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Generation, Transmission and Distribution, IEE Proceedings-

Issue 5 • Date Sep 1994

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Displaying Results 1 - 20 of 20
  • High-performance controllers for HVDC transmission links

    Publication Year: 1994 , Page(s): 422 - 428
    Cited by:  Papers (18)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    The paper presents the design of a very simple fuzzy logic controller for HVDC transmission links for fast stabilisation of transient oscillations. The performance of this controller is compared with variable structure and adaptive controllers for a variety of short circuits and system operational changes. Unlike both adaptive and VSS controllers which require at least functionally an accurate model of the system dynamics, the fuzzy controller does not require a mathematical model of the system to estimate the control input under disturbance conditions. The transient simulation studies presented reveal the superior performance of the simple fuzzy controller in damping out system transients View full abstract»

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  • Genetic and genetic/simulated-annealing approaches to economic dispatch

    Publication Year: 1994 , Page(s): 507 - 513
    Cited by:  Papers (82)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    The paper first develops and presents the implementation of basic and incremental genetic-algorithm approaches for the determination of the global or near-global optimum solution for the economic dispatch problem. To improve the performances of these algorithms, another algorithm is developed based on the combination of the incremental genetic-algorithm approach and the simulated-annealing technique. This algorithm is then further developed to minimise the memory requirement. A method to overcome the discretisation problem in encoding generator loadings is proposed. A method for ensuring that the dispatch solutions generated in the solution process are feasible and valid is included in the algorithms. The developed algorithms are demonstrated through their applications to determine the economic loadings of 13 generators in a practical power system. In the application study, the effects of valve-point loading and ramping characteristics of the generators are taken into account. The developed algorithms are shown to be general and are computationally faster than the earlier simulated annealing-based method View full abstract»

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  • Probabilistic approach to transient stability evaluation

    Publication Year: 1994 , Page(s): 537 - 544
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    A new probabilistic approach to transient stability evaluation of electrical power systems is proposed. The method is relevant to planning studies, where load level is a major source of uncertainty. The probabilistic nature of both the load demand and the circuit breaker operating time is taken into account for the purpose of obtaining analytical evaluation of the instability probability. The approach is based upon the analytical computation of the probability distribution function of the critical clearing time for stability in terms of the load demand distribution. It allows the expression of the instability probability as an analytical function of all the relevant system parameters. The-method is illustrated with reference to a simple (one machine-infinite bus) system, and the results are compared with those obtained by means of statistical (Monte Carlo) simulation. The time requirement of the two methods is comparable, but the proposed analytical approach offers a remarkable advantage over the Monte Carlo method for a sensitivity analysis with respect to the system parameters View full abstract»

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  • SVD technique for estimation of harmonic components in a power system: a statistical approach

    Publication Year: 1994 , Page(s): 473 - 479
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The paper presents a statistical approach to the estimation of harmonic components in a power system. Mathematically it is based on singular value decomposition (SVD). Three different techniques are investigated: the standard averaged SVD, the total LS and double SVD. The results of numerical experiments illustrating the features of all these approaches are presented and discussed View full abstract»

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  • Effect of the battery energy storage system on the time-of-use rates industrial customers

    Publication Year: 1994 , Page(s): 521 - 528
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The paper develops a new algorithm known as advanced multi-pass dynamic programming (AMPDP), and it applies this algorithm to the solution of the optimal operation schedule of the battery energy storage (BES) system of time-of-use rates industrial customers. A suitable BES model is also presented. Two industrial customers with one year of recorded load curves are used as examples to test this algorithm. The results show that this algorithm can quickly converge to the optimal operation schedule while meeting all constraints. Therefore, the effect of BES on the time-of-use rates industrial customers can be studied View full abstract»

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  • Thermal unit commitment using genetic algorithms

