Online ISSN
1751-8695
Print ISSN
1751-8687
IET Generation, Transmission & Distribution
Volume 6, Issue 7, July 2012
Volumes & issues:
Volume 6, Issue 7
July 2012
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- Author(s): F.E. Pérez ; R. Aguilar ; E. Orduña ; J. Jäger ; G. Guidi
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 593 –604
- DOI: 10.1049/iet-gtd.2011.0592
- Type: Article
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p.
593
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This work describes a transmission line protection scheme with two protection functions: directional zone and fault classification. The proposed scheme requires no information from remote ends and uses current measurements of only one phase of the three-phase systems for determining the fault direction, the faulted line and the fault type. Information concerning the high-frequency components of transient current signals is extracted with discrete wavelet transform (DWT) by using an adaptive wavelet, which has been specifically designed for relaying purposes, as analysis filter. After that, Bayesian linear discriminant analysis is employed for data classification. The present work highlights that the adaptive wavelet used here presents advantages for transmission line protection rather than predefined mother wavelets. Results demonstrate that the proposed scheme effectively distinguishes the faulted zone, the fault direction and the fault type. Therefore it offers primary protection to total line length, remote backup protection for the next transmission line and also the possibility to implement single-pole tripping. Current signals of roughly 2 ms are analysed then the proposed methodology can be implemented in high-speed protection schemes for extra- and ultra-high voltage (EHV/UHV) networks. - Author(s): M.M. Sahebi ; E.A. Duki ; M. Kia ; A. Soroudi ; M. Ehsan
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 605 –611
- DOI: 10.1049/iet-gtd.2011.0806
- Type: Article
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p.
605
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Different reasons such as power system restructuring, electricity price variation in some hours of a day and growth in the fuel price, have led to more attention to demand response (DR) programmes for consumers. Two important issues in DR programmes are emergency demand response programming (EDRP) and Interruptible/Curtail able (I/C) programme that is utilised as interruptible load contracts (ILC). The EDDR is utilised to decrease the consumption in peak load or critical hours of the day. This occurs by means of customer's behaviour in response to the incentives. However, the curtailment of voluntarily loads in the critical hours considering the consumer requirements is an action that can be performed in DR. A model has been proposed for EDRP and ILC implementation in the unit commitment (UC) programme. Then, the effect of these two DR programmes have been compared in long-term UC problem with fuel constraints. The proposed methodology has been formulated as a mixed integer linear problem and implemented in GAMS environment. The proposed model is applied to a 6-bus test system and a modified IEEE 118-bus system to demonstrate its effectiveness. - Author(s): G.A. Mahmoud
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 612 –618
- DOI: 10.1049/iet-gtd.2011.0530
- Type: Article
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p.
612
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The voltage stability problem of distribution networks is associated with a rapid voltage drop because of heavy system load. The decline of voltage stability level will restrict the increase of load served by distribution companies. One of the serious consequences of the voltage stability problem is a system blackout, and this problem has received much attention of distribution companies. In this study, a new voltage stability index (VSI) is developed for identifying the most sensitive bus to the voltage collapse in radial distribution network. The analysis is based on the catastrophe theory to find a new VSI and the voltage stability boundary of a distribution system. Two tested 15- and 30-bus systems analysed to give an illustration of the feasibility of the proposed method. - Author(s): S. Bhattacharyya ; S. Cobben ; W. Kling
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 619 –626
- DOI: 10.1049/iet-gtd.2011.0801
- Type: Article
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619
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Modern customers use many electronics devices that are quite sensitive to the quality of power supply. Voltage dip is an important power quality (PQ) issue that can cause damage to various customers’ devices and might lead to partial or complete interruption of the operation of an installation. Hence, a customer should know the approximate number and types of voltage dips that can happen at the point of connection (POC) so that he can take preventive measure to protect his installation from voltage dip-related problems. In the recent years, the EN50160 standardisation committee has developed a classification methodology to define voltage dips. The committee also recommended that voltage dip-related responsibilities should be clearly defined in the standard to solve disagreements among the different parties in the network. In this study, first voltage dip simulation is done on a typical medium voltage (MV) network, and approximate number of events in a year at a customer's POC is estimated. Furthermore, the guidelines are proposed to distinguish voltage dip-related responsibilities of the involved parties in the network. Finally, a case study is described in which the proposed guidelines about voltage dip-related responsibilities are applied. - Author(s): J.-C. Peng ; Y.-G. Zeng ; H. Jiang
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 627 –635
- DOI: 10.1049/iet-gtd.2011.0536
- Type: Article
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p.
