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Volume 125
Issue 10
Proceedings of the Institution of Electrical Engineers
Volume 125, Issue 10, October 1978
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Volume 126 (1979)

Volume 125 (1978)

Volume 124 (1977)

Volume 123 (1976)

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Volume 121 (1974)

Volume 120 (1973)

Volume 119 (1972)

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Volume 125, Issue 10
October 1978
Radar target imaging by rotation about two axes
 Author(s): R. Voles
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 919 –921
 DOI: 10.1049/piee.1978.0218
 Type: Article
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Analysis of the output of a coherent radar observing a model target rotated about two axes yields a 2dimensional image of the target in the crossrange plane. A simple visualisation of the process is presented, and the basic relationships governing the performance are derived. It is shown that a variety of nonimaging functions may also be provided for use in special situations.
Digitalfiltering facility for computer processing
 Author(s): H.J. Wells
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 922 –924
 DOI: 10.1049/piee.1978.0219
 Type: Article
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A set of Fortran subroutines is described that enables Butterworth, Chebychev or elliptic filters having a lowpass, highpass or bandpass response to be designed and implemented in a form ready to filter a data sequence with only three lines of userwritten program. The software is modular in that separate routines are used for the functions of transferfunction computation, network synthesis and filter simulation. This approach leads to several advantages, which include the ability to implement multiple filters simultaneously. The existence of gerneralised algorithms for network synthesis and simulationenables this filtering facility to be used without knowledge of digitalfilter theory.
Theory of the circulardisc printedcircuit antenna
 Author(s): S.A. Long ; L.C. Shen ; P.B. Morel
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 925 –928
 DOI: 10.1049/piee.1978.0220
 Type: Article
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A planar conducting structure, an electrically small distance above a ground plane, can be constructed to radiate in the direction normal to its plane while still retaining its lowprofile characteristics. A circular disc structure is analysed theoretically to provide aid in the design of such antennas. The currents, fields, total radiated power, directive gain, losses, Qfactor and efficiency are all calculated at several frequencies for various values of the thickness, permittivity, and loss tangent of the dielectric material that separates the antenna from the ground plane.
Modes of propagation in cylindrical waveguides with anisotropic walls
 Author(s): B.MacA. Thomas and H.C. Minnett
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 929 –932
 DOI: 10.1049/piee.1978.0221
 Type: Article
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The modes of propagation in cylindrical waveguides with idealised anisotropic walls are investigated. The walls are assumed to be lossless and to be specified by longitudinal and circumferential surface reactances. It is shown that for every surface there is a second surface which supports modes with identical propagation characteristics and that these modes are duals of the first set with the E and H fields interchanged. In general, the propagating modes are either fast HE_{m} hybrids or EH_{m} hybrids; the latter may be fast, but are sometimes slow, surface waves. For some surfaces modified TM_{m}and TE_{m}modes are sufficient to satisfy the boundary conditions; when m = 0 these modes can propagate for any combination of the surface reactances. Mode charts for the case of unity azimuthal dependence (m = 1) are presented for a wide range of anisotropic surfaces to illustrate the types and characteristics of the modes which may propagate. Particular attention is given to balanced hybrid modes and the surfaces which will support them.
Radiation properties of microwave reflector antennas covered with a water film
 Author(s): A.S. Marinčić and B.D. Popović
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 933 –934
 DOI: 10.1049/piee.1978.0222
 Type: Article
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Using simple models, firstorder effects of a thin water film over the reflector surfaces of symmetrically fed microwave reflector antennas on the antenna radiation pattern and crosspolarisation in the frequency range 10–15 GHz are investigated. It is shown that the influence of the water film on crosspolarisation and the mainmode radiation pattern can usually be neglected, but that the minimum in the tracking mode can be substantially deteriorated. In addition, it was found that, in the frequency range 11–15 GHz, under certain circumstances the antenna gain can be reduced by as much as between 1 and 2 dB.