    Publication Year: 1994 , Page(s): 459 - 465
    Cited by:  Papers (33)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Unit commitment is a complex decision-making process because of multiple constraints which must not be violated while finding the optimal or near-optimal commitment schedule. The paper discusses the application of genetic algorithms to determine the short-term commitment order of thermal units in power generation. The objective of the optimal commitment is to determine the on/off states of the units in the system to meet the load demand and spinning reserve requirement at each time period, such that the overall cost of generation is minimised, while satisfying various operational constraints. The paper examines the feasibility of using genetic algorithms, and reports preliminary results in determining a near-optimal commitment order of thermal units in a studied power system View full abstract»

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  • Computational study of very fast transients in GIS with special reference is effects of trapped charge and risetime on overvoltage amplitude

    Publication Year: 1994 , Page(s): 485 - 490
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Very fast transient phenomena in gas insulated substations (GIS) have been studied by computer simulation. The influence an overvoltage amplitude of trapped charge, risetime and section length of GIS is described. Under identical conditions, the amplitudes of overvoltages caused by very fast transients at the same point in a circuit, but having different trapped charges, are connected by a simple relation due to the linear nature of the circuit. In the case of high predicted overvoltages, the assumption of 1 pu trapped charge causes a large overestimation of the overvoltage which can be in excess of 20%, in comparison with the overvoltage due to 0.4 pu trapped charge, a value which, in practice, is rarely exceeded. For an open ended circuit, the assumption of zero risetime can cause an overestimation of more than 30% in the overvoltage in comparison with the case of 5 ns or more risetime. Variation of the trunk section length has a greater effect on the overvoltages than that of a branch section. The difference in the overvoltages at an open end for various section lengths can be in excess of 50%. In some cases even a small variation of section length causes a very large change in overvoltages View full abstract»

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  • A parallel processing algorithm for co-ordination of directional overcurrent relays in interconnected power systems

    Publication Year: 1994 , Page(s): 514 - 520
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The problem of coordinating the setting of directional overcurrent relays in an interconnected power system is considered. The power system is decomposed into subsystems to give a constraint matrix of a diagonal structure with linking variables. Each subsystem is solved using the sparse dual revised simplex algorithm of linear programming. Benders algorithm for linear programming may be used to coordinate the solution from each subsystem and the master system. The authors propose a new parallel processing algorithm for this coordination procedure which depends on the interaction balance principle of linear programming. This algorithm has been applied to various size systems and the results compared with those obtained using a conventional linear programming algorithm and Benders algorithm. It is shown that the proposed algorithm is more computationally efficient than previous methods View full abstract»

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  • Substation power-transformer-loading analysis and computer simulations of loadability under realistic operating conditions

    Publication Year: 1994 , Page(s): 413 - 421
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    Transformer loading analyses and computer simulations of transformer thermal behaviour under realistic/typical operating conditions (loading and ambient-temperature profiles) indicate that substation (DS) power transformers in Ontario Hydro can be loaded to 1.8-1.9 p.u. Of the ratings during annual (winter) peak load periods without sacrifice of normal transformer life expectancy or reliability of supply to achieve the goal of making the best use of transformer capabilities. Adoption of the proposed increases in loading limits will result in a significant cost saving for Ontario Hydro, estimated at $4,500,000 (NPV 1991 Canadian dollars) over three years (of a reduction of $10,000,000 per year on DS capital cost) View full abstract»

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  • Adaptive load shedding for isolated power systems

    Publication Year: 1994 , Page(s): 491 - 496
    Cited by:  Papers (27)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Emergency control of frequency in an isolated power system is considered. In many such systems, limited load shedding is permitted under certain generation loss conditions to reduce the expense of spinning reserve provision. It is important in these circumstances to minimise consumer disruption through proper-design of the load shedding arrangements. An adaptive load shedding scheme is proposed, based on intelligent relays supplied with updated values of key system parameters in addition to the usual measurement of frequency. Results are presented to demonstrate the ability of the proposed scheme to reduce potential load shedding to a value close to the theoretical minimum View full abstract»