627
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This study presents a strict method for resolving line-transferred power (or decomposing line-power flow) into source-driven component powers over lines. First, three properties of conservation and symmetry and additivity inherent in circuit laws are derived. Incorporating them with circuit-laws' equation, a model for resolving line-transferred power is built. The three properties make all conditions or hypothesis in Shapley theorem satisfied. Then the deductive reasoning of Shapley theorem is used to solve the model, which immediately gives a discrete and non-analytical resolution formula in terms of line-transferred powers caused by excitations of possible combination of sources. Representing the power by source currents (or electromotive forces), a continuous and analytical resolution formula in terms of source currents (or electromotive forces) is then proved mathematically. The resolution formula is invariantly the same for all sources including the slack source. It is also applicable to find the source-driven component powers flowing into loads and out of sources in arbitrarily complicated grids. Simulation results show the features of the proposed method. - Author(s): C.-M. Huang ; S.-J. Chen ; Y.-C. Huang ; H.-T. Yang
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 636 –645
- DOI: 10.1049/iet-gtd.2011.0559
- Type: Article
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p.
636
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This study presents a comparative study for four evolutionary computation (EC) methods to the optimal active–reactive power dispatch (ARPD) problem. Theoretically, there is a coupling relation between ARPDs. However, because of high X/R ratio existing in the transmission line, the problem of ARPD can be decomposed into two individual sub-problems by the decoupling concept, that is, ARPD problems. In this study, the evolutionary programming (EP), particle swarm optimisation (PSO), differential evolution (DE) and the proposed hybrid differential evolution (HDE) algorithms are used to separately solve the ARPD problem. To evaluate the performance of each method, the IEEE 30-bus and Taiwan Power Company (TPC) 345 kV simplified systems are employed as the study cases. The results indicate that the proposed HDE can obtain better results than the other methods in terms of active power transmission losses, voltage deviation, operating cost and convergence performance. - Author(s): S. Segura ; L.C.P. da Silva ; R. Romero ; D. Salles
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 646 –656
- DOI: 10.1049/iet-gtd.2011.0517
- Type: Article
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646
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The capacitor placement problem (CPP) has been widely studied throughout the years. However, traditional methodologies either do not consider non-linear loads in the formulations or are highly dependent on the spectrum of the harmonic currents. Therefore the traditional methodologies have become unsuitable for distribution system planning studies. The proposed approach formulates the CPP as a multi-objective optimisation model while including economic and technical aspects in the minimisation process. An additional objective function introduces a quadratic minimisation of the voltage harmonic distortions produced by the harmonic currents drawn by non-linear loads according to the IEEE Std. 519–1992 limits. A new constraint based on a resonance index (RI) is also introduced as a form to extend the capacitors’ lifetime. Furthermore, an aging model of capacitor dielectric insulation under a non-sinusoidal waveform scenario is used to estimate the expected real lifetime of capacitors. The proposed methodology was exhaustively tested on a 69-bus system and the results show that the methodology is adequate for planning capacitors and eliminates the need to focus in great detail on harmonic system data. - Author(s): A.C. Zambroni de Souza ; R. Leme ; K.L. Lo ; J.C. Stacchini de Souza ; A.B. Almeida
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 657 –664
- DOI: 10.1049/iet-gtd.2011.0685
- Type: Article
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p.
