline is given of one possible approach to the design of a worldwide system using twelve station-keeping, attitude-stabilised satellites in a subsynchronous (8h) orbit at 14000km height in the equatorial plane of the Earth.
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ZY table for analysing a ladder network
Fresnel gain of aperture aerials
Survey of aerials and aerial distribution techniques in the h.f. fixed service
Root-locus study of synchronous-machine regulation
  • Author(s): C.A. Stapleton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 761 –768
  • DOI:  10.1049/piee.1964.0129
  • Type: Article
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  • p. 761 –768 (8)
    The general equations of a synchronous machine, with continuous regulation and connected by tieline to a large system, are reduced by small-departure methods to linear relationships from which is derived the characteristic equation for a particular situation.An examination of the coefficients of this equation over a range of operating levels shows that the results obtained for one operating point would be valid over a considerable range.Stability and dynamic response depend on the roots of the equation, and root-locus diagrams are introduced to demonstrate their value in displaying variations in performance of several parameters of the regulator circuit, such as gain, exciter time constant and the constants of certain derivative circuits used for stabilising.
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Inductance coefficients of rotating machines expressed in terms of winding space harmonic
  • Author(s): R.B. Robinson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 769 –774
  • DOI:  10.1049/piee.1964.0130
  • Type: Article
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  • p. 769 –774 (6)
    The paper develops expressions for the self- and mutual-inductance coefficients of machine windings for the general case of nonsinusoidal winding distributions and nonuniform air gap. These expressions involve the harmonics of the winding distribution and the air-gap permeability. For some sample cases, numerical values are given and the departures from the ideal sinusoidal case assessed.The coefficients evaluated in the paper are those which form the starting point of the generalised mathematical theory of machines. The results are of significance in showing how, and to what extent, departures from the ideal machine modify the coefficients and introduce new terms not amenable to the usual mathematical treatment.
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Solution of transient-stability problems through the number-series approach
  • Author(s): N. Dharma Rao  and  H.N. Ramachandra Rao
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 775 –788
  • DOI:  10.1049/piee.1964.0131
  • Type: Article
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  • p. 775 –788 (14)
    The paper presents a numerical method for the solution of transient-stability problems utilising the number-series approach. Significant generator characteristics which are normally neglected, such as transient saliency, field decrement and damping, are included in the transient-stability study. The swing equation is arranged in a block-schematic form separating the linear and nonlinear parts. Data for the swing curve are obtained from convolution of the impulse response of the linear block with its input; the convolution integral is evaluated by standard numerical methods such as the trapezoidal and Simpson's rules.Rational bases are presented for the selection of a suitable time increment for a specified accuracy. The results obtained by the number-series method are compared with those of the fourth-order Runge-Kutta method. Finally, general hints and suggestions are given for programming the number-series method on a digital computer.
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Voltage effects of capacitive load on the synchronous generator
  • Author(s): J.L. Dineley  and  K.J. Glover
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 789 –795
  • DOI:  10.1049/piee.1964.0132
  • Type: Article
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  • p. 789 –795 (7)
    The paper defines the problem of calculating the transient terminal-voltage rise due to self-excitation of a synchronous generator when a capacitive load is switched, and a typical case neglecting magnetic saturation is computed, first by an analytical method and then by use of analogue computer. The advantage of computational aid is indicated.Established indirect analytical methods of including the effects of magnetic saturation are described. The analogue-computer method is then extended to evaluate the problem of the effects of magnetic saturation on the terminal-voltage transient, produced by self-excitation, by a direct method.
