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Generation, Transmission and Distribution, IEE Proceedings-

Issue 3 • Date May 1995

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Displaying Results 1 - 17 of 17
  • Fuzzy logic power system stabiliser

    Publication Year: 1995 , Page(s): 277 - 281
    Cited by:  Papers (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    Using speed and power output deviations as the controller input variables, a fuzzy logic based controller (FLC) has been developed to perform the function of a power system stabiliser and to provide a supplementary signal to the excitation system of a synchronous machine. The complete range for the variation of each of the two controller inputs is represented by a 7×7 decision table, i.e. 49 rules. The FLC design steps and a procedure for tuning its parameters are described. Simulation studies for a variety of disturbances on the power system with the FLC-based power system stabiliser demonstrate its effectiveness in improving system performance View full abstract»

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  • Distribution system service restoration using the artificial neural network approach and pattern recognition method

    Publication Year: 1995 , Page(s): 251 - 256
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Service restoration of a distribution system is investigated by using artificial intelligence. The purpose is to reach a proper restoration plan for the unfaulted zone after a fault has been identified and isolated. To reduce the outage period and improve service reliability, the restoration plan must be devised in a very short period. In the paper, two approaches using artificial intelligence, i.e. the artificial neural network (ANN) approach and the pattern recognition method, are developed to determine the restoration plan in a very efficient manner. The effectiveness of the proposed approaches is demonstrated by the restoration of electricity service following a fault in a distribution system in Taipei, Taiwan. It is concluded from the example that a proper restoration plan can be reached very efficiently using the proposed approaches. Therefore, it can be used by distribution system operators to reach a restoration plan View full abstract»

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  • Phase-shifting transformer with fixed phase between terminal voltage and voltage boost: tool for transient stability margin enhancement

    Publication Year: 1995 , Page(s): 257 - 262
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    The development of power electronics has enabled rapid and nearly continuous control of phase-shifting transformers (PSTs). As a consequence, new possibilities for solving problems concerning not only steady-state but also dynamic conditions in power systems are offered by electronically controlled PSTs. In the paper, the basic operating principles of a PST with fixed phase between terminal voltage and voltage boost (FP-PST) are presented. A mathematical model of a FP-PST is introduced, which is a representation of a longitudinal transmission system with a FP-PST included. It is shown that the location and the orientation of a FP-PST have a crucial impact on the behaviour of the power system. For the chosen test system, by applying the mathematical model, the most suitable location and orientation of a FP-PST were determined to solve problems concerning the first swing stability. On the same basis, appropriate FP-PST control is introduced to ensure the maximal stability margin for given FP-PST dimensions, small back swing and effective damping of subsequent swings. Modelling of the test system and FP-PST and dynamic simulation were performed in the stability mode of the NETOMAC program system. The minimal dimensions of a FP-PST were determined to ensure that the system remains stable after a fault followed by line tripping. Finally, the results of the dynamic simulation are presented View full abstract»

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  • Composite system spinning reserve assessment in interconnected systems

    Publication Year: 1995 , Page(s): 305 - 309
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    Deterministic methods to evaluate unit commitment and spinning reserve requirements cannot explicitly recognise the stochastic nature of a power system. Probabilistic techniques can, however, be used to incorporate a wide range of stochastic system parameters. The usual techniques of probabilistic unit commitment in an interconnected power system consider the tie-line constraints but not the transmission facilities within the systems. In a real power system, the transmission facilities within the systems have limits and do fail. Units committed from only probabilistic generation studies, therefore, provide optimistic values. In the paper, the usual techniques of unit commitment are extended to calculate a risk value from a composite system point of view. The effect on the risk value of rapid start and hot reserve units are considered View full abstract»

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  • Private investment in power and deviations from the least cost expansion plan

    Publication Year: 1995 , Page(s): 269 - 276
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    Established least cost electricity generation expansion planning philosophy is now coming under serious pressure because of the worldwide restructuring of the electricity supply industry. This restructuring usually includes private investment in power projects. Despite the importance of the long-term optimal strategy, the `next' least cost project may, sometimes, be unattractive to private investors for a various reasons, but power system planners may be constrained, by policy or financial pressures, to accept compromises. The paper examines this problem, develops techniques for assessing the impact of such deviations, examines affects on prices, and suggests trade-off methods for resolving economic and tariff related conflicts of interest View full abstract»

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  • Dynamically corrected fast estimators of current and voltage magnitude

