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Generation, Transmission and Distribution, IEE Proceedings-

Issue 5 • Date Sep 1999

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Displaying Results 1 - 21 of 21
  • Multipurpose overhead lines protection algorithm

    Publication Year: 1999 , Page(s): 441 - 445
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A numerical algorithm for multipurpose overhead lines protection, based on one terminal data and derived in the time domain, is presented. The fault location, direction and its nature (arcing or arcless fault) are estimated using the least squares error technique. The faulted phase voltage is modelled as a serial connection of fault resistance and arc voltage, offering more sophisticated line protection. The algorithm can be applied to both the ordinary and high-impedance fault detection, distance protection, intelligent autoreclosure, as well as for directional relaying. The new approach does not require the line zero-sequence resistance as an input datum. The algorithm is derived for the case of most frequent single-phase-to-ground asymmetrical faults. The results of algorithm testing through computer simulation are given. The influence of remote infeed, fault resistance, higher-order harmonics, power system frequency, network topology, line parameters and other factors are investigated and systematically presented View full abstract»

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  • Optical-fibre-based investigations of contact travel, gas pressure and particle concentration in SF6 puffer circuit breakers

    Publication Year: 1999 , Page(s): 453 - 458
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Experimental results have been obtained about conditions within SF 6 puffer circuit breakers during and after the interruption of fault currents up to 45 kA peak using optical-fibre sensors based on chromatic modulation. The particular parameters measured with the optical-fibre sensors were the contact travel, the gas pressure in both the puffer piston chamber and the circuit-breaker tank, the radiative emission from the electric arc and the concentration of micron-sized particles produced by the arcing. The experimental results are compared where possible with theoretical calculations from a computational-fluid-dynamics computer package. The possible role of the particulate material in the longer-timescale conditions within the circuit-breaker tank is considered and the need for a better understanding of the particulate-material properties and formation is highlighted View full abstract»

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  • Using Monte Carlo simulation for overall distribution system reliability worth assessment

    Publication Year: 1999 , Page(s): 535 - 540
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    This paper describes a Monte Carlo simulation approach to overall distribution system reliability worth assessment and illustrates it by application to the distribution systems of all the five load buses associated with a complex test system. The paper presents the results of a series of simulations studying the impacts of various probability distributions for restoration times on the two reliability worth indices, namely load point expected cost (ECOST) and interrupted energy assessment rate (IEAR). Different radial system operating philosophies are incorporated and their impacts are analysed. Furthermore, the contributions from radial segment and subtransmission failure modes, such as first-order active failures, first-order total failures and all the possible second-order overlapping failures, to overall distribution worth indices are analysed. All the information generated by the simulation studies can provide useful reference to the electric power utilities and planners in the decision-making stage View full abstract»

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  • FACTS control design based on power system nonparametric models

    Publication Year: 1999 , Page(s): 409 - 415
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The paper presents two applications of the sampled regulator design method (SRDM) to flexible AC transmission systems (FACTS) control, using unified power flow controller (UPFC) DC capacitor voltage control and static VAr compensator (SVC) AC voltage control, based on nonparametric models of the power system. The SRDM was developed in the 1980s for the design of a class of sampled regulators for uncertain, nonlinear systems and can guarantee control system stability, optimality and robustness. The design only requires knowledge of the open-loop system step response-a nonparametric model-which is particularly attractive for applications in power systems, where field tests to obtain nonparametric models are usually much easier to apply than the development of parametric models. A comprehensive demonstration of the SRDM for UPFC DC capacitor voltage control and SVC AC voltage control in example power systems is given View full abstract»

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  • Inductance and winding eddy loss of air-cored reactors

    Publication Year: 1999 , Page(s): 416 - 420
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A method of calculating the inductance and winding eddy loss of a particular type of air-cored shunt reactor has been developed. It is applicable to air-cored reactors bounded axially by conducting screens and radially by magnetic shunts. The results obtained using this method are compared with those from a finite element analysis. The calculated inductances are also compared with test results on a model View full abstract»