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South Midland Centre: Chairman's address. Problems of the supply engineer in the 20th Century
Electrical services at Shell Centre
  • Author(s): D.E. Bird  and  A.E. Gaster
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 799 –809
  • DOI:  10.1049/piee.1964.0134
  • Type: Article
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  • p. 799 –809 (11)
    The paper deals with the electrical installation of the Shell Centre, the central office of the Royal Dutch/Shell group of companies in London and the largest fully air-conditioned building in Europe. A brief description of the buildings is given, followed by an account of the progress of the design from the provision of electrical supplies and a description of the high-voltage and low-voltage distribution.Electrical supplies from two separate sources enable half the lighting to be connected to each supply and all power plants to be switched to either supply. Most floors above ground level are laid out on the same general lines as standard office floors and divided into offices by demountable partitions. Switching of the lights can be adjusted, according to the partition layout, without any modification to the permanent wiring, and this system is described together with an extensive and intensive underfloor duct system with permanently wired floor socket outlets.The paper deals also with the electrical supplies to lifts and escalators, air-conditioning-plant rooms and special departments. Information is given on the clock system, various sound systems, alarms and security control and amenity and recreation areas such as restaurants, kitchens, underground garages, swimming pool and cinema/theatre etc. A brief description is given of the heating and air-conditioning plant, owing to the considerable quantity of electrical services employed.
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Discussion on “The 400 kV grid system for England and Wales”
Some factors affecting the accuracy of distance-type protective equipment under earth-fault conditions
Developments in the design of large power transformers
  • Author(s): H.W. Kerr  and  S. Palmer
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 823 –832
  • DOI:  10.1049/piee.1964.0137
  • Type: Article
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  • p. 823 –832 (10)
    Demands for greatly increased power transformer ratings within transport limits which change only slowly have compelled transformer designers to devise new forms of construction which make the best possible use of materials.The paper illustrates this by giving an account of some design problems and some particular solutions. Details are given of a boltless core construction and its effect on noise level. The influence on transformer size and losses of the use of transposed-strip conductor is discussed, and an account is given of a method of calculating disc-winding temperature rise with a digital computer. Stray load losses in the transformer structure can be of considerable magnitude, and methods of reducing them are considered. Some test results are given for core-clamp losses, and a simple method of predicting the effect of magnetic tank shields is described.Finally, a brief account is included of a construction which allows large power transformers to be dismantled for transport and reassembled in such a way that abnormal site testing and processing are avoided.It is concluded that by all such means transformer designers will be able to meet demands for still greater transformer ratings.
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Railway electrification in India
  • Author(s): H.D. Awasty
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 833 –848
  • DOI:  10.1049/piee.1964.0138
  • Type: Article
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  • p. 833 –848 (16)
    The paper refers briefly to the d.c. electrification and to some operating statistics on the Indian Railways and gives a few details of the electrification schemes undertaken in the Second and Third Five-Year Plans, using a 25 kV single-phase industrial-frequency system. Power supply arrangements, traction overhead equipment, ancillary civil, signalling and telecommunication engineering work and a.c. rolling stock are described. It outlines the technical improvements made in fixed installations and rolling stock in the light of experience gained so far, the organisation set up for the execution of electrification projects and the efforts made to develop the manufacture of rolling stock and other equipment in India.
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Novel principle of transient high-voltage generation
The fifty-fourth Kelvin Lecture. High-energy accelerators for nuclear-physics research
Analysis of halfwave magnetic servoamplifier with biased-rectifier control
  • Author(s): B.K. Bose
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 111, Issue 4, p. 869 –876
  • DOI:  10.1049/piee.1964.0141
  • Type: Article
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  • p. 869 –876 (8)
    Halfwave bridge-type magnetic servoamplifiers, which have been widely used for instrumentation and control problems, have been improved by adding biased rectifiers in the control circuit. It has been shown that such amplifiers give higher gain than the conventional type of halfwave amplifier and maintain the large input impedance required by the synchrocontrol transformer output.The paper gives a systematic mathematical analysis of d.c. and fundamental-frequency gain of halfwave magnetic servoamplifiers with biased-rectifier control, considering resistive and capacitive loads. Graphical illustrations have been added to mathematical analysis wherever necessary. The result of the analysis shows good correspondence with experimental values.
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