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  • Predictive assessment of bulk-system-reliability performance indices

    Publication Year: 1994 , Page(s): 466 - 472
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The past reliability performance of a bulk electricity system can be quantified using a wide range of indices. There is also a wide range of available techniques for predicting the future performance of a bulk system. There appears, however, to have been relatively little attention given to attempting to predict indices in the same form as those actually measured. The paper examines the general concepts associated with past-performance and predictive-assessment indices and illustrates by application to two systems how this linkage can be established View full abstract»

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  • Speedup and synchronisation overhead analysis of Gauss-Seidel type algorithms on a Sequent balance machine

    Publication Year: 1994 , Page(s): 437 - 444
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    The parallelisation and implementation of Gauss-Seidel (G-S) algorithms for power flow analysis have been investigated previously. Numerous runs to demonstrate the speedup have been illustrated on a Sequent Balance shared-memory multi-instruction, multidata access (SM MIMD) machine. The authors extend the idea and investigate-the effects of acceleration factors. It is shown on systems ranging from teens to thousands that when the acceleration factors are used, the implementation using colour-by-colour synchronisation is more reliable and has better convergence rate, even though it takes a longer time to synchronise. The authors also analyse the dependence of synchronisation overhead in terms of system sizes, network connection and number of processors. Comparisons between G-S and fast decoupled load-flow algorithms are also made. The implications on nCUBE implementations are also discussed. It is also shown that the idea of parallel G-S algorithm can be easily extended to solve the transient stability problem which involves a set of algebraic differential equations View full abstract»

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  • Short-term hydrothermal scheduling part. I. Simulated annealing approach

    Publication Year: 1994 , Page(s): 497 - 501
    Cited by:  Papers (35)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The paper develops a short-term hydrothermal scheduling algorithm based on the simulated annealing technique. In the algorithm, the power balance constraint, total water discharge constraint, reservoir volume limits and constraints on the operation limits of the hydrothermal generator and the thermal generator are fully accounted for. The relative operation capacities of the hydroplant and the thermal plant are also considered. A relaxation method for checking the limits is proposed and included in the algorithm. The performance of the algorithm is demonstrated through a test example View full abstract»

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  • Generalised convertor models for iterative harmonic analysis in power systems

    Publication Year: 1994 , Page(s): 445 - 451
    Cited by:  Papers (18)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    There is an increasing interest in steady-state analysis of electric power systems with convertors. Harmonic analysis can be performed in the frequency domain with iterative methods that are comprehensive and efficient but may present convergence problems; this drawback can be overcome by employing appropriate models of convertors. The authors present steady-state mathematical models of line commutated convertors to be included in an iterative harmonic analysis of a power system. To avoid convergence problems and to save the accuracy of the results as well as the computational efficiency, the models are developed including AC and DC frequency dependent impedances and by solving AC and DC side equations as a whole, thus keeping a closed form solution. All nonideal conditions are taken into account View full abstract»

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  • Global robust adaptive control of power systems

    Publication Year: 1994 , Page(s): 429 - 436
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A robust, adaptive control scheme is presented which stabilises a nonlinear model of a power system to disturbances anywhere in the power system. The control is local, in the sense that the control of each machine depends only on information available at the machine. Simulation results are presented which show that the control is very effective against instabilities of current importance such as sustained oscillations following a major system disturbance View full abstract»

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  • Studies on impulse behaviour of a transformer winding with simulated faults by analogue modelling

