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Generation, Transmission and Distribution, IEE Proceedings-

Issue 5 • Date Sept. 2002

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Displaying Results 1 - 18 of 18
  • Reliability evaluation of hybrid multiterminal HVDC subtransmission systems

    Page(s): 571 - 577
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (433 KB)  

    An approach to determining the reliability of a hybrid multiterminal HVDC subtransmission system is presented. The performance analysis of a multiterminal HVDC subtransmission system is divided into three main segments: the rectifiers, the inverters and the underground cable system. The reliability models associated with the three segments are developed and a reliability evaluation procedure is presented. Two sets of indices, namely the basic load point indices and the system performance indices, are calculated to measure the reliability of a system. The proposed technique is applied to a hypothetical multiterminal HVDC subtransmission scheme and the results are presented. View full abstract»

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  • Review of the basic insulation level for 400 kV oil-filled cable systems under lightning events

    Page(s): 550 - 556
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The lightning impulse duty for 400 kV underground power cables using ATP is investigated and the recommended design level based on a probabilistic analysis is reassessed. A comprehensive study of the transient overvoltages experienced by cables within the UK National Grid's transmission system has been performed. The paper investigates the effects of transient overvoltages due to lightning. To determine the peak voltages that a cable would experience, direct lightning strikes and backflashovers onto the overhead-line phase conductor were simulated both near a cable termination and at air-insulated substation (AIS) and gas-insulated substation (GIS) zones. A second paper will present the investigation into transient overvoltages due to switching, faults and other temporary overvoltages (TOV). A probabilistic approach to argue for a reduction of the basic insulation level (BIL) for 400 kV cables to a value of 1050 kVp is used. View full abstract»

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  • Evaluation of convergence rate in the auxiliary problem principle for distributed optimal power flow

    Page(s): 525 - 532
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (469 KB)  

    An approach to paralleling optimal power flow is described that is applicable to very large interconnected power systems and is suitable for distributed implementation. The proposed scheme is based on an augmented Lagrangian approach using the 'auxiliary problem principle'. The objective is to find a set of control parameters with which the auxiliary problem principle can be best implemented in solving distributed optimal power flow problems. The paper is a useful guide to the choice of control parameters that are highly problem dependent and sensitive to problem data. Several IEEE Reliability Test Systems and the Korea Electric Power System demonstrate alternative parameter sets that are the key elements in achieving fast convergence. View full abstract»

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  • Goal-attainment method for optimal multi-objective harmonic filter planning in industrial distribution systems

    Page(s): 557 - 563
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    A formulation of multi-objective optimisation for single-tuned harmonic filter planning in industrial distribution systems is presented. The objectives are total harmonic current distortion at the point of common coupling, total harmonic voltage distortion and harmonic filter investment cost. The minimisation of all the objectives is required in harmonic filter planning. The reactive power compensation constraints, the harmonic distortion constraints, the power source variation constraints and the filter de-tuning constraints are all taken into consideration. The goal-attainment method based on the simulated annealing approach is applied to solving general multi-objective harmonic filter planning problems by assuming that the decision-maker has goals for each of the objective functions. A desirable, global optimal solution generated is guaranteed by the solution methodology. Results of application of the proposed method to general multi-objective harmonic filter planning are also presented. View full abstract»

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  • Initialisation of the augmented Hopfield network for improved generator scheduling

    Page(s): 593 - 599
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (479 KB)  

    An artificial neural network algorithm for generator scheduling is proposed. The algorithm employs an infeasible Lagrangian dual maximum solution to initialise the neurons of an augmented Hopfield network. The proposed algorithm produces cheaper solutions when compared with Lagrangian relaxation or a randomly initialised augmented Hopfield network. The algorithm also has shorter convergence times than the augmented Hopfield network, but is not as fast to converge as Lagrangian relaxation. View full abstract»

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  • Transmission embedded cost allocation using sensitivity analysis

    Page(s): 627 - 632
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (379 KB)  

    The paper describes the principle and the implementation of a methodology to evaluate transmission network capacity use, for bilateral/multilateral transactions in an electricity pool, using sensitivity analysis on the pool dispatch model. In this methodology, transmission network capacity use is a function of the additional real power flow on transmission lines, due to the new transactions. This capacity use value provides a fast, accurate and equitable means of allocating transmission cost to the new transactions without performing new pool dispatch. An illustrative example on a 16-busbar system is used to show the implementation of the pricing methodology. View full abstract»

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  • Enhanced genetic algorithm-based fuzzy multi-objective approach to distribution network reconfiguration

    Page(s): 615 - 620
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (447 KB)  

