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Advances in Power System Control, Operation and Management, 1991. APSCOM-91., 1991 International Conference on

Date 5-8 Nov 1991

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Displaying Results 1 - 25 of 159
  • Identification of hunting frequency and equivalent transmission line impedance in a multi-machine system for stability applications

    Publication Year: 1991 , Page(s): 81 - 85 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    A generating unit in an interconnected power system often participates in both local and inter-area modes of oscillations. The spectral and temporal distributions of these modes are largely determined by the dynamics of the rest of the system. An adaptive stabilizer, capable of damping all modes of oscillation would require estimations of the dominant frequency of oscillation and the external equivalent line impedance as seen from the terminal of the machine concerned. The authors describe two new methods, one for identification of the external impedance and the other to obtain the power spectral density during hunting. The identified parameters are used in an adaptive PSS to evaluate it's performance in a multi-machine system. View full abstract»

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  • Fuzzy recognition of power system transient stability

    Publication Year: 1991 , Page(s): 367 - 372 vol.1
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    A fuzzy recognition approach to assess power system transient stability is presented by the author. The heuristic selection of primary variables gets rid of time-consuming offline computation. The approximate computation of system dynamic energy at the fault clearing time greatly enhances the computing speed but does not influence the correctness of the recognition results. An approach to recognise the power system machine that will first lose synchronism from other system machines is presented. This method is proved in a test system with 3 generators and 6 buses View full abstract»

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  • Sample size reduction in Monte Carlo based use-of-system costing of power systems

    Publication Year: 1991 , Page(s): 373 - 378 vol.1
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Accuracy of the results obtained through Monte Carlo based models greatly depends on the number of samples used in the simulation and the variance of the means of the associated random variables. Variance reduction techniques can be employed to reduce the sample size needed to achieve a given precision in the estimated values. Three such techniques, antithetic sampling, stratified sampling, and use of a control variable are investigated by the authors in the context of marginal costing of real powers. These methods have been implemented using a modified version of the IEEE 118 bus network and it is shown that the reduction in the sample size can exceed 75% in certain cases View full abstract»

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  • Neural network transient stability assessment of a single-machine system under asymmetrical fault conditions

    Publication Year: 1991 , Page(s): 572 - 577 vol.2
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The authors propose a neural network approach for transient stability assessment and for critical fault clearing time estimation for a single-machine system under asymmetrical fault conditions. They describe the back-propagation neural network configurations adopted and detail the different stages in the training process of the neural networks. Results obtained by applying the neural network approach to a single-machine system show that fast and accurate assessment of transient stability boundaries can be achieved but the approach requires further improvement for use in the estimation of critical fault clearing times View full abstract»

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  • Simulation of an induction generator connected to a simple system using 0dq transformation

    Publication Year: 1991 , Page(s): 709 - 715 vol.2
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    An induction generator connected to an infinite bus through a grounded wye-grounded wye transformer, a transmission line, and with load and capacitance compensation, is studied using generator and system mathematical models in the stationary reference frame. Constraints for abnormal situations on the high voltage side of the transformer have been derived and the abnormalities have been simulated on a 386 personal computer. It is shown that when symmetry can be assumed, the 0dq transformation should be used to simplify the analysis of the power system transients. Since no specific phases are needed in the 0dq reference frame, multi-point faults can be easily modeled View full abstract»

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  • Study of multiprocessor-based parallel architecture for transmission line protection

    Publication Year: 1991 , Page(s): 146 - 151 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    As quality, speed and performance demands are exacting on protective equipment, a perfected design and vigorous testing of the relay equipment are necessary to establish their suitability of functioning for the purpose they are for. The interest of the work is to verify the designed relay performance under, as far as possible, a real situation with signals from instrument transformer type transducers. MC683000 microprocessor based compact relay software is developed to run the relay system in a master slave structure which is capable of handling all types of faults. A laboratory model transmission line (analog) with electromechanical relays as back-up protection system, has been used for testing of the relay. Current and potential transformers are used to acquire relay input signals. The actual input signals of the model transmission line are sampled and filtered. The performance of the relay is verified for various kinds of faults View full abstract»

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  • Short-term thermal generation scheduling with application of probabilistic and deterministic methodologies