    Publication Year: 1995 , Page(s): 310 - 316
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Fast digital estimation of current and voltage magnitude for power system protection purposes is considered. The magnitude estimators applied nowadays very frequently employ sine/cosine nonrecursive filters, and their response time is determined by the filter data window, which is usually not shorter than one period of the fundamental frequency. The response time of such estimators can be significantly reduced (in the fastest variant up to two sampling periods) by use of a new dynamic correction method which is presented in the paper. It is shown that application of the method to the estimator design simplifies the estimator structure, since the orthogonal filters are not necessary for magnitude calculations. Thus the computational burden in real-time implementations can be reduced remarkably and the optimisation of the filtration process can be carried out. Results of simulation tests of the proposed method are also included View full abstract»

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  • Eigenvalue approach clustering algorithm for building equivalent models of distribution systems

    Publication Year: 1995 , Page(s): 282 - 288
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A method for representing a large distribution system is developed. The method is based on utilising the clustering technique to build an equivalent distribution system. The behaviour of the original large system may then be studied by analysing the equivalent (simpler) system, with less computational time and with high accuracy. Such behavioural features may include voltage regulation, equipment loading and total system losses. The use of the equivalent system leads to saving in both computer and distribution systems operator(s) time. The use of the clustering techniques significantly reduces the complexity of the problem yet, at the same time, provides very accurate results View full abstract»

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  • Efficient methods for identifying weak nodes in electrical power networks

    Publication Year: 1995 , Page(s): 317 - 322
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The paper presents two computationally efficient and simple methods of identifying weak buses in electrical power systems. The main purpose of identifying weak buses is to maintain control of voltages at these buses, in particular to prevent voltage collapse. The first method is based on the right singular vector, corresponding to a minimum singular value of the power-flow Jacobian matrix, which indicates sensitive voltages. The second method is based on the voltage collapse proximity indicator. The presented methods are successfully applied to several systems View full abstract»

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  • Identification of synchronous generator saturation models based on on-line digital measurements

    Publication Year: 1995 , Page(s): 225 - 232
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Accurate stability analysis requires the precise modelling of electric machine saturation phenomena. The paper presents a technique suitable for identifying several typical machine saturation models. It is shown that the technique can be used to identify nonlinearities associated with saturation and cross-magnetisation effects. An algorithm is designed to estimate all parameters of the machine models and the associated saturation functions. Numerical studies on a synchronous generator are included, using online measured data of the Taipower system recorded by the plant transient recording and analysis system View full abstract»

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  • Chaotic ferroresonance in power transformers

    Publication Year: 1995 , Page(s): 247 - 250
    Cited by:  Papers (19)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The solution of the nonlinear equation for a typical ferroresonant circuit containing a power transformer is shown to be dependent on the accurate description of the magnetisation curve. A detailed analysis of many simulation results demonstrates that the probability of chaos increases as losses decrease and the nonlinearity of the transformer magnetisation rises. The effect of varying the transformer core losses and the value of the source voltage on the chaotic solution of the system has been studied. The concept of transient chaos as compared with steady-state chaos is also discussed View full abstract»

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  • Incorporating nonlinearities of measurement function in power system dynamic state estimation

    Publication Year: 1995 , Page(s): 289 - 296
    Cited by:  Papers (22)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    Dynamic state estimation in power systems is based on the extended Kalman filter (EKF) scheme. The EKF system uses a linearised measurement equation, neglecting the nonlinearities of the measurement function. Under certain circumstances (e.g. large load changes) this leads to degradation in the filter performance. Two algorithms are proposed for dynamic state estimation which incorporate the measurement function nonlinearities in the EKF scheme. The performance of the schemes are compared with the standard linear EKF scheme under various conditions and comparative results are presented View full abstract»

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  • Constrained optimisation procedure for evaluating cyclic loading of power transformers

    Publication Year: 1995 , Page(s): 240 - 246
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    The paper reports new developments in computational methods for evaluating the normal cyclic rating (NCR) and long-term emergency rating (LTER) of transformers. It makes two major improvements to the procedures given in the international standard in the subject: IEC354. One improvement derives from an interpretation of NCR and LTER formulations as a constrained optimisation procedure. Starting from a given load profile, the procedure maximises transformer loading levels subject to constraints formed from maximum values of permissible internal temperatures and of a defined insulation ageing factor. The second advance is based on a separation of variables in the evaluation of the integral which gives the relative ageing factor. This measure makes major savings in the computing overheads of practical evaluations. The two developments together lead to reliable procedures for NCR or LTER evaluations in practice as encountered in a power authority or utility. They can be relied on to give a solution without user intervention. Convergence to a solution is independent of the transformer thermal characteristics relevant to rating studies and of the loading profiles for which they are carried out. The results summarise some of the studies used in validating a comprehensive software system that implements the procedures which the paper reports. The new procedures have been tested and compared with existing procedures for many practical cases and found to achieve significant advantage, sometimes dramatically so View full abstract»

