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Generation, Transmission and Distribution, IEE Proceedings-

Issue 4 • Date Jul 1994

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Displaying Results 1 - 22 of 22
  • Reliability assessment of composite hydrothermal generation and transmission systems using sequential simulation

    Page(s): 257 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The studies reported in this paper extend the application of sequential simulation to the reliability analysis of composite power systems containing mixed hydrothermal generation. The paper summarises the basic characteristics of sequential simulation. It also summarises the main elements to be considered and modelled for the reliability analysis of these types of systems to jointly account for energy limitations, generation capacity and transmission deficiencies. A composite hydrothermal reliability test system (CHT-RTS) based on the original IEEE reliability test system is used to illustrate the analysis of composite power systems containing mixed hydrothermal generation View full abstract»

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  • High-voltage insulation co-ordination: timelags of parallel-plate, rod-plane, rod-rod gaps, cap and pin insulators and surge diverter

    Page(s): 397 - 400
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    Percentage overvoltages against timelag characteristics show that, while for simulated lightning strokes a rod-rod gap, set to yield the same 50 percentage sparking voltage as a rod-plane gap, will protect it and cap and pin insulators for all magnitude of overvoltages, for a simulated switching surge a rod-rod gap is wholly inadequate. For complete protection, uniform field geometries like those produced by Rogowski profiled electrodes are required and this is almost achieved with surge diverters View full abstract»

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  • Application of wind speed forecasting to the integration of wind energy into a large scale power system

    Page(s): 357 - 362
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The use of numerical weather prediction (NWP) model as used by national meteorological agencies is assessed in conjunction with a physical flow model and a statistical model as a means of predicting wind power that could be generated by a large number of wind turbines spread throughout the UK. Economic benefits have been demonstrated, and are evaluated in the form of fossil fuel savings using a numerical simulation model which emulates the power plant scheduling of the England and Wales National Grid. The results highlight the importance of effective planning of on-line reserve capacity to cover sudden deficits in wind power generation View full abstract»

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  • Realtime fault detection and classification in power systems using microprocessors

    Page(s): 315 - 322
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    A method is proposed for real-time fault detection and classification in power systems. The method can be implemented in low-cost units based on 8-bit microprocessors. These units are part of a multiprocessor system which allows the detection of single line to ground faults, double line and double line to ground faults, and three-phase faults. The detection of an overcurrent triggers two simultaneous processes executed in real time: the waveforms of the voltage and current signals are registered and a probabilistic criterion is used for fault confirmation. The process of confirmation is based on the estimation of the three phase voltage phasors by means of a set of Kalman filters, and on the calculation of the fault probability. If the fault has been classified correctly, a recording is made with the samples acquired, including five cycles of the prefault signals and 150 cycles of the postfault signals. This recording is use by the multiprocessor system to calculate the fault distance and to generate an accurate fault recording. The algorithm has been verified using a computer simulation of the different types of faults, and has been optimised so as to detect and correctly classify faults in less than 20 ms View full abstract»

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  • Design of universal variable-structure controller for dynamic stabilisation of power systems

    Page(s): 363 - 368
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A study on the application of variable-structure control techniques for improving power system dynamic stability is presented. The basic concepts and design criteria of variable structure control are briefly discussed. The procedure of designing a variable-structure controller for a synchronous machine connected to infinite busbar using a simple linear model obtained by linearising nonlinear characteristics of the system is explained. The effect of variation of machine output power, transmission line reactance and infinite bus voltage on the design of the controller is investigated. A controller algorithm that guarantees proper operation irrespective of machine output power, transmission line reactance and infinite bus voltage is discussed. The performance of the controller is verified using a more elaborate synchronous machine model in which the effect of damper windings is treated. The results of the simulation studies show that with the proposed controller the stability of the power system is improved significantly View full abstract»

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  • Voltage stability as affected by discrete changes in the topology of power networks

    Page(s): 346 - 352
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    An analysis of the effect of electrical network changes over the stability condition of a power system is presented. The study focuses on three different types of change: transformers with on-load tap changers, line outages and maximum excitation limiters in generators. For each of these changes, the static stability of load flow equations and the dynamic stability of the differential equations of the power system are analysed. As a byproduct of these studies, a strategy to detect voltage collapse problems is proposed View full abstract»

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  • New approach to distance protection for resistive double-phase to earth faults using adaptive techniques

    Page(s): 369 - 376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    Distance protection is prone to mal-operation under resistive double-phase to earth fault conditions. This is caused by the relay measuring the incorrect impedance to the fault due to the influence of infeed from the remote end of the line. The paper describes two adaptation techniques, one for use with the earth elements, and one for use with the phase elements, which enable the correct impedance to be measured, and hence improve distance protection performance under such fault conditions View full abstract»

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  • Self-tuning load frequency control: multilevel adaptive approach

