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Generation, Transmission & Distribution, IET

Issue 9 • Date September 2009

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Displaying Results 1 - 9 of 9
  • Design and evaluation of a compensating algorithm for the secondary voltage of a coupling capacitor voltage transformer in the time domain

    Page(s): 793 - 800
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (202 KB)  

    This study describes the design and evaluation of a compensating algorithm for the secondary voltage of a coupling capacitor voltage transformer (CCVT) in the time domain by considering the hysteresis characteristics of the core. The major error of the CCVT is the voltage across the capacitor and the tuning reactor caused by a non-sinusoidal exciting current. The proposed algorithm estimates the voltage across the capacitor and the reactor by considering the effect of the hysteresis characteristics of the core and adds it to the measured secondary voltage to obtain the correct voltage. The algorithm reduces the errors of the CCVT significantly both in the steady state and during a fault. The performance of the algorithm is verified under the various fault conditions by varying the fault distance, the fault inception angle and the fault impedance with the EMTP generated data. Test results clearly indicate that the algorithm can increase the accuracy of a CCVT significantly under the fault conditions as well as in the steady state. The algorithm helps to improve the performance of a protection relay or a metering device. View full abstract»

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  • Electromagnetic disturbances of control circuits in power stations and substations experienced in Japan

    Page(s): 801 - 815
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    This study has summarised electromagnetic disturbances of control circuits in power stations and substations experienced in Japan for ten years from 1990. Altogether 330 disturbances informed from Japanese utilities are classified by disturbed equipments and causes, and the surge incoming routes and the characteristics of the disturbances are investigated. Also, case studies are demonstrated. Finally, the influence of the disturbances to power system operation, countermeasures carried out and costs are presented. View full abstract»

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  • Flicker responses of different lamp types

    Page(s): 816 - 824
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (853 KB)  

    Nowadays, more and more lamp types are being used. Since different lamp types have different working principles, they also have different flicker responses. This paper shows the measurement results of different flicker responses for various types of lamps. These results prove that the UIE/IEC flickermeter, which has been used widely around the world for many years, cannot be used to advise on the flicker level of all lamp types. This is because of the fact that this flickermeter is based on a 230 V, 60 W or 120 V, 60 W incandescent lamp and can be used as reference only for this type of lamp or as reference to the standard. The UIE/IEC (International Union for Electricity Applications/International Electrotechnical Committee) flickermeter and the existing standards are therefore insufficient for other lamp types. This paper describes a proposal to improve the UIE/IEC flickermeter. View full abstract»

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  • Microgenetic multiobjective reconfiguration algorithm considering power losses and reliability indices for medium voltage distribution network

    Page(s): 825 - 840
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (789 KB)  

    This study proposes and applies an evolutionary-based approach for multiobjective reconfiguration in electrical power distribution networks. In this model, two types of indicators of power quality are minimised: (i) power system's losses and (ii) reliability indices. Four types of reliability indices are considered. A microgenetic algorithm ('GA) is used to handle the reconfiguration problem as a multiobjective optimisation problem with competing and non-commensurable objectives. In this context, experiments have been conducted on two standard test systems and a real network. Such problems characterise typical distribution systems taking into consideration several factors associated with the practical operation of medium voltage electrical power networks. The results show the ability of the proposed approach to generate well-distributed Pareto optimal solutions to the multiobjective reconfiguration problem. In the systems adopted for assessment purposes, our proposed approach was able to find the entire Pareto front. Furthermore, better performance indexes were found in comparison to the Pareto envelope-based selection algorithm 2 (PESA 2) technique, which is another well-known multiobjective evolutionary algorithm available in the specialised literature. From a practical point of view, the results established, in general, that a compact trade-off region exists between the power losses and the reliability indices. This means that the proposed approach can recommend to the decision maker a small set of possible solutions in order to select from them the most suitable radial topology. View full abstract»

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  • Graphical determination of network limits for wind power integration

