By Topic

Electrical Engineers, Proceedings of the Institution of

Issue 5 • Date May 1965

Filter Results

Displaying Results 1 - 25 of 36
  • Analysis of radar-integrator performance

    Page(s): 839 - 848
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1070 KB)  

    The measurement of incoherent radar-echo powers much smaller than receiver noise can be achieved by using long-period postdetector integration. Suitable very stable integrators usually operate by integrating over successive discrete periods, `dumping¿ the total and restarting at the end of each period. This behaviour is different from that of the continuous integrator of the `sliding rectangular window¿ type, which may be considered as a passive low-pass filter. In the discrete-interval integrator the `dumping¿ phase is independent of the signal and the filtering analogue is not clear. It is shown that the signal/noise improvement produced by the discrete-interval integrator may be calculated by sampling theory, taking into account the continuously varying nature of the signal. Integration over periods ta is found to produce the same improvement as a low-pass filter of equivalent noise cutoff frequency 1/2ta. The relationship between the sampling and filtering approaches is studied, and methods are derived for calculating the reduction of detectable receiver input echo power for c.w. radars and for pulse radars having range gates narrower and wider than the pulse width. The effect of the i.f. filter response on the improvement produced by an integrator is illustrated by examples. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characteristics of atmospheric radio noise observed at Singapore

    Page(s): 849 - 860
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1391 KB)  

    Measurements of the amplitude probability distributions of atmospheric radio noise in a power bandwidth of approximately 400c/s, made at the Radio Research Station, Singapore, from September 1958 to July 1960, are presented for frequencies of 24 kc/s, 145 kc/s, 11 Mc/s and 20 Mc/s. Results are normalised to the r.m.s. amplitude to show the diurnal and seasonal variations of noise structure. The temporal variations in parameters derived from the distributions are also illustrated and the results explained by reference to the prevailing meteorological and ionospheric conditions. Parameters relating to noise amplitude are the mean power and the average value of the noise-envelope voltage; those relating to noise structure are the ratio of the r.m.s. to the average value and the dynamic range. The programme of measurements was similar to that made at the Radio Research Station in England during the International Geophysical Year. Wherever possible, the Singapore data are compared with the corresponding results for England. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development of secondary surveillance radar for air-traffic control

    Page(s): 861 - 871
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1547 KB)  

    The considerations leading to the development of secondary surveillance radar (s.s.r.) for air-traffic control are listed. The evolution of s.s.r. is described from a simple responder capable of operation with primary radar to a complex system employing special frequencies and coding facilities on the ground-to-air and air-to-ground channels. The evaluation at London Airport of a relatively simple independent s.s.r. system in 1954 and 1956 and subsequent international discussions on the subject led to standardisation of system characteristics in 1957 by the International Civil Aviation Organisation (ICAO). Development of a British system designed to satisfy all the ICAO requirements was finished at the end of 1960 and was evaluated at London Airport during 1961. It was concluded that this system could reliably form the basis of an air-traffic-control radar recognition system. An experimental height-transmission equipment employing the air-to-ground coding system is described, and requirements for future system development are outlined. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diazigzag aerial

    Page(s): 872 - 876
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The characteristics of a new travelling-wave aerial (consisting of a conventional zigzag aerial to which a conducting mast is connected at alternate crossover points) are described. Electrical performance is improved, with regard to operating bandwidth, for two versions of this aerial, and, in one case, v.s.w.r. also is improved. Both aerials are mechanically stronger than the simple zigzag aerial. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation coefficient for the current distribution along a cylindrical antenna immersed in a warm plasma

    Page(s): 877 - 882
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (775 KB)  

    A perfectly conducting, infinitely long cylindrical wire of radius a surrounded by an insulating layer of a cylindrical sheath of free space of radius b is immersed in a homogeneous, warm plasma of infinite extent. Using the linearised plasma theory and approximate boundary conditions, the dispersion equation for the propagation coefficient along the wire is derived. The numerical solution of the dispersion equation for a wide range of values for the radius of the cylindrical wire and the width of the insulating sheath shows that the propagation coefficient along the cylindrical wire is close to that of the plasma mode in an unbounded plasma, in the frequency range for which the electromagnetic and the plasma space waves are excited, that is for frequencies above the plasma frequency. It is therefore concluded that, for a finite antenna immersed in a warm plasma without or with an insulating sheath, it is appropriate to include in the approximation for the current distribution along the antenna a part which has the propagation coefficient of the order of magnitude of the plasma wave. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transverse-network representation for inhomogeneously filled circular waveguide

    Page(s): 883 - 894
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1177 KB)  

    A transverse-network representation for hybrid modes in inhomogeneously filled waveguides is derived using a method employed previously in the representation of slotted waveguides. It is shown that hybrid modes may be represented by a pair of coupled radial-line modes of pure H and E type. General expressions for the input impedances and admittances of the H- and E-type radial lines are developed at the rod boundary, and particular expressions for the unbounded rod and Goubau line are also presented. The influence of the above impedances and admittances upon the propagation characteristics of dielectric-loaded waveguides is considered for circularly symmetric and asymmetric modes. In particular, it is shown that the appearance of a backward-wave region can be interpreted as a frequency-pulling effect of one radial-line resonator upon the other. The extension of the representation to inhomogeneous waveguides with azimuthally nonuniform terminations is also briefly mentioned. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Darlington's conjectures

