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Volume 118
Issue 8
Proceedings of the Institution of Electrical Engineers
Volume 118, Issue 8, August 1971
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Volume 118, Issue 8
August 1971
Electronicexchange design and flexibility of operation
 Author(s): T.H. Flowers
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 955 –962
 DOI: 10.1049/piee.1971.0193
 Type: Article
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Storedprogramcontrolled exchanges which, because of their flexibility, are generally preferred for new systems, have economic difficulties of application in practice. In a general review of the problems involved, the design of electronic exchanges is analysed, and the flexibility of the various kinds of control is assessed. It is shown that flexibility of call establishment is flexibility not of processing but of information storage, which is realisable in all systems. In respect of changes of supervision during the lifetime of an exchange, storedprogramcontrolled systems have an advantage over other systems which has to be assessed as cost saving during the lifetime of the exchange against cost at the initial installation. On this basis, it seems that the amount by which the capital cost of storedprogramcontrolled exchanges could exceed that of others is small. A system of exchanges designed for wiredlogic control and for information storage which is controllable from a distance, and in which, depending on the application, wired logic is replaced by stored program to an extent determined by economy, may be the best way of relising in one system the advantages of both forms of control. A system on this basis is described in companion papers.
Electronic exchange system. Part 1: Structure
 Author(s): T.H. Flowers
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 963 –971
 DOI: 10.1049/piee.1971.0194
 Type: Article
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Continuing from another paper, the equipment for the structure of an electronic telephone exchange is described together with the reasons for the choices made. Analogue circuits are switched by p.a.m./t.d.m. (pulseamplitudemodulation/timedivisionmultiplex) switches and p.c.m. (pulsecodemodulation) circuits by t.d.m. switches of the same kind. The use of t.d.m. switches profoundly influences the choice of processors for supervisory, signalling and other lowlevel functions, which, in turn, have some effect on the highlevel common and unique common processors which are the subject of Pt. 2 of the paper.
Electronic exchange system. Part 2: Control
 Author(s): T.H. Flowers
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 972 –979
 DOI: 10.1049/piee.1971.0195
 Type: Article
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The structure and lowlevel control equipment of an electronic telephoneexchange system are described in Pt. 1 of the paper. Pt. 2 expands the control to the higher levels of register and unique common control and describes the operation of the whole system. The main problem and objective of the control system is to be economical for all sizes of exchange, for which purpose its cost must be approximately proportional to the size of exchange with only a small constant cost independent of size. To this end, advantage is taken of the low cost, concomitant with the use of t.d.m. (timedivision multiplex) switches, of guidewire path selection and distributed processors to reduce the cost of the unique common processor, the cost of which is minimised by a combination of wired and storedprogram logic, the storedprogramlogic part being remotely located and shared with other exchanges if an exchange is too small to support it alone.
Characteristic impedance of TEM lines by variational methods
 Author(s): K. Foster and R. Anderson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 980 –982
 DOI: 10.1049/piee.1971.0196
 Type: Article
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A variational principle based on duality is developed which is related to the complementary variational principle recently established. As a result, classes of solutions other than those normally obtained can be found for the characteristic impedance of TEM lines. In principle, two separate upper and two separate lower bounds can be determined. A simple example, for which the exact solution is known, is used to illustrate the methods.
Effective starting process for NewtonRaphson load flows
 Author(s): B. Stott
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 983 –987
 DOI: 10.1049/piee.1971.0197
 Type: Article
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The results of a noniterative simplified load flow are used as starting values for the NewtonRaphson algorithm. This scheme improves the reliability of the NewtonRaphson method, to the extent that convergence for any physically feasible problem is envisaged, and gives highaccuracy solutions in two or three iterations. The starting process has a number of other valuable uses and may be employed on its own to give fast approximate a.c. load flows.
Phasortrajectory representation of nearresonance transients in quasilinear a.c. circuits
 Author(s): A. Semlyen
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 988 –992
 DOI: 10.1049/piee.1971.0198
 Type: Article
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Some transients in linear a.c. circuits can be advantageously described by a slowly varying phasor. This is true also for a quasilinear RLC network, linearised at the point of nearresonance operation, for a smallperturbation stability analysis. The linearisation of a nonanalytical complex function indicates a tensorial relationship between the variables, but this is not uncommon in other well known electriccircuit applications such as synchronous machines and current transformers. The stability analysis is performed by calculating, step by step, the trajectory of a small initial perturbance phasor. It is illustrated by the example of a series RLC circuit and a capacitive voltage divider with a quasilinear inductive load.
Method of digital computation of thyristor switching circuits
 Author(s): J.S.C. Htsui and W. Shepherd
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 993 –998
 DOI: 10.1049/piee.1971.0199
 Type: Article
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A general form of computation logic is established for singlephase and 3phase circuits containing one or more thyristors. Two examples studied in detail are the singlephase RLC circuit with one thyristor and the 3phase, fullwave, 6thyristor bridge circuit with an RLC load. Good agreement was found between computed and experimental results.
