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Electrical Engineers, Proceedings of the Institution of

Issue 3 • Date March 1977

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Displaying Results 1 - 25 of 26
  • Analysis and simulation of message-switched loop data networks

    Publication Year: 1977 , Page(s): 193 - 197
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    The loop or ring-type data networks using full duplex-communication links between the nodes have been investigated. The results presented in the paper concern two specific modes for handling the messages. These are termed `store and forward¿ and `check and forward¿. Both modes have been analysed using extensions of the single-server queueing theory and also simulated extensively using GPSS software. The message traffic is Poisson distributed and can arise from any node with equal probability. The destination is selected to be any other node again with equal probability. The study has also considered the performance of the two modes for traffic having priorities. One conclusion arrived at in this investigation is that the traffic with priorities can be better handled by a network which handles messages in either store and forward or check and forward mode depending on the priority of the message. View full abstract»

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  • Multiport-network analysis by matrix renormalisation employing voltage-wave S-parameters with complex normalisation

    Publication Year: 1977 , Page(s): 198 - 204
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    Network analysis, in terms of S-parameters, is invariably carried out in modern textbooks by employing the power-wave concept. It is shown that this approach is not relevant to practical measurement; furthermore, the complication of square roots, real parts, conjugates, moduli and conjugate transpose matrices is carried throughout the mathematics. These difficulties are overcome by employing the voltage-wave concept with complex normalisation, whereby the analysis is carried out in terms of port-voltage and port-current relationships, from which, power flow relationships are readily obtained in a straightforward manner. The new method of network analysis presented is not only completely general and rigorous, but simple to apply and faster than any other known technique. It is based on a once-for-all solution of the most general problem of all in 3-port analysis, namely, a 3 × 3 renormalising matrix, each element of which embodies three renormalising factors. Examples are given of the derivation of some 2-port and 3-port network equations, but in a more general form in which the port normalising impedances are not only different but complex. It is concluded that the voltage-wave S-parameter approach, with complex normalisation, should not only be revived and taught in academic institutions, but that it should take precedence over the power-wave approach which has a very restricted application. In a companion paper, a reappraisal is made of computer-corrected network analyser design and calibration. View full abstract»

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  • Reappraisal of computer-corrected network analyser design and calibration

    Publication Year: 1977 , Page(s): 205 - 212
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (962 KB)  

    A rigorous analysis is carried out of a typical dual-directional coupler network analyser to demonstrate the application of a new circuit analysis technique based on the principle of matrix renormalisation, described in a companion paper, to cascaded multiport networks. The manner in which previously published calibration equations were derived is explained in detail. The analysis is carried out external to the network in terms of voltage excitation and the voltage responses at the accessible ports of the network under mismatched conditions. Each section of the network is represented by a generalised scattering matrix defined in terms of voltage-wave S-parameters with complex normalisation. In this manner, a knowledge of the internal flow paths of the network is unnecessary, in contrast to the flowgraph method employing the nontouching loop rule. The analysis shows that current methods of network analysis, based on the power-flow concept, have given rise to certain misconceptions because source mismatch does not contribute to systematic error-as is generally believed. In addition, these misconceptions appear to have led to the adoption of general design principles for network analysers that are unnecessarily complicated because the effects of mismatches, discontinuities and poor directivity can be completely eliminated by calibration in terms of air-dielectric line standards, provided that all port mismatches are invariant between the reflection and transmission modes of operation. View full abstract»

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  • New form of inverter-fed synchronous motor with induced excitation

    Publication Year: 1977 , Page(s): 213 - 217
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A new form of inverter-fed brushless synchronous motor is described, having a cylindrical rotor with internal flux barriers and a 3-phase rotor winding connected to two diodes. An improved analysis and calculation method is presented for this and related types of machine. Very good synchronous performance and correlation with theoretical predictions are demonstrated by practical tests. View full abstract»

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  • Temperature distribution in the coil of a transformer winding

    Publication Year: 1977 , Page(s): 218 - 222
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (521 KB)  

    Numerical solutions are presented for temperature distributions in the coils of a disc-type transformer winding. The numerical method was applied to plane coils corresponding to those used in a full-scale model of an oil-cooled disc-type transformer winding. The agreement between theoretical and experimental results was found to be very good. View full abstract»

