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Generation, Transmission and Distribution, IEE Proceedings-

Issue 6 • Date Nov 1995

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Displaying Results 1 - 18 of 18
  • Automatic map reading for distribution system design

    Page(s): 549 - 554
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The paper describes how an architect's map is understood and used to give an electrical equivalent indicating the position and magnitude of electrical loads. The work shows that all of the houses on a map can be recognised, even for occluded and noisy cases, by the use of several basic image processing techniques. The road layout, which consists essentially of long narrow strips, is recognised also. This information may be passed directly to the distribution system design software View full abstract»

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  • Reconfiguration of radial distribution networks: application of heuristic methods on large-scale networks

    Page(s): 631 - 638
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (916 KB)  

    Heuristic methods for the reconfiguration of radial distribution networks have been presented by several researchers. The objective of the studies involved is either to minimise resistive line losses during normal operation, or to balance load and relief overloads, e.g. during service restoration procedures. In the paper the two basic strategies employed and the adequate methods developed for both objectives are presented, improved and generalised. An efficient approach to the load balancing problem, using switch exchange operations, is presented. An overall algorithm for the reduction of the size of the network model without decreasing computations accuracy of all methods is also presented. The adequate computer programs are applied on a real, large-scale 20 kV Greek network, for the optimisation of its operation under normal operating conditions and after the occurrence of an outage. General conclusions are drawn regarding the comparison of the two strategies as modelled in the paper and the opportunities network reconfiguration offers for operation improvement View full abstract»

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  • Modelled operation of the Shetland Islands power system comparing computational and human operators' load forecasts

    Page(s): 555 - 559
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    A load forecasting technique, based upon an autoregressive (AR) method is presented. Its use for short term load forecasting is assessed by direct comparison with real forecasts made by human operators of the Lerwick power station on the Shetland Islands. A substantial improvement in load prediction, as measured by a reduction of RMS error, is demonstrated. Shetland has a total installed capacity of about 68 MW, and an average load (1990) of around 20 MW. Although the operators could forecast the load for a few distinct hours better than the AR method, results from simulations of the scheduling and operation of the generating plant show that the AR forecasts provide increased overall system performance. A detailed model of the island power system, which includes plant scheduling, was run using the AR and Lerwick operators' forecasts as input to the scheduling routine. A reduction in plant cycling, underloading and fuel consumption was obtained using the AR forecasts rather than the operators' forecasts in simulations over a 28 day study period. It is concluded that the load forecasting method presented could be of benefit to the operators of such mesoscale power systems View full abstract»

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  • Generation, Transmission and Distribution

    Page(s): 0_3 - 0_4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (92 KB)  

    First Page of the Article
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  • Reactive power/voltage control in a distribution substation using dynamic programming

    Page(s): 639 - 645
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The reactive power/voltage control in a distribution substation is investigated. The purpose is to properly dispatch the shunt capacitors and onload tap changers at the distribution substation based on the forecast hourly loads of a main transformer and its primary bus voltage such that the reactive power flows through the main transformer, and the transformer secondary bus voltage deviations from the desired values can be minimised. Practical constraints on secondary bus voltage limits and the maximum allowable number of switching operations in a day for the onload tap changers are taken into account. An approach based on dynamic programming is presented to reach the desired dispatching schedule. To demonstrate the usefulness of the proposed approach, reactive power/voltage control in a distribution substation within the service area of Taipei City District Office of Taiwan Power Company is performed. It is found that a proper dispatching schedule for the shunt capacitors and onload tap changers can be reached by the proposed method View full abstract»

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  • Optical fibre investigation of the arc dynamics of a spiral arc current limiting interrupter

    Page(s): 608 - 612
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    An optical fibre system with 48 optical fibre probes, a 48-line digital input/output card and software to import 48 bits of data at a data acquisition rate of 42×103 samples/s has been developed and used to investigate the arc dynamics of a spiral arc current-limiting interrupter. Arc position, arc velocity and the current interrupting characteristics for two separate electrode configurations, ring-ring and rod-ring, were analysed using experimental results. A cylindrical test chamber with 115 mm height between the electrodes and 270 mm circumference gave an average arc root velocity of over 100 m/s and an arc root rotation of about ten times per cycle. The effect of electrode polarity, slot size and overall design parameters on the performance of the spiral arc current-limiting interrupter were considered View full abstract»