    Page(s): 895 - 900
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    A lumped linear nonseries-parallel 3-terminal RC network containing three internal nodes is analysed by taking specific numerical examples. Although in every case a series-parallel equivalent is obtainable, there are considerable differences between the various cases. Three examples are considered in detail in the paper. In two of these, one extra factor is required, and in all three cases excess elements are required, to obtain a series-parallel equivalent. A brief note is included on the results of an automatic analysis of a number of examples of this network using a digital computer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • RC active filters using an amplifier as the active element

    Page(s): 901 - 912
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1169 KB)  

    A new synthesis technique, involving a voltage amplifier with shunt feedback or a current amplifier with series feedback, is developed for RC active filters. Illustrative examples together with some experimental results are included; close agreement with theory is demonstrated. Tables have been prepared giving Horowitz's optimum polynomial decomposition for various Butterworth and Cheby¿shev low-pass filtering characteristics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bandpass filtering characteristics

    Page(s): 912 - 914
    Save to Project icon | PDF file iconPDF (295 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Methods of measuring radio interference from high-voltage insulators

    Page(s): 919 - 924
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (673 KB)  

    A critical study of the methods available for the measurement of radio interference from high-voltage insulators has been made by comparing the results obtained with the various methods for a range of insulators. It was found that the method which measured the noise current through a resistor coupled to the high-voltage system by a capacitor gave consistent results for all insulators. The second method, which measures the noise currents in the earth lead of the insulator, gave results which depended upon the size of the insulators. This method was subsequently modified by using an artificial earth plane connected to the measuring set. The results then approached those of the first method. A third method assumes that the onset voltage of visual corona is the criterion for the onset of radio interference. It was found that some radio interference was generated before visual corona commenced and that the levels at the critical visual corona voltages depended upon the types of insulators used. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radio interference from high-voltage insulators and factors which affect the interference level

    Page(s): 925 - 930
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (693 KB)  

    Investigations were made into the origins and causes of radio interference from high-voltage insulators, and factors which affect the interference level were studied. Pin-type, multicone post-type and pedestal-type insulators were used. In pin-type insulators, over their working voltage range practically all interference was generated in the region of contact between the high-voltage conductor and the porcelain. The interference was reduced to a very low level by applying a conducting paint or a semiconducting glaze to the insulator head. In multicone post-type and pedestal-type insulators most of the interference originated in the metal-cap/first-shed region, and the cement joint between the metal cap and first shed was the predominant source of interference. Control of the voltage stresses by using stress distributor and guard ring, and application of conducting paints to the cement joint, caused a large reduction in the interference and increased the voltage at which interference was first observed. Radio interference from pin-type insulators was also studied in air of different humidities. Increasing humidity caused a decrease in radio interference. The effect was relatively small in the drier conditions, but large reduction in interference was observed in humidity conditions near the saturation value. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Balancing bundle-conductor transmission-line constants without transpositions

    Page(s): 931 - 940
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1099 KB)  

    Transpositions, although considered necessary to balance the constants of an h.v. overhead transmission line, are costly and sometimes troublesome in operation; hence the desirability of balancing the line constants without transpositions. Possibilities of separately balancing inductances, earth capacitances and mutual capacitances between phases are considered, by adjusting the equivalent radii of the various phases. As the necessary variations in equivalent radii are considerable, only bundle conductors can be utilised, with suitable subconductor spacings. Simple relations are established for the ratio of subconductor spacings of the central and outer phases of a single-circuit line with symmetric horizontal phase configuration, for inductive and earth-capacitive balancing, first without considering the effect of earth wires. The effect of earth wires is to introduce a multiplying factor. These results show that simultaneous balancing of the constants is not possible for the horizontal arrangement. Balancing of mutual capacitances, though possible, may not be practicable. The Donau-type double-circuit transmission line with one earth wire, as used in the West German 380kV transmission system, is analysed in detail, but the equations are very involved. Simultaneous balancing of inductances and earth capacitances is theoretically possible, by suitably situated earth wires and corresponding subconductor spacings. The suitability of this method has to be judged in each case individually, after working out the details as outlined in the paper. Other methods of balancing some of the constants, in conjunction with this method, may be required for complete balancing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Calculation of travelling waves on transmission systems by finite differencess

    Page(s): 941 - 948
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    The paper is concerned with attenuation and distortion of travelling waves on transmission systems. The conventional calculation of such phenomena is based on matrix operational methods: a different approach is suggested, namely the method of finite differences, which as an iterative numerical method is ideally suited to consideration of nonlinearities. A central-difference formula is employed to illustrate the behaviour of standard waves on model systems, subject to stability criteria. The authors set out mainly to investigate the general procedure of such a method, and expect that the work will be further extended to be of practical use in the study of travelling waves. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of I.v. distributors from standard cable sizes

    Page(s): 949 - 956
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (821 KB)  