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  • Frequency-domain digital simulation of synchronous generators operating under faulted conditions

    Publication Year: 1977 , Page(s): 223 - 228
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (806 KB)  

    The paper details a method by which the equations describing a 3-phase synchronous machine may be transformed into the frequency domain to provide a means of digitally simulating faults at the generator terminals. Evaluation of the Fourier integrals involved in determining the machine response is achieved by means of the fast-Fourier-transform algorithm, and numerical results are presented together with the criteria necessary to achieve an accuracy comparable with that attainable using direct-phase quantities. The methods provide a basis for combining synchronous sources with transmission lines having frequency-variant parameters, and which are not therefore amenable to simulation using other than frequency-domain techniques. Studies using the new method indicate that, when predetermining the armature currents of a faulted machine, considerable economies in computing time may be effected, and the possibility of improving the simulation to simulate more accurately rotor eddycurrent effects by utilising the direct- and quadrature-axis frequency response emerges. View full abstract»

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  • Transient analysis of d.c. motor controlled by power pulses

    Publication Year: 1977 , Page(s): 229 - 230
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    Three methods of transient analysis of a d.c. separately excited motor, controlled by a chopper with square-wave output voltage, are derived. These methods are compared with regard to accuracy and usefulness. The methods require much less computation time than necessary for a step-by-step solution of the system differential equations, and, in some cases, can be used for deriving a transfer function of the pulse controlled motor. View full abstract»

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  • Erratum: Review of trends in excitation systems and possible future developments

    Publication Year: 1977
    Save to Project icon | PDF file iconPDF (97 KB)  
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  • Erratum: High-voltage switchgear

    Publication Year: 1977
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  • Electric train heating with diesel locomotives

    Publication Year: 1977 , Page(s): 231 - 236
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1014 KB)  

    With the replacement of steam locomotives by diesel and electric tractors, it was natural to look to electrical energy as a heat source for passenger trains. When substantial parts of the main lines were electrified at 25 kV, the opportunity to change from steam heating to electric heating was taken. To maintain compatibility between electric and diesel locomotives some of the latter were required to be capable of providing a power source for electric train heating. The train-heating-supply systems which became standard are discussed, together with the various means of providing these supplies from a diesel locomotive. As an example of the method generally adopted for British railways, the train-heating installation on one particular type of locomotive is described in some detail, together with some of the practical problems encountered and the solutions adopted to overcome these. As a more recent example, the heating system fitted to British Rail's new high-speed train is discussed. In conclusion, the paper attempts to indicate likely directions for future developments. View full abstract»

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  • Quantitative comparison of commutation circuits for bridge inverters

    Publication Year: 1977 , Page(s): 237 - 246
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (958 KB)  

    The large number of published circuits for forced commutation inverters has created a selection problem for the user and designer. The cost of commutation components, with reference to rating, is often disregarded when selecting a particular circuit. The efficiency of the commutation circuit and its effect on the efficiency of the main circuit, is also often disregarded. The paper compares on a per unit basis the commutation, and powercircuit components, for five typical inverter circuits, and provides guidance on which configuration is likely to suit a particular application. While the comparison is restricted to a single-phase bridge invertor, results can frequently be extrapolated to polyphase circuits. View full abstract»

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  • Constrained dispatch of active power by linear decomposition

    Publication Year: 1977 , Page(s): 247 - 251
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The decomposition of the constrained allocation problem for active power generation is considered, and a problem formulation developed which enables the grouping of the constraints to form a structure suitable for linear decomposition. Dantzig and Wolfe showed that a finite convergence algorithm is a suitable solution of the decomposed primal problem in which a series of linear, constrained subproblems are co-ordinated by a global problem of transformed variables. The solution of a large dispatch problem is presented and the computational requirements contrasted with conventional primal and dual linear-programming techniques. The technique is concluded to permit significant computational savings and also to be suitable for implementation on a multilevel or multiprocessor computer system. View full abstract»

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  • Online control of generator transient stability by minicomputer

    Publication Year: 1977 , Page(s): 252 - 258
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (849 KB)  

