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Generation, Transmission and Distribution, IEE Proceedings-

Issue 4 • Date Jul 1995

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Displaying Results 1 - 16 of 16
  • Modelling multistate problems in sequential simulation of power system reliability studies

    Publication Year: 1995 , Page(s): 343 - 349
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    The paper presents a new approach for taking into account multistate units and common-mode outages in sequential Monte Carlo simulation. Although the state space transition diagrams for multistate units and common-mode outages are well established, they can only be utilised in random or nonsequential simulation, and not in sequential simulation. Using an equivalent or derating-adjusted forced outage rate for generating units instead of a multistate model can lead to pessimistic results. Usually, the common-mode failure rate is small compared with independent failure rates, but such failures may have severe consequences on the power system performance. Many utilities are, therefore, now using multistate and common-mode representations for composite power system adequacy analysis. The conventional sequential simulation is capable of evaluating composite generation-transmission systems without these failure modes. The effectiveness of the technique is demonstrated using several small examples. Also, the adequacy of the RBTS and the IEEE-RTS is evaluated, and the results are compared with those given by an analytical technique. These again demonstrate the applicability and effectiveness of the approach View full abstract»

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  • Application of synchronised phasor measurements to real-time transient stability prediction

    Publication Year: 1995 , Page(s): 355 - 360
    Cited by:  Papers (24)  |  Patents (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    With new systems capable of making synchronised phasor measurements there are possibilities for real-time assessment of the stability of a transient swing in power systems. In the future, online control will be necessary as operating points are pushed closer toward the margin and fast reaction time becomes critical to the survival of the system. A piecewise constant-current load equivalent (PCCLE) technique is developed which utilises synchronised phasor measurements to provide fast-transient stability swing prediction for use with high-speed control. A numerical simulation is conducted on IEEE 39-bus system equipped with ten phasor measurement units to test the effectiveness of the PCCLE technique View full abstract»

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  • Controlled series compensation for improving the stability of multi-machine power systems

    Publication Year: 1995 , Page(s): 361 - 366
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    The application of controlled series compensators (CSCs) to increase the damping of dynamic oscillations in multimachine power systems is described. A CSC controller design is presented based on a linearised model of the power system around a given nominal operating point. The pole placement technique is used for calculating the controller feedback gains. A procedure for determining an optimum location for installing a CSC in a power system to provide the most effective damping is investigated. A technique for coordinating CSCs when it is necessary to use more than one CSC in a power system is also discussed. Computer simulations are used to demonstrate the effectiveness of CSCs in increasing the damping of power system dynamic oscillations. A simple power system with nine buses and three synchronous machines is used to demonstrate the design procedure View full abstract»

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  • Neural network-based algorithm for power transformer differential relays

    Publication Year: 1995 , Page(s): 386 - 392
    Cited by:  Papers (38)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    A neural network-based algorithm for the protection of a one-phase power transformer is considered. The neural network input is a four-dimensional vector obtained by a fast-frequency analysis of the differential current. Primary and secondary currents are measured with current transformers the saturation of which is taken into account. A set of training cases is generated with the help of the electromagnetic transients program. The neural network-based algorithm is compared with a conventional differential algorithm. It is found to be more efficient, especially in the case of saturation of the current transformers View full abstract»

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  • Effect of radiative and convective heat transfer on thermal transients in power cables

    Publication Year: 1995 , Page(s): 436 - 444
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A model to study the thermal behaviour of a system of directly buried electrical power cables is presented. The model completely describes the conditions of heat transfer at the soil-air interface. In particular, the different incidences that the various radiative components have on the evolution of temperature in the system examined are evaluated. The method is applied to the case of a three-phase line placed under a daily cyclic load, based on experimental observations made on a line with cable of similar characteristics. Different evaluations are carried out assuming different characteristics for the soil and the climatic conditions View full abstract»

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  • Security-constrained multiobjective generation dispatch using bicriterion global optimisation