Noise reduction in optical measurement systems
 Author(s): A.M. Smith
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 935 –941
 DOI: 10.1049/piee.1978.0223
 Type: Article
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The cost of conventional current and voltage measurement equipment has led to an increasing interest in systems using a minimum of expensive insulation. At CERL, several optical systems for the measurement of current and voltage have been produced. These devices are found to suffer from noise due to intensity fluctuations of the light source and the wandering of the light beam across the photodetector surface caused by vibration and atmospheric turbulence. In the paper several possible techniques to reduce this noise are outlined, and a novel modulation scheme which has produced an improvement in the signal/noise ratio of over 20 dB is described. A device for the simultaneous measurement of voltage and current, making use of this system, is soon to go on trial at a generating station.
Transient stability region of synchronous generator with saturable exciter
 Author(s): H. Yee and M.J. Muir
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 943 –947
 DOI: 10.1049/piee.1978.0224
 Type: Article
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A method is described for estimating the critical clearing time for a singlemachine infinitebusbar power system where the generator is fitted with a saturable voltage regulator. The method is similar to Lyapunov's direct method, in that integration of the postfault swing equations is dispensed with. Instead an estimate is made of the extent of the region of stability in the state space. The procedure involves calculation of the unstable singular point and an eigenvalue analysis of the linearised system matrix evaluated at this point. There are advantages compared with Lyapunov's method, using the usual Lyapunov function, since line conductances, transient saliency and the presence of a saturable exciter can be taken into account easily.
Influence of winding design on the axial flux in laminatedstator cores
 Author(s): P.J. Tavner ; J. Penman ; R.L. Stoll ; H.O. Lorch
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 948 –956
 DOI: 10.1049/piee.1978.0225
 Type: Article
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p.
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The magnetic field of an isolated winding of helical form is obtained both theoretically and by measurement on a small model. The axial and radial fields of that winding are compared with those of straight windings with conventional ends, both when the windings are in air, and inside a slotless, laminated core. It is found that a knowledge of the field in air of a winding is not of itself helpful in predicting the axialfield distribution when the winding is placed inside a laminated core. Experimental results of the axialflux distribution inside the core are also presented. They demonstrate that axial flux is reduced when the winding radius and overhang are reduced. The axial flux continues to decrease even when the endwinding ceases to project from the core end.
New 2speed induction motors
 Author(s): K.C. Rajaraman
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 957 –958
 DOI: 10.1049/piee.1978.0226
 Type: Article
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p.
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A new method of pole changing of 3phase machine windings is described. A standard (60°spread, fullpitched) winding for P_{1} poles is used. Pole change is effected by redistributing the coils among the phases without reversing any part. On change to P_{2} poles, the winding has an effective spread of 120°, is exactly balanced and has a good m.m.f. waveform. Krebs's 12terminal deltadelta connection is used. The controller is a simple 6phase doublethrow switch. Test results of experimental 6/4, 8/6 and 8/4 pole cage induction motors are given. Windings suitable for constanttorque and constantpower drives give higher outputs than comparable versions of existing 2speed windings.
Tubularaxle induction motors for railway traction
 Author(s): R.W. Stokes ; M.J. Lilley ; M. Lockwood ; N.M. Rash ; E. Spooner
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 959 –966
 DOI: 10.1049/piee.1978.0227
 Type: Article
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A 3phase electrictraction system for railway vehicles is described. The traction motor is an insideout induction machine, built within a tubular axle, driving the wheels directly without gearing. The concept offers potential savings in manufacturing and maintenance costs. Good agreement has been obtained between predictions and measured performance on a series of experimental motors, and production versions are now being designed.
42nd parsons memorial lecture. Power generation in the future
 Author(s): R. Hawley
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 967 –977
 DOI: 10.1049/piee.1978.0228
 Type: Article
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p.