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  • Optimal pricing of transmission services: application to large power systems

    Publication Year: 1995 , Page(s): 263 - 268
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The paper describes the application of a previously reported optimal transmission pricing method to a large power system. The transmission prices are determined by a global benefit optimisation algorithm that allocates both capacity and operational costs on a time-of-use basis. It is shown that optimal prices may be derived using a conventional mathematical programming algorithm and results are presented in relation to the IEEE 24 bus test network. A particular feature of the present method is the inclusion of both power system security and energy transportation costs. This is achieved by a specialised technique for iterating between benefit maximisation and a system security assessment. Results presented illustrate time-of-use transmission tariffs, together with the variation of capacity costs with system security standards View full abstract»

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  • Experimental investigations of high-voltage motor switching surges

    Publication Year: 1995 , Page(s): 233 - 239
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The paper presents the results of experimental investigations of surges appearing on the insulation of high-voltage (HV) motors for normal switching operations and during an interrupt of aborted start. High-voltage motors were switched by oil-minimum circuit breakers, air magnetic and vacuum switching devices. Investigations were performed mostly on 6 kV isolated neutral station service cable networks of thermal power plants, industrial or similar installations. On the basis of the results, certain measures are proposed for limiting transients, thereby increasing the reliability of HV motor operation View full abstract»

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  • Modelling and control of thyristor-controlled series compensators

    Publication Year: 1995 , Page(s): 297 - 304
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    A linearised discrete-time model of a thyristor-controlled series-compensated transmission line is presented, in which a thyristor-controlled reactor (TCR) is used as the compensating device. The discretisation is performed at the peaks of the capacitor voltage of the series compensator. Since these peaks are broad, rather than sharp spikes, they are quite good indicators of variations in the fundamental component. During transients this will result in variation from uniform sampling. However, the system degenerates to a uniform sampled system in the steady state, and thus all the standard tools for the stability analysis of a standard discrete-time model can be applied. As a part of the linearised model, two different output equations are determined. They are the line current, which is in quadrature with capacitor voltage, and the real power flowing through the line. These output equations are then used for control design. The model developed is validated through digital computer simulation studies, in which the robustness of the closed-loop system is investigated through eigenvalue plots as a function of the operating points View full abstract»

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  • Artificial neural network-based method for transient response prediction

    Publication Year: 1995 , Page(s): 323 - 329
    Cited by:  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The paper describes the application of an ANN-based approach to the prediction of the dynamic behaviour of a synchronous generator following a disturbance in a simple power system. Case data representing the oscillation in rotor angle caused by the disturbance is accumulated from offline simulation using an accurate digital model. Neural networks are trained to map this case data in relation to the initial operating conditions and details of the particular disturbance involved. The response of a one-machine, infinite-bus system is considered after the occurrence of a three-phase short circuit in one element of a double transmission line connecting the synchronous generator to the bus, and of a shock local load change. Numerical results comparing the predicted response using the ANN model with that obtained from direct use of the benchmark model are presented in terms of both accuracy and speed. These suggest that the ANN model might be used in conjunction with an online fault identification system in the study of transient stability or in the provision of information for predictive control. Because only very simple mathematical calculations are required once the neural networks have been trained, the computation time is very short in comparison with the direct use of numerical simulation View full abstract»

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  • Frequency domain technique for designing stabilisers for a power plant with identical generators

    Publication Year: 1995 , Page(s): 330 - 336
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    A new technique for designing power-system stabilisers for a power plant with identical generators is proposed. By exploring the special structure of the system and using modal techniques, two different transfer functions of the plant connected with the external power system are constructed by using reduced-order models. These transfer functions are used in a frequency domain procedure for determination of the time constants and gains of the stabilisers. For comparison, a conventional decentralised signal and a summation of similar signals from the generators are applied to the stabilisers to control the local modes. Based on the conventional frequency domain technique for designing a stabiliser for a single machine, the proposed technique explains statements from other papers, and produces new important results View full abstract»

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