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Generation, Transmission and Distribution, IEE Proceedings C

Issue 6 • Date Nov 1989

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Displaying Results 1 - 13 of 13
  • The delta resonator: a new approach to load compensation theory in three-phase power systems

    Page(s): 381 - 384
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    The authors reconsider the theoretical approach to the compensation of unbalanced three-phase loads by means of delta-connected purely-reactive admittances. A new component called the delta resonator is introduced, leading to a new and simpler view which gives further insight into the nature of the problem View full abstract»

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  • Analysis of a circular earthing plate

    Page(s): 385 - 390
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A Fredholm integral equation of the first kind is developed for finding the charge distribution on a circular conducting plate buried in a homogeneous earth. The method of moments is used to solve the functional equations. Techniques are developed to evaluate and differentiate a singular integral by numerical means. An extremely fast rate of convergence is gained by expanding the charge distribution in functions with an appropriate singularity. It is observed that currents are dispersed into the earth in a small region near the edge of the disc. Contrary to popular perceptions, the earthing resistance of a disc is not inversely proportional to its area. A simple empirical formula for enumerating the earthing resistance of a disc in terms of its radius, its depth of burial, and the conductivity of the earth is derived View full abstract»

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  • Expert system for protection current transformer design specification preparation

    Page(s): 391 - 400
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (804 KB)  

    The authors develop an expert system to assist protection engineers in preparing design specifications for protection current transformers used in differential protection of power transformers based on the rule-based expert system methodology. The relationships of the design quantities and the design process are expressed as dependency trees. The transparency of the reasoning process of the developed system is enhanced by including in the system an explanation subsystem. The system is implemented using Prolog. An application of the expert system is presented, demonstrating the suitability of the design selection knowledge representation method and the inference process developed together with the capability of the explanation subsystem View full abstract»

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  • Structure of measurement Jacobian matrices for power systems

    Page(s): 407 - 412
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    In steady-state modelling of power systems, the measurement equations together with the system states may be ordered so that the measurement Jacobian matrix H displays a particular block-sparsity structure, which will become more apparent as system size increases. The resulting partitioned form for H may be regarded as a simply specified decomposition of the measurement equations. The decomposition may then be exploited using a theorem which enables the rank of H to be determined from a set of rank tests on reduced-order matrices. This result has implications for the testing of numerical observability on power systems, particularly when the new rank tests are distributed within a multiprocessor computer system. A novel feature of this approach to the determination of numerical observability is that a degree of localisation of unobservable states becomes possible. The fundamental structure of the decomposition described for H is suitable for exploitation in other areas of steady-state power systems analysis such as state estimation View full abstract»

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  • Double-iterative algorithm for the analysis of power and harmonic flows at AC/DC convertor terminals

    Page(s): 319 - 324
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    The accuracy of the formulation of the convertor models normally used in single-phase and three-phase AC/DC loadflows is restricted by the assumptions of perfectly smooth direct currents and of perfectly sinusoidal commutating voltages. Conversely, the harmonic current injections from convertor plant are calculated from nominal and generally symmetrical conditions and are thus unreliable. An algorithm integrating load-flow and harmonic analysis is proposed in which these assumptions are not made, thus allowing evaluation of their effect on the fundamental and harmonic flow solutions. It is shown that the interaction between the harmonic and load flows cannot be ignored even in the presence of filters, particularly when the convertor plant or AC system parameters are unbalanced View full abstract»

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  • Soil physical route survey and cable thermal design procedure

    Page(s): 341 - 346
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    A thermal rating procedure is proposed for cables buried in sandy soils. The procedure uses a recently developed model to account for the effects of drying-out. The model requires as soil characteristics density, suction tension curve and saturated hydraulic conductivity. As boundary conditions it requires the ambient temperature and moisture content at cable level. In a reconnaissance survey of the cable route the thermally limiting soil sections are identified on the basis of estimated soil properties and local hydrology. Soil characteristics are determined in the laboratory for these sections only. The worst-case moisture content is derived from the lowest water table expected as indicated by hydromorphic characteristics of the soil profile View full abstract»

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  • Nonrecursive methods for real-time determination of basic waveforms of voltages and currents

