Online ISSN
1751-8695
Print ISSN
1751-8687
IET Generation, Transmission & Distribution
Volume 3, Issue 10, October 2009
Volumes & issues:
Volume 3, Issue 10
October 2009
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- Author(s): S. Kazemi ; M. Fotuhi-Firuzabad ; M. Sanaye-Pasand ; M. Lehtonen
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 891 –902
- DOI: 10.1049/iet-gtd.2008.0658
- Type: Article
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p.
891
–902
(12)
Loop restoration scheme (LRS) is a special feeder automation (FA) scheme, which is used by utilities to improve distribution system reliability. The LRS is controlled and managed by its automatic control system (ACS). The impacts on distribution system reliability indices of implementing LRS mainly depend on the type of its ACS. Two common types of ACS of LRS are presented and used in this study. Successful operation of ACS is dependent on the protection and automatic control functions of switching devices of LRS. Different failure modes of these switching devices can therefore affect the procedure of ACS in fault detecting, isolating and service restoration. The impacts of failure of protection and automatic control functions of switching devices and fuse of lateral distributors on reliability indices are illustrated. The worth of implementing LRS and its ACS type is represented by the reduction in expected customer interruption cost. A distribution test system is utilised to examine the impacts of two common types of ACS of LRS on the distribution system reliability. Selecting the type of ACS of LRS by utilities relies on the desired level of load-point and system reliability improvement. This study aims to quantitatively assess the impacts of two common types of ACS of LRS on the distribution system reliability. - Author(s): T.-H. Chen and N.-C. Yang
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 903 –910
- DOI: 10.1049/iet-gtd.2008.0616
- Type: Article
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p.
903
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(8)
This paper introduces a novel three-phase power flow approach for unbalanced radial distribution systems. The proposed approach is developed based on the branch frame of reference, rather than the traditional bus frame of reference. On the basis of the branch frame of reference, a simple direct iterative method can be applied. Hence, the proposed approach may be called the ‘direct ZBR method’. Basic graph theory and injection current technique are also applied in the proposed approach. The clear theoretical foundation and the simple topology of the radial distribution network make the proposed method efficient and reliable. To demonstrate the better convergence performance and the efficiency of the proposed approach, four three-phase IEEE test feeders are used for comparisons. The test results show that the proposed method has robust convergence characteristics and high performance, especially for large-scale radial distribution systems. - Author(s): W. Li ; B. Zhang ; J. He ; R. Zeng ; X. Li ; Q. Wang
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 911 –918
- DOI: 10.1049/iet-gtd.2009.0020
- Type: Article
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p.
911
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A simulation method to calculate the ion flow field of AC–DC hybrid lines is proposed. The charge simulation method (CSM) and the finite element method (FEM) are applied to calculate the electric field, while a time-dependent upwind differential algorithm is applied to calculate the migration of space charges. Furthermore, a variable time-step discretisation method is introduced to accelerate the computational process. The calculation results of ground level electric field and ion current density of a reduced-scale AC–DC hybrid line model are compared with previous experimental and calculating works. Satisfactory agreement is obtained between our calculation results and the experimental ones. As an application, the ion flow field of a hybrid 1000 kV AC/800 kV DC transmission line is simulated and analysed. - Author(s): R.V. de Oliveira ; R. Kuiava ; R.A. Ramos ; N.G. Bretas
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 919 –929
- DOI: 10.1049/iet-gtd.2008.0424
- Type: Article
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p.
919
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The design of supplementary damping controllers to mitigate the effects of electromechanical oscillations in power systems is a highly complex and time-consuming process, which requires a significant amount of knowledge from the part of the designer. In this study, the authors propose an automatic technique that takes the burden of tuning the controller parameters away from the power engineer and places it on the computer. Unlike other approaches that do the same based on robust control theories or evolutionary computing techniques, our proposed procedure uses an optimisation algorithm that works over a formulation of the classical tuning problem in terms of bilinear matrix inequalities. Using this formulation, it is possible to apply linear matrix inequality solvers to find a solution to the tuning problem via an iterative process, with the advantage that these solvers are widely available and have well-known convergence properties. The proposed algorithm is applied to tune the parameters of supplementary controllers for thyristor controlled series capacitors placed in the New England/New York benchmark test system, aiming at the improvement of the damping factor of inter-area modes, under several different operating conditions. The results of the linear analysis are validated by non-linear simulation and demonstrate the effectiveness of the proposed procedure. - Author(s): F. Yang and C.S. Chang
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 930 –940
- DOI: 10.1049/iet-gtd.2009.0172
- Type: Article
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p.