    Publication Year: 1991 , Page(s): 178 - 183 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The authors present a method of calculating short-term thermal plant generation scheduling using both probabilistic and deterministic methods, by using each method in sequence. First, the probabilistic approach, which takes into account uncertainties on both generation and demand sides, together with dynamic programming is used to determine the scheduled thermal units. Then, the deterministic approach is applied, through a dispatching technique, to determine the generation and reserve contribution from each generating unit. A multi-state Markov model is used to cope with the uncertainties on the generation side. A normal distribution function specified by the mean and standard deviation values, is employed to represent the demand uncertainties. With the proposed method, the optimum schedules can be obtained without losing any stochastic property considerations on both the generation and demand sides. The simulation is carried out with a small fictitious power system and the results show the benefits of the proposed method compared to a conventional method using only a deterministic approach View full abstract»

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  • Graphic-assisted expert system for power system black restart

    Publication Year: 1991 , Page(s): 514 - 517 vol.2
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Power system breakdown poses problems for power system planners and operators. The authors present an expert system which can assist the operators during system blackout, with an emphasis on the practical aspects of the problem. The structure and rules used in the expert system to aid the operators in making correct decisions are discussed. The authors also describe user friendly computer colour graphic software that has been developed in conjunction with the expert system. which allows the operator to obtain instant information about line connection and power flows at any location View full abstract»

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  • Assessment of pumped storage plant benefits in fuel budgeting and operational planning

    Publication Year: 1991 , Page(s): 379 - 384 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Storage in power systems can have several roles and can affect system costs in many ways. Probabilistic production costing calculations based on load duration curve techniques only take into account the cost benefits of artificial energy exchange (AEE) by pumped storage power plants. The authors present a methodology to calculate the cost benefits of pumped storage plants to provide for AEE and reduced start-up and shut-down costs of thermal power plants in probabilistic production costing. Results of a sample study are also shown. The technique is based on an equivalent load duration curve, which is used to calculate the expected operating costs of the system. An equivalent load transition frequency function is added to calculate the expected start-up costs of the system View full abstract»

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  • An expert system for short-term load forecasting

    Publication Year: 1991 , Page(s): 330 - 334 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Time series approaches, as conventional algorithms in the short-term load forecasting of electric power systems yield considerably high accuracy under the circumstance of no abrupt disturbances such as sharp changes of weather and in special holiday, or, if the results of these algorithms are manually adjusted by experienced operators in order that they can be further used. An expert system for short-term load forecasting is proposed by the authors. The time series approach is combined with heuristic inference and a composition method is developed to forecast the hourly load up to 48 hours in advance. The influence factors such as weather, holidays, season and dispatch control are considered. The structure of the expert system, programmed in PROLOG language, is described by the authors. This expert system is tested by actual power system load data of 210 days. The average forecasting errors of these tests are discussed by the authors View full abstract»

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  • Knowledge-based algorithms for security/economy control of distribution systems

    Publication Year: 1991 , Page(s): 431 - 436 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    In this paper, several knowledge-based online algorithms are described, which assist the system operator to perform comprehensive distribution controls in a distribution SCADA environment with real-time databases. A typical Hong Kong distribution network with zone substations and open-ended multiple outgoing feeder groups is used as an example for testing the validity of the approach. The authors review an expert system and describes the extension for providing comprehensive controls of the zone substation. By generalizing the procedures for the reallocation of outgoing feeder loads, adequate security margins are achieved for every apparatus on the zone-substation busbars against overloads during outage of a supply transformer View full abstract»

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  • Consumer rationality assumptions in the real time pricing of electricity

    Publication Year: 1991 , Page(s): 391 - 396 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    Dynamic tariffs such as RTP and time-of-day (TOD) function as load management tools because they interact with consumer behaviour. The prediction of how consumers will respond to the magnitude and, for example, the diurnal, weekly or seasonal variation of price, would require the setting up of a model to represent consumer behaviour. The model relies on the concepts of demand elasticity across time, degree of consumer economic rationality and, on the supply side, on the price formation model. The authors explore a range of assumptions in respect of these matters View full abstract»

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  • The development of vacuum and SF6 distribution switchgear

    Publication Year: 1991 , Page(s): 195 - 200 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The nonoil technologies of vacuum and SF6 have become well established and in so doing have almost completely taken over from oil. The author examines the development of vacuum and SF6 from their origins and reviews the progress made which has led to the modern designs which offer a long life maintenance free performance. The development of an SF6 transverse rotating arc circuit breaker is described in some detail together with its further application into outdoor cable connected and overhead line equipment. Details are also given of the special environmental tests carried out on vacuum and SF 6 switchgear to satisfy the stringent requirements laid down by China Light and Power to cater for the climatic conditions in Hong Kong View full abstract»