    Page(s): 347 - 352
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    Using the Fourier technique, Kalman filter theory and Walsh functions, nonrecursive algorithms for online determination of basic waveforms of signals are introduced, investigated and compared. The Fourier algorithms very efficiently reject the higher harmonics. For nonharmonic random noise of higher frequencies the new nonrecursive algorithms based on the Kalman filter theory have better filter properties than Fourier ones. The Walsh methods are very simple for computer implementation, but their filter properties are not very convenient, especially for the odd harmonics View full abstract»

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  • Random energisation transients in EHV systems

    Page(s): 325 - 330
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Inter-phase switching surges are considered to be a leading element in the dimensioning of insulation. The authors outline the effects of random pole closure of circuit breakers on the statistical features of phase-to-phase overvoltages, the relative magnitude of their phase-to-ground components and their time displacement. These features are computationally derived for a model 500 kV transmission line. Design recommendations are given based on prespecified risks of insulation failure on single phases and between phases View full abstract»

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  • Determination of first swing stability limit of multimachine power systems through Taylor series expansions

    Page(s): 373 - 380
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A new technique of determining first swing stability limit of a power system through checking the existence of peaks of rotor angles of the severely disturbed generators in the postfault period is presented. The existence of peaks is checked by observing the roots of time derivatives of rotor angles of these generators expressed through truncated Taylor series expansions. The stability limit and hence the critical clearing time corresponds to the maximum value of fault duration for which at least one of the roots of the derivative of the angle is real positive. The proposed method has been tested on four different power networks and the critical clearing times obtained were found to be in very good agreement with those obtained by simulation of system dynamics. The method is computationally very fast compared with the existing methods View full abstract»

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  • Ripple control signal interference due to a lightly loaded rural distribution line

    Page(s): 401 - 406
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    Amplification of ripple control voltages on lightly loaded distribution lines can cause interference to consumer equipment, necessitating a method of modifying the line parameters in an effort to alleviate the problem. The techniques and assumptions used in modelling the parameters and distributed load of a particular rural distribution line in the North Canterbury Electric Power Board supply system are presented, to allow the use of a general purpose linear interactive network simulation computer program to assist in analysing the problem. Results of the computer simulations are compared to actual test values. The most satisfactory method of solving the problem is decided by considering these results, along with equipment costs and other electrical characteristics of the line. It is recommended that power factor correction capacitors be connected to the secondaries of several distribution transformers along the line View full abstract»

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  • Integrated excitation and turbine control in a multimachine power system

    Page(s): 331 - 340
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    The authors are concerned with modelling and optimal control studies, by computer simulation of a multimachine power system comprising three interconnected generator units. The most effective generating unit, for the application of control, is determined by using eigenvalue analysis. A multi-input/multi-output linear model of the system, as seen from this unit, is obtained by least-squares identification. On the basis of this model a multivariable controller is designed, by minimising a quadratic performance index using the dynamic programming procedure. This local controller employs output feedback, and provides integrated control of the exciter and turbine-valve inputs. Multivariable controllers are also designed and applied to the other generating units, to allow comparative system performance to be examined. System behaviour is assessed in relation to small and large-disturbance studies. Simulation results include responses to three-phase short circuits, and dynamic and transient stability boundaries View full abstract»

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  • Electromagnetic design of turbogenerator stator end regions

    Page(s): 361 - 372
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1028 KB)  

    The authors review the electromagnetic design of turbogenerator end regions. Three-dimensional finite element analysis is employed to investigate existing design concepts and evaluate their effectiveness in reducing stator core end losses. The solution method includes both eddy current reaction and magnetic nonlinearity effects. Concentration is made upon the various sources of axial flux, their relative magnitudes and their vector addition during load conditions. A number of design features are considered in some detail, illustrating how the manner in which they influence losses on load is generally very complex. In many cases it is shown that these features result in a number of important effects which were not perceived at the time of their introduction View full abstract»

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  • Extension of Senn's method to the analysis of PLC systems applied to delta transmission lines

    Page(s): 353 - 360
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    A method proposed by W.H. Senn has proven to be a powerful tool in the analysis of power line carrier (PLC) systems on horizontal transmission lines. A similar method, applicable to the more general case of delta transmission lines, would be highly desirable. The validity of Senn's method, when applied to delta lines, is investigated first. Secondly, an extension to the method in order to account for the departure from the horizontal line geometry is proposed. The performance of Senn's method and of its extension are assessed by comparisons with exact modal transformations. It is concluded that the application of both Senn's method as a first approximation and its extension allow for the design of reliable PLC systems on delta transmission lines View full abstract»

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