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Generation, Transmission and Distribution, IEE Proceedings C

Issue 2 • Date Mar 1990

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Displaying Results 1 - 13 of 13
  • Information technology - telecommunications and information exchange between systems - local and metropolitan area networks - specific requirements. Part 12: demand-priority access method, physical layer and repeater specifications

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    This international standard defines the protocol and compatible interconnection of data communication equipment via a repeater-controlled, star topology local area network (LAN) using the demand-priority access method. The purpose of this protocol is to provide a higher speed LAN with deterministic access, priority, and optional filtering. Pursuant to this, the protocol will (a) provide a minimum data rate of 100 Mb/s; (b) provide smooth migration from ISO/IEC 8802-3 and ISO/IEC 8802-5 LANs; (c) support either ISO/IEC 8802-3 or ISO/IEC 8802-5 frame format and MAC service interface to the LLC; (d) support a cascaded star topology over twisted pair and fibre-optic generic building wiring; (e) allow topologies of 2.5 km and greater with three levels of cascading; (f) provide a physical layer bit error rate (BER) of less than 10-8; (g) provide fair access and bounded latency; (h) provide two priority levels: normal and high; (i) provide a low-latency service through high priority for support of multimedia applications over extended networks; and (j) support an option for filtering individually addressed packets at the repeater to enhance privacy. View full abstract»

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  • Numerical analysis of a class of foundation grounding systems

    Page(s): 123 - 128
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Although foundation grounding systems are known to have very good electrical characteristics, only a limited number of papers dealing with their analysis have been published. A novel theoretical method is proposed for analysis of foundation grounding systems. The method is illustrated by considering a specific system in the form of a horizontal grid, laid in a rectangular concrete foundation. Theoretical results were found to agree favourably with those obtained experimentally on a small-scale model, as well as with the empirical data of other authors. A simple approximate formula for a practical assessment of the grounding resistance of such grounding systems is presented View full abstract»

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  • Influence of the terminal capacitor on the performance characteristics of a self excited induction generator

    Page(s): 168 - 173
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    The influence of the excitation capacitor on the steady state performance characteristics of an isolated self-excited induction generator feeding a balanced load is examined. It is shown that the terminal capacitor must have its value within a certain range to sustain self-excitation. If the value of the excitation capacitor is outside this range, self-excitation will not be possible. Moreover, if the load impedance is below a certain value, self-excitation will not be achieved irrespective of the value of the excitation capacitor. In the capacitance range where self-excitation is possible, it's value strongly influences the induction generator performance characteristics. The value of capacitance can be selected so that the terminal voltage is constant, regardless of the generator output power. It is further shown that under such condition, the value of capacitance is influenced by the load as well as by the load power factor. The generator performance is however independent of the load power factor and is only affected by the magnitude of the load impedance View full abstract»

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  • Investigation of transient induced voltage to a communication line from an overhead power transmission line

    Page(s): 129 - 138
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    A transient voltage induced on a communication line by an overhead power transmission line is investigated using analytical formulas of the voltage and the maximum voltage value and on results calculated with EMTP and using a frequency-domain method. A large transient induced voltage, which is several times greater than the steady-state induced voltage during a line-to-ground fault, is generated because of the different propagation times of the aerial and earth-return modes in the case of a switching surge with no source inductance and that of a line-to-ground fault surge. The transient induced voltage in the switching surge case, with a source inductance, can be neglected because it is of the same order as the steady-state induced voltage during a fault. Based on a parametric analysis of the induced voltage, it was found that, the transient and steady-state induced voltages generally increase as the line length and earth resistivity increase, and as the source inductance and separation between the power and communication lines decrease View full abstract»

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  • Three level time decomposition quasi-static active and reactive power flow control

    Page(s): 95 - 100
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    A three-level time-decomposition quasi-static power-flow control model of power systems is presented. The model enables the simple solution and computation of the primary, secondary and tertiary quasi-static power flow control effects. The active and reactive power flow control characteristics are considered. The model exploits the Newton-Raphson method for the computation of all three control subproblems. Computational efficiency is ensured by the specific application of the inversion matrix lemma and the decoupled model constant coefficient matrices. The developed model is intended for security and emergency analysis/control computations View full abstract»

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  • A fuzzy approach in the determination of unstable machines