657
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This study addresses the problem of reactive power redispatch under bilateral power transactions. The proposed approach is to reduce active loss in a critical area, under the voltage collapse point of view, which is identified by the tangent vector technique. A methodology that uses an augmented load flow Jacobian is proposed to redispatch the reactive power and can be easily implemented in ordinary power flow programmes. Tests with the IEEE 14-bus test system and with a real Brazilian-107 bus system are carried out to illustrate the proposed approach. Results obtained by solving an optimal power flow problem are also presented for validation purposes. - Author(s): L. Guo ; C.X. Guo ; W.H. Tang ; Q.H. Wu
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 665 –672
- DOI: 10.1049/iet-gtd.2011.0748
- Type: Article
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p.
665
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This study presents a new framework for power transmission risk assessment, which considers not only historical failure statistics of transmission systems but also operation failure risks of system components. The component failure risks are integrated into the new framework based on operation condition assessment of components using the Evidential Reasoning (ER) theory. In this study, the traditional outage probability model of transmission line has been modified to build a new framework for power transmission system risk assessment. The proposed ER-based approach can provide a suitable mechanism to map component assessment grades to failure risks based on the probabilistic behaviours of power system failures. Under the new framework, both up-to-date component failure risks and traditional system risk indices can be processed with the proposed outage model. As a result, failure probabilities are related not only to historical statistic data but also to operation data of components and derived risk indices can reflect current operation conditions of components. In simulation studies, the ER approach is used to evaluate component conditions and link such conditions to failure rates using up-to-date component operation data, including both online and offline data of components. The IEEE 24-bus RTS-1979 system is used to demonstrate that component operation conditions greatly affect the overall transmission system failure risk. - Author(s): P. Xu ; X. Wang ; V. Ajjarapu
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 673 –679
- DOI: 10.1049/iet-gtd.2011.0573
- Type: Article
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p.
673
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A continuation power flow method with adaptive step size is proposed. Two approaches are used to predict the step size. First, convergence monitor is proposed to predict step size. This step size is compared with the step sizes obtained by the first-order sensitivity of Q-generation and voltage with respect to a parameter. Whichever step size is smaller is chosen to reduce the possibility of divergence and to deal with discrete controls. Convergence monitor is capable of detecting possible divergence in corrector within three iterations. The method of detecting limit-induced bifurcation is proposed by means of sensitivity. The proposed approach is tested on a 300 bus system as well as a practical system. The performance shows that it needs much less time and does not need the critical buses preselected. - Author(s): R. Benabid ; M. Boudour ; M.A. Abido
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 680 –692
- DOI: 10.1049/iet-gtd.2011.0296
- Type: Article
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A novel power injection model with multi-control functions of the static synchronous series compensator (SSSC) is presented. In this model, no simplification is performed and the complex impedance of the series coupling transformer and the charging susceptance as well as the complex impedance of the line are all taken into consideration. The proposed model is developed while the original admittance and the Jacobian matrix are kept unchanged. The new Jacobian corresponding to the SSSC device is integrated with the original Jacobian. Furthermore, the proposed model is general since it takes into account any possible bus type at the end of the line where SSSC is installed. In addition, two new control modes of SSSC namely the active and the reactive power losses control are proposed. The model is validated on IEEE 6-bus, IEEE 30-bus and realistic Algerian 114-bus. The simulation results demonstrate the effectiveness of the proposed SSSC model with the newly proposed control functions. It is also observed that the proposed Newton–Raphson power flow algorithm applied to a large and realistic power system is computationally inexpensive and the proposed model has satisfactory performance for steady state analysis and optimisation of the power system with SSSC device. - Author(s): X. Gu and H. Zhong
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 693 –700
- DOI: 10.1049/iet-gtd.2011.0591
- Type: Article
