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Generation, Transmission and Distribution, IEE Proceedings C

Issue 6 • Date November 1982

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Displaying Results 1 - 13 of 13
  • Load-curtailment model for economic loading of thermal generation

    Page(s): 233 - 238
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    Economic loading of thermal generation systems has to take account of possible generation loss. A frequently stated requirement is that there should be sufficient emergency reserve to cover loss of the largest infeed. The cost of fulfilling this requirement can be considerable in the case of small systems, where the largest infeed is likely to be a significant proportion of installed capacity. A method is given which allows the operator to strike a balance between the cost of holding emergency reserve and the cost to consumers of possible loss of supply. The method uses a special-purpose dual simplex linear programming algorithm. View full abstract»

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  • Availability modelling of stochastic power sources

    Page(s): 239 - 248
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1385 KB)  

    Energy sources which are stochastic in their behaviour include solar radiation, wind energy and run-of-the-river hydroplant. In addition to conventional considerations of plant availability, reliability models for these sources must also represent the stochastic character of the prime energy supply. The paper initially develops probabilistic models for representing power availability and then proceeds to obtain stochastic transition rates for predicting changes of availability. Power gereration is written as a function of intrinsic variables, which describe the state of the relevant elements of the physical environment. Computations of conditional probability are employed to evaluate the probability density profile of power availability. Transition-rate evaluation depends on relationships of time variation for intrinsic variables, in the presence of uncertainty which is modelled by noise functions. The results of these evaluations can be used to integrate stochastic power sources with the reliability index computations of the entire power system to which they may be connected, or used individually, as in the case of isolated sources. View full abstract»

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  • Dynamic behaviour of a 25m variable-geometry vertical-axis wind-turbine generator

    Page(s): 249 - 259
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1055 KB)  

    The paper describes the development of a dynamic model of a 25 m variable-geometry vertical-axis wind turbine coupled to a generator which is in turn connected to the public electricity supply system. The model represents a 25 m prototype machine which it is proposed to be built at Carmarthen Bay in South Wales. This work was carried out as part of a detailed design study of the 25 m prototype, supported by substantial funding from the Department of Energy. Studies carried out on the model were used to investigate the behaviour of the wind-turbine generator when subjected to certain disturbances such as random wind fluctuations, gusting, three-phase and single-phase faults. These disturbances are typical of those that would impinge upon such a machine during its working life, and against which the machine should operate in an acceptable manner and remain stable when connected to a synchronous system. In addition, it was seen to be important to be able to predict and investigate any system resonances that may occur, so that these could be designed out of the machine. View full abstract»

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  • Analysis of self-excited induction generators

    Page(s): 260 - 265
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (663 KB)  

    An analytical technique using the `Newton-Raphson¿¿ method is presented to identify the saturated magnetising reactance and the generated frequency of a self-excited induction generator for a given capacitance, speed and load. The technique is shown to be very efficient in analysing such systems under steady state. Computed results are compared with the experimentally obtained values on a laboratory machine, and a reasonable correlation has been observed. Effects of various system parameters on the steady-state performance have been studied, and the results presented provide guidelines for optimum design of such systems. View full abstract»

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  • Equivalent circuit representation of a superconducting alternator

    Page(s): 266 - 277
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1215 KB)  

    An equivalent circuit has been derived to represent the d and q axes of an air-cored superconducting alternator. The windings and screens in the machine are represented by the branches in the ladder-type network. The circuits have been used to obtain expressions for the damping coefficients and screening ratios during small oscillations. A modified screening ratio is proposed which differs from the conventional definition, but which is easier to apply to this type of machine. The circuits have been extended to permit an electrically thick screen to be represented by a number of layers, and the effect of the number of layers chosen, on the screening and time constants, is shown. View full abstract»

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  • Co-ordinated single-variable excitation control and governing of turboalternators