    Page(s): 115 - 122
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    The authors present a fuzzy approach in the determination of the unstable machines in transient stability studies of multimachine electric power systems. This approach is based on the derivation of an index that can identify the unstable machine by using the values of the generator rotor angles and accelerations. The index actually computes the degree of instability of every system machine, when a three-phase fault is established on any power system location, causing no topological changes after its clearance. The unstable machine will be the one having the largest value of instability index. The derivation of this index is based on the principles of pattern recognition, fuzzy sets theory and the Taylor series expansion technique. Two examples illustrating the methods application are given, including the analysis of the interconnected Hellenic power system View full abstract»

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  • Self tuning control for turbogenerators in multimachine power systems

    Page(s): 146 - 158
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    The application of self-tuning automatic voltage regulators to generators in a multimachine power system is described. The regulators have supervision schemes which ensure effective operation under all conditions. The performance of the regulator has been evaluated using a detailed multimachine power system model. Results are presented which show that the self-tuning regulator provides good control in a multimachine environment, when operating in conjunction with conventional regulators on other generators. A comparison with a conventional regulator shows that the self-tuner gives better performance View full abstract»

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  • Evaluating the approximate probability distributions of load point reliability indices in power distribution networks

    Page(s): 174 - 176
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    The concepts and applications of probability distributions for load-point reliability indices in power distribution networks are discussed. An understanding of the subtleties involved will aid in assessing works in the associated literature View full abstract»

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  • Interruptible load considerations in spinning reserve assessment of isolated and interconnected generating systems

    Page(s): 159 - 167
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    The authors present a technique which includes interruptible loads in the probabilistic assessment of the operating reserve in isolated and interconnected generating systems. This technique is then used to evaluate the magnitude and corresponding maximum allowable time delay of load interruption required to reduce the unit commitment risk in the absence of other capacity adjustments. They also present a probabilistic technique which can be used to evaluate the inherent interruptible load carrying capability of an isolated and interconnected generating system which exists without having to commit any extra units other than those required to carry the firm load. The study provides an insight into load interruption and its effect on the system risk. The techniques developed are illustrated by numerical examples. These techniques can be used in short and medium term operational planning View full abstract»

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  • Modelling and state estimation of power plant steam turbines

    Page(s): 80 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1112 KB)  

    The development of a robust state estimator for ill-conditioned systems based upon the Levenberg-Marquardt algorithm in connection with Givens orthogonal row processing technique is described. The estimator works in two stages: the square-root-free Givens transformation is applied to the measurement Jacobian matrix to reduce it to the product of a unit upper triangular matrix and a diagonal matrix, then the square-root-free Givens transformation is again used to transform a diagonal matrix whose diagonal element is equal to the Levenberg-Marquardt parameter. The estimator is applied to a 250 MW, double-flow, single reheat steam turbine which has seven feedwater heaters. Tests results show that the estimator performs well under a wide range of measurement errors and measurement redundancy ratios. A sample of estimated results for rated loading condition are presented View full abstract»

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  • Optimal load flow for electrical power systems with multiterminal HVDC links

    Page(s): 139 - 145
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    A model for obtaining the optimal operating point of electrical power systems with multiterminal HVDC links is drawn. The model takes into account all the boundary conditions on AC and DC quantities, and can describe both series and parallel configurations of the convertors. Numerical applications to a test network are carried out View full abstract»

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  • Examination of severe contingencies in a small area of a large composite power system using adequacy equivalents

    Page(s): 107 - 114
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The quantitative evaluation of the adequacy of a major load point or of an overall power system involves the examination of both generation and transmission facilities. The main task in such an analysis is to consider all those credible outage events which can significantly affect the performance of the network. The number of events which must be examined is dependent upon the intent behind the studies and the adequacy indices being calculated. This may involve a detailed examination of a large number of events involving multiple component outages. The consideration of the required outages, however, is severely restricted in a practical network by the required computation time. The authors present a new and efficient approach to include the effect of high-level independent outages in a part of a network which utilises an adequacy equivalent developed for the remaining part of the network. The applications and advantages of using the proposed method are illustrated by presenting results for two test systems which are described View full abstract»

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  • Optimal siting of power system stabilisers

    Page(s): 101 - 106
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Presents a methodology to identify the critical eigenvalues, or modes, in electric power systems, and a procedure to determine the optimal siting for power system stabilisers. The critical modes are identified using the contributions of the different eigenvalues to a quadratic performance measure and explicit expressions for these contributions are derived. Feasibility and minimum number of decentralised controllers are obtained from sensitivity analysis. The most effective locations for power system stabilisers are then determined using eigenvalue dynamics and a multimachine power system example is given to illustrate the proposed techniques View full abstract»

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