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Generation, Transmission and Distribution, IEE Proceedings C

Issue 6 • Date November 1980

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Displaying Results 1 - 13 of 13
  • Editorial

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    Freely Available from IEEE
  • Design of synchronous generator excitation controllers in multimachine power systems using inverse Nyquist array

    Page(s): 350 - 356
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (835 KB)  

    Using a four-machine power system as an example, a basis for a systematic procedure is described for determining the feedback-gain settings of excitation controllers in a multimachine system over a wide spectrum of system-loading conditions. For illustrative purposes, electrical power and speed are used as the local feedback signals on each machine in addition to voltage feedback, whose gain setting is assumed fixed. For a given loading condition the inverse Nyquist array (i.n.a.) method is employed to estimate a range of feedback-gain settings for dynamic stability. For all machines of interest, a set of fixed gain settings is then chosen which provides a satisfactory small-signal dynamic performance over the range of system loading conditions. Some advantages of this application of the i.n.a. method are highlighted. View full abstract»

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  • Controller testing facility on 32.5 MW water turbine

    Page(s): 357 - 359
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (255 KB)  

    As part of a collaborative programme of work between university and industry on the control of hydro-generating units supplying power to the UK national grid, equipment has been installed on a 32.5 MW unit which permits the testing of new controllers in a realistic, operational environment. A central feature of this equipment, which includes a new independent high-pressure servomotor, is that it permits the generating unit to be returned quickly to operational use with its existing controller. Full integration with the power station operator's controls, automatic control scheme and protection, permit the controllers under test to be evaluated under normal operational conditions. View full abstract»

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  • Microprocessor-based adaptive water-turbine governor

    Page(s): 360 - 369
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    Conventional governors of water-turbine-generator sets can be set up to provide either stability when supplying an isolated load or rapid response when connected to a large, predominantly thermal, system. In the paper, an adaptive microprocessor-based governor is described which goes some way to satisfying both requirements. Results are given for tests on a 32.5 MW turbine generator. View full abstract»

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  • Z-transform electromagnetic transient analysis in power systems

    Page(s): 370 - 378
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    The paper develops a new electromagnetic transient formulation for multiconductor power transmission lines based on the z-transform. Beginning with the basic relationships of propagation in the frequency domain, the successive steps of z-transform analysis are developed leading to recursive sequences for solution in the time domain. The case of lossless propagation is considered initially in introducing z-transform analysis in its application to transmission-line electromagnetic transient evaluations, following which a general formulation is derived into which series-path line parameter frequency-dependence is directly reflected. Test analyses based on a z-transform model complemented by a simplified equivalent-source representation and applied to a 160 km, 400 kV untransposed single-circuit transmission line confirm the high inherent accuracy and low computing-time requirements of the method. View full abstract»

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  • Development of z-transform electromagnetic transient analysis methods for multinode power networks

    Page(s): 379 - 385
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    The paper continues and extends the recent development of z-transform electromagnetic transient analysis in power systems as reported in a companion paper. Whereas the original development was based on the configuration of a single transmission line and a simplified equivalent-source model, the present paper extends this to the more general case of multinode-power-transmission networks. In those terms, the formulation developed in the present paper provides for distributed-parameter transmission-line models with series-path nonlinear frequency dependence, together with lumped-parameter circuit elements of linear and nonlinear forms, in any arbitrary combination and interconnection. This general electromagnetic transient analysis formulation is complemented by means of representing any circuit-breaker switching sequence and any short-circuit fault constraint. An assessment of the inherent accuracy and stability of the multinode z-transform solution scheme derived is made from comparisons with solutions from formal frequency-domain analysis. View full abstract»

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  • Time convolution and z-transform methods of electromagnetic transient analysis in power systems

    Page(s): 386 - 394
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    From the starting point of multi conductor power-transmission-line equations in scattering form in the frequency domain, the paper first summarises the principal aspects of numerical time-convolution and z-transform methods as applied to electromagnetic transient analysis in power-network systems. Against that background, the paper provides a detailed comparative study of the two analysis methods with particular reference to the representation of the nonlinear frequency-dependence of transmission-line parameter sets, multinode-system modelling, storage requirements, execution times, solution accuracy, and algorithm stability. View full abstract»

