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Volume 120
Issue 5
Proceedings of the Institution of Electrical Engineers
Volume 120, Issue 5, May 1973
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Volume 126 (1979)

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Volume 120 (1973)

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Volume 120, Issue 5
May 1973
Spectralenergy dispersal in digital communicationsatellite systems
 Author(s): A.K. Jefferis
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 529 –532
 DOI: 10.1049/piee.1973.0111
 Type: Article
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p.
529
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Communicationsatellite systems employing analogue or digital modulation techniques generally require some means of artificially dispersing their spectra to reduce interference to other services sharing the same frequency bands. In digital systems, the dispersal can be obtained by the modulo2 addition of a pseudorandom sequence to the information signal. Expressions have been derived for the maximum spectral power in the signals of timedivision multipleaccess systems employing p.s.k. modulation and using this means of dispersal. The spectral density due to the preambles in such signals is also determined. An example of the practical application of the expressions is given.
Waiting time in commoncontrol queuing system
 Author(s): W.C. Chan ; W.K. Chung ; S.T. Nichols
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 533 –538
 DOI: 10.1049/piee.1973.0112
 Type: Article
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p.
533
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The paper presents a detailed study of a general combined delay and loss commoncontrol queuing system with a Poisson input, firstcomefirstserved queue discipline and negative exponential distribution for the operating times of the common control and the service times of the servers. In terms of the system state probabilities, a new approach is developed for the investigation of the waitingtime distribution in the system. This approach makes use of the stochastictransition signalflowgraph representation. Formulas for calculating the loss probability and waiting probability are also given.
Studies on waveguidefed slot antenna
 Author(s): S.M. Prasad ; B.N. Das ; S.M. Prasad
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 539 –540
 DOI: 10.1049/piee.1973.0113
 Type: Article
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p.
539
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The paper presents investigations of the effect of stored energy inside a waveguide, near a displaced narrow longitudinal slot, on the immittance properties of the radiating slot. It is shown that internal stored energy accounts for the discrepancy between the theoretical and experimental results of the immittance characteristics observed in earlier studies. The effect of stored energy is to contribute an additional reactive term in the expression for the immittance of the slot. By the addition of this extra reactive term to the theoretical expression for the immittance, it has been possible to predict the point of resonance with better accuracy. Further, an expression is derived for the immittance presented by a slot to the transmissionline representation of the waveguide, as a function of slot length, displacement etc. by the application of the principle of duality to the dipole antenna.
Concept of phase centre of an array applied to elevationangle measurements
 Author(s): P.J.D. Gething
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 541 –543
 DOI: 10.1049/piee.1973.0114
 Type: Article
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p.
541
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A linear receiving array can be regarded as possessing a phase centre the position of which varies with the direction of arrival of the signal. This concept has proved useful in a study of the effects of imperfect ground reflection on elevationangle measurements made with the wavefrontanalysis technique. A distinction is drawn between groundinterference minima and freespace nulls.
Thin monopole antenna: finitesize beltgenerator representation of coaxialline excitation
 Author(s): B.D. Popović and B.D. Popović
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 544 –550
 DOI: 10.1049/piee.1973.0115
 Type: Article
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p.
544
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The real system of a vertical monopole, obtained as a simple protrusion of the inner conductor of a coaxial line through the ground plane, is approximated by a monopole base driven by a finitesize belt generator. A simple formula is derived for determining the size of the belt generator so that it is equivalent to the coaxialline excitation. The integral equation for current obtained with the finitesize belt generator is similar to the well known equation for the deltafunction generator. However, the new equation has an integrable solution, convergent at all points. In particular, the monopole admittance obtained from the modified integral equation closely approaches, in the limit, the apparent admittance of the monopole, as measured by reflection measurements on the coaxial line and referred to the ground plane.
Sequentialcircuit characterisation and synthesis using a ‘transitionequation’ approach
 Author(s): D.A. Pucknell
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 551 –556
 DOI: 10.1049/piee.1973.0116
 Type: Article
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p.
