By Topic

Generation, Transmission and Distribution, IEE Proceedings-

Issue 4 • Date Jul 1999

Filter Results

Displaying Results 1 - 11 of 11
  • Optimal reactive power planning against voltage collapse using the successive multiobjective fuzzy LP technique

    Page(s): 343 - 348
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A new and comprehensive method for optimal reactive power planning (ORPP) against voltage collapse (VC) is given. The problem has the objectives of optimally siting and sizing new capacitors at prospective locations such that the transmission loss is minimum, an acceptable voltage profile is obtained, and the voltage stability is improved. To plan against VC, modal analysis is used to generate a participation-factor-based voltage collapse sensitive index (VCSI). VCSI is used to rank and select the best few prospective buses to site new capacitors. Using fuzzy models, all the violated load bus voltage constraints are fuzzified and their enforcements are maximised. The nonlinear programming problem of ORPP is solved in the successive multiobjective fuzzy LP framework. The proposed method was tested on modified IEEE 6-bus system and on a 191-bus Indian electric utility system. The results of the studies are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modelling the degradation of condition indices

    Page(s): 386 - 392
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    To ensure that the electricity distribution network achieves satisfactory levels of reliability and safety it is necessary to have well-founded and justifiable asset management policies in place. For many items of electricity distribution equipment, failures have been rare and inferences about future lifetimes are difficult to make. The paper argues that in such situations, importance should be given to obtaining condition information to aid asset management. A key requirement in using such data is the capability to model changes in an item's condition and the Markov model is proposed as being particularly suitable. The application of the Markov model to a collection of oil condition data, recorded during maintenance activity, is explained. The impact of such a model in making asset management decisions is then illustrated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Control setting of unified power flow controllers through a robust load flow calculation

    Page(s): 365 - 369
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    The unified power flow controller (UPFC) provides a promising means to control power flow in modern power systems. Essentially, the performance depends on proper control setting achievable through a power flow analysis program. The paper presents a reliable method to meet the requirements by developing a Newton-Raphson based load flow calculation program through which control setting of the UPFC can be determined directly. Case studies have been performed on standard IEEE 14-bus and 57-bus systems to show that the proposed method is robust and effective View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Security and revenue reconciliation in optimal transmission pricing

    Page(s): 355 - 359
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    Methodologies for optimal transmission pricing deal with the optimal use of the transmission network with capital and operational costs minimised. An alternative method is presented which includes transmission security in the pricing mechanism. The main feature of this method is that power system security can be separated from the capacity cost and the cost of transmission losses in the final transmission price, thereby helping the network operator or planner to identify those areas requiring attention. To ensure sufficient revenue is recovered to enable the transmission system to make a return on assets and to operate and maintain the system, a new way of achieving revenue reconciliation is proposed. This technique allows the rerouting of power flows with adjusted price while recovering the required revenue. These novel extensions to the optimal transmission pricing problem are applied to a 24-node network for illustrative purposes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • PWM-controlled series compensation on a radial feed power system

    Page(s): 377 - 385
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    A series compensation scheme is described employing two pulse width modulation (PWM) switched reactor modules in parallel with a capacitor. The two-module PWM-switched reactors provide continuously variable reactance by employing simple duty ratio control. The switching instants of the two reactor modules are controlled to have 180° phase shift, but equal duty ratio, to achieve harmonic cancellation. The complete series compensator provides a wide range of capacitive and inductive compensation. The harmonic distortion produced by this series compensation scheme with multiple-controlled reactors is analysed. An experimental model of the proposed compensator has been constructed and tested; this was inserted in a radial feed transmission line, to reduce the level of fluctuation of the receiving power on a nominal load subjected to another large load switching. For the two-module system, the voltage harmonics have been found to be well below the IEEE 519-1992 recommended limit, with a switching frequency of only 300 Hz. At the same time, the influence of the large load switching can be significantly reduced by the application of this compensator. The simplicity of the scheme and the quality of the results indicates its potential as another useful power quality controller View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Neural network based power system damping controller for SVC