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  • Efficient heuristic partitioning algorithm for parallel processing of large power systems network equations

    Page(s): 625 - 630
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    An efficient heuristic algorithm for automatic partitioning of a power system network is presented. The algorithm was designed for use in conjunction with a diakoptics-based coarse grain parallel method for solving large, sparse linear systems arising from network analysis. It exploits the techniques of factorisation path graph partitioning and equivalent post-ordering. Test results for systems up to 811 busbars and 1476 transmission lines are included for comparison purposes. This indicates that the method is able to divide a power system network model into a number of equal sized subnetworks in order to optimise the use of parallel computer systems for network analysis while the resultant number of fill-in elements is kept to a minimum View full abstract»

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  • Performance comparison of the three-phase active-power-filter algorithms

    Page(s): 646 - 652
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    A three-phase active-power-filter algorithm is proposed. Its performance is simulated and compared with that of two typical three-phase active-power-filter algorithms, an instantaneous-reactive-power algorithm and a synchronous-detection algorithm under ideal and nonideal conditions. The simulation results indicate that the performance of the proposed algorithm is better than that of the conventional algorithms. A prototype is developed to demonstrate the performance of the proposed three-phase active-power-filter algorithm. The test results show that the performance of the proposed algorithm is satisfactory View full abstract»

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  • Efficient computation of rodbed grounding resistance in a homogeneous earth by Galerkin's moment method

    Page(s): 653 - 660
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    This paper computes the grounding resistance of rodbeds in a homogeneous earth by a moment method with Galerkin's approach. The self and mutual resistances matrix result is quite small. It shows that an N rod assembly requires only an N×N matrix. The resistance of the rodbed grounding system calculated using this method has a percentage difference of less than 2% from the point matching moment method. Galerkin's moment method does not match the boundary potential at one point of a segment, but matches the boundary potential that is averaged over the whole segment. Such a simple change in the moment method makes the method variational and results in a very small error even with a substantial saving in computation effort. The effects of various system parameters on the rodbed parameters (such as rod sunken depth, rod length and radius, rod spacing, rodbed configuration, and number of the rods) are investigated and discussed in detail. The paper ends with a discussion on the accuracy of the surface ground potentials with the coarse segmentation of one segment per rod View full abstract»

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  • An investigation into breaker reclosure strategy for adaptive single pole autoreclosing

    Page(s): 601 - 607
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    The effectiveness of single pole autoreclosure (SPAR) in maintaining power system stability is largely determined by the speed with which secondary arc extinction, and hence autoreclosure, can be achieved. Some work in adaptive autoreclosure has introduced the strong possibility of bringing some measure of adjusting dead times by accurately identifying arc extinction times. However, although the secondary arc extinction time provides a good indication of when to reclose, reclosure of the circuit breakers immediately following arc extinction will normally result in a restrike of the fault. This is because a further finite time is required to allow the fault arc path to deionise fully, so that the transmission line may withstand the full system voltage on reenergisation. The paper is thus concerned with identifying the length of this additional delay period (after secondary arc extinction), so that in conjunction with adaptive autoreclosure techniques, the optimal reclosure time can be determined View full abstract»

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  • Computer analysis of small-signal stability of power systems including network dynamics

    Page(s): 613 - 617
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    The paper describes a comprehensive approach for computer formulation of power system linearised state equations that also include those of the transmission network. Based on this formulation, an eigen analysis package for investigation of high-frequency (above 5 Hz) dynamics has been developed. The salient feature of formulation is that it allows modular addition and variation of component models, without rearrangement of the overall state space formulation. The package provides a flexible tool for systematic analyses of small-signal stability impacts of novel devices, e.g. power electronic apparatus and their controllers. The paper also presents an application of the state space formulation and the eigen analysis package for a multi-SVC system View full abstract»

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  • Fuzzy-logic-based VAr stabiliser for power system control