Development of overhead equipment for British Railways 50Hz a.c. electrification since 1960
 Author(s): A.G. Goldring and A.D. Suddards
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 999 –1011
 DOI: 10.1049/piee.1971.0200
 Type: Article
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An account is given of the development of overhead equipment for use on British Railways electrification schemes during the period 1960–1970. These developments have led to equipment having improved dynamic performance and lower cost. Concurrently, the efficiency of installation has been increased. Economies have followed the disappearance of steam locomotives, allowing the use of less expensive materials for metal fittings and insulators. Other improvements have arisen from steady development and the application of new techniques. Dynamic performance has been improved by the use of sagged simplecatenary equipment, damping of the pantographs and optimisation of span profiles, dropper spacings etc. Cadmiumcopper conductors have in nearly all cases, been replaced by harddrawn copper or by steelreinforced aluminium. Supporting structures have been simplified, and sometimes replaced by headspans, and tensioning and anchoring arrangements have been improved. Resinbonded glassfibre arms combining the functions of spring support and insulator have been used to improve tunnel equipment, and many other improved insulators using glass fibre and other materials have been developed. By careful attention to detail, the multiplicity of individual components has been reduced to a much smaller number of interchangeable components. Bonding techniques have been improved, and bonding has been simplified. Economics have been achieved by detailed planning and coordination of constuction and operating activities.
Discussion on “Commutation phenomena in electrical machines. Part 3: Experiments using the commutator of a production machine”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, page: 1012 –1012
 DOI: 10.1049/piee.1971.0201
 Type: Article
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Optimal operation of gassupply system
 Author(s): K.L. Lo and A. Brameller
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1013 –1021
 DOI: 10.1049/piee.1971.0202
 Type: Article
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This paper illustrates by example how a method of optimisation used in the electricalengineering field is extended and applied to that of gas engineering. This approach of optimising a general gas system is formlated as a general nonlinear programming problem. All the system parameters are expressed in mathematical representation. The usage of natural gas is also included. An iterative approach based on the Lagrangianmultipliers method with penalty functions for the inequality constraints is presented as the method of solution. A small sample system which consists of the essential parameters of a gas system is solved. A compact storage scheme is employed which makes the method commercially attractive.
Discussion on “Suppression of noise in airblast circuit breakers”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1022 –1024
 DOI: 10.1049/piee.1971.0203
 Type: Article
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p.
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Effects of finite length in solidrotor induction machines
 Author(s): H. Yee
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1025 –1033
 DOI: 10.1049/piee.1971.0204
 Type: Article
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p.
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The author presents an analytical solution of Maxwell's equations for the fields in a finitelength, solidrotor induction motor in which the rotor is not fitted with conducting endrings. It has been assumed as a boundary condition that zero flux enters the ends of the rotor; this is borne out by tests on a typical machine. The solutions for the field distributions are approximate only, but the approximations are good over a wide range of slip. A major advantage of the solutions is that they are expressed in closed, rather than series, form. It is shown that the field distributions and the equivalentcircuit impedances may be considerably different from those obtained by ignoring finitelength effects. Some simple criteria are derived to assess the importance of finitelength effects on machine impedances. The analysis is carried out ignoring rotor saturation and slotting.
Method of measuring sequence voltages on solidly earthed systems
 Author(s): T.R. Mukunda
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1033 –1034
 DOI: 10.1049/piee.1971.0205
 Type: Article
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p.
1033
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Zubov's method and transientstability problems of power systems
 Author(s): A.K. De Sarkar and N. Dharma Rao
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1035 –1040
 DOI: 10.1049/piee.1971.0206
 Type: Article
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In this paper, Zubov's method of construction of Lyapunov functions is applied to the transientstability problem of a synchronous machine swinging against an infinite busbar. In the machine model, the transient saliency and the variablefield flux linkage are taken into account, but changes in primemover input have been neglected. Crosssections of the stability surface for various principal planes are shown and compared with the actual stability surfaces as obtained by numerical integration. It is shown that the application of Zubov's method results in considerable improvement of stabilityboundary estimates over those given by the ‘quadraticplusanintegralofthenonlinearity’ type of Lyapunov functions which have previously been used for transient stability studies. Zubov's method generally requires machine computations. A section of the paper is, therefore, devoted to providing guidelines for digitalcomputer implementation of this method.
Online parameter estimation using matrix pseudoinverse
 Author(s): N.K. Sinha and W. Pille
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1041 –1046
 DOI: 10.1049/piee.1971.0207
 Type: Article
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A method based on the matrix pseudoinverse is presented for the online identification of discretetime systems of known order. Recursive algorithms are described which provide minimumnorm estimates of the parameter vector when insufficient data are available, and leastsquares estimates with adequate data. These estimates can be updated easily with each pair of additional inputoutput data, as matrix inversion is not required. When the order of the system is not known, it may be determined offline using one of the two methods described. A recursive algorithm for calculating the residual error is also derived. A number of examples are given to illustrate the usefulness of the methods.
Phenomenon of isolated jump resonance and its applications
 Author(s): S.S. Lamba and R.J. Kavanagh
 Source: Proceedings of the Institution of Electrical Engineers, Volume 118, Issue 8, p. 1047 –1050
 DOI: 10.1049/piee.1971.0208
 Type: Article
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Under certain conditions of periodic excitation where both the input amplitude as well as the input frequency are varying, nonlinear multimodal systems can be forced exhibit a response in which jumps down occur for both an increase as well as a decrease in input frequency from a median value. This interesting phenomenon is termed ‘isolated jump resonance’. Systems of this type exhibit considerable sensitivity to changes in input frequency or amplitude at the occurrence of the jumps. Application of such systems as sensitivie detectors of frequency deviations in a periodic signal are proposed. A discussion of design considerations is given and a description is included of a system which has been constructed.
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