    Page(s): 285 - 290
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A multilevel adaptive load frequency control (LFC) based on the self-tuning regulator (STR) is investigated. The technique identifies each subarea separately as an autoregressive moving average submodel and parameters are identified by using the recursive least-squares method. The parameters of the predicted submodel are used to ensure the subarea control error calculation. The application of the proposed algorithm is suggested as a suitable alternative to the integral control used normally for the LFC. This work differs from previous work in that the proposed technique permits optimality at all levels while providing a decomposed solution. The effectiveness of the control algorithm has been verified through numerical studies on the 20-machine, 118 bus IEEE test system View full abstract»

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  • Model-based fuzzy control of power system static/dynamic security using the pattern recognition approach

    Page(s): 270 - 278
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Using databases derived from the pattern recognition approach, the paper presents a methodology for utilising fuzzy models to enhance the quality of decision-making using fuzzy-logic algorithms. In the paper, two multi-objective fuzzy-logic control algorithms for controlling power system static/dynamic security are presented and analysed. The first algorithm is based on the successive inferences of fuzzy implication rules for each individual objective, and the second algorithm is an application of the method of fuzzy linear programming. Using results from these algorithms, the paper discusses the properties, advantages and limitations of applying fuzzy decision-making logic in the pattern-recognition approach and concludes by highlighting potential areas for further development View full abstract»

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  • Integrated digital power transformer protection

    Page(s): 323 - 328
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    In the paper the hardware and software prototype realisation of the integrated digital three-phase power transformer protection for selective operation with all kinds of short circuits, ground faults and turn-to-turn faults is presented. The proposed integrated protection concept was developed on the basis of a nonlinear mathematical transformer model which includes nonlinear effects of saturation, hysteresis and eddy currents. The protection algorithm includes a percentage differential relay with harmonic restraint at inrush and overexcitation conditions, an overcurrent relay with instantaneous and time-lag operation, a sensitive relay for selective operation at high-impedance ground faults and a fault recorder. The protection algorithm was implemented on powerful signal processor. Presented are the results of real-time laboratory and field testing which include the comparison of the standard static protection performance with the proposed digital one in relation to speed and accuracy View full abstract»

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  • Voltage stability indicator for identification of the weakest bus/area in power systems

    Page(s): 305 - 309
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    Application of Newton optimal power flow (OPF) to identify the weakest bus/area, which is most likely to cause voltage collapse, is presented in this paper. The S-V curve (complex power to voltage) is examined via Newton OPF. Marginal costs (Lagrange multipliers) regarding power flow equations, VAr generations, voltages and taps, etc., to the system MW losses are obtained from Newton OPF. The weakest bus/area in the system is identified by an indicator achieved with these marginal costs via the Kuhn-Tucker theorem. This indicator helps users know which bus/area is most likely to cause voltage collapse. The IEEE 30-bus and a practical 251-bus systems are used to show the capability and feasibility of the proposed approach View full abstract»

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  • Novel method for solving radial distribution networks

    Page(s): 291 - 298
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The paper presents a novel method using load flow for solving radial distribution networks. The radial feature of the network has been fully exploited to develop an algorithm by a unique lateral, node and branch numbering scheme. The proposed method involves only the evaluation of simple algebraic voltage expressions without any trigonometric functions. Thus, computationally, the proposed method is very efficient and requires less computer memory storage as all data is stored in vector form. The proposed method can easily handle different types of load characteristics. Several Indian rural distribution networks have been successfully solved using the proposed method known as the forward sweeping method View full abstract»

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  • Maximum efficiency of interconnected transmission lines

    Page(s): 353 - 356
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The maximum transmission efficiency of an electric power line is analysed to compare the performance of symmetrically compensated AC transmission lines. The line load under the condition of maximum transmission efficiency is expressed analytically and is compared with the line loadability given by the St. Clair curve. The theory of maximum transmission efficiency is extended to include asymmetrical networks of interconnected lines. Numerical applications illustrate the main results View full abstract»

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  • Frequency-dependent impedance of vertical conductors and a multiconductor tower model

    Page(s): 339 - 345
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    The paper proposes a frequency-dependent characteristic impedance of a vertical multiconductor system above an imperfectly conducting earth and a multiconductor multistair model with a number of legs between tower arms to represent an actual tower for a lightning surge analysis. Surge impedances calculated by the proposed formula and model show a satisfactory accuracy compared with a number of experimental and field test results of vertical conductors and actual towers. It is observed that an imperfectly conducting earth causes no significant effect on the characteristic impedance of a tower, and the wave propagation velocity is nearly the light velocity in free space in the entire frequency range View full abstract»

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  • Efficient method for alleviating voltage limit violations using local optimisation