    Page(s): 370 - 376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The development of a neural network based power system damping controller (PSDC) for a static VAr compensator (SVC), designed to enhance the damping characteristics of a power system network representing a part of the Electricity Generating Authority of Thailand (EGAT) system is presented. The proposed stabilising controller scheme of the SVC consists of a neuro-identifier and a neuro-controller which have been developed based on a functional link network (FLN) model. A recursive online training algorithm has been utilised to train the two networks. The simulation results have been obtained under various operating conditions and disturbance cases to show that the proposed stabilising controller can provide a better damping to the low frequency oscillations, as compared to the conventional controllers. The effectiveness of the proposed stabilising controller has also been compared with a conventional power system stabiliser provided in the generator excitation system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Undervoltage load shedding for induction motor dominant loads considering P, Q coupling

    Page(s): 337 - 342
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    A technique is presented that is suitable for undervoltage load shedding (UVLS) of dominant induction motor loads in power systems. To derive the algorithm, the induction motor voltage-dependent characteristics are formulated along a line parallel to the previously proposed generic dynamic load model. The load model is derived from the third-order induction motor model and is expressed in terms of real power, reactive power and slip, while retaining its dynamic characteristics. For the period following the initial induction motor transients (t>3 s), the model has been further simplified, explicitly representing the real and reactive power coupling in load dynamics. In the event of a voltage unstable situation, at a given voltage, the proposed UVLS criterion can be used to calculate the amount of load to be shed at any time to arrest voltage instability. It is shown that, when the induction motor dynamics are approximated using the first-order generic dynamic load models proposed in literature, the predicted amount of load to shed is approximately 2-3 times the amount obtained using the proposed method. This is owing to the real and reactive power coupling in the load dynamics. The proposed method is general and can be applied to any power system, provided the proportion of induction motor loads is approximately known View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigation of a unified power flow controller

    Page(s): 400 - 408
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Power flow in an AC transmission system depends on three basic parameters: transmission line impedance, voltage magnitude and phase angle. Maximum utilisation of the power system can be ensured by the control of these parameters in real-time. It is shown experimentally that a unified power flow controller (UPFC) can control each of the parameters either selectively or simultaneously in appropriate combinations. It is also shown that a UPFC can control independently the real and reactive power flow in a transmission circuit. Results from computer simulations and a hardware laboratory model are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Active filter used as a controlled reactance to prevent harmonic resonance in interconnected offshore power systems

    Page(s): 393 - 399
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Harmonic resonance is of particular concern in the design and operation of interconnected offshore power systems. This paper shows that it is possible to attenuate such resonance using an active filter. A new control method is proposed which can assess the system condition from a harmonic point of view and take into account the relative distribution of exciting frequencies and system resonant modes. Measured system busbar voltage is the only feedback required by the filter controller and the power system condition is initially unknown and variable. A series of time domain simulation results are presented to illustrate the effectiveness and limitations of the 'active harmonic damper' while some practical design considerations are highlighted View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Method for rating power cables buried in surface troughs

    Page(s): 360 - 364
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    An alternative method is detailed by which the ambient temperature parameter as applied to the calculation of ratings of power cables buried in surface trough installations can be determined. Improvement in the accuracy of cable rating calculations will allow greater utilisation of the cable asset and assist for example in the planning of system outages for maintenance work. The proposed model calculates the temperature at the cable burial depth based on measurements of solar radiation, windspeed and air temperature. The model is based on physical laws rather than empirical approaches that have been shown to be generally conservative in application. Results based on weather data monitored over a two-year period show that the ambient temperature of the soil at cable depth can be accurately determined and the model provides a significant improvement on existing methods View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Expert system for enhancing voltage security/stability in power systems

    Page(s): 349 - 354
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    The paper presents an expert system for enhancing both the voltage security and the voltage stability in power systems. The expert system is implemented to improve the voltage profile when contingencies are less severe and to adopt appropriate control actions to prevent the system from collapsing when severe contingencies are encountered. The sensitivity for a change of the load voltage to a variation of the on-load-tap-changer (OLTC) tap is used to verify the requirement of locking OLTC taps for operators. A new model, incorporated with variables for both the real power and the terminal voltage, for the reactive-power limit of a generator is presented for the voltage-stability studies. A real 256-bus system is used to serve as an example for demonstrating the performance of the proposed expert system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.