    An enhanced genetic algorithm (EGA)-based fuzzy multi-objective approach to solve a network reconfiguration problem in a radial distribution system Is presented. Maximising the fuzzy satisfaction allows the operator to simultaneously consider the multiple objectives of the network reconfiguration to minimise power loss, violation of voltage and current constraints, as well as switching number, while subject to a radial network structure in which all loads must be energised. The optimisation technique of the EGA is then adopted to solve the fuzzy multi-objective problem efficiently. Test results verify the feasibility of applying the proposed method to manipulate the combinatorial optimisation network reconfiguration in distribution systems. View full abstract»

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  • Robust tuning of power system stabilisers using a Lyapunov method based genetic algorithm

    Page(s): 585 - 592
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (497 KB)  

    A genetic algorithm based method is proposed to tune the parameters of a power system stabiliser (PSS). This method integrates the classical parameter optimisation approach, involving the solution of a Lyapunov equation, within a genetic search process. It also ensures that for any operating condition within a pre-defined domain, the system remains stable when subjected to small perturbations. The optimisation criterion employs a quadratic performance index that measures the quality of system dynamic response within the tuning process. The solution thus obtained is globally optimal and robust. The proposed method has been tested on two different PSS structures: the lead-lag PSS and the derivative PSS. System dynamic performances with PSS tuned using the proposed technique are highly satisfactory for different load conditions and system configurations. View full abstract»

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  • Lessons learned from the power outages on 29 July and 21 September 1999 in Taiwan

    Page(s): 543 - 549
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    Two of the most severe power outage events took place in Taiwan in the year 1999. One occurred at 11:31 p.m. on 29 July when the #326 transmission tower collapsed due to a landslide, which disconnected around 83% (8.46 million) of the electricity consumers from the energy supply. About two months later, a devastating earthquake struck at 1:47 a.m. on 21 September. The quake halted the power supply to over 6.8 million users. Officials estimated the minimum total cost of the damage from both events to be several billion New Taiwan Dollars (NTD) (i.e. USD $1≈NTD $35), including manufacture losses and facility damages from high-tech industrial parks, asset damages and purchasing new equipment from the utility, and business losses from other industry sectors. The paper provides a technical review of both power failures and lessons learned from the outages. The paper summarises the system characteristics and the network conditions prior to, during and after both incidents. Finally, the lessons learned from both power failures and future strategies to be adopted by Taiwan Power Company (TPC) are concluded. View full abstract»

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  • Three-phase single-stage high-voltage DC converter

    Page(s): 505 - 509
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (375 KB)  

    Two techniques for generating-high DC voltage using a three-phase power supply are presented. The laboratory model of the converters is developed and tested. The converter system is based on a single-stage power conversion using an isolated flyback converter topology and cascaded voltage doubler circuit. The power switching devices in the controlled bridge are controlled by the three-phase pulse width modulation (PWM) switching technique. Low harmonic current distortion in the AC side is considered in this design. A field programmable gate array (FPGA) is used to generate the three-phase PWM pattern which makes the overall circuit compact and less discrete components are involved. Furthermore, the control bridge consists of three power switching devices with twelve diodes, and is thus less complicated to control. The performance of the converters are compared in terms of efficiency, voltage stress across the devices and voltage gain. View full abstract»

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  • Decentralised DC load flow and applications to transmission management

    Page(s): 600 - 606
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (505 KB)  

    A method for the decentralised solution of the DC load flow (DC-LF) problem of large, multi-area power systems is presented. The method transforms the original large set of the linear, sparse DC-LF equations into a number of smaller sparse quadratic programming (QP) problems, one for each area, which are iteratively solved using the auxiliary problem principle (APP) until they converge to the original problem solution. The applications of the decentralised DC-LF solution to the decentralised management of large, interconnected power systems by coordinated transmission system operator (TSO) actions are discussed. Test results on the IEEE-RTS 96 (up to five areas) are presented. View full abstract»

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  • Assessment of generator impact on system power transfer capability using modal participation factors

    Page(s): 564 - 570
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (555 KB)  

    Open access permits all generators to transmit active power into a system. Due to differences in location, output and other factors, however, some generators need more reactive power support than others. Each generator therefore consumes a different amount of reactive power capability of the system. It is very important to develop a quantitative index that can measure the reactive service needs of various generators. Potential applications for such an index include a fair compensation scheme for the procurement of reactive support services from generators, and a market signal for system security oriented generator dispatch. A modal analysis based generator participation factor is proposed to solve the problem. The theory of generator participation factor is presented. A five-bus system demonstrates the concepts and applications. Further case studies are performed using a real-life large-scale power system. Margin sensitivity studies are conducted to confirm the validity of the proposed index. View full abstract»

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  • Locational marginal price forecasting in deregulated electricity markets using artificial intelligence

    Page(s): 621 - 626
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Bidding competition is one of the main transaction approaches in deregulated electricity markets. Locational marginal prices (LMPs) resulting from bidding competition represent electricity values at nodes or in areas. A method using both neural networks (NNs) and fuzzy-c-means (FCM) is presented for forecasting LMPs. The recurrent neural network (RNN) was addressed and the traditional NN-based on a backpropagation algorithm was also investigated for comparison. The FCM helped classify the load levels into three clusters. Individual RNNs according to three load clusters were developed for forecasting LMPs. These RNNs were trained/ validated and tested with historical data from the PJM (Pennsylvania, New Jersey, and Maryland) power system. It was found that the proposed neural networks were capable of forecasting LMP values efficiently. View full abstract»