    Publication Year: 1995 , Page(s): 406 - 414
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    The paper is devoted to the dynamic performance assessment and model reduction for longitudinal interconnected power systems. Based on this, simple expressions are established to represent variations of security levels with the power transfer between subsystems. These expressions are used to extend the authors' work on a bicriterion optimisation approach for determining the most appropriate generation-dispatch solution taking into account the fuel and environmental costs, and to provide security constraints/checks during optimisation View full abstract»

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  • Pertinent factors in the adequacy evaluation of an overall electric power system

    Publication Year: 1995 , Page(s): 337 - 342
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Reliability evaluation of generating facilities, composite generation and transmission systems, and of distribution systems, are usually conducted independently, and the reliability indices obtained for each assessment are used to make decisions on the facilities concerned. These assessments often assume the other parts of the system to be fully reliable and capable of performing their intended function. This form of analysis therefore gives an optimistic appraisal of the overall system behaviour. The paper considers the influence of element outages in all parts of an electric power system in order to obtain a more practical appraisal of the overall system indices. The relative contributions to the system indices of composite generation and transmission failures and distribution zone failures are also assessed. In particular, the impact on the system performance indices of pertinent factors such as load curtailment philosophy, contingency level, terminal station outages, additional generation and/or transmission and/or distribution facilities etc., are evaluated. The concepts associated with overall electric power system adequacy assessment are illustrated by application to a comprehensive test system View full abstract»

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  • Combined active and reactive despatch. I. Problem formulation and solution algorithm

    Publication Year: 1995 , Page(s): 393 - 400
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A fully coupled active-reactive despatch using linear programming is presented. The purpose of combined active and reactive despatch (CARD) is to achieve the overall objective of minimum generation cost and/or to improve other system parameters, subject to constraints that ensure system security. CARD allows a series of time steps to be considered. The duration of each time stage may be chosen so that despatching points occur at any critical points of the predicted load curve within the despatch period. The problem is expanded such that the linear program variables include the output at the end of each time step, with the objective function value integrated over all stages. System constraints are replicated at each time stage. Dynamic rate limits are also included. The reactive power despatch is regarded as static within each step, but is influenced by the generator active power rate of change limitations View full abstract»

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  • Hybrid expert system and simulated annealing approach to optimal reactive power planning

    Publication Year: 1995 , Page(s): 381 - 385
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The reactive power source planning problem has a significant influence on secure and economic operation in electric power systems. To achieve both goals, system maximum security and minimum cost in operation, reactive power planning is posed as a multiobjective optimisation problem in terms of mathematical language. In the paper, the authors present an effective algorithm based on hybrid expert system simulated annealing (ESSA) to circumvent the complicated planning problem. A more practical problem formulation with multiobjectives and constraints is presented. Then, ESSA is introduced to search the global optimal solution considering both quality and speed at the same time. Simulation cases are used to evaluate the proposed algorithm View full abstract»

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  • Dynamic modelling of battery energy storage system and application to power system stability

    Publication Year: 1995 , Page(s): 429 - 435
    Cited by:  Papers (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A useful and systematic dynamic model of a battery energy storage system (BES) is developed for a large-scale power system stability study. The model takes into account converter equivalent circuits, battery characteristics and internal losses. Both charging mode and discharging mode are presented. The model is expressed in equivalent transfer function blocks, and it can be easily used in dynamic stability analysis of a power system. To examine the dynamic behaviour of the model, applications to the damping of turbogenerator torsional oscillations are performed. Active and reactive power modulation by the BES can be controlled according to system requirements. Eigenvalue analysis and dynamic simulations are performed to demonstrate the damping effect of the BES View full abstract»

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  • Stochastic modelling of high-speed reclosing in probabilistic transient stability studies