    A bang-bang control scheme to improve system recovery after large disturbances is derived from a linear-system model. Consideration is given to the practical constraints imposed on the state and control variables of a typical power plant. The implementation of the method is carried out on a laboratory micromachine working online with a digital PDP 8 computer. Results are favourably compared to those shown by other studies performed by digital simulation despite the simlicity of the model used to obtain the basic control law. View full abstract»

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  • Analysis of an inverter-fed induction motor via state-transition signal-flow graph technique

    Publication Year: 1977 , Page(s): 259 - 260
    Save to Project icon | PDF file iconPDF (279 KB)  
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  • Part symmetrisation of 3-phase windings

    Publication Year: 1977
    Save to Project icon | PDF file iconPDF (158 KB)  
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  • Lumped-parameter modelling and identification of distributed-parameter systems. Part 1: Discrete, parallel and cascade models

    Publication Year: 1977 , Page(s): 261 - 265
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (542 KB)  

    A method of characterising distributed-parameter systems using lumped discrete models is proposed. These models are classified as parallel and cascade, and they are based on spatial and temporal pulse responses derived from the Green's function associated with the boundary conditions of the system. A technique for representing such models using difference equations in space and time is given and procedures for using the models to derive the outputs in time and space from the system are described. The computer-simulation results are used to confirm the analysis. View full abstract»

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  • Deionisation of an interrupted vacuum arc

    Publication Year: 1977 , Page(s): 266 - 272
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (865 KB)  

    Measurements have been made of time-dependent saturation ion currents flowing to a probe and to the discharge electrodes following the forced extinction of high-current (1¿5 kA) vacuum arcs of short duration (¿1 ms) on copper electrodes. The results have been utilised to derive ion-flux distributions irrespective of ion-charge number, assuming collisionless plasma expansion from the cathode spots, and significant differences have been found compared with previous measurements on steady-state discharges. The results on interrupted and steady-state discharges are reconcilable if a source of low-energy ions exists, which is constrained in the cathode-spot region in the steady state and which is released at the zero current condition when the constraining forces vanish. View full abstract»

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  • Emitting-site lifetimes, currents and current densities on arc cathodes with 100 nm thick copper-oxide films

    Publication Year: 1977 , Page(s): 273 - 276
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (666 KB)  

    Static arcs of durations between 3.8ns and 40 ¿s have been initiated, in atmospheric-pressure air, on copper cathodes with an oxide film 100nm thick. By using a scanning electron microscope, the number and size of craters left by emitting sites and the total surface area (containing all of these many craters), from which the oxide had been stripped away, have been measured as a function of arc current as well as of arc duration. These results indicate that for this oxide film, a single cathode emitting site has an average lifetime which is only about 4.5 ns and this is therefore much smaller than has been thought to be the case for copper oxide, which indicates that the large increase in conduction through the oxide occurred by switching rather than by electroforming. The very small arc durations have yielded a close estimate of the number of coexisting sites, thus giving average site currents of about 11 mA at densities of about 1.4 × 1012 A/m2 View full abstract»

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  • Electric fields inside a series of curved corners

    Publication Year: 1977 , Page(s): 277 - 284
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (791 KB)  

    The 2-dimensional electric fields internal to five different corner configurations made from three conductors are investigated. These corners are such that the sections in the plane considered consist of two semi-infinite straight lines at right angles joined by a conductor which is part of a circular arc. By methods involving conformal transformations, complex inversion and elliptic integrals, exact solutions giving the electric intensity are obtained. Graphs are given showing the variation of electric intensity along the conductor surfaces, and also along the axis of symmetry where appropriate. The results should be useful in assessing the effects of rounding off corners in electrical constructions. The same theory, with suitable change of symbols, gives the magnetic fields of the configurations. Also the results, with small modifications, may be applied to calculate the mechanical forces. View full abstract»

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  • Editorial

    Publication Year: 1977
    Save to Project icon | PDF file iconPDF (93 KB)  
    Freely Available from IEEE
  • Development and trials of the 400 kV integral pipe-cooled cable system

    Publication Year: 1977 , Page(s): 286 - 294
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1208 KB)  