551
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The characteristics of combinational and sequential circuits or networks can be expressed in ‘transitionequation’ form. Transition characteristic equations carry complete information on the behaviour of the circuit, and are readily derived for any circuit or from any reasonable circuit data sheet. Synchronous, clock and asynchronous inputs can be shown, and also the nature of the clock activation, where appropriate. Propagation delays may also be manipulated with the characteristic expressions. Network characteristics can also be expressed in terms of desired transitions from one state to another, and this leads to straightforward synthesis procedures when circuit characteristics are in transitionequation form. Analysis is equally straightforward. The paper briefly introduces transition characteristic equations by way of JK flipflops and NAND gates, and then uses a simple example to illustrate the approach to synthesis. It is clearly shown that the transition equations allow for several different approaches to be taken to the same problem. Hazards due to propagation delays are also revealed, which is particularly helpful, for example, when dealing with ‘ripplethrough’ arrays.
New activeRCnetwork realisation for nthorder transfer functions. Signalflowgraph approach
 Author(s): C. Acar
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 557 –559
 DOI: 10.1049/piee.1973.0117
 Type: Article
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p.
557
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A general synthesis method is given for the realisation of nthorder transfer functions by active RC networks containing n unitygain amplifiers, one differentialinput operational amplifier and a minimum number of capacitors.
Erratum: Computer technique for solving 3dimensional electronoptics and capacitance problems
 Author(s): A.B. Birtles ; B.J. Mayo ; A.W. Bennett
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, page: 559 –559
 DOI: 10.1049/piee.1973.0118
 Type: Article
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p.
559
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Erratum: New definitions for loudness ratings
 Author(s): D.L. Richards
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, page: 559 –559
 DOI: 10.1049/piee.1973.0119
 Type: Article
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p.
559
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Erratum: Precision hardware circulararc generation for computer graphicdisplay systems using linesegment data
 Author(s): D.L. Richards
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, page: 559 –559
 DOI: 10.1049/piee.1973.0120
 Type: Article
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p.
559
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Overheadline parameters for circuitbreaker application
 Author(s): E. Bolton ; D. Birtwhistle ; P. Bownes ; M.G. Dwek ; G.W. Routledge
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 561 –573
 DOI: 10.1049/piee.1973.0121
 Type: Article
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p.
561
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The paper presents the results of a comprehensive series of measurements and calculations by a collaborative committee aimed at determining values of overheadline parameters (particularly for lines 1–8 km long), significant in circuitbreaker application. Line models used in the calculations are discussed, as are refinements made to the models as the work progressed to give a final accuracy of calculation within ±5%. Measurement techniques are described, and the results of surge impedance and 50 Hz inductance and resistance measurements presented. Typical values calculated for the CEGB standard 275 kV and 400 kV lines are given, together with the effect of varying parameters such as frequency, line height and earth resistivity. A particular study was made of the effect of high towerfooting resistance, which was found to increase the 50 Hz inductance per unit length for the shorter line lengths. High footing resistance of the sendingend tower also increases surge impedance, but this is of no importance in practice. From a circuitbreaker viewpoint, the effect of subconductors touching due to attraction under short circuit is shown to be significant, since it increases the rate of rise of transient recovery voltage.
Optimisation of economic dispatch through quadratic and linear programming
 Author(s): N. Nabona and L.L. Freris
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 574 –580
 DOI: 10.1049/piee.1973.0122
 Type: Article
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p.
574
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Mathematical programming offers attractive advantages as an optimising technique. Unfortunately, the optimisation of economic dispatch in power systems is a nonlinear problem, and so it is, in principle, beyond the reach of mathematical programming. In the paper, this difficulty is resolved by the derivation of linear constraints through the system sensitivity relations and by the use of a 2ndorder approximation to the powergenerationcost function. Quadratic programming is employed to solve the problem, and, with only one application of the algorithm, the results are comparable to those obtained from gradient techniques. The use of quadratic programming and the change of type of control variables during optimisation obviate the need for penalty functions. The computing times taken by the algorithm when it is applied to test systems are encouragingly short. Security constraints can be easily incorporated, and, if required, the minimumreactivepower problem can be solved. A solution of the minimumloss problem with linear programming is also illustrated.
Discussion on “Remote measurement of phase angle”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 581 –582
 DOI: 10.1049/piee.1973.0123
 Type: Article
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p.
581
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Discussion on “Some aspects of effects of longitudinal and normal stress on power loss and flux distribution within a transformer core”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 583 –584
 DOI: 10.1049/piee.1973.0124
 Type: Article
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p.
583
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Design of lowvoltage distribution networks. Interactive computer method based on the calculus of variations
 Author(s): M.J. Carson and G. Cornfield
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 585 –592
 DOI: 10.1049/piee.1973.0125
 Type: Article
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p.