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  • Load-frequency control and inadvertent interchange evaluation in restructured power systems

    Page(s): 607 - 614
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    The subject of load-frequency control (LFC) from the point of view of the restructuring process of the electrical industry is addressed. LFC is treated as an ancillary service essential for maintaining the electrical system reliability at an adequate level. Reference is made to the guidelines suggested by the Union for the Co-ordination of Transmission of Electricity. Specific autonomy conditions, involving particular constraints on regulator parameters, are analytically derived and implemented for two control schemes: the pluralistic and hierarchical LFC. The results of simulations performed on a power system based on an IEEE Reliability Test System arranged into a three-control-area configuration are reported for the different LFC schemes. Evaluation of inadvertent interchanges is performed and suggestions on their accounting are proposed. View full abstract»

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  • Artificial neural network based peak load forecasting using Levenberg-Marquardt and quasi-Newton methods

    Page(s): 578 - 584
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    Daily electrical peak-load forecasting has been done using the feedforward neural network based on the Levenberg-Marquardt back-propagation algorithm, Broyden-Fletcher-Goldfarb-Shanno back-propagation algorithm and one-step secant backpropagation algorithm by incorporating the effect of eleven weather parameters, the type of day and the previous day peak load information. To avoid the trapping of the network into a state of local minima, the optimisation of user-defined parameters viz. learning rate and error goal has been performed. Training data set has been selected using a growing window concept and is reduced as per the nature of the day and the season for which the forecast is made. For redundancy removal in the input variables, reduction of the number of input variables has been done by the principal component analysis method of factor extraction. The resultant data set is used for the training of a three-layered neural network. To increase the learning speed, the weights and biases are initialised according to the Nguyen and Widrow method. To avoid over-fitting, an early stopping of training is done at the minimum validation error. View full abstract»

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  • Control of a battery supported dynamic voltage restorer

    Page(s): 533 - 542
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    Control of a dynamic voltage restorer (DVR) based on Space Vector PWM is described. The control algorithm is able to compensate for any type of voltage sag and uses a software phaselocked loop to track phase jumps during a fault. The control algorithm restores the depressed voltages to the same phase and magnitude as the nominal pre-sag voltages and then gradually tracks to the phase of the depressed voltages. Experimental results are shown to validate the control algorithm using a three-phase prototype with a power rating of 10 kVA. View full abstract»

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  • Optimal configurations for taps of windings and power electronic switches in electronic tap-changers

    Page(s): 517 - 524
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (445 KB)  

    One of the major criteria in the design of an electronic tap-changer of a power transformer is cost. The cost generally depends on the number, voltage and current rating of each power electronic switch. In addition, the structure of the transformer and insulating requirements will be simpler and its relevant cost will be lower if the number of taps are reduced. On the other hand, more voltage steps over the particular range of voltage regulation leads to the possibility of more precise voltage regulation, which is very desirable. A classification method for the taps and electronic switches is presented and all possible configurations are determined. Then a comparison between different configurations is made and an optimal configuration is obtained based on the cost. An example is given and a procedure discussed for selecting an optimal configuration in a particular application with special design purposes. View full abstract»

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  • Dynamic current-zero behaviour of wall-stabilised arc in different arc-quenching media

    Page(s): 510 - 516
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (459 KB)  

    SF6 gas is the medium currently used to quench the arc in gas circuit breakers (GCBs) and gas insulated switchgear (GIS). It has become increasingly necessary to look at alternatives to SF6 for the following reasons: (i) high cost; (ii) sensitivity to particle contamination; and (iii) concerns regarding global warming and hence the possibility of imposed rules for decreased SF6 production. From a practical standpoint, the complete elimination of SF6 as an arc-extinguishing medium is improbable. On the other hand, a reduction in the amount of SF6 and the inclusion of a buffer gas is worthy of consideration. In order to determine the suitability of a buffer gas, it is necessary to understand the buffer gases' fundamental plasma properties. A comparative prediction of the thermal breakdown strengths of the following gases: SF6, N2, O2, air, CO2, H2, He and N2-PTFE after current-zero is presented. The thermophysical properties of a N2-PTFE mixture are also calculated. A one-dimensional wall-stabilised arc model is solved numerically to determine the thermal breakdown strength of the aforementioned buffer gases in the presence of a uniform electric field intensity having a certain rate of rise. Calculations are done for two typical arc radii: 2.5 and 1.5 mm. Predictions confirm the suitability of He, CO2, N2 and air as a buffer gas to SF6 and helium is found to be the best buffer choice. View full abstract»

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