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  • An artificial intelligence approach to transient stability assessment [of power systems]

    Publication Year: 1991 , Page(s): 359 - 362 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    An artificial intelligence approach to online transient stability assessment is briefly discussed, and some crucial requirements for this algorithm are identified. Solutions to these are proposed. Some new attributes are suggested so as to reflect machine dynamics and changes in the network. Also a new representative learning set algorithm has been developed View full abstract»

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  • Studies of machine dynamic behaviour and system recovery in a natural gas liquefaction plant

    Publication Year: 1991 , Page(s): 921 - 926 vol.2
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    One of the most important requirements of a critical industrial process such as gas liquefaction is that, following an electrical disturbance, the maximum number of essential electrical drives on the system are kept running to ensure continuity of operation. To effect this, some less critical load may need to be shed to allow more important motors to re-accelerate or restart and dynamic studies by digital computer are necessary to determine the optimum patterns. Some of the problems inherent in this process are considered, with examples of typical plant behaviour View full abstract»

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  • Computer-aided setting calculation for distance zone 2 and zone 3 protection

    Publication Year: 1991 , Page(s): 152 - 157 vol.1
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Distance protection has been widely used in the protection of EHV and UHV transmission lines. One of the advantages of using distance protection is that its built-in zone 2 and zone 3 elements provide local relay back-up as well as remote system back-up protection. Typically the reach settings of zone 2 and zone 3 are taken respectively as the protected line plus 25% of the shortest second line and the protected line plus the longest second line plus 25% of the longest third line. Distance reach setting determination can be a relatively complicated procedure in view of the large volume of data that has to be processed. With the help of computer, the impedance seen by a distance relay at a particular fault location under various generation and system configuration can be calculated. The use of a computer allows the protection engineer to concentrate on judgment and evaluation of the performance of the distance relay at the chosen reach setting, such as the zone 2 or 3 coverage, the load encroachment and the power swing problem. With computerization, the time for distance setting review is shortened. The systematic approach allows regular reviews to be conducted as required, such as after the introduction of new generation plants, new circuits or transformers in the system View full abstract»

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  • Application of three-phase load flow to power system distribution automation

    Publication Year: 1991 , Page(s): 472 - 478 vol.2
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The authors introduce three-phase distribution power flow in a rigid approach for large-scale distribution systems. The solution method is the optimally ordered triangular factorization YBus, Method (implicit ZBus Gauss Method). This method not only takes advantage of the sparsity of system equations but also has very good convergence characteristics from a distribution systems point of view. The detailed component models along with suitable solution techniques are the essence of more accurate simulation results of a system. Detailed component models, therefore, are needed for all system components in the simulation. Utilizing the phase frame representation for all network elements, a program, entitled `Generalized Distribution Analysis Systems-GDAS', with a number of features and capabilities not found in existing packages has been developed for large-scale distribution system simulations. The system being analyzed can be unbalanced. It can be a radial, network (loop), or mixed type distribution system. Furthermore, because the individual phase representation is employed for both system and component models, the system can comprise single, double, and three-phase systems simultaneously. Additionally, with detailed component models, the program can also perform system loss and contingency analyses View full abstract»

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  • Electric power system dynamics- modes and coherent generators

    Publication Year: 1991 , Page(s): 865 - 870 vol.2
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    The authors discuss the relationship between the oscillatory modes and coherent groups of an electric power system, and, in particular the effect of group aggregation on modes. It is shown that one typical aggregation method is equivalent to a similarity transformation on the linearised system equations. The analysis, and results obtained for a test system, suggest a hierarchical organisation of modes and coherent groups. The extent to which modes can be given a specific physical significance is clarified, as is the ability of different generators to affect particular modes View full abstract»

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  • Optimal scheduling of large hydro-thermal power system

    Publication Year: 1991 , Page(s): 184 - 188 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    A synthesized algorithm for hydro abundant systems with parallel and cascade hydro power stations is presented. By using dynamic programming, network flow programming and the decomposition method, and taking account of nonlinearity of the hydro system and time-varying starting costs, an affective method is proposed to enhance computing accuracy and computing speed. The results show that the algorithm proposed is efficient and reliable View full abstract»

