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Generation, Transmission and Distribution, IEE Proceedings-

Issue 2 • Date 2 March 2004

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Displaying Results 1 - 21 of 21
  • Locating faults in parallel transmission lines under availability of complete measurements at one end

    Publication Year: 2004 , Page(s): 268 - 273
    Cited by:  Papers (28)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Fault location in parallel transmission lines with availability of complete measurements from one end of the lines is considered. Generalised models of fault loops and faults are used for formulation of the fault location algorithm. The derived algorithm has a very simple first-order formula and does not require knowledge of impedances of the equivalent systems behind the line terminals as well as use of pre-fault measurements. Application of the fault location algorithm to impedance measurement of the adaptive distance protection is considered. An issue of improving the fault location accuracy by compensating for shunt capacitances of the lines is addressed. Results of the evaluation with use of ATP-EMTP simulations are reported and discussed. View full abstract»

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  • Generalised neuron-based adaptive power system stabiliser

    Publication Year: 2004 , Page(s): 213 - 218
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (303 KB)  

    Artificial neural networks (ANNs) can be used as intelligent controllers to control nonlinear, dynamic systems through learning, which can easily accommodate the nonlinearities and time dependencies. However, they require long training time and large numbers of neurons to deal with complex problems. To overcome these drawbacks, a generalised neuron (GN) has been developed that requires much smaller training data and shorter training time. Taking benefit of these characteristics of the GN, a new generalised neuron-based adaptive power system stabiliser (GNPSS) is proposed. The GNPSS consists of a GN as an identifier, which tracks the dynamics of the plant, and a GN as a controller to damp low-frequency oscillations. Results show that the proposed adaptive GNPSS can provide a consistently good dynamic performance of the system over a wide range of operating conditions. View full abstract»

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  • Shunt compensation for power quality improvement using a STATCOM controller: modelling and simulation

    Publication Year: 2004 , Page(s): 274 - 280
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (390 KB)  

    The paper deals with compensation of frequently time-variable loads by means of STATCOM controllers. An arc furnace is considered as a heavily distributing load. The STATCOM system was used to ensure good power quality at the point of common coupling. For analysis of the system performance, the PSCAD/EMTDC programme was applied. Simulation models of the load and two types of STATCOM controllers, 12-pulse and 24-pulse, are discussed in the paper. A PSCAD model of a measurement block is also proposed for power quality assessment. Some results of simulation are presented, which show the compensation effectiveness. View full abstract»

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  • Available transfer capability assessment in a competitive electricity market using a bifurcation approach

    Publication Year: 2004 , Page(s): 133 - 140
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (301 KB)  

    An application of bifurcation criteria is proposed for available transfer capability (ATC) determination in a competitive power market having bilateral as well as multilateral transactions. The Hopf bifurcation limit has been considered for determination of the dynamic ATC. The saddle node bifurcation and bus voltage limits have been used for static ATC determination. The proposed method has been applied for ATC determination on a 39-bus New England system and a 68-bus system having static loads as well as in the presence of induction motor loads. The impact of SVC placement in the system for the enhancement of ATC has also been studied. View full abstract»

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  • Newton-like method for line outage simulation

    Publication Year: 2004 , Page(s): 225 - 231
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (283 KB)  

    Line outage simulation is a necessary part of contingency analysis. The Newton-based full AC load flow method is commonly used for this purpose despite its time consuming computational process. A compensation scheme and a partial refactorisation method is proposed for the efficient solution of the first iteration of the post-contingency full AC load flow. Two Newton-like load-flow methods, the fixed Newton method and the modification of the right-hand-side vector method, are also described to continue the calculation until convergence is obtained. These methods eliminate the need for complete refactorisation of the jacobian matrix. The two methods are compared with the Newton-based full AC load flow method and the fast decoupled load flow in three test systems to demonstrate their convergence characteristics. View full abstract»

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  • Dynamic equivalents of power systems with online measurements Part 2: Applications

    Publication Year: 2004 , Page(s): 179 - 182
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    For Pt.1 see ibid., vol.151, no.2, p.175-8, March 2004. Final validation of a dynamic equivalent (DE) has been used to obtain the equivalent parameters from field tests and apply them to practical stability studies. Microcomputer-based equipment was developed for online measurement and identification, from which several valuable field results were captured. The results were then applied to dynamic response simulation and stability limit calculation. View full abstract»