    Page(s): 841 - 849
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    A graphical method is presented for determining the capability of individual system nodes to accommodate wind power generation. The method is based upon constructing a capability chart for each node at which a wind farm is to be connected. The capability chart defines the domain of allowable power injections at the candidate node, subject to constraints imposed by voltage limits, voltage stability and equipment capability limits being satisfied. The chart is first derived for a two-bus model, before being extended to a multi-node power system. The graphical method is employed to derive the chart for a two-node system, as well as its application to a multi-node power system, considering the IEEE 30-bus test system as a case study. Although the proposed method is derived with the intention of determining the wind farm capacity to be connected at a specific node, it can be used for the analysis of a PQ bus loading as well as generation. View full abstract»

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  • Single network adaptive critic design for power system stabilisers

    Page(s): 850 - 858
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    The recently developed single network adaptive critic (SNAC) design has been used in this study to design a power system stabiliser (PSS) for enhancing the small-signal stability of power systems over a wide range of operating conditions. PSS design is formulated as a discrete non-linear quadratic regulator problem. SNAC is then used to solve the resulting discrete-time optimal control problem. SNAC uses only a single critic neural network instead of the action-critic dual network architecture of typical adaptive critic designs. SNAC eliminates the iterative training loops between the action and critic networks and greatly simplifies the training procedure. The performance of the proposed PSS has been tested on a single machine infinite bus test system for various system and loading conditions. The proposed stabiliser, which is relatively easier to synthesise, consistently outperformed stabilisers based on conventional lead-lag and linear quadratic regulator designs. View full abstract»

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  • Maclaurin series-based lagrangian method for economic dispatch with valve-point effect

    Page(s): 859 - 871
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (519 KB)  

    Power utilities in general use Lagrangian method to solve economic dispatch (ED) problem for ease of implementation. This is possible only if the cost function of generating units is convex. Owing to valve-point effect exhibited by multi-valve steam turbines, the cost function is non-convex. The Maclaurin series-based Lagrangian method is proposed to solve complicated, non-convex and non-linear ED problems. In this method, the rectified sinusoid function is represented by Maclaurin sine series expansion and is solved using the Lagrangian method. The problem is solved iteratively using lambda iteration method. The proposed methodology is validated using IEEE 30-bus test system. In addition, the effectiveness of the new algorithm is demonstrated with 3, 13 and 40 generator test systems available in the literature. The results obtained substantiate the applicability of the proposed method for solving ED problems with non-smooth cost functions at par with stochastic search techniques generally used. View full abstract»

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  • Reactive power cost allocation by using a value-based approach

    Page(s): 872 - 884
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (574 KB)  

    This study proposes a value-based approach to allocate the cost of reactive power production/absorption and the useful VAr reserve provided by the generators. Reactive power support can be segregated into two broad categories: the utilised component of the support and the reactive power reserve component for system security. The utilised reactive power capacity can be decomposed further into the support required for meeting the reactive power loads and that required to meet additional reactive power transmission losses for the MW load shipment. A value-based sensitivity approach has been utilised to compute utilisation factors (UFs) for allocation of the cost of reactive power production/absorption and reserve provision. This method provides transparency in determining the relative utilisation and supply of reactive power by sources to the customers. System operator (SO) can utilise this method for allocation of the cost incurred by the reactive power providers to the load serving entities. Case studies on five-bus test system, IEEE 24-bus reliability test system (RTS) and 75-bus Indian system demonstrate the proposed approach. View full abstract»

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  • Transmission line pilot protection based on phase segregated model recognition

    Page(s): 885 - 890
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (319 KB)  

    A new type of transmission line pilot protection based on phase segregated model recognition is presented, since the capacitance model and the inductance model are established, respectively, for the external fault and the internal fault. When the internal fault occurs, the capacitance model error is larger than the inductance model error. When the external fault occurs, the inductance model error is larger than the capacitance model error. By computing the model error, the actual state of transmission lines is obtained. Theoretical analysis and electromagnetic transients program (EMTP) simulation demonstrate that this novel protection principle is unnecessary to compensate the distribution capacitance current and has fast operation speed and good performance on resisting transition resistance and transient components. View full abstract»

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IET Generation, Transmission & Distribution is intended as a forum for the publication and discussion of current practice and future developments in electric power generation, transmission and distribution.

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