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  • An expert system for failure analysis and restoration

    Publication Year: 1991 , Page(s): 518 - 520 vol.2
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    The authors present an expert system for failure analysis and restoration operation of local power networks (FAROES), which estimates fault sections using information from protection relays and circuit breakers, and gives operators an appropriate restoration plan by using the knowledge base of expertise and heuristics on power system operations. The system is developed in combination with specific conditions of the Zheng Zhou local power network and is implemented on an IBM-PC by the use of the Turbo PROLOG language View full abstract»

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  • A cut set approach for HVDC converter reliability evaluation

    Publication Year: 1991 , Page(s): 757 - 761 vol.2
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The reliability evaluation of HVDC systems has been gaining much significance in the recent past. A new approach for converter equipment failure analysis is proposed. The AC to DC converter equipment circuit in HVDC systems is treated as a flow network by incorporating capacity constraints. An algorithm is proposed to obtain all path sets that give the required flow at the DC terminal. This takes combination of fewer paths only. By multiplying these path sets, using Boolean algebra, all minimal cut sets that do not transmit the required flow can be obtained. From these minimal cut sets, the expression for the probability of failure of transmission of required flow at the DC terminal can be obtained View full abstract»

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  • A computer-vision based power plant monitoring system

    Publication Year: 1991 , Page(s): 335 - 340 vol.1
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A power plant monitoring system is extremely important for ensuring normal operation of the whole power plant as well as initiating alarms to avoid further development of unattended fault within the power generating system. Conventionally, such work is accomplished by a panel meter/human interface arrangement. Intensive manhour requirements and limitations in flexibility are the main drawbacks of such an arrangement. The authors introduce a new concept in system monitoring. The human interface is replaced by a computer vision-based system so that the time-consuming work such as data logging, trend recording and alarm triggering can be carried out by a computer employing the concept of `image understanding'. Human error could be minimised with improved accuracy and operation efficiency View full abstract»

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  • Optimal output feedback controller design for large-scale electrical power systems

    Publication Year: 1991 , Page(s): 221 - 226 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The authors report on a novel application of optimal output feedback control theory to the design of power system stabilisers (PSSs) for large-scale electrical power systems. An interconnected power system comprising three generating units is considered for this application. Simulation results, in terms of step responses, are given to illustrate the improvement in the power system performance View full abstract»

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  • Replacement of oil-insulated circuit-breakers/switches by vacuum counterparts

    Publication Year: 1991 , Page(s): 207 - 210 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Since 1978, the Hong Kong Electric Company Limited (HEC) has switched to the use of 11 kV vacuum circuit breakers (VCB) in both new projects of primary substations and uprating of existing primary substations. From then on the population of oil circuit breakers (OCB) diminished. By 1989, there were approximately 600 VCBs in the 11 kV system. The in-service OCBs were reduced to some 410 pieces and were supplied by two manufacturers in late 1960s and early 1970s. Both manufacturers were asked to inspect the busbars and housing of the switchboards, and confirm that the residual life was more than fifteen years. The simple and economical way of upgrading is to replace the oil circuit breaker carriages without disturbing the busbars. The author describes the joint efforts devoted by switchgear manufacturers and HEC to design and type test replacement vacuum breakers to achieve cost-effectiveness and minimal supply interruption. Experience of the breaker replacement and the saving in operational costs after employment of vacuum breakers are also presented View full abstract»

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  • Control of electric thermal storage under real time pricing

    Publication Year: 1991 , Page(s): 397 - 403 vol.1
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    Real time prising (RTP) is an electricity rate based on the actual time-varying costs of providing electric service. It changes with time as the costs of generation, transmission, and distribution change in time. RTP rate can contain both the short-term and long-term costs of electricity supply and revenue recovery requirements. As a complete demand-side management (DSM) option, RTP provides a market force mechanism for DSM programs where customers decide on their options based on rational economic self interest. An experiment on the automatic control of electric thermal storage (ETS) systems under RTP rates shows that the benefits of ETS systems to utilities can be increased by close to 50% under RTP rates compared to the time of use (TOU) based control. Under RTP and ETS charging occurs at times of lowest costs to the utility. These times of lowest costs may or may not coincide with the off-peak periods rigidly defined in TOU rates. Compared to the present utility incentives in USA for load shifting and ETS installations under TOU rates, the additional costs of RTP-based control retrofitting can be easily justified View full abstract»

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