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Today the utilisation of the world's sources of energy for the generation of power is the subject of intense and urgent investigation. That such researches would be critical to the needs of civilisation was seen clearly at the end of the last century by Charles Parsons. Parsons' steam turbine and his development, in parallel, of the dynamo marked a turning point in the history of electricalpower generation, but his interest covered a far wider range. He concerned himself with many aspects of energy conversion, and many current ventures have associations with his early ideas. Moreover, his scientific curiosity led him to explore in other quite different directions, into such diverse subjects as telescopes and the manufacture of diamonds. Against a background sketch of Parsons' life and achievements, this lecture comments on a number of promising alternatives for the generation of electricity in the future.
Diffusion of moisture through powertransformer insulation
 Author(s): A.F. Howe
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 978 –986
 DOI: 10.1049/piee.1978.0229
 Type: Article
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p.
978
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Moisture in powertransformer insulation has long been recognised as a major cause for the deterioration of the dielectric and for shortening the ‘servicelives’ of units. Engineers have, therefore, striven to find a method that will accurately predict the degradation of the insulation in service conditions. This must involve a knowledge of how the moisture concentration varies in the insulation with time and load. Until recently, there has been no really satisfactory method of doing this, but now, with the advent of fast, largestorage computers, it is practicable to determine these changes in concentration numerically. Accurate computation depends on realistic mathematical modelling of the diffusion processes in both the liquid and solid insulants. These calculations are complex because the rate of moisture transfer depends on the materials, moisture distribution, temperature and oil velocity. The computations involve the simultaneous solution of the fundamental diffusion and heattransfer equations. A program has been developed to execute these calculations and it should prove to be a powerful tool for both transformer designers and electricitysupply engineers. The program produces sufficient information for engineers to decide whether the insulation of a transformer is in a satisfactory condition for the unit to be used. The reliability of the computations depends on the provision of accurate data, including a value for the diffusion coefficient of moisture through transformer oil. The magnitude of this parameter was unknown and the paper describes the establishment of a technique for measuring the quantity.
Current distribution and leakage impedance of various types of foilwound transformers
 Author(s): M.M. ElMissiry
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 987 –992
 DOI: 10.1049/piee.1978.0230
 Type: Article
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p.
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This paper presents an accurate method for calculation of current distribution and leakage impedance of foilwound transformers. It takes into consideration the curvature of the winding and the presence of iron boundaries. Transformers having various combinations of foilwound, wirewound and sectionalised windings are analysed. The influence of the various factors on current distribution and leakage impedance is examined in detail. These factors include the spacing between windings and iron boundaries, the type of windings, the number of sections on the outer winding and various asymmetrical arrangements of windings. Measurements of leakage flux show good correlation with computed results.
Implementation of nonhomogeneous theory in the transient analysis of crossbonded cable systems
 Author(s): D.J. Wilcox and K.J. Lawler
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 993 –998
 DOI: 10.1049/piee.1978.0231
 Type: Article
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p.
993
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The paper concerns the implementation of recently developed nonhomogeneous theory to the transient analysis of crossbonded cable systems. This theory shows that wave propagation along a chain of identical major sections may be treated in much the same way as wave propagation along a homogeneous system. Computational requirements are then essentially independent of the actual system length, thereby overcoming the major deficiency of classical recursive methods. However, to implement the theory, it is first necessary to determine the natural propagation characteristics associated with a single major section. Methods suggested hitherto have been based on the manipulation of the nodal admittance matrix. Unfortunately this matrix is not well conditioned and serious numerical difficulties are encountered. A new approach to the implementation of nonhomogeneous theory is given in the paper. This approach, which avoids the nodal admittance matrix altogether, is inherently stable for computational purposes.
Transient phenomena in crossbonded cable systems: analytical results
 Author(s): D.J. Wilcox and K.J. Lawler
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 999 –1005
 DOI: 10.1049/piee.1978.0232
 Type: Article
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p.
999
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The paper presents results of digital computer studies of the transient behaviour of crossbonded cable systems. These results are based on a realistic mathematical cable model which takes account of such factors as skin effect in the conductors and metallic sheaths and of mutual coupling between individual cables due to current penetration into the soil. Unlike previous work on the subject, the results are not restricted to short systems. Results are given for prospective sheath overvoltages as a function of system length and these are compared with classical predictions based on firstincidentwave theory. Further studies investigate the action and performance of cablecovering protection units.