930
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Reducing the overall cost and improving the reliability are the two primary but often conflicting objectives in power system. Preventive-maintenance schedules thus need to be optimised to trade-off among multiple objectives. An integrated methodology with three functional blocks is proposed in this study. The first block models the stochastic deterioration process of individual component with a continuous-time Markov model, of which transition rates are influenced by different maintenance extents and aging of components. The second block evaluates the reliability of a composite power system, taking into account the configuration and failure dependence of the system. Particularly, this block identifies the minimum cut sets with consideration of protection trip and operational switching. The third block employs the Pareto-based multi-objective evolutionary algorithm to find the optimal solutions in a large search space and provide a holistic view of relationships among conflicting multiple objectives. A novel representation of maintenance activities is introduced in this study specifying both the maintenance timings and extents, and is proven to outperform the authors' previous representation, specifying the maintenance frequencies only. Optimisation of the reliability, maintenance failure costs is carried out on the Roy Billinton Test System (RBTS) demonstrating the potential of this approach in handling complex systems. - Author(s): J.F. Zhang ; C.T. Tse ; K.W. Wang ; C.Y. Chung
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 941 –948
- DOI: 10.1049/iet-gtd.2009.0089
- Type: Article
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941
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Many uncertainties exist in power systems and they will affect the stability analysis results. Voltage stability considering uncertainty in load parameters will be discussed. With the assumption that parameter variation is normal distribution, the probabilistic characteristics of eigenvalues under the uncertainties of dynamic load parameters can be obtained. Distribution of the critical eigenvalue will determine the stability probability of a power system. The stability margin can be inferred from the probabilistic critical load level, which is the maximal load level where system is ‘probabilistically’ stable. Case studies on three test systems illustrate that the stability margin will be reduced with load uncertainty. The proposed probabilistic results are validated using deterministic method of Monte Carlo on multi 10 000 sample studies. - Author(s): M. Ali ; Z.Y. Dong ; P. Zhang
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 949 –959
- DOI: 10.1049/iet-gtd.2009.0076
- Type: Article
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p.
949
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With the deregulation and constant expansion in power systems, the demand of high performance computing (HPC) for power system adequacy and security analysis has been increased rapidly. HPC also plays an important role in ensuring efficient and reliable communication for power system operation and control. In past few years, grid computing technology is catching up much attention from the power engineers and researchers. Grid computing technology is an infrastructure, which can provide HPC and communication mechanism for providing services in these areas of power system. A review is presented on the research which has been carried out in the last few years in this area regarding the applicability of grid computing technology in power system reliability and security analysis, operations, monitoring and control systems. We also introduce more grid computing applications for the future research directions in order to provide more open access and more efficient and effective computing services to meet the increasing needs of the power industry. This review presents a comprehensive and clear picture of the benefits of using this technology in terms of efficiency and cost. - Author(s): P.S. Georgilakis
- Source: IET Generation, Transmission & Distribution, Volume 3, Issue 10, p. 960 –969
- DOI: 10.1049/iet-gtd.2009.0184
- Type: Article
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p.
960
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After the completion of core manufacturing and before the assembly of transformer active part, 2N small individual cores and 2N large individual cores are available and have to be optimally combined into N transformers so as to minimise the total no-load loss (NLL) of N transformers. This complex combinatorial optimisation problem is called transformer no-load loss reduction (TNLLR) problem. A new approach combining differential evolution (DE) and multilayer perceptrons (MLPs) to solve TNLLR problem is proposed. MLPs are used to predict NLL of wound core distribution transformers. An improved differential evolution (IDE) method is proposed for the solution of TNLLR problem. The modifications of IDE in comparison to the simple DE method are (i) the scaling factor F is varied randomly within some range, (ii) an auxiliary set is employed to enhance the population diversity, (iii) the newly generated trial vector is compared with the nearest parent and (iv) the simple feasibility rule is used to treat the constraints. Application results show that the performance of the proposed method is better than that of two other methods, that is, conventional grouping process and genetic algorithm. Moreover, the proposed method provides 7.3% reduction in the cost of transformer main materials.
Impacts of automatic control systems of loop restoration scheme on the distribution system reliability
Three-phase power-flow by direct ZBR method for unbalanced radial distribution systems
Calculation of the ion flow field of AC–DC hybrid transmission lines
Automatic tuning method for the design of supplementary damping controllers for flexible alternating current transmission system devices
Optimisation of maintenance schedules and extents for composite power systems using multi-objective evolutionary algorithm
Voltage stability analysis considering the uncertainties of dynamic load parameters
Adoptability of grid computing technology in power systems analysis, operations and control
Differential evolution solution to transformer no-load loss reduction problem
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