    Publication Year: 1994 , Page(s): 401 - 412
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    The paper highlights some critical observations made in the course of investigations on surge performance of a transformer winding by analogue modelling. The studies cover winding responses to both full and chopped standard lightning impulses where time-to-chop was varied over a wide range to find the maximum stresses across winding discs. Three specific zones along the winding were selected for studies. These were the line-end and earth-end sections each spanning about 6% of the entire winding length, while the midwinding disc was chosen to represent the midwinding section. Two types of faults were simulated: series faults both permanent and voltage-dependent; and parallel faults through resistance with preset faulting levels. Winding responses to faults under impressed impulses were observed and scanned using both neutral-current (Hagenguth) and tank-current methods of fault detection. Important observations are corroborated by oscillograms of winding responses. The results suggest and confirm appropriate methods of fault detection on fault occurrence in the specified sections along the winding View full abstract»

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  • Short-term hydrothermal scheduling. II. Parallel simulated annealing approach

    Publication Year: 1994 , Page(s): 502 - 506
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    For pt.I see ibid., vol.141, no.5, p.497-501 (1994). The paper develops a coarse-grained parallel simulated annealing algorithm for short-term hydrothermal scheduling. The design of the algorithm has taken into consideration load balancing, processor synchronisation reduction, communication overhead reduction and memory contention elimination. The parallel algorithm is implemented on an i860 processor in a simulated environment and is applied to a test example. The scheduling results are presented and are compared with those found by a sequential algorithm. The results indicate that the algorithm can achieve a near linear reduction in computation time View full abstract»

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  • Scheduling of hydroelectric generations using artificial neural networks

    Publication Year: 1994 , Page(s): 452 - 458
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    An approach based on artificial neural networks (ANNs) is proposed for the scheduling of hydroelectric generations. The purpose of hydroelectric generation scheduling is to figure out the optimal amounts of generated powers for the hydro units in the system for the next N (N=24 in the work) hours in the future. Input data include system hourly loads and the natural in flow of each reservoir. In the proposed ANN approach, a clustering ANN is first developed to identify those days with similar hourly load patterns and natural inflows. These days with similar load patterns and inflows are said to be of the same group. A total of four groups are used in the work. Then a multilayer feedforward ANN is developed for each group to reach a preliminary generation schedule for the hydro units. Since some practical constraints may be violated in the preliminary schedule, a heuristic rule based search algorithm is developed to reach a feasible suboptimal schedule which satisfies all practical constraints. The effectiveness of the proposed approach is demonstrated by the short-term hydro scheduling of Taiwan power system which consists of 10 hydro plants. It is concluded that the proposed approach is very effective in reaching proper hydro generation schedules. Moreover, the proposed approach is much faster than conventional dynamic programming approach View full abstract»

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  • Ignition of an electrical arc in a capillary: arc parameters in the initial period

    Publication Year: 1994 , Page(s): 480 - 484
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    Fuse-to-varistor current commutation offers considerable promise for easier and cheaper high fault current interruption in distribution systems. Commutation relies on the fast generation of high voltages by the fuse. The fuse arc ignition period has been examined, with an emphasis on expulsion fuses. In the paper, relationships between the energy of the fuse arc ignition, the arc pressure and the peak voltage are presented and compared with experimental data. It is demonstrated that the actual arc length, energy and pressure are all proportional to each other. The arc length was approximately determined using streak records available in the literature. During the ignition period it was found that the sum of the length of individual arcs increased as a function of the time squared. It was also established that the pressure rise in capillary confinements is due to vaporisation of the fuse element rather than the walls of the enclosure View full abstract»

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  • A new numeric technique for high-speed evaluation of power system frequency

    Publication Year: 1994 , Page(s): 529 - 536
    Cited by:  Papers (48)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A new numerical technique for evaluating power system frequency from either a voltage or current signal is presented. The technique uses discrete time values of the input signal, taken at a fixed sampling rate, to provide an estimate of power system frequency accurate to within typically 0.001 Hz. The technique is shown to be capable of tracking frequency under dynamic power systems conditions and is immune to the effect of harmonics. It is further shown that the algorithm can be easily adapted to process three-phase signals such that the positive phase sequence component can be utilised thus increasing the reliability of the measurement under fault conditions View full abstract»

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