New approach to design of ironcored inductances carrying direct current
 Author(s): Alexander Yair and Meir Steinkoller
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1006 –1008
 DOI: 10.1049/piee.1978.0233
 Type: Article
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p.
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A new method is proposed for direct design of inductances in LCtype filters of rectifier circuits. This approach permits direct choice of the required core followed by unambiguous determination of the number of turns and the airgap length. This is done using the load voltage and current, the type of rectifier and the ripple of the rectified current specified by the designer.
Practical implementation on a 5 kVA synchronous generator of an adaptive excitation controller strategy for a wide range of operating conditions
 Author(s): V.A. Phung and M.J. Gibbard
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1009 –1014
 DOI: 10.1049/piee.1978.0234
 Type: Article
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p.
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The feasibility of implementing an adaptivecontrol strategy to the excitation of a synchronous generator is examined in the laboratory. The aim of this work, which extends previously reported investigations based on an optimalcontrol strategy, is to design a practical controller that is not only suitable for continuous operation, but also meets tight steadystate and dynamic performance criteria over a wide range of leading powerfactor steadystate operating conditions. Optimalcontrol theory is used as a means of determining ‘offline’ the required feedback gains, use being made of a linearised model of the system for specific operating conditions. A minicomputer, which acts as the realtime controller, estimates the ‘pseudo’ steadystate operating point at any instant and selects the appropriate feedback gains from a ‘lookup’ table stored in memory. The experimental system is tested for a wide range of disturbances of a significant magnitude, and the results compared with predicted responses based on a nonlinear machine model. Good agreement is obtained, and performance criteria are achieved.
Discussion on “Development and trials of the 400 kV integral pipecooled system”, “Study of mechanical behaviour of cables in integralpipe watercooled systems” and “Design and construction of the 400 kV cable system for the Severn Tunnel”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1015 –1020
 DOI: 10.1049/piee.1978.0235
 Type: Article
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p.
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Discussion on “Development of internally oilcooled cable systems”, “Field trials of 400 kV internally oilcooled cables” and “UK requirements and future prospects for forcedcooled cable systems”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1021 –1026
 DOI: 10.1049/piee.1978.0236
 Type: Article
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p.
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Discussion on “Arc instability and current chopping in an airblast interrupter”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1027 –1029
 DOI: 10.1049/piee.1978.0237
 Type: Article
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p.
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Discrete control of an a.c. turbogenerator by output feedback
 Author(s): P.A.W. Walker and O.H. Abdalla
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1031 –1038
 DOI: 10.1049/piee.1978.0238
 Type: Article
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p.
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The paper develops a constantlinearoutput feedback optimalcontrol system for an a.c. turbogenerator system, requiring only the measurement of readily available signals from the power system. The control law is derived from the output prediction formulation of linearsystem dynamics, releasing the designer from the need for either stateestimation techniques, or the selection of the number of output measurements to be equal to the number of states. The method is applied to a single machine connected to an infinite busbar, and the performance of the controlled machine investigated in a wide range of operating conditions. These include step changes in demand, and a 3phase fault at the generator terminals, the results being compared to those achievable with full statefeedback optimal control.
Optimised control of water distribution systems
 Author(s): B. Coulbeck and M.J.H. Sterling
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1039 –1044
 DOI: 10.1049/piee.1978.0239
 Type: Article
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p.
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Typical system operating conditions are analysed to determine cost factors and control requirements, and hence permit development of system performance criteria. Combining a suitable optimisation technique and a simplified model enables a computer algorithm to be devised which can be applied to give optimal control of complex systems, taking account of all significant cost factors and operational constraints. The control scheme incorporates a simulation of the overall dynamics of a water system, which is used with historical operating data for validation purposes. The results confirm the theoretical predictions, and show that benefits can be obtained from online computercontrolled operations.