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  • Predictive current control of distribution static compensator for reactive power compensation

    Publication Year: 1999 , Page(s): 515 - 520
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The paper describes modelling and current control techniques of a distribution static compensator (D-STATCOM). Current control is based on the predictive and the space vector pulsewidth modulation (PWM) scheme. The predictive current-controlled PWM D-STATCOM can maintain its performance with reactive power compensation and a fixed switching frequency. By using the space vector control, low ripple and offset in the current and the voltage as well as fast dynamic responses are achieved using a small DC link capacitance View full abstract»

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  • Fixed transmission rights for zonal congestion management

    Publication Year: 1999 , Page(s): 471 - 476
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Declaring that engineering studies and experience are the criteria to defining zonal boundaries, or to define a zone based on the fact that it is a densely interconnected area and paths connecting these densely interconnected areas are interzonal lines, will render insufficient and fuzzy definitions. The zone definition is given a certain criterion based on the locational marginal price (LMP). This concept is used to define zonal boundaries and to decide whether any zone should be merged with another zone or split into new zones. The paper combines zonal and fixed transmission rights (FTR) schemes to manage congestion. This combined scheme is utilised with LMPs to define zonal boundaries more appropriately. The scheme presented gains the best features of the FTR scheme, which are providing financial certainty, maximising the efficient use of the system and making users pay for the actual use of congested paths View full abstract»

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  • Steady-state analysis of single-phase self-excited induction generator

    Publication Year: 1999 , Page(s): 421 - 427
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A methodology of selection of capacitors for optimum excitation of single-phase SEIG is explained. Computed results are validated by experimental investigations under varying loads and various excitation capacitors. The results are explained to obtain useful guidelines for design and improvements of small self-regulated SEIG units View full abstract»

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  • Inverse matrix modification lemma and Thevenin theorem for compensated network solutions

    Publication Year: 1999 , Page(s): 496 - 500
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    The close relationship between the inverse matrix modification lemma (IMML) and the Thevenin theorem is investigated. Making reference to the modified network solution by compensation, the IMML formula is demonstrated using the Thevenin theorem (or its dual Norton theorem) and superposition. Such equivalence allows either approach to be applied to network modification cases with the same computation burden. However, the Thevenin-Norton approach leads to a reduced number of operations compared to IMML in those contingency cases involving solid connections (bus join). Examples of the compensation procedure based on the Thevenin-Norton approach are given with reference to an IEEE test system, and to actual large-scale power networks View full abstract»

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  • Switching control for power systems with line losses

    Publication Year: 1999 , Page(s): 435 - 440
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    The control of initial swinging due to large power system disturbances justifies the use of controllers in a full-on full-off mode. Current control designs are based on linear controllers with saturating elements using local feedback signals. The paper develops a switching control strategy for the damping of power system interarea modes using multiple FACTS devices and angle transducers. The design is based on maximising the convergence rate of a system kinetic energy function. The function provides correct analysis of lossy systems so that the the load modulation by static VAr compensators, as well as the damping from controlled series capacitors, can be incorporated. Fast suppression of oscillations using multiple FACTS devices is demonstrated View full abstract»

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  • Analysis of equivalent 10 Hz voltage flicker in power systems

    Publication Year: 1999 , Page(s): 447 - 452
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    A new method for analysing the effect of voltage flicker on bus voltages is presented in this paper. The Y-matrix and the stochastic theory are used for obtaining an equivalent 10 Hz voltage fluctuation (ΔV10) at each bus in the distribution systems. The computation of the proposed method is achieved in MATLAB using the sparse command. The simulation results show that the proposed method is able to estimate all ΔV10 quickly, but accurately, in the system. The impact of the voltage flicker sources incorporated with linear loads and compensators on the system voltages is also discussed using the simulation results View full abstract»

