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Generation, Transmission and Distribution, IEE Proceedings-

Issue 5 • Date 13 Sept. 2004

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Displaying Results 1 - 15 of 15
  • Park-based and zero sequence-based relaying techniques with application to transformers protection

    Publication Year: 2004 , Page(s): 619 - 624
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    Two relaying techniques for protecting power transformers are presented and discussed. Very often, differential relaying is used for this purpose. A comparison between the two proposed techniques and conventional differential relaying is thus presented. The first technique, based on the measurements of zero sequence current within a delta winding, performs best in multiwinding transformers, since only measurement of the coil currents is needed. Thus, great simplicity is achieved. The second one is based on the differential procedure, but its analysis of asymmetries in the plot in Park's plane avoids problems related to spectral analysis in conventional differential relaying. The technique is justified from the analysis of symmetrical components. Misoperation in conventional differential relaying has been observed in some cases as a function of switching instant and fault location. This issue is discussed in the paper, and a statistical analysis of a large number of laboratory tests, in which both factors were controlled, is presented. As a conclusion, both relaying techniques proposed succeed in protecting the transformer. Additionally, the Park-based relay exhibits three characteristics of most importance: fastest performance, robustness and simplicity in its formulation. View full abstract»

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  • Intelligent neural-network-based adaptive power-line conditioner for real-time harmonics filtering

    Publication Year: 2004 , Page(s): 561 - 567
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (370 KB)  

    Conventional approaches for harmonic filtering usually employ either passive or active filtering techniques or a combination of both. The paper proposes an alternative intelligent adaptive power line conditioner (I-APLC), which is a form of neural-network-based adaptive harmonic filtering. The I-APLC makes use of one supervised learning rule (backpropagation) which underlies the adaptive self-learning in realising the optimal filter weight vector. Experimental results obtained via a prototype model of the DC variable-speed motor verified that I-APLC is feasible in terms of real-time tracking, adaptive harmonic filtering, faster training and convergence speeds, and simplicity in the online hardware implementation. View full abstract»

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  • Selection of optimal number and location of thyristor-controlled phase shifters using genetic based algorithms

    Publication Year: 2004 , Page(s): 630 - 637
    Cited by:  Papers (21)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (366 KB)  

    In recent years, major structural changes were introduced to the power sector all over the world. As a consequence, transmission expansion activities must be implemented to upgrade the utilities' power delivery systems. Some application of flexible AC transmission system (FACTS) technologies to existing high-voltage power systems has proved that the use of FACTS technology may be a cost-effective option for power delivery system enhancements. Undoubtedly, FACTS devices can minimise costly capital investments, but selecting the appropriate number and placement of these devices can be a challenge. To face this challenge, the paper deals with a methodology, based on a genetic algorithm, to identify the optimal number and location of FACTS devices in an assigned power-system network for maximising system capabilities, the social surplus and to satisfy contractual requirements in an open power market. In order to validate the usefulness of the approach suggested herein, a case study using the IEEE 30-busbar power system is presented and discussed. View full abstract»

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  • Identification of Tagaki-Sugeno-Kang fuzzy model for power transformers' predictive overload system

    Publication Year: 2004 , Page(s): 582 - 589
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Improvement of the utilisation factors of mineral-oil-filled power transformers is of critical importance in the competitive market of electricity. Utilities need to change dynamically the loadability rating of transformers without penalising their serviceability. As a key issue of loadability, all aspects of the thermal performance, and in particular those related to the determination of tolerable windings hot-spot temperature (HST), overload practice and its impact on remanent life expectation should be investigated. This paper deals with a methodology for the identification of a Takagi-Sugeno-Kang (TSK) fuzzy model able to reproduce the thermal behaviour of large mineral-oil-filled power transformers for implementing a protective overload system. The TSK fuzzy model, working on the load current waveform and on the top oil temperature (TOT), gives an accurate global prediction of the HST pattern. To validate the usefulness of the approach suggested herein, some data cases, derived from various laboratory applications, are presented to measure the accuracy and robustness of the proposed fuzzy model. View full abstract»