    Publication Year: 1995 , Page(s): 350 - 354
    Cited by:  Papers (23)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The traditional design of a power system includes testing the stability of the system under specified basic contingencies. This `worst case' approach has been used widely and successfully by most power utilities. It is obvious that a wide range of contingencies are possible at any location in the system. This leads to the realisation that a stochastic approach could be used in the analysis to include the probabilities associated with all possible contingencies to obtain a more realistic appraisal of the system stability. A stochastic modelling for high-speed reclosing is presented, and two sets of probabilistic transient stability indices are introduced View full abstract»

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  • Combined active reactive despatch. Part 2: test results

    Publication Year: 1995 , Page(s): 401 - 405
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    A series of tests have been conducted on the combined active and reactive despatch algorithm presented in a companion paper. The ability of the algorithm to optimise the performance of the system and to maintain system variables and derived variables within their permissible limits is established. A further objective has been to assess the robustness and computational speed of the program. Five different objective functions have been tested, with the aim of investigating the impact on both generation fuel cost and security when different security measures are introduced alongside cost minimisation. These security measures are maximisation of reactive reserve margins, maximisation of load voltages, avoidance of voltage collapse, and improving the ability of the system to maintain higher system load. The overall objective function is a weighted combination of these various objectives View full abstract»

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  • Damping of subsynchronous oscillations using adaptive controllers tuned by artificial neural networks

    Publication Year: 1995 , Page(s): 415 - 422
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Artificial neural networks (ANNs) are utilised to adapt the controller gains of two widely used control schemes i.e. static VAr compensators (SVC) and excitation controllers (EC), for the damping of subsynchronous resonance (SSR) on a power system. To have good damping characteristics of SSR modes over a wide range of operating conditions, the parameters of the adaptive controllers are adapted based on generator loading conditions. Multilayer feedforward artificial neural networks (ANNs) are developed to serve for the purpose of controller parameter adaptation. The inputs to the ANN include the real power output P and reactive power output Q which characterise generator loading conditions. The outputs from the ANN are the desired controller gains. Time domain simulations are also performed on the IEEE first benchmark model to demonstrate the effectiveness of the proposed adaptive control schemes View full abstract»

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  • Thermal generator scheduling using hybrid genetic/simulated-annealing approach

    Publication Year: 1995 , Page(s): 372 - 380
    Cited by:  Papers (18)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    A hybrid genetic/simulated annealing approach is established for solving the thermal generator scheduling problem. It develops a method for encoding generator schedules in the hybrid approach. The method leads to a large chance of producing feasible schedules in the solution process. For the infeasible schedules produced, methods are developed to restore their feasibility. The methods developed are incorporated into the hybrid algorithm GAA2 for the determination of the most economical schedules. The original GAA2 developed previously is employed to access the cost of the generator schedules. The hybrid approach has the ability to deal with the nonconvexity of the scheduling problem. Its usefulness is demonstrated by its application to a real-life power system consisting of 13 generators View full abstract»

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  • Advances in global optimisation for generation expansion planning

    Publication Year: 1995 , Page(s): 423 - 428
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The paper brings together several important and practically relevant aspects of generation expansion planning in the context of restructuring and changing emphasis in the electricity supply industry. Expert planning judgements, consumer shortage cost differentials resulting in a need for different classes of service and price formation, and consumer price elasticity, are given consideration in the planning programme described. Effects of these factors on the final, or global, optimum are explored View full abstract»

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  • Identification of coherent generators by spectrum analysis

    Publication Year: 1995 , Page(s): 367 - 371
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    A new method of identifying the coherency of a group of generators using spectrum analysis technique is presented. First, the rotor angles of generators in the early part of the transients are predicted by the Taylor series expansion of the power system model. The values obtained are taken as sample data for the spectrum analysis with an FFT algorithm. The coherency criteria based on the spectra are presented and the coherent groups of generators can be quickly identified. A 34-bus 9-machine power system is used to illustrate that the proposed method is a fast and practical one View full abstract»

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