By Topic

Generation, Transmission and Distribution, IEE Proceedings-

Issue 4 • Date Jul 2001

Filter Results

Displaying Results 1 - 18 of 18
  • Time-sequential simulation technique for rural distribution system reliability cost/worth evaluation including wind generation as alternative supply

    Publication Year: 2001 , Page(s): 355 - 360
    Cited by:  Papers (23)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    Wind turbine generators (WTGs) are being actively considered as embedded generation sources in rural distribution systems. A time-sequential simulation technique is presented for the reliability cost/worth evaluation of a distribution system including WTGs. A three-state model of a WTG is presented, considering variable wind speed and the forced outage rate. A test rural distribution system is utilised to illustrate the proposed technique. The system reliability performance using WTGs as an alternative supply is investigated. The effects on the distribution system reliability of the WTG parameters are examined and illustrated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric behaviour of polluted porcelain insulators

    Publication Year: 2001 , Page(s): 269 - 274
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The dielectric behaviour of polluted porcelain insulators is investigated by means of experimental tests and simulation methods. The elaboration of the experimental results, using well known mathematical models of polluted insulators, leads to the identification of the arc constants. It was found out that the arc constants are independent of the insulator type and of the experimental pollution procedure (salt fog or solid layer cool fog method). This allows the formulation of a generalised simulation model of polluted insulators. The critical parameters for the flashover (voltage, current and gradient) are computed by means of the developed model, using only the geometric dimensions of the insulator, the pollution severity and the arc constants. Different types of porcelain insulators are investigated and the variation of the critical parameters upon the density of the pollution layer is determined. The influence of the geometrical dimensions and of the shape of the insulator to the critical parameters is also investigated. Furthermore, analytical relations are defined, between the computed critical parameters and the salt deposit density as well as the dimensions, the shape and the type of the insulator View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal multiobjective planning of dynamic series compensation devices for power quality improvement

    Publication Year: 2001 , Page(s): 361 - 370
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    An optimisation algorithm using tabu search is presented for optimal planning of series compensation devices for power quality improvement in distribution systems. The proposed algorithm is posed for optimal placement of two types of devices, named the series voltage restorer and the fault current limiter. A multiobjective problem is formulated to optimise a composite set of fuzzy performance indices comprising the cost expenditure of installed series compensation devices, voltage boosts across sensitive loads and overall voltage improvement. To ensure robustness, distribution networks are reinforced for preselected internal faults, external faults and simultaneous disturbances. Five case studies are presented to demonstrate the properties of the proposed algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Behaviour of grounding loop with bentonite during a ground fault at an overhead line tower

    Publication Year: 2001 , Page(s): 275 - 278
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The results of a single-phase short-circuit experiment at a 35 kV overhead line are presented. During the experiment, the grounding loops, backfilled with bentonite and waste drilling mud, were exposed to real ground fault currents. As a consequence of the increased thermal stresses of bentonite and waste drilling mud, only short time increases of the resistance of the grounding loops were registered. It is shown that, independently of the manner of the neutral point grounding in 35 kV and 110 kV networks, as a backfill material, bentonite retains its positive characteristics even after being exposed to real ground fault currents View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modelling of random variation of three-phase voltage unbalance in electric distribution systems using the trivariate Gaussian distribution

    Publication Year: 2001 , Page(s): 279 - 284
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    This paper deals with probabilistic modelling of the random variation of three-phase voltage unbalance. With field measurement and an analysis of three-phase voltage unbalance, trivariate Gaussian distribution has been employed to model the random variation of three-phase voltages, and a simulation method based on the Monte Carlo technique has been developed to generate voltage data, the statistical properties of which are close to those of the measured voltages. Comparison of the probability distribution functions of the complex voltage unbalance factor between Monte Carlo simulation and the measurement is then carried out for validation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A harmonic domain solution for systems with multiple high-power AC/DC converters

    Publication Year: 2001 , Page(s): 312 - 318
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The unified Newton solution used to derive converter/system interactions in the harmonic domain is extended in the paper to systems with multiple AC/DC converters in different locations. The extended solution is used to investigate potential interactions between the HVDC link and aluminium smelters in the New Zealand system. The inaccuracies of conventional direct harmonic solutions are highlighted by comparison with the results obtained with the proposed general iterative solution View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimisation of capacitor allocation using an interactive trade-off method