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  • Framework for the analysis of reactive power dispatch in energy pools

    Publication Year: 2004 , Page(s): 167 - 174
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (282 KB)  

    This paper proposes a framework for the simulation and analysis of the reactive power distribution in electric energy markets of the pool type. Firstly, the analytical formulation of the OPF problem, with three optional performance indexes for the reactive power dispatch, is discussed. These OPF objectives are used to determine the reactive power distribution for a given active power dispatch (obtained through merit-order strategy, for instance). An allocation strategy is used to assess the participation of each power system agent in the loss/reactive power distribution. This strategy uses the premise of co-operative game theory. Numerical results obtained with the Ward-Hale 6-bus test system illustrate the main aspects of the proposed methodology. View full abstract»

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  • Robust control in a multimachine power system using adaptive neuro-fuzzy stabilisers

    Publication Year: 2004 , Page(s): 261 - 267
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    A robust artificially intelligent adaptive neuro-fuzzy power system stabiliser (ANF PSS) design for damping electromechanical modes of oscillations and enhancing power system synchronous stability is presented. An actual power system is decomposed into separate subsystems, each subsystem consisting of one machine. The local ANF PSS is associated with each subsystem. The local feedback controllers rely only on information particular to their subsystem. The input signals are the speed, power angle and real power output. Nonlinear simulations show the robustness of the ANF PSS. View full abstract»

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  • Strategic forward contracting in electricity markets: modelling and analysis by equilibrium method

    Publication Year: 2004 , Page(s): 141 - 149
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (309 KB)  

    Contractual arrangement plays an important role in mitigating market power in electricity markets. The issue of whether rational generators would voluntarily enter contract markets through a strategic incentive is examined, and the factors which could affect this strategic contracting behaviour. A two-stage game model is presented to formulate the competition of generators in bid-based pool spot markets and contract markets, as well as the interaction between these two markets. The affine supply function equilibrium (SFE) method is used to model competitive bidding for the spot market, while the contract market is modelled with the general conjectural variation method. The proposed methodology allows asymmetric, multiple strategic generators having capacity constraints and affine marginal costs with non-zero intercepts to be taken into account. It is shown that the presence of forward contract markets will complicate the solution to the affine SFE, and a new methodology is developed in this regard. Strategic contracting behaviours are analysed in the context of asymmetric, multiple strategic generators. A numerical example is used to verify theoretical results. It is shown that the observability of contract markets plays an important role in fostering generators' strategic contracting incentive, and that this contracting behaviour could also be affected by generators' cost parameters and demand elasticity. View full abstract»

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  • Comparison of two simple high-frequency earthing electrodes

    Publication Year: 2004 , Page(s): 219 - 224
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (293 KB)  

    Lightning strikes on high-voltage transmission lines may create hazardous touch potentials on adjacent substation equipment and damage control equipment. When designing suitable substation earthing electrodes to overcome this problem and safely dissipate the transient fault currents to ground, it is essential to consider the behaviour of the current flow. The steady-state frequency equivalent to a lightning strike is at least 0.25 MHz, which corresponds to a current skin depth δ of about 10 m in homogeneous soil of conductivity 0.01 S/m. This surface effect causes the impedance of an electrode system to be considerably larger than the power-frequency resistance. Thus a dedicated electrode is normally placed in parallel with the low-frequency earthing system, usually taking the form of a simple vertical rod of copper-coated steel about 5 m long. The work presented suggests that a long rod is not ideal for the purpose. Using a relatively simple numerical finite-difference procedure it has been found that a flat disc electrode parallel to the surface of the ground achieves a significant improvement over the performance of a vertical rod. Both rod and disc have been solved in the frequency domain, but the rod has also been analysed in time-stepping form so that the peak voltage for a given imposed current can be compared with that deduced from the equivalent steady-state complex impedance. View full abstract»

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  • Dynamic equivalents of power systems with online measurements. Part 1: Theory

    Publication Year: 2004 , Page(s): 175 - 178
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (289 KB)  