    An analytical study is made with the aid of a digital computer of the economic design of uniformly loaded a.c. distributors under balanced-phase loading conditions. The optimum profile of a continuously tapered distributor is obtained by an application of the calculus of variations, and the method is developed to cover the corresponding practical problem of designing a stepped distributor from standard cable sizes by introducing Lagrangian multipliers. Optimisation is carried out with respect to conductor volume and also with respect to costs over the life of the cable, taking energy losses into consideration. In the latter case, Kelvin's law is shown to hold below a certain critical length. It is demonstrated that significant savings may be achieved by incorporating these methods in practical design work for new housing estates. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Further developments in the design and performance of high-voltage terminal boxes

    Page(s): 957 - 964
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1157 KB)  

    Since the publication in 1962 of a paper on the basic dielectric and safety requirements of terminal boxes, considerable successful experience has been gained in the former respect, and further developments have taken place in the latter respect. A method has been found, and proved by test, to obviate the explosion danger of compound-filled sealing boxes used in conjunction with terminal boxes, one of the few problems left over from the previous investigation. The design of phase-segregated connector-type terminal boxes with containment up to 10 kA reduces the occurrence of flame exhaust to the case of severe multiple faults for impedance-earthed systems. The ultimate complete elimination of any exhaust from a terminal box under any fault condition, as well as from the apparatus served by the terminal box, requires the use of fuses in order to limit the fault energy to a manageable value. The paper describes tests up to 750 MVA, 11 kV on phase-insulated and phase-segregated connector-type terminal boxes with pressure-relief. The same terminal boxes without pressure relief were completely successfully tested with fuse protection suitable for a 3000 hp heavy-duty squirrel-cage motor with a 250 MVA, 3.3 kV and a 750 MVA, 11 kV supply. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parallel operation of transductor-controlled silicon-rectifier equipment with waterwheel-driven d.c. generators supplying an aluminium potline

    Page(s): 965 - 976
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1142 KB)  

    Transductor-controlled silicon-rectifier equipment has recently been commissioned in an aluminium factory in Scotland. The equipment runs in parallel with the existing Pelton waterwheel-driven d.c. generators to supply the 60¿70 reduction furnaces which make up the aluminium potline. The anode effects in the potline introduce transient current and voltage fluctuations on the system. Parallel-connected transductors with voltage-feedback windings are employed to match the load sharing of the rectifier equipment with the d.c. generators, and at the same time reduce load fluctuations on the a.c. supply. In order to predict the transient performance of the equipment, the complete system was represented on an analogue computer. The subsequent tests, during the commissioning of the rectifier equipment, supported the findings of the analogue study, though no direct comparison was possible owing to the random nature of the anode effect. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Geometric construction of the stability limits of synchronous machines

    Page(s): 977 - 985
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (811 KB)  

    The paper analyses the conditions for stability of synchronous generators, or motors in steady-state operation, with and without assistance from voltage-regulating equipment. A simple geometric construction on a `capability chart¿ of the machine is used to display the operating limits and to demonstrate the influence of exciter time constant and damping coefficient on dynamic stability. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Method of predicting the thermal loading of an oil circuit breaker

    Page(s): 986 - 994
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1151 KB)  

    The various factors influencing the temperature rises in bulk-oil circuit breakers are discussed and details of direct measurements on a certain circuit breaker with unplated contacts are given. A method for dretermining transient temperatures in the bushings using an electrical resistance capacitance heat-flow analogue in conjunction with the direct measurements is described. This method gives temperatures at points which are not readily measurable by direct means but which are of great importance, i.e. the hot-spot temperatures occurring in the bushing insulation. Steady-state and transient temperatures rises for points in the circuits breaker for which direct measurement and analogue predicted values are available show good agreement. The effects of various values of contact resistance on the bushing insulation temepratures are investigated over a range of contact resistance. The results illustrate the current uprating possible if contact resistances are kept to low values. The changes in the contact resistance of unplated contact with length of service are discussed from information obtained from supply authorities, and the effects of regular maintenance are shown. The relation between the bushing hot-spot temperature rises and the rises of the top oil are examined and indicate that the addition of 10°C to the oil temperature gives a safe estimate of the hot-spot temperature. The effects of eddy-current heating are also discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simple phase-detection relay for distribution networks

    Page(s): 995 - 999
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    For the detection of reverse power flow in medium-voltage networks, induction-disc-type relays are usually employed. This paper describes a simple phase-detection relay which is capable of indicating revers power flow in certain types of network. The relay described uses the characteristics of Zener diodes and is simple in design, cheap in cost and is capable of extensive application. The performance of a laboratory-prototype relay under steady-state and transient conditions is described. It is shown that the relay operates irrespective of the phases on which the fault occurs. A linear coupler from which the current signal can be derived helps to reduce unwanted transient effects. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Printed-disc inverse-time overcurrent relay

    Page(s): 1000 - 1006
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    The paper describes a new type of electromechanical inverse-time overcurrent device for the protection of power-supply circuits. The various time/current characteristics of the new relay and the methods by which they are obtained are given, and some basic features are discussed. A method of compensating for the timing errors caused by ambient-temperature change is described. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

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

Full Aims & Scope