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  • Optimising location of unified power flow controllers using the method of augmented Lagrange multipliers

    Publication Year: 1999 , Page(s): 428 - 434
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The unified power flow controller (UPFC) has been proved to be an effective means for regulating voltage profile and power flow in modern power systems. Optimising its location becomes a concern when coming to the practical implementation stage. This paper proposes a mathematical model to work out a pragmatic approach based on the augmented Lagrange multiplier method to determine optimal location for UPFCs to be installed. Investment consideration of UPFCs and real power loss of the network concerned are integrated into the objective functions. The proposed method takes account of steady state security constraints of the power systems represented by models having large scale and nonlinear mathematical properties. Case studies show that the optimally located UPFC can improve the steady state performance and significantly increase the loadability of the system View full abstract»

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  • Well-being framework for composite generation and transmission system reliability evaluation

    Publication Year: 1999 , Page(s): 528 - 534
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The basic objective of generation and transmission systems is to serve every major load point in the system as reliably and economically as possible. The probability of failure that is related to the load characteristics is important in the reliability study of generation and transmission systems. This paper describes a probabilistic method, designated as system well-being analysis, for evaluating the effect of peak load, load factor, load curtailment philosophy and percentage load curtailed. Contingency level selection, a dominant factor that influences the accuracy and efficiency of probability study is also considered. This approach incorporates the conventional risk index as well as the accepted deterministic criteria identified as being in the healthy and marginal states. By including deterministic criteria in conjunction with probabilistic methods, well-being indices based on these criteria can be used by the system operator to alleviate the difficulties encountered in interpreting a single risk index. A technique for calculating the well-being indices in generation and transmission systems, together with the effects of individual load attributes. Is illustrated by application to an educational test system designated as the RBTS View full abstract»

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  • Generating capacity planning criteria determination for developing countries: case study of Nepal

    Publication Year: 1999 , Page(s): 491 - 495
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Reliability is virtually taken for granted in most developed countries, This is not the case in developing countries where many basic development projects compete for the available scarce resources. Many electric power projects are cancelled or postponed owing to a lack of resources, environmental problems and other social concerns. A more rational and consistent evaluation approach is therefore required to justify future power projects in developing countries. The paper describes how a basic reliability cost/worth approach to generating capacity evaluation can be used by utilities in developing countries to make decisions on future power projects. The approach is illustrated by application to the Nepal Integrated Electric Power System, which can be considered as a representative model for many electric power systems in developing countries View full abstract»

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  • Phillips-Heffron model of power systems installed with STATCOM and applications

    Publication Year: 1999 , Page(s): 521 - 527
    Cited by:  Papers (23)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The paper establishes the linearised Phillips-Heffron model of a power system installed with a static synchronous compensator (STATCOM) and demonstrates the application of the model in analysing the damping effect of the STATCOM and designing a STATCOM stabiliser to improve power system oscillation stability. Both cases of single-machine infinite-bus and multimachine power systems are studied and example power systems are presented. These show the negative damping influence of a STATCOM DC voltage regulator on power system oscillations and the effectiveness of the STATCOM stabiliser superimposed on a STATCOM AC voltage regulator to counterattack the negative damping effect View full abstract»

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  • Anticipatory load shedding scheme for loadability enhancement

    Publication Year: 1999 , Page(s): 483 - 490
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    The paper presents a new anticipatory load shedding protection scheme implemented centrally from the energy control centre for loadability enhancement. Most of the schemes available in literature for this purpose are based on information at the current operating condition which are blind to load increase scenarios and the associated switchings in voltage controlled buses. The proposed scheme anticipates the danger of voltage instability in a time frame of interest by incorporating these effects. If the normal controls are exhausted, the algorithm based on successive application of LP restricts/sheds the required amount of low priority loads in advance so that the power system survives the voltage instability threat even during the worst power system period. Results for IEEE 30 bus and an Indian 91 bus power systems have been obtained to demonstrate the effectiveness of the proposed algorithm View full abstract»