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  • Medium-term marginal costs in competitive generation power markets

    Publication Year: 2004 , Page(s): 604 - 610
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (278 KB)  

    The meaning and significance of medium-term marginal costs for a generation company in a competitive power market in analysed. A methodology to compute and decompose medium-term generation marginal costs in a competitive environment is proposed. The methodology is based on a market equilibrium model. The aim is to provide a useful tool for generation companies so that they can manage their resources in an optimal way, helping them with their operation, decision-making processes, asset valuations or contract assessments. View full abstract»

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  • Phase-decoupled method for three-phase power-flow analysis of unbalanced distribution systems

    Publication Year: 2004 , Page(s): 568 - 574
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (319 KB)  

    This paper presents a three-phase power-flow solution method for unbalanced distribution networks, in which each phase is modelled in a decoupled way and therefore can be solved independently. All component models are described using only individual phase voltages, admittances and independent current sources. The component models are decoupled into each phase through compensation current injections whenever necessary. The solution method is based on the Zbus Gauss approach, with implicit factorisation of the Ybus matrix for each phase. The approach significantly reduces the overall amount of computation needed to solve sequential three-phase power-flows, becoming itself eligible for use on the real-time operation of modern distribution systems. Test results, showing both the accuracy and speed-up performances of the decoupled approach when applied to several networks, are presented. View full abstract»

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  • Permanent-magnet synchronous generator with inset rotor for autonomous power-system applications

    Publication Year: 2004 , Page(s): 597 - 603
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (675 KB)  

    The analysis and performance of a three-phase synchronous generator with an inset permanent-magnet rotor is presented. Relevant performance equations are developed based on the two-axis model. The conditions for achieving zero voltage regulation, extremum points in the load characteristic and maximum power output, are deduced analytically. The finite-element method is used for computing the magnetic-field distribution, from which the effects of saturation on the synchronous reactances are quantified. Experiments performed on a 2.5 kVA prototype generator show that the saturated two-axis model gives a more accurate prediction of the load characteristics of the generator. View full abstract»

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  • Fuzzy OPF incorporating UPFC

    Publication Year: 2004 , Page(s): 625 - 629
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (367 KB)  

    A new optimal reactive power flow (ORPF) method is proposed which considers the inclusion of unified power flow controllers (UPFC). The modelling and inclusion of UPFC in the solution of power flow equations is presented. The ORPF problem is formulated as a fuzzy optimisation problem considering the objectives of minimising system transmission loss and obtaining the best voltage profile. The fuzzy formulation of the ORPF problem is solved using an EP algorithm. The proposed method is applied on the 6-bus and 57-bus IEEE test systems and on a 191-bus Indian electric power system. The results demonstrate the applicability of the method. View full abstract»

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  • Identification of the defective equipments in GIS using the self organizing map

    Publication Year: 2004 , Page(s): 644 - 650
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    Condition monitoring for gas insulated switchgear (GIS) requires an accurate and reliable identification of the defective equipment in it for maintenance purposes. In this paper, a feature extraction procedure is explored, which is based on the power spectral density (PSD) of the denoised partial discharges (PDs) emanating from the defective equipment in the GIS. Furthermore, artificial intelligence techniques, in particular, the self organising map (SOM), are investigated for their roles as classifiers to precisely identify this defective equipment, based on the PSD feature patterns. The performance of the SOM-based classifier is ascertained by using the PDs acquired from GIS in the Korean 154-kV EHV transmission networks. View full abstract»

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  • Control scheme for a universal power quality manager in a two-phase synchronous rotating frame

    Publication Year: 2004 , Page(s): 590 - 596
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (873 KB)  

    A universal power quality manager (UPQM) is presented. The active power balance of this UPQM is analysed. Based on the analysis a control scheme is established in a two-phase synchronous rotating dq-frame. In this control scheme the series active filter (AF) is controlled as a current source and makes the input current sinusoidal, while the shunt AF is controlled as a voltage source and it keeps the load voltage at the normal value. The performance of a UPQM with the proposed control scheme under different nonlinear load and source disturbance conditions is experimentally investigated. View full abstract»