    Page(s): 618 - 624
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    The paper presents a new approach to the design of a robust controller for the auxiliary control loop of a static VAr system using both fuzzy logic and variable structure system (VSS) concepts. Also, the design of a simple fuzzy controller using the least number of rules for stabilisation of a synchronous generator connected to a large power system is presented. The performances of fuzzy, variable structure fuzzy and VSS stabilisers are compared with a conventional stabiliser for a variety of transient disturbances, highlighting the effectiveness of these stabilisers in providing significant damping to the system oscillations View full abstract»

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  • Team algorithms in distributed load flow computations

    Page(s): 583 - 588
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    This paper reports the use of a general technique to combine several different methods to solve complex systems of algebraic equations in the context of load flow calculations of electrical power networks. Such a combinations of methods, referred to as `team algorithms', seem specially well suited to be used with distributed memory computer systems, in an asynchronous environment. Experimental results solving example problems in a commercially available parallel computer system show that a `synergetic effect' with considerable speedup can be obtained using these `team algorithms' View full abstract»

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  • Unit commitment by parallel simulated annealing

    Page(s): 595 - 600
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    The paper investigates the application of parallel simulated annealing for unit commitment problems. Two parallel simulated annealing concepts, speculative computation and serial subset, are applied to a unit commitment problem of ten thermal generators. The authors also propose a combined scheme where speculative computation is used in the initial phase and the serial subset is used in the final phase. The parallel simulated annealing schemes are tested with an example problem and the results show that the parallel schemes can considerably speed up the computation of simulated annealing View full abstract»

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  • Corrective action planning to achieve a feasible optimal power flow solution

    Page(s): 576 - 582
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    Increased loadings in most power systems sometimes lead operation into the infeasible region, particularly following a severe contingency. In this situation, optimal power dispatch may not remain feasible. It is important to develop a technique to both quantify the degree of infeasibility and to provide recommendations to return the system operation into the feasible region. Such an algorithm is developed in the paper based on an optimisation technique and eigenvalue analysis. The proposed method has been tested on three sample systems and can be effectively used for corrective action planning to ensure feasible optimal operation of the system View full abstract»

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  • Detection of Jacobian singularity and network islanding in power flow computations

    Page(s): 589 - 594
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The paper provides a tool to investigate the occurrence of Jacobian singularities in power flow computations by Newton methods. In particular, a numerical procedure is presented that establishes the rows or columns of the Jacobian matrix that are linearly dependent. The method proposed is straightforward and may be easily implemented as an extension of any existing factorisation routine. Although the results presented are general, attention is focused on the detection of network islanding in the base case power flow or following a branch outage: the buses belonging to an island are identified at the cost of only one backward substitution computation. Examples of application of the procedure are shown with reference to a small network. Tests were successfully carried out using medium and large scale systems View full abstract»

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  • Power-demand forecasting using a neural network with an adaptive learning algorithm

    Page(s): 560 - 568
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    An artificial neural network with an adaptive-Kalman-filter-based learning algorithm is presented for forecasting weather-sensitive loads. The proposed model can differentiate between weekday and weekend loads. This neural-network model has been implemented using real load data. The results reveal the efficiency and accuracy of the proposed approach in terms of short learning time, rapid convergence and the adaptive nature of the learning algorithm View full abstract»

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  • Hydro-dominated short-term hydrothermal scheduling via a hybrid simulation-optimisation approach: a case study

    Page(s): 569 - 575
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    The paper is concerned with the problem of short-term hydrothermal scheduling for hydro-dominated power systems. The problem is to determine hydro and thermal generation scheduling for a day or a week ahead, usually on an hourly basis, simultaneously satisfying hydraulic, thermal and electrical operational constraints while optimizing a criterion of performance. Reservoir release targets suggested by mid/long-term operational planning models are also considered. The paper presents a case study based on a hybrid optimisation-simulation approach. The procedure consists of hydraulic system simulation on an hourly basis, with release decisions based on optimal DC power flow. Reservoir release targets are enforced through a dual-penalty approach which assigns shadow costs to hydro generation. The case study was conducted using part of the Brazilian interconnected power system and progressively developed through the use of various scripts. The study provides an insightful analysis of the nature of the problem and reveals a practical and efficient technique for its solution View full abstract»

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