    Dynamic equivalents (DE) can reduce the computing effort and emphasise the main characters of a power system. A DE model has been developed in which identifiability is studied. Identifiability has not only a theoretical meaning, but also practical value. It is shown that some parameters of the model are unidentifiable when using only the steady-state data before disturbance and during disturbance, but identifiable when using only the steady-state data before disturbance and during disturbance, but identifiable when using only the data before and during disturbance, but identifiable when utilising the data after disturbance. View full abstract»

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  • Parallel tabu search algorithm for constrained economic dispatch

    Publication Year: 2004 , Page(s): 157 - 166
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (321 KB)  

    A parallel tabu search (PTS) algorithm for solving ramp rate constrained economic dispatch (CED) problems for generating units with non-monotonically and monotonically increasing incremental cost (IC) functions is proposed. To parallelise tabu search (TS) algorithms efficiently, the neighbourhood decomposition is used to balance the computing load, whereas competitive selection is used to update the best solution reached among subneighbourhoods. The proposed PTS is implemented on a 32-processor Beowulf cluster with an Ethernet switching network on a generating unit system size in the range 10-80 units over the entire dispatch periods. With different subneighbourhood sizes, the proposed PTS compromises the experimental speedup and solution quality for the best performance. PTS is potentially viable for the online implementation of CED because of the substantial generator fuel cost savings and high speedup upper bounds. View full abstract»

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  • Application of the direct Lyapunov method to improve damping of power swings by control of UPFC

    Publication Year: 2004 , Page(s): 252 - 260
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (475 KB)  

    Large interconnected power systems often suffer from weakly damped swings between synchronous generators and subsystems. This paper presents an approach, based on the use of the nonlinear system model and application of the direct Lyapunov method, to improve damping of power swings using the unified power flow controller (UPFC). A state-variable control strategy has been derived as well as its implementation using locally available signals of real and reactive power. The results of simulation tests, undertaken using a small multi-machine system model, have been presented. View full abstract»

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  • Influence of artificial neural network structure on quality of short-term electric energy consumption forecast

    Publication Year: 2004 , Page(s): 241 - 245
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The influence of an artificial neural network structure on the quality of short-term electric energy consumption forecasts is described. The problem of short-term electric energy consumption forecasting is very important in the daily activity of electricity distribution companies and other industrial enterprises. Accurate electric energy consumption forecast enables optimisation of the costs of electric energy purchase and planning of technological processes. There are many different forecasting methods on the market. The most accurate methods are those based on an artificial neural network technique. An attempt to investigate the influence of a one-directional ANN structure (number of hidden layers and number of neurons in layers) on the short-term forecast quality is presented. The quality of an ANN learning process is also investigated. Negative phenomena observed during the learning process, especially the phenomena of an artificial neural network overlearning, are shown. Computational experiments have been executed on the test problems. Proper data from electricity distribution companies have been taken into account. Results obtained show that the ANN structure has an essential influence on the quality of electric energy consumption forecasts. View full abstract»

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  • Application of RBF neural network to fault classification and location in transmission lines

    Publication Year: 2004 , Page(s): 201 - 212
    Cited by:  Papers (19)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (370 KB)  

    The application of radial basis function (RBF) neural networks for fault classification and location in transmission lines is presented. Instantaneous current/voltage samples have been used as inputs to artificial neural networks (ANNs). Whereas, for fault classification, prefault and postfault samples of only the three-phase currents are sufficient, for fault location, postfault samples of both currents and voltages of the three phases are necessary. To validate the proposed approach simulation studies have been carried out on two simulated power-system models: one in which the transmission line is fed from one end and another, in which the transmission line is fed from both ends. The models are subjected to different types of faults at different operating conditions for variations in fault location, fault inception angle and fault point resistance. The results of the simulation studies which are presented confirm the feasibility of the proposed approach. View full abstract»

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  • Editorial: modern electric power systems 2002

    Publication Year: 2004 , Page(s): 239 - 240
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    First Page of the Article
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  • Real-time transient simulation of multimachine power system networks in the phase domain

    Publication Year: 2004 , Page(s): 192 - 200
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (489 KB)  