    Publication Year: 2001 , Page(s): 371 - 374
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A novel formulation for the optimal capacitor allocation problem is presented. This involves cost investment, operating efficiency, system security and service quality, which are of priority concern to the system planner. However, these objectives contradict each other and have trade-off relations. Conventional approaches that optimise a single objective have difficulty in resolving such problems. An interactive trade-off algorithm is presented. Based on the E-constrained technique to obtain a compromised or most satisfactory noninferior solution. Through the interactive steps, the planner can provide his or her preference or system operating policy on each objective to resolve the multi-objective optimisation problem. Numerical examples involving the Taipower system demonstrate the effectiveness of the proposed approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of losses in design of distribution circuits

    Publication Year: 2001 , Page(s): 343 - 349
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The impact of losses on the design of distribution cable and overhead networks is discussed. A minimum life-cycle cost methodology that balances the capital investment against the cost of the system losses is used as a basis for circuit design. The results obtained indicate that the utilisation of distribution circuits, particularly at lower voltage levels, should be quite low. The analysis also shows that the optimal design of the circuits with cost of losses taken into account is likely to satisfy the security requirements at no additional cost in most of the system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital fault-location algorithm including grounding impedance at fault place

    Publication Year: 2001 , Page(s): 291 - 295
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The influence of fault-place grounding impedance is usually not taken into account in algorithms for ground-fault distance estimation. The fault-place grounding impedance depends on the design characteristics of ground wires and tower footing resistances. The paper shows the possibility of taking into account the fault-place grounding impedance in the algorithm for ground-fault distance estimation. An algorithm taking into account fault-place grounding impedance has a better accuracy and only slightly greater complexity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Static security assessment of a power system using query-based learning approaches with genetic enhancement

    Publication Year: 2001 , Page(s): 319 - 325
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    A new approach of using query-based learning in neural networks to solve static security assessment problems in a power system is proposed. This learning method is intrinsically different from the learning performed by randomly generated data. Query-based learning is a methodology that requires asking a partially trained neural network to respond to the questions. The response of the query is then taken to the oracle. An oracle makes judicious decisions that help improve the quality of training data, thereby guaranteeing the assessment results. Moreover, to further improve the learning performance, the method is enhanced by the aid of genetic algorithms. Therefore the neural network is intelligently guided to a near-optimal initialisation. The probability of learning stagnation can be thus decreased. This method was tested on the Taiwan Power System through the utility data. Test results demonstrated the feasibility and effectiveness of the approach for the applications considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiobjective optimal feeder reconfiguration

    Publication Year: 2001 , Page(s): 333 - 336
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    A formulation for the feeder reconfiguration to reduce power loss, increase system security and improve power quality by considering operational constraints is presented. The problem formulation proposed is a constrained, multiobjective and nondifferentiable optimisation problem. The optimal feeder configuration can simultaneously attain the above objectives. However, these objectives are noncommensurable such that it is difficult to solve this class of problem by conventional approaches that optimise a single objective. Thus; these objective functions are first formulated in fuzzy sets to represent their imprecise nature. A fuzzy satisfied method based on evolutionary programming is then introduced to determine the optimal solution. The proposed approach is implemented in a software package and its effectiveness is verified through numerical examples on the Tai-power system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal allocation of reactors for light load operation

    Publication Year: 2001 , Page(s): 350 - 354
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Reactive power sensitivities are used to allocate optimal reactive power compensation for light load operation. Both locations as well as reactor values are determined. The proposed optimisation algorithm determines the effective location by dropping the ineffective locations during the optimisation process, taken into consideration system constraints View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dynamic interlocking for fault-level limiting