    The need for reduction in wayleave requirements for cables for undergrounding of CEGB 400 kV very-heavy-duty lines has led to the development of the integral pipe-cooled cable system. The thermal design of the system is described and the various practical problems, pertaining to the installation of larger 400 kV cables in pipes, are outlined. Two field-trial installations have been constructed, the second being designed to resolve problems of cable movement which were not fully solved due to practical limitations in the first trial. The main results of both trials are reported. The applications, limitations and economic advantages of this cable system are briefly discussed. View full abstract»

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  • Study of mechanical behaviour of cables in integral-pipe water-cooled systems

    Publication Year: 1977 , Page(s): 295 - 302
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1020 KB)  

    The movement of cables in integral-pipe water-cooled systems, owing to the thermal expansion which occurs under load, has been studied theoretically. The axial thrust on the anchor joints and the strain variations in the cable sheath have been calculated for certain assumed cable configurations; e.g. the cable may be assumed to take up a helical configuration or to `snake¿ sinusoidally along the bottom of the pipe. The principle of minimum energy has been used to determine the percentage of total cable length taken up in a given configuration in those cases where a mixed, e.g. part helical part sinusoidal, configuration is considered, and to establish the preferred configuration (from amongst those studied) for a given temperature rise. The theoretical predictions have been compared with results obtained in two CEGB field experiments, a full report of the work is given in a companion paper, and the degree of agreement achieved has allowed certain general conclusions to be drawn concerning the effect of the various cable parameters, e.g. flexural rigidity, mass, dimensions and the pipe diameter, on the behaviour of cables in such systems. Particular attention has been paid to the problem of metal fatigue in the cable sheath due to cyclic strain variations which will follow the cable loading patterns. Finally, provisional design criteria for the mechanical design of such systems have been suggested. View full abstract»

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  • Design and construction of the 400 kV cable system for the Severn Tunnel

    Publication Year: 1977 , Page(s): 303 - 316
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2051 KB)  

    The paper describes the reasons for the construction of a cable tunnel under the Rivers Severn and Wye, and the application of an integrally cooled pipe-type cable system to the crossing. Difficulties of applying, to the tunnel scheme, the results of a field trial involving a buried pipe/cable scheme are examined, and the solutions described. The final design of cable and cooling system is given which enables a 4 × 400 mm2 s.c.a. overhead line to be matched in current carrying capacity by a single cable per phase. View full abstract»

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  • Development of internally oil-cooled cable systems

    Publication Year: 1977 , Page(s): 317 - 325
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1320 KB)  

    The paper describes the considerations underlying the development of 400 kV internally oil-cooled cable systems, on both theoretical and practical grounds, with particular reference to coolant selection and duct diameters, cooled-section length and critical areas for development. Various conductor designs are described and their merits, leading to the adoption of two cable designs using copper and aluminium conductors, are discussed. Accessory design is also considered; particularly the design of stop joints suitable for operation at large continuous oil-flow rates. The requirements for ancillary plant and oil pumps are stated, and the results of investigation of long-term circulation on the dielectric properties of cable oil are reported. The paper also considers possible practical cooling schemes. Future applications of this technique for cooling very-heavy-duty cable circuits are indicated, and the advantages of extension of operating limits (such as temperature and pressure) for the cable are discussed. The basis for calculation of coolant flow and pressure drop is stated. View full abstract»

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  • Field trials of 400 kV internally oil-cooled cables

    Publication Year: 1977 , Page(s): 326 - 333
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1130 KB)  

    An account is given of two cable trials successfully completed at West Thurrock, which have proved the basis for the design of an internally oil-cooled underground cable system utilising one cable per phase, and capable of matching the rating of a 400 kV 4 × 400 mm2 overhead line. The design and construction of the aluminium and copper conductor cables, stop joints, sealing ends, straight joints and the hydraulic systems for both oil and water cooling and heat exchanger installations are described. The supervisory equipment and measurement equipment are outlined, together with the monitoring procedures for the cable oil, cable and accessories. The installation and commissioning experience and salient results of the trials which included 100 load cycles are given. The current-loading objectives of the trial were fully achieved and showed no constraints of the cable system which would limit the development of the system for higher ratings. View full abstract»

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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

Full Aims & Scope