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  • Estimation of transformer winding temperatures and coolant flows using a general network method

    Page(s): 395 - 405
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    The windings of large modern transformers are generally cooled by pumping oil through a network of ducts in the winding. The resulting value of the hottest conductor temperature and the position it occurs in the winding are important parameters in the design and operation of a transformer. There is a standard method for estimating the value of this hot spot but there is very little information on the position at which it occurs. Also, devices have been developed which when inserted in a winding will measure the local temperature. These instruments could be used to measure the hot-spot temperature of a winding in a transformer on load. However, it would obviously be advantageous if the position of the hot spot could be estimated so that the device could be installed in the optimum position. The work reported here attempts two things: first, to improve on the standard method for estimating the winding temperature distribution and hot-spot temperature and secondly to estimate the position of the hot spot. The computer program developed to do this can be used to estimate the flows, fluid temperatures and boundary temperatures for any network of flow paths. However, only its application to a transformer is considered here. The method used to obtain the required predictions is described, and estimates are presented of the winding temperature distribution for a particular design of transformer operating with a steady load. View full abstract»

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  • Role of metal debris in the performance of stop-joints as used in 275 kV and 400 kV self-contained oil-filled cable circuits

    Page(s): 406 - 419
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    In an investigation into a series of falures of 275 kV and 400 kV cable stop-joints, examination of unfailed joints taken from service revealed bands of accumulated debris in the oil channels of the joints. The debris was identified as being mainly copper and its properties were studied. A mechanism of failure of the stop-joints was proposed on the basis of small scale experiments, this was that metallic particles can form lines in an electric field and if the line is sufficiently long gas can be generated at the points of contact. The relationship between the length of line and the field required to generate gas has been determined. The next stage in the failure mechanism is the build up of gas and the formation of bubbles in the oil channel. These bubbles, composed mainly of hydrogen, discharge and eventually cause failure. The proposed mechanism has been tested in various simulants of stop-joints and has been shown to be feasible and consistent with the evidence from failed joints. Some remedial measures for both new and existing circuits are proposed. View full abstract»

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  • Book review: Optimal Economic Operation of Electric Power Systems

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    Freely Available from IEEE
  • Partial discharges in power-cable joints: their propagation along a crossbonded circuit and methods for their detection

    Page(s): 420 - 429
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    A method of measuring the discharge activity on cable systems has been developed to assist in assessing and monitoring cable joints. Partial discharge activity in the cable joints is detected by measuring the currents produced in the links between bonding cables which are brought to the surface to achieve sheath transpositions. The high-frequency components of this current may be detected using current transformers around the links and a radio-frequency amplifier. The output of the latter may then be used to give an alarm indication of any significant rise in these components caused by discharges in the joints. To relate the measurements at a link position to the discharge activity in the cable joint an analytical model of the cable system has been developed to describe the propagation of pulses through a crossbonded-cable system. The results of this analysis have been compared with measurements made on two operational cable circuits, and its impact on the design of a monitoring system discussed. Instrumentation is being developed for installation on CEGB 275 and 400 kV cable circuits. Sensors and the detector would be fitted at each stop-joint bay with an alarm activated in a substation when the level exceeds a preset value. View full abstract»

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  • Equivalent nonlinear lumped-parameter network representations for a.c.s.r. conductors

    Page(s): 430 - 433
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    The internal impedance for any a.c.s.r. conductor is calculable from an equivalent network representation in combination with materials-characteristics curves. Effects due to helical lays, temperature variation, magnetic characteristics and frequency variation at power frequencies are readily incorporated into the procedure. Experimental results are compared with results from the procedure, with excellent agreement in all cases. View full abstract»

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  • Digital simulation of fuse breaking tests

    Page(s): 434 - 440
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    A mathematical model is described which simulates the interruption of short-circuit current by a current-limiting fuse. The development of a model for the arcing period is described, based upon experiments conducted by the authors and others. The waveforms of fuse voltage and current predicted by the model bear a striking similarity to those observed during short-circuit tests on fuses. View full abstract»

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