    Page(s): 279 - 284
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Alleviation of voltage limit violation at certain critical buses is a serious problem in the interconnected power system. In this paper, an attempt is made, based on the concept of local optimisation, to alleviate the voltage limit violation by using controls at the local level during any severe disturbance to avoid system collapse. The method is efficient and robust in comparison with existing methods, as the new secure operating point is obtained with minimum control action. The algorithm developed in this paper gives satisfactory results when tested under steady-state conditions on 24 bus IEEE (RTS) and 57 bus IEEE systems under severe and extreme loading conditions View full abstract»

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  • Prediction of customer load point service reliability worth estimates in an electric power system

    Page(s): 390 - 396
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The basic concepts associated with quantitative reliability evaluation are reasonably well accepted in the electric power industry. The justification of new facilities and system modifications now normally includes specific reference to reliability and one approach that is receiving considerable attention is the assessment of the societal worth or benefit associated with power system reliability, and conversely the costs to consumers of power supply interruptions. The paper presents three different methods for evaluating system customer load point reliability worth factors designated interrupted energy assessment rates (IEAR). These factors consider the influence of outages in all parts of the electric power system. The developed IEAR can be used with the available adequacy indices to assess the severity associated with unsupplied energy owing to supply interruptions. The IEAR can be used as customer related indices in making decisions regarding load curtailment philosophies and reliability related rate setting. The concepts of using a customer damage function in association with customer reliability indices are presented and illustrated using a reliability test system View full abstract»

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  • Probabilistic iterative harmonic analysis of power systems

    Page(s): 329 - 338
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    The most adequate way to take into account the uncertainties which affect the modelling of harmonic penetration is to express the input data by random variables and to apply probabilistic techniques of analysis. In this paper a probabilistic method is proposed for assessing harmonic distortion levels in power systems. This method transfers to the field of probabilistics a deterministic iterative procedure which is extremely useful for analysing multiconvertor systems. The proposed method, called the `probabilistic iterative harmonic method', employs a Monte Carlo simulation technique. A numerical application to a test system is also discussed View full abstract»

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  • Voltage stability assessment of isolated power systems with power electronic converters

    Page(s): 310 - 314
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    This paper extends the concept of small signal models to the frequency domain and then presents a new method for isolated power system voltage stability analysis. An approximation for the voltage and reactive power relationship of the cycloconverter is proposed and verified by time domain simulation. Small signal models for various nonlinear, power system components including power electronic converters are derived, based upon which, the incremental network of the system is formed. The voltage stability indices of various buses, which are defined in the bus impedance matrix of the incremental network, can be calculated using the conventional factorisation method without the need to determine the matrix eigenvalues and eigenvectors. The model and algorithm can also be used to predict the stiffness of the system with respect to voltage fluctuations during operation View full abstract»

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  • Development and implementation of a variable-window algorithm for high-speed and accurate digital distance protection

    Page(s): 383 - 389
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    The paper describes a new variable-window algorithm suitable for microprocessor-based high-speed distance protection. It is designed to calculate the apparent impedance while the data window is increased to a desired size after fault occurrence. High-frequency and DC transient characteristics are extensively investigated. The results of real-time testing show the improved performance in both operating time and reach accuracy View full abstract»

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  • Electricity restriction costs

    Page(s): 299 - 304
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    This paper presents a summary of the main results obtained in the first survey of consumers carried out in Brazil on the subject of electricity interruption costs. First, the broad idea related to energy restriction costs is discussed and the conceptual differences between each kind of restriction is reviewed (e.g. interruption costs, deficits costs and `no-billing' costs). The survey methodology is briefly described and the main results are given. For the sake of comparison, a set of results from other countries (USA, Canada) are discussed. A numerical example is given to highlight a practical application. Finally, the combined use of electricity restriction costs is discussed View full abstract»

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  • Electrical arc ignition in narrow slots: high-voltage generation

    Page(s): 263 - 269
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    A narrow-slot fuse can be used to commutate current to a parallel connected varistor for which a high fuse arc power is required. During the voltage rise two characteristic periods are observed. The first is dominated by the fuse element decomposition process, and the second by axial flow development and metal vapours removal. In the first period the energy accumulation in the arc column is of importance. It is influenced by a radial mass shift and very high pressure of the fuse element vapours. In that time, the axial gas-flow is negligible. Relations between fuse dimensions, plasma parameters and the ignition voltage rate of rise are presented. The fuse element surface evaporation, its deformation and the arc length development have been considered View full abstract»

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  • Genetic algorithm solution to the economic dispatch problem

    Page(s): 377 - 382
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Two genetic algorithm (GA) solutions to the economic dispatch problem are presented. An advantage of the GA solutions is that they do not impose any convexity restrictions on the generator cost functions. Another advantage is that GAs can be very effectively coded to work on parallel machines. Test results with systems of up to 72 generating units with nonconvex cost functions show that both GAs outperform the dynamic programming solution to the economic dispatch problem. Furthermore, the execution time of the second GA solution increases almost linearly with the number of generators View full abstract»

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