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  • Towards a fast and robust interior point method for power system applications

    Publication Year: 2004 , Page(s): 575 - 581
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (314 KB)  

    An interior point method (IPM) for solving the optimal power flow (OPF) problem is presented. The IPM uses a combination of the predictor corrector, multiple predictor corrector and multiple centrality correction methods (all belong to the family of higher order interior point methods). The proposed IPM uses the best properties of each method to obtain a more robust IPM with faster convergence characteristics. The active power loss minimisation, minimum load shedding and maximum loadability problems are formulated as an OPF problem and solved with the proposed methodology. The IEEE 30, 57, 118, and 300 bus systems, and two realistic power systems, a 464 bus corresponding to the interconnected Peruvian system, and a 2256 bus corresponding to part (South-Southeast) of the interconnected Brazilian system were tested successfully. Results have indicated that good convergence performance is obtained and the computational time is small. View full abstract»

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  • Decomposition approach and analysis for a Z-matrix building process

    Publication Year: 2004 , Page(s): 638 - 643
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    An effective and procedural decomposition approach for Z-matrix building is proposed in this paper. There have been many papers in the literature regarding the Z-matrix building algorithms for large-scale power systems. Those methods mostly emphasised the relationship between the bus voltages and bus current injections. This paper provides a new perspective in observing the relationship. Bus voltages, bus current injections and branch currents were all investigated. The building algorithm can be accomplished by a simple search technique with two proposed matrices and is easily implemented. With these two matrices, the relationships among bus current injections, branch currents and bus voltages can be found. Those matrices will be very helpful in observing the structural changes in short-circuit analysis and contingency analysis. Numerical examples show that the proposed method is very effective and suitable to be used for large-scale power systems. View full abstract»

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  • Protection technique based on Δ-zero sequence voltages for generator stator ground fault

    Publication Year: 2004 , Page(s): 651 - 657
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    A mathematical model on a coil basis is used to study the characteristics of the zero sequence voltage of a generator. The proposed technique for the stator ground fault detection simultaneously takes into account the fault contributed zero sequence fundamental voltage and the fault contributed third-harmonic voltage (Δ-zero sequence voltage). The effect of the start-up component based on the wavelet transform is also highlighted. As information both on the fault contributed zero sequence fundamental voltage and the third-harmonic voltage is used simultaneously, the scheme can obtain higher sensitivity. Results from the experiment and in the field show that the proposed technique can detect the ground fault with high sensitivity and reliability during all operating conditions. View full abstract»

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  • Risk evaluation of transmission system operation modes and its application at British Columbia Transmission Corporation

    Publication Year: 2004 , Page(s): 658 - 664
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (274 KB)  

    Risk evaluation has been applied in transmission system development planning for years. However, it has not been sufficiently addressed in selecting transmission operation modes. A basic fact is that the risk evaluation for system development planning focuses on long-term system reinforcements but does not simulate operational measures in a short period. Selecting the most reliable transmission operation mode under different conditions requires simulation of operation measures such as load transfers, generation pattern changes, switching actions and temporary network reconfigurations. The paper presents basic concepts and modelling considerations to simulate operation measures. It also addresses two other issues that have to be considered in operation risk evaluation: inclusion of dynamic ratings of circuits and a simulation capability over any time length. Selection of the lowest risk operation mode in the BCTC metro system was used as an example to illustrate the concepts and method presented. View full abstract»

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  • Maximising energy capture from distributed generators in weak networks

    Publication Year: 2004 , Page(s): 611 - 618
    Cited by:  Papers (21)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (365 KB)  

    The paper discusses the implications of the increasing capacity of synchronous generators at the remote ends of rural distribution networks where the line resistances are high and the X/R ratios are low. Local voltage variation is specifically examined and two methods of compensation are proposed. The first of them is a deterministic system that uses a set of rules to switch intelligently between voltage and power factor control modes, while the second is based on a fuzzy inference system that adjusts the reference setting of the automatic power factor controller in response to the terminal voltage. Extensive simulations have verified that the proposed approaches may increase the export of real power while maintaining voltage within the statutory limits. View full abstract»

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