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An optimisation method of network reconfiguration is proposed by introducing a two-layer unit-restarting framework for power system restoration. The unit restarting during the network reconfiguration is treated as a two-layer restoration process–network-layer unit restarting and plant-layer unit restarting. Based on the two-layer framework, the optimisation of the network reconfiguration is modelled as a multi-objective optimisation problem, in which the network-layer unit restarting, the plant-layer unit restarting and restoration of the important loads are separately modelled as three optimisation sub-problems with their own models and solving algorithms. The lexicographic optimisation method is then used to solve the multi-objective optimisation problem by integrating the solving processes of the three sub-problems. The proposed optimisation method of network reconfiguration can determine the restarting sequence of all the units and realise the coordinative optimisation of the unit restarting and restoration of the important loads. The effectiveness of the proposed method is validated by the numerical results of a restoration example based on the New England 10-unit 39-bus power system. - Author(s): G. Valverde ; A.T. Saric ; V. Terzija
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 701 –709
- DOI: 10.1049/iet-gtd.2011.0545
- Type: Article
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This study proposes the use of Gaussian mixture models to represent non-Gaussian correlated input variables, such as wind power output or aggregated load demands in the probabilistic load flow problem. The algorithm calculates the marginal distribution of any bus voltage or power flow as a sum of Gaussian components obtained from multiple weighted least square runs. The number of trials depends on the number of Gaussian components used to model each input random variable. Monte Carlo simulations are used to compare the approximations. The effect of correlation between variables is taken into consideration in both formulations. The main advantage of the Gaussian components method is that the probability density functions of any variable is directly obtained. Test results in the 14-bus system and the 57-bus system provide a broad explanation of the advantages and constraints of the approximations, particularly in presence of correlated variables. - Author(s): N.G. Chothani ; B.R. Bhalja ; U.B. Parikh
- Source: IET Generation, Transmission & Distribution, Volume 6, Issue 7, p. 710 –718
- DOI: 10.1049/iet-gtd.2011.0459
- Type: Article
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p.
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This study presents a new support vector machine (SVM)-based fault zone identification scheme, which correctly identifies faults occurring inside and outside the protection zone of a busbar. A 220 kV substation with double busbar scheme present in an existing Indian system is considered for validation of the proposed fault zone identification algorithm for busbar protection. Fault simulations are performed using PSCAD/EMTDC software package and the outcome is then interfaced with MATLAB, where fault zone identification algorithm is implemented. A total of 44 650 internal and external fault cases with varying fault resistances, fault inception angles, fault locations, types of faults and source impedances have been used for validation of the proposed scheme. Even though the proposed scheme utilises only 29.63% of the total simulation cases (63 450) for the training of SVMs, it gives an overall fault zone identification accuracy of more than 90% when tested with using remaining 70.37% simulation cases for validation. The proposed scheme successfully discriminates between in-zone and out-of-zone faults with high fault zone identification accuracy for different fault and system conditions. Moreover, the proposed scheme remains stable during cross-country faults and severe current transformer (CT) saturation condition.
High-speed non-unit transmission line protection using single-phase measurements and an adaptive wavelet: zone detection and fault classification
Simultanous emergency demand response programming and unit commitment programming in comparison with interruptible load contracts
Voltage stability analysis of radial distribution networks using catastrophe theory
Proposal for defining voltage dip-related responsibility sharing at a point of connection
Resolution of line-transferred power in grids yielded by circuit-laws' symmetry under deductive reasoning of Shapley theorem
Comparative study of evolutionary computation methods for active–reactive power dispatch
Strategic capacitor placement in distribution systems by minimisation of harmonics amplification because of resonance
Reactive power redispatch for loss reduction using a modified power flow Jacobian
Evidence-based approach to power transmission risk assessment with component failure risk analysis
Continuation power flow with adaptive stepsize control via convergence monitor
Development of a new power injection model with embedded multi-control functions for static synchronous series compensator
Optimisation of network reconfiguration based on a two-layer unit-restarting framework for power system restoration
Probabilistic load flow with non-Gaussian correlated random variables using Gaussian mixture models
Development of a new bus zone identification algorithm using support vector machine
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