    Page(s): 278 - 284
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    The feasibility of implementing a control strategy for the co-ordinated excitation control and governing of an AC turbogenerator is examined. The proposed control scheme uses only one extra control signal, that of rotor acceleration, in addition to the two conventional feedback signals of terminal voltage into the excitation system and rotor-speed deviation into the governing system. Theoretical studies are performed using multivariable function-minimisation techniques which have been extended to include dynamic-sensitivity calculations. An experimental investigation is performed on a laboratory micromachine system to confirm the results of the theoretical investigation. The method gives significant improvements in system performance following a large disturbance, with good correlation between theory and practice View full abstract»

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  • Optimisation of discrete-type load-frequency regulators considering generation-rate constraints

    Page(s): 285 - 289
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (601 KB)  

    In the paper a method of designing discrete-type load-frequency regulators of a two-area reheat-type thermal system with generation-rate constraints is presented. The construction of the regulators is based on the conventional tie-line bias control. The regulator parameters are optimised by minimisirig a discrete-type quadratic performance index with a term for presenting a generation-rate constraint. The optimisation of the parameters is achieved by using a Newton-Raphson iterative algorithm. The control effects by the proposed regulators are examined by digital simulations of the system. Furthermore, a suitable means for preventing excessive and unnecessary control action is also proposed considering the constraint. View full abstract»

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  • Some aspects of multilevel load-frequency control of a power system

    Page(s): 290 - 294
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (474 KB)  

    The application of multilevel control strategies for load-frequency control of interconnected power systems is assuming importance. A large multiarea power system may be viewed as an interconnection of several lower-order subsystems, with possible change of interconnection pattern during operation. The solution of the control problem involves the design of a set of local optimal controllers for the individual areas, in a completely decentralised environment, plus a global controller to provide the corrective signal to account for interconnection effects. A global controller, based on the least-square-error principle suggested by Siljak and Sundareshan, has been applied for the LFC problem. A more recent work utilises certain possible beneficial aspects of interconnection to permit more desirable system performances. The paper reports the application of the latter strategy to LFC of a two-area power system. The power-system model studied includes the effects of excitation system and governor controls. A comparison of the two strategies is also made. View full abstract»

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  • Foundation uplift resistance: The effects of foundation type and of seasonal changes in ground conditions

    Page(s): 295 - 305
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1529 KB)  

    Various theories for estimating foundation uplift design are discussed. The shape of the foundation and the way it has been constructed, the type of applied loading and the strength of the soil surrounding the foundation, all affect its uplift behaviour. Tests on all these aspects are described. It is possible that any one of the above factors could be the cause of a foundation being under design strength, but the combination of more than one factor could be critical. Proposals are made for further studies, the conclusions from which should allow more accurate designs to be made in the future. View full abstract»

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  • Power-system digital back-up protection

    Page(s): 306 - 314
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (984 KB)  

    The purpose of power-system back-up protection is to disconnt faulty primary equipment not isolated by the main protection and associated circuit breakers. Conventional back-up techniques are difficult to apply in a large power system and heavy reliance on main protection is required. In this paper, both substation-based and centrally co-ordinated back-up protection methods, using microprocessors and minicomputers, are described. In a power system with a reliable communication network between substations, a fault-directing method is proposed to perform centralised digital back-up protection. If the communication network is not available, a substation-based back-up method is suggested. Both methods can reduce back-up fault-clearance time with correct discrimination, high reliability and cost effectiveness. View full abstract»

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  • Accurate representation of commutation overlap effects in steady-state multi AC/HVDC link studies

    Page(s): 315 - 317
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (387 KB)  

    Most steady-state HVDC link representations, such as multi AC/HVDC loadflow analysis and state estimation, do not model commutation overlap angle effects; instead they assume convertor switching to be instantaneous. A simple technique is presented and tested which allows the commutation overlap to be explicitly included in conventional HVDC link representation with only a slight modification. The resulting algorithms are shown to accurately model the commutation overlap process under normal HVDC link operating conditions (overlap angle <60¿¿) and convergence of the algorithm is not degraded View full abstract»

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  • Conference report. Third international conference on sources and effects of power system disturbances

    Page(s): 317 - 319
    Save to Project icon | PDF file iconPDF (469 KB)  
    Freely Available from IEEE
  • IEE Conference Publication 210

    Page(s): 319 - 320
    Save to Project icon | PDF file iconPDF (264 KB)  
    Freely Available from IEEE