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  • Security dispatch using the Hopfield neural network

    Publication Year: 1999 , Page(s): 465 - 470
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    A restructuring of the improved Hopfield neural network (NN) approach, which has previously been proposed for solving power system economic dispatch, is proposed for solving real-time economic dispatch problems with security constraints. A new mapping process is formulated and a computational method for obtaining the weights and biases is described using a slack variable technique for handling inequality constraints. Side constraints are handled by a modified activation function for which a symmetric ramp function is chosen for the input-output function and applied to each element of the variable set. The Hopfield NN approach is tested on the IEEE 30-bus system for different demands View full abstract»

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  • Automatic fuzzy model identification for short-term load forecast

    Publication Year: 1999 , Page(s): 477 - 482
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The conventional fuzzy modelling of short-term load forecasting has a drawback in that the fuzzy rules or the fuzzy membership functions are determined by trial and error. An automatic model identification procedure is proposed to construct the fuzzy model for short-term load forecast. An analysis of variance is used to identify the influential variables of the system load. To set up the fuzzy rules, a cluster estimation method is adopted to determine the number of rules and the membership functions of variables involved in the premises of the rules. A recursive least squares method is then used to determine the coefficients in the concluding parts of the rules. None of these steps involves nonlinear optimisation and all steps have well bounded computation time. This method was tested on the Taiwan Power Company's (Taipower) load data and the performance of the proposed method is compared to those of Box-Jenkins (B-J) transfer function and artificial neural network (ANN) models View full abstract»

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  • Capacitor placement in radial distribution systems for loss reduction

    Publication Year: 1999 , Page(s): 501 - 505
    Cited by:  Papers (21)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    Reduction of I2R loss in distribution systems is very essential to improve the overall efficiency of power delivery. The I2R loss can be separated into two parts based on the active and reactive components of branch currents. The paper presents a method of minimising the loss associated with the reactive component of branch currents by placing shunt capacitors. This method first determines a sequence of nodes to be compensated by capacitors. The size of the optimal capacitor at the compensated nodes is then determined by optimising the loss saving equation with respect to the capacitor currents. The performance of the proposed method was investigated on two distribution systems consisting of 15 and 33 buses and it was found that a significant loss saving can be achieved by placing optimal capacitors in the system View full abstract»

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  • Block diagram model for fundamental studies of a synchronous generator-static VAr compensator system

    Publication Year: 1999 , Page(s): 507 - 514
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The unified block diagram model of a generator and flexible AC transmission system (FACTS) devices has been presented in the open literature, and used for fundamental investigation of damping torque contributions from FACTS devices into power systems. The model, however, does not always yield a realistic response since only the main field winding is assumed to exist in the generator model. The authors extend the generator model to incorporate the damper windings in the q- and d-axes. This allows a more realistic investigation of the dynamic interactions between the SVC and synchronous generator. The small-signal, dynamic performance of generator-SVC models, with a different number of generator windings on the d- and q-axes, is compared by means of the block diagram model presented in this paper. The analysis is carried out using frequency response methods View full abstract»

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  • Effects of very fast transient overvoltages on transformer

    Publication Year: 1999 , Page(s): 459 - 464
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    An analytical solution is found using the Laplace transform to describe the very fast transient overvoltage (VFTO) in the gas insulated switchgear (GIS) connected directly to a transformer. The oscillation frequencies, and other properties, are explicitly given in terms of system parameters. The magnitude of VFTO at the transformer is suppressed due to the transformer capacitance, Magnitudes of the initial abrupt voltage change and oscillatory voltage are assessed. The abrupt voltage is larger, but not enough to induce a harmful voltage in the transformer. The oscillatory components may damage the winding insulation at the occurrence of resonance View full abstract»

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