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Generation, Transmission and Distribution, IEE Proceedings-

Issue 1 • Date Jan 1994

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Displaying Results 1 - 11 of 11
  • Magnetic field analysis of asymmetrical machines by finite element method

    Page(s): 53 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Magnetic and electric asymmetry have been used by many electrical machine designers to develop useful devices. The main feature of such designs is the nonsinusoidal variation of the magnetic field with time. The effect of harmonics on the overall performance is normally studied analytically either by using the symmetrical components method or the rotating field concept. Both methods lead to a cascade type equivalent circuit which can be used to predict performance and as an aid to optimise the design. For accurate analysis, however, a detailed simulation of the magnetic field distribution is needed. This would normally require the time stepping finite element method. In this paper, a simple finite element technique to solve nonlinear time periodic magnetic field problems in asymmetrical electrical machines is proposed. The approach is based on a steady-state magnetodynamic formulation together with application of harmonic balance to the diffusion equation. The theory is verified on a special low speed generator with asymmetry on both stator and rotor View full abstract»

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  • Modelling risk in energy contracts with investor owned generation

    Page(s): 75 - 80
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    Investor owned generation capacity construction is being encouraged all over the world by both the current deregulatory climate and the need to defray the heavy capital demands of plant. Such schemes require contracts between investor and host utility on the price of electricity, and may include penalties for nondelivery, and compensation for failure to accept contracted energy. While it is widely appreciated that uncertainty of future conditions has an important bearing on what the terms of the contract should be, a theoretical framework for examining the influence of uncertainty has not, as yet, been developed for this problem. This paper proposes a theoretical model for linking the degree of future uncertainty, the expected production costs of investor plant and the expected production cost of host utility, with the electricity prices and penalty charges which are stipulated in the energy contract between the two parties. The insight gained from these mathematical models will be useful in contractual decision making View full abstract»

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  • High-voltage fuse behaviour with varistor commutation

    Page(s): 33 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    Expulsion fuse operation using parallel connected ZnO varistors for current commutation offers new protection opportunities for this simple switching element. The advantages of low cost and full-range protection can be retained with the addition of current limitation and hence almost unlimited breaking capacity. Pad-mounted and cubicle applications may also be possible. The relations among varistor voltage, fuse element cross-section, fault current, circuit conditions and energy dissipated during current breaking operation have been analysed. It has been found that maximum energy dissipated by a fuse-varistor arrangement depends on the fuse element cross-section and the varistor voltage; these parameters play crucial roles in fuse dimensioning View full abstract»

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  • Brushless exciter model

    Page(s): 61 - 67
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The IEEE model of a brushless exciter can be found in many software packages for the simulation of power system behaviour. Yet the model is simplistic and does not represent the exciter alternator accurately. This paper describes the reasons for the inaccuracy of the IEEE representation and proposes an alternative model. Good agreement is obtained between results from a micromachine test system and the alternative model View full abstract»

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  • Integer-linear-programming eigenvector-based approach for multipartitioning power system state-estimation networks

    Page(s): 11 - 18
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    Heuristic algorithms are developed to partition an observable power system state estimation (PSSE) network into two or more observable subnetworks. The proposed heuristic algorithms partition a spanning tree of an observable PSSE network and guarantee the observability of all the partitioned subnetworks. These partitioning algorithms are based on using an integer-linear-programming eigenvector-based approach to have a good initial partition, and then on using an interchange method to obtain the optimal partition. The performance of these heuristic algorithms are evaluated by using several IEEE standard networks View full abstract»

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  • Analysis of transformer-generator interaction in the harmonic domain

    Page(s): 38 - 46
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The harmonic interaction between the synchronous generator rotor and stator and the electromagnetic transformer nonlinearities is simulated by a unified harmonic domain equivalent. Comparisons are made between conventional models and a detailed harmonic domain solution that incorporates the process of generator frequency conversion and magnetic saturation, multilimb transformer core saturation, electrical winding connections, mutual coupling between windings and harmonic contribution of the transmission network View full abstract»

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  • Application of GTO voltage-source inverter for tapping HVDC power

    Page(s): 19 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The application of a 12-pulse GTO voltage-source inverter (VSI) for tapping a small amount of HVDC power (10-15%) is investigated. The control strategy for a parallel multiterminal DC power system is briefly reviewed. A comparison of VSI and line-commutated inverter characteristics indicates that the GTO VSI offers some technical advantages for tapping applications. To confirm this, detailed digital time-domain simulations based on the Electromagnetic Transients Program for DC power systems are conducted. The simulated responses of the HVDC system embedding the GTO VSI tap under various planned and unplanned disturbances, demonstrate the technical feasibility of a small parallel tap using a GTO VSI. In addition, control strategies and protection requirements are identified for the proposed HVDC tap View full abstract»

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  • Fast harmonic power flow calculation using parallel processing

    Page(s): 27 - 32
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    The paper presents a novel approach to the study of power system harmonics, in which advantage is taken of the fact that the coupling between harmonics of different orders is negligible. Parallel processing techniques are adopted for the first time to solve this problem and it is shown that considerable savings in computing timings can be achieved. The results of simulations performed with the program are compared with measurements on a real system to validate the approach. The system is modelled using phase coordinates and frequency dependence of the parameters and this allows the program to deal with difficult problems such as the unbalanced flow of harmonic currents, electromagnetic coupling between phase quantities etc. The solution process utilises sparse techniques applied to 3×3 blocks which ensures better numerical stability View full abstract»

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  • Economic emission load dispatch with line flow constraints using a classical technique

    Page(s): 1 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    An attempt is made to explore the feasibility of developing an approach to solve the power system economic emission load dispatch (EELD) problem with line flow constraints using a classical technique based on co-ordination equations. The inability of the classical technique to handle the line flow constraints so far is circumvented innovatively by expressing the line flows in terms of active power generations through distribution factors. These distribution factors are elegantly developed from existing load flow information using a perturbation technique. The proposed model based on the classical technique for EELD is tested on IEEE 14- and 30-bus test systems and the results are compared with those obtained by quadratic programming, the Hessian method, the Ricochet gradient method and the linear programming method View full abstract»

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  • Consideration of dependent outages in security-constrained adequacy evaluation of composite systems

    Page(s): 47 - 52
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    A security-constrained adequacy evaluation technique for composite power systems to include the effect on the adequacy indices of dependent outages of system components is presented. The effect of these outages on the reliability indices at different load levels is examined and compared. The resulting system indices can be used to provide a physical appreciation of the various factors that influence the actual system reliability, and to alleviate some of the difficulties encountered by both power system planners and operators with traditional adequacy evaluation View full abstract»

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  • Parallel processing of sparse power system equations

    Page(s): 68 - 74
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    Algorithms for parallel computation of the sparse matrix equations found in power system modelling are discussed and evaluated. A number of matrix factoring algorithms have been applied to a 60-busbar power system network with useful results. The greatest speed-up was achieved by a method that matches the number of parallel activities to the number of processors available. The PERT-based scheduling algorithm works well for small problems and should give useful results for larger networks View full abstract»

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