Control of resonant vibration in a springfatiguetesting instrument
 Author(s): H.A. Barker ; A.E. Noble ; V.O. Mills
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1045 –1050
 DOI: 10.1049/piee.1978.0240
 Type: Article
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p.
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The paper describes the design and implementation of control systems in an instrument for the fatigue testing of springs. A manual control system is used to establish a spring in a condition of mechanical resonance at a chosen amplitude of vibration, and an automatic control system is used to maintain this condition throughout the duration of a fatigue test. The problem of measuring the vibration amplitude is described, and the nature of the problem of controlling a resonant spring is discussed. For automatic control, an algorithm for the simultaneous extremal control of forcing signal frequency and regulatory control of forcing signal amplitude is developed, and implemented by means of a microprocessor. The methods used may be of more general application, particularly in vibration testing, and possible design improvements for such applications are discussed.
Theory of separable processes with applications to the identification of nonlinear systems
 Author(s): S.A. Billings and S.Y. Fakhouri
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1051 –1058
 DOI: 10.1049/piee.1978.0241
 Type: Article
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p.
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By considering the class of separable random processes, a generalised WienerHopf equation is derived for systems under Gaussian excitation that can be described by a model consisting of a linear system in cascade with a static nonlinear element, followed by another linear system. This result, together with a similar relationship for the 2ndorder crosscorrelation function, is used to formulate an identification and structure testing algorithm for this class of nonlinear system. The results of a simulation study are included to illustrate the validity of the algorithm.
Routhapproximant timedomain reducedorder models for singleinput singleoutput systems
 Author(s): A.S. Rao ; S.S. Lamba ; S. Vittal Rao
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1059 –1063
 DOI: 10.1049/piee.1978.0242
 Type: Article
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p.
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The problem of deriving reducedorder models of a higherdimensional system from its statespace description is considered under the constraint that the modelreduction procedure should not involve the evaluation of system eigenvalues, should not involve any optimisation algorithm and should yield a stable lowerorder model for a stable system. The Routhapproximant modelling procedure in the frequency domain has the above characteristics. This paper presents a timedomain adaptation of the Routhapproximant frequencydomain modelling procedure to achieve the above objectives for s.i.s.o. systems. The lowerorder timedomain model matrices are derived by a suitable truncation of the original system matrices in their γδ canonic structure. The aggregation matrix relating the system and model state vectors is also derived. A numerical example is included to illustrate the procedure.
Analysis and synthesis of dynamic systems containing time delays via blockpulse functions
 Author(s): Ganti Prasada Rao and T. Srinivasan
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1064 –1068
 DOI: 10.1049/piee.1978.0243
 Type: Article
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p.
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This paper presents a method of numerically integrating differential equations containing time delays via blockpulse functions. The resulting solutions are piecewise constant with minimal meansquare error. The method is based on the use of a newly developed ‘delay matrix’ and enlarges the scope of useful applications of blockpulse functions to problems of dynamic systems. Examples of linear and nonlinear delay systems are included.
Distribution of electrons and ions in a corona discharge
 Author(s): E.U. Landers
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 10, p. 1069 –1073
 DOI: 10.1049/piee.1978.0244
 Type: Article
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p.
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A new method of computing the distribution of electrons and ions in the spacecharge field of corona is described. For any point in a coaxial cylindrical geometry the resultant current density is well known because of the symmetry conditions. The proportion of electrons, and positive and negative ions in the current density, however, can be determined only by calculation of the ionisation and attachment processes. Since the coefficients for these processes are nonlinear functions of the local field strength, and the field strength in turn depends on the spatial distribution of electrons and ions, an iterative method of computing has been developed. The basically different distributions of electrons and of ions for positive and negative polarity determined by this method are helpful in explaining the underlying physical phenomena. The calculated results show very good agreement with measurements from the literature, where the radius of the visible corona glow and the particlecharging in the proximity of the corona wire had been examined.
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