    This paper details implementation of the mathematical model of a synchronous generator in the direct time phase domain suitable for transient analysis in a real-time simulation environment. The network model, which is a full multimachine model in the phase domain, has been implemented on a multipurpose real time station (RTS). A solution method for solving the direct time phase domain model of the generator in the multimachine environment, where transmission imbalances are fully taken into account, has also been proposed. The method is based on discretisation of the state equations for the generator and the interconnecting network. The proposed model and solution method is compared with an industry standard power system package, PSCAD/EMTDC™. The model enables a unified approach to be adopted in the study of both symmetrical and asymmetrical operating conditions. A thorough analysis is performed to evaluate the model performance in real-time, where the frame time of simulation is a subject of study. View full abstract»

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  • Network voltage controller for distributed generation

    Publication Year: 2004 , Page(s): 150 - 156
    Cited by:  Papers (31)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (290 KB)  

    Present distribution network voltage design practice limits the distributed generation capacity that can be connected to 11 kV networks. It has been shown previously that adoption of a more active approach to network voltage control can significantly increase distributed generation capacity. One way to do this is to control the target voltage of automatic voltage control relays at primary substations. A basic design for a controller to do this has been created, comprising three algorithms. A statistical state estimation algorithm estimates the voltage magnitude at each network node supplied by the primary substation, using real-time measurements, network data and load data. The estimate accuracy depends on the number and placement of real-time measurements. Studies using an 11 kV feeder model showed that an acceptable accuracy could be obtained with one or two measurements. The state estimator uses pseudo measurements for unmeasured loads. A load model was constructed using load profiles to calculate the pseudo measurements. The calculated pseudo measurements were inaccurate, but it was found that acceptable state estimate accuracy could be obtained with inaccurate pseudo measurements. A control algorithm alters the AVC relay target voltage, based on the maximum and minimum node voltage magnitude estimates. A simulation on a four-feeder network showed that the algorithm enabled the generator power export to be more than doubled. View full abstract»

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  • Hybrid algorithm for optimisation of m-loop electric power distribution networks

    Publication Year: 2004 , Page(s): 246 - 251
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (317 KB)  

    A heuristic method using artificial neural networks (ANN) for designing m-loop electric power distribution networks is presented. The task is to connect transformer stations (with given locations and loads) into m loops in order to minimise the given aim function, subject to technical constraints. The problem of designing the described network is similar to the travelling salesman problem and is a NP-hard problem. As the optimisation criterion, the minimal annual cost of electric power network was chosen. The network structure obtained with use of ANN is improved in the last stage of the proposed algorithm by the simulated annealing method or by manual exchange of transformer stations. Definition of the problem, as well as a short algorithm and some results of tests performed on m-loop electric power network models, are presented in the paper. View full abstract»

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  • Use of ARX algorithms for modelling micro-turbines on the distribution feeder

    Publication Year: 2004 , Page(s): 232 - 238
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (334 KB)  

    The deregulation of utilities and the emerging power markets are creating renewed interest in operating micro-turbines in parallel with the utility system. As micro-turbines proliferate, it is necessary to reduce the model order of each micro-turbine to enable computational analysis. The application of the autoregression with exogenous signal (ARX) identification algorithm is presented to compute low-order micro-turbine models, suitable for analysis. This algorithm consists of a procedure for calculating the transfer function of a micro-turbine from samples of its input and output. Each micro-turbine reduced-order model influences the grid in the same manner as an actual micro-turbine would, modulating real and reactive power in response to voltage and frequency changes on the grid. View full abstract»

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  • Using adaptive fuzzy inference system for voltage ranking

    Publication Year: 2004 , Page(s): 183 - 191
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    Voltage ranking is an important part of power system security assessment. The commonly used performance index method with a low exponent could suffer from masking effects. This paper proposes a generic compensation factor to reduce the masking problem. An adaptive fuzzy system is used for the calculation of the generic compensation factor. A simplification of the defuzzification process is proposed for improvement of computational efficiency. Convergence analysis shows that values calculated by the adaptive fuzzy system are good approximations. The parameters would only need to be calculated offline once. They can then be applied to various systems for voltage ranking applications. To save computational efforts further, a hybrid strategy is introduced to reduce the number of fuzzy rules. A good ranking method needs an efficient method to derive voltage deviations. Besides the commonly used 1P-1Q calculation method, an alternative method is used for the calculation of voltage deviations. A new version of the ranking assessment diagram is proposed for the presentation of ranking results. Ranking results from two test power systems have been presented to verify the effectiveness of the proposed strategy. View full abstract»

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