585
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(8)
UK electricity boards spend a significant proportion of their capital expenditure on lowvoltage distribution systems. Because of the relatively low equipment cost, this leads to a large volume of design work. At present, most of this work is done by hand. The paper describes a method that has been developed to assist engineers in the design of these networks. The method is based on an interactive use of a computer program that derives network configurations, automatically, from single loadflow computations. The kernel of the method is a routefinding algorithm whose theoretical basis is derived from the calculus of variations. The application of the method to the design of networks supplying housing estates, including the problem of evaluating alternative sites for single or multisubstations feeding these networks, is described. Results are presented for practical design studies based on a 500house estate.
Reduction of cablejoint temperatures by oscillation of oil in the conductor duct a theoretical study
 Author(s): D.J. Horrocks ; M.J. Thelwell ; B.M. Weedy
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 593 –594
 DOI: 10.1049/piee.1973.0126
 Type: Article
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p.
593
–594
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The effect of oil oscillation in the conductor duct on the temperature distribution in a lowpressure oilfilled cableandjoint system has been studied by means of a thermal analogue of the system and a digital computer. It is seen that, for a 400 kV cable and joint with integral or sheath cooling, a 50% reduction in the conductortemperature differential between the joint centre and the remote cable is achieved with oil flows of the order of 10^{−5} m^{3}/s and an oscillation period of 20 min.
Lightningsurge distribution in h.v. d.c. convertors
 Author(s): J. Arrillaga and S. ElBatal
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 595 –600
 DOI: 10.1049/piee.1973.0127
 Type: Article
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p.
595
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A complete model of a typical h.v.d.c. converter station suitable for fast transient studies is used to investigate the lightningsurge distribution within the convertor plant. The model is also used to assess the effect of the surge capacitor on the incident wave and the influence of the d.c.reactor size and the lightningsurge characteristics on the surge transfer to the convertor side.
Erratum: Control by digital computer of multiterminal h.v. d.c. system under fault conditions
 Author(s): A.K. David and B.J. Cory
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, page: 600 –600
 DOI: 10.1049/piee.1973.0128
 Type: Article
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p.
600
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Discussion on “Behaviour of h.v. d.c. links under unbalanceda.c.fault conditions” and “Control by digital computer of multiterminal h.v. d.c. system under fault conditions”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 601 –603
 DOI: 10.1049/piee.1973.0129
 Type: Article
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p.
601
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(3)
Discussion on “Supply to arc furnaces: measurement and prediction of supplyvoltage fluctuation”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 603 –607
 DOI: 10.1049/piee.1973.0130
 Type: Article
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p.
603
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Efficient multiple solutions for changes in a network using sparsity techniques
 Author(s): A. Brameller
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 607 –608
 DOI: 10.1049/piee.1973.0131
 Type: Article
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p.
607
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Electricfield distribution around an isolated stranded conductor
 Author(s): P.A. Laura
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, page: 608 –608
 DOI: 10.1049/piee.1973.0132
 Type: Article
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p.
608
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Reducedgradient method for economic dispatch
 Author(s): R.N. Dhar and P.K. Mukherjee
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 608 –610
 DOI: 10.1049/piee.1973.0133
 Type: Article
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p.
608
–610
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Polish developments in inductance coils for lightning protection of power stations and substations
 Author(s): S. Szpor
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 610 –612
 DOI: 10.1049/piee.1973.0134
 Type: Article
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p.
610
–612
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Effects of flexibility on a momentumstabilised communicationsatellite attitudecontrol system
 Author(s): J.M. Gething ; J.A. Holt ; D. Smart ; K.F. Gill
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 5, p. 613 –619
 DOI: 10.1049/piee.1973.0135
 Type: Article
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p.
613
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Transfer functions are derived for the coupled rollyawaxes control system of a momentumstabilised satellite. Firstmode approximation to the flexural response of movable solar paddles is included in the dynamic equations. The performance of the control system for varying degrees of flexibility is studied using rootlocus techniques. The presence of a single flexural mode in the system transfer functions causes an additional polezero pair to appear on, or just to the left of, the imaginary axis in the rootlocus diagrams. Instability, recognised by rootloci crossing into the right half s plane does not occur. However, flexible modes could be excited by disturbing forces, and, depending on the amplitude of the ensuing motions, would seriously degrade the attitude performance of the satellite.
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