    Publication Year: 2001 , Page(s): 285 - 290
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    The purpose of dynamic interlocking for fault-level limitation is to replace hardwired interlocks with more flexible computer-based systems. An early version of dynamic interlocking was implemented at Drax power station in the UK a number of years ago using a purpose-built microprocessor system, running software with the network model hard-coded into it. This dynamic interlocking system could not be applied to another power system without redesigning both the hardware and software. To overcome the dedicated nature of the first system, a new dynamic interlocking system was built and subsequently installed in Heysham 2 nuclear power station in the UK. The software operates on-line and in real-time. The core software for this new system was general purpose so that it could be applied to any power system. To configure the software for any new network the user has only to enter the appropriate network data through a graphical user interface. The paper describes the core software that was subsequently installed in Heysham 2 nuclear power station, including practical experience of its operation. The work was completed in 1985 and implemented on specialised hardware. Despite this, the core software is even more relevant today than at that time because advances in hardware technology have created the opportunity to construct a universally applicable dynamic interlocking system. The advent of circuit breakers with built-in microprocessor systems and communication interfaces, as well as the power of SCADA systems, has created the opportunity to install dynamic interlocking systems on many plants using the generalised software described here and standard hardware. Such systems have the potential to reduce installation costs, greatly improve the flexibility of plant operation and reduce maintenance costs View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On load tap-changer conditioned based maintenance

    Publication Year: 2001 , Page(s): 296 - 300
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    Recent years have witnessed a strong trend in electrical supply undertakings to enhance the quality of supply and at the same time to reduce operating costs. One means of achieving this is to improve the effectiveness of maintenance strategies. The paper examines the routine maintenance strategies of power transformers' on-load tap-changers and introduces new regimes which match the period between visits to the duty of the equipment. Hitherto the maintenance has been period-based with conservative intervals to preclude failure. The paper describes a condition-based maintenance strategy. Applying this to utility tap-changers has resulted in the maintenance intervals frequently being more than doubled. Thus maintenance costs are halved and system reliability is improved by targeting those units in need of attention and by avoiding spurious outages View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interactive best-compromise approach for operation dispatch of cogeneration systems

    Publication Year: 2001 , Page(s): 326 - 332
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    An interactive best-compromise approach is presented, based on evolutionary programming, to solve the economical operation of cogeneration systems under emission constraints. A biobjective function including both the minimisation of cost and emission is formulated. The cost model includes fuel cost and tie-line energy cost. Emissions with SOx and NOx are derived as a function of fuel enthalpy. All constraints including fuel mix ratios in a boiler, operational constraints and emission constraints must be met in the search process. The steam and fuel mix is found by considering the time-of-use dispatch between cogeneration systems and utility companies. Data from a real cogeneration system are given to illustrate the effectiveness of the proposed method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Condition monitoring of power transformer on-load tap-changers. II. Detection of ageing from vibration signatures

    Publication Year: 2001 , Page(s): 307 - 311
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The paper describes a technique for online automatic condition assessment of an on-load tap-changer (OLTC) using a self-organising map (SOM). With a condition indicator giving the correct indication of the current condition status, an estimate can be made of the remaining life of the equipment. The condition assessment technique is demonstrated using the signatures collected by online monitoring systems installed on selector type OLTCs in distribution substations. Using the realtime fault detection procedure, reliable identification of incipient faults in the equipment can be achieved for the pre-specified false alarming rate View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Assessing the value of generator reactive power support for transmission access

    Publication Year: 2001 , Page(s): 337 - 342
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    The new electricity markets consider reactive power support as an essential system support service. In order to procure reactive support competitively from the markets, one needs to quantify the value of the various VAr sources available in the system. Research results are presented on the development of concepts and methodologies for equitable reactive power support valuation. Contribution to system security improvement is the main consideration for assessing the relative values of the VAr sources. The dynamic VAr support from generators is of much greater importance in the value assessment. A simple system is used first to demonstrate and define the problem. A solution method is proposed along with case study results on a large-scale power system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Condition monitoring of power transformer on-load tap-changers. I. Automatic condition diagnostics

    Publication Year: 2001 , Page(s): 301 - 306
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Automatic diagnostics for an on-load tap-changer (OLTC) requires a reliable technique that can classify vibration signals measured using an accelerometer mounted on the tank. In the paper, the authors investigate the automatic classification of OLTC vibration signatures using a self-organising map (SOM) and develop a feature extraction procedure that can extract essential features from the original vibration signature. The proposed SOM signature classifier is evaluated with a database established for one type of distribution class OLTC. The application results reveal the practical advantages of SOM for a number of tasks in OLTC condition diagnostics View full abstract»

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