By Topic

Generation, Transmission and Distribution, IEE Proceedings-

Issue 2 • Date Mar 1996

Filter Results

Displaying Results 1 - 13 of 13
  • Interactive expert system for optimal design of electricity distribution systems

    Publication Year: 1996 , Page(s): 151 - 156
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    An expert system to optimise the design of distribution systems is developed, The expert system is divided into three main parts. Optimising the location of substation, determining the optimal conductor layout, and obtaining the best conductor profile. An iterative procedure that improves on a user-defined initial location is employed to determine the optimal site to locate the substation. The programming approach allows the designer to choose the second best site if the optimal site is not acceptable. The heuristic search technique of best-first searching is used to determine the optimal cable layout and load allocation. The objective function developed to determine the optimum conductor profile strikes a balance between the capital cost and the cost of losses. The modular programming approach allows the design engineer to focus on any of the three sections of the design. Often the location of substations is determined by regulation. In such a situation the design engineer can adopt to optimise the conductor layout and the conductor profile of the distribution system. If the conductor sizes available fail to satisfy the user-defined constraints, the designer can rerun the conductor optimising section after making the relevant changes to the inventory database View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Artificial neural network power system stabiliser trained with an improved BP algorithm

    Publication Year: 1996 , Page(s): 135 - 141
    Cited by:  Papers (20)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The paper presents an artificial neural network (ANN) power system stabiliser (NNPSS). The neural network in the proposed NNPSS is trained by an improved BP algorithm. The main difference between the proposed BP algorithm and the conventional BP algorithm is that two variable factors, a learning rate factor ε and a momentum factor α, are used. This significantly improves the convergence of the ANN's training. A four layer (7-7-4-1) ANN is used to design the NNPSS. The NNPSS is trained by samples obtained from power systems controlled by nonlinear power system stabilisers. The ability of the trained NNPSS to handle unknown disturbances using measurable variables has been investigated in two power systems, a single machine to infinite bus power system and a three machine power system. Test results show that the NNPSS is effective in damping out power system oscillations and is robust to the variations of both the system parameters and the system operating conditions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Newton solution for the steady-state interaction of AC/DC systems

    Publication Year: 1996 , Page(s): 200 - 210
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (916 KB)  

    The steady-state interaction of a six-pulse power converter with a Thevenin equivalent of the three-phase AC and DC power systems is solved. The power converter is represented by harmonic phasor mismatch equations, and the interaction between the power converter and AC and DC systems is embodied in the solution of harmonic mismatch equations for the power converter terminal conditions. Since there are a large number of simultaneous nonlinear equations to be solved, a sparse Newton-type solution is developed that exploits the harmonic three-port nature of the power converter, and the relatively weak interaction between switching angles and terminal harmonics. The resulting solution is fast, and closely matches a time domain simulation of the test system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Computer-aided design of a new nonunit protection scheme for EHV teed circuits

    Publication Year: 1996 , Page(s): 142 - 150
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    The paper describes a new technique for protecting EHV teed transmission lines that is based on nonunit principles but exhibits the properties of a unit protection scheme. Fault generated (HF) signals are extracted by coupling a capacitor of a conventional capacitor voltage transformer (CVT) with a specially designed measurement circuit. Power line carrier line traps are used to confine the HF signals to the protected zone and their bandstop characteristics are used as a basis for discriminating between internal and external faults. A digital signal processing unit is used to process the signals and produce a trip output. Some simulated results are presented to show the ability of the scheme to rapidly detect faults on different teed circuits under a variety of system and fault conditions encountered in practice View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel grid-connected photovoltaic inverter

    Publication Year: 1996 , Page(s): 219 - 224
    Cited by:  Papers (44)  |  Patents (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Detailed analysis and simulation results of a novel solar photovoltaic inverter configuration interconnected to the power grid are presented. From the simulation results, it is confirmed that the harmonic distortion of the output current waveform of the inverter fed to the grid is within the stipulated limits laid down by the electric utility companies. Typical hardware aspects are also discussed in detail and the applicability of the design is verified View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Synchronous generator damping enhancement through coordinated control of exciter and SVC

    Publication Year: 1996 , Page(s): 211 - 218
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Damping improvement of a weakly connected generating system through control of excitation and static VAr compensators has been investigated. Stabilising signals derived through a minimum time quasioptimum feedback strategy have been tested on a synchronous generator infinite bus system connected through a long transmission line. The response was compared with standard linear state and output regulator formulations. It was observed that although excitation control enhances the stability of the system, the SVC provides most of the damping. The proposed feedback strategy with coordinated control of excitation and SVC were found to provide a much superior response compared to the standard techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fuzzy reasoning for knowledge-based assessment of dynamic voltage security

    Publication Year: 1996 , Page(s): 157 - 162
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    An easy-to-use knowledge-based fuzzy approach is proposed to evaluate the dynamic voltage security including both voltage collapse and unacceptable voltage profiles following disturbances. The dynamic voltage-stability behaviour of the power system, however complex and nonlinear in nature, is simply mapped into a fuzzy severity index by means of approximate fuzzy reasoning and a series of fuzzy calculus. In addition to providing a mere two-region demarcation, the fuzzy severity index can also generally give a relative severity indication to discriminate between various post-disturbance system states. A systematic methodology for initial fuzzy-parameter setting and fuzzy-variable selection is also presented and discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transient stability screening using artificial neural networks within a dynamic security assessment system

    Publication Year: 1996 , Page(s): 129 - 134
    Cited by:  Papers (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    Accurate assessment of transient and dynamic stability provided by an online dynamic security assessor allows the power system to be operated closer to its stability limits with considerable economic benefit through the running of less out-of-merit generation. As part of such assessors, contingency screens are used to filter out those contingencies which pose no stability problems. Those contingencies which pass through these filters are evaluated in detail to determine their effects on the system stability. The paper describes an approach where an artificial neural network is successfully used to provide a fast transient stability screen within a dynamic security assessment system. Results are presented for a number of test networks based on a reduced model of the UK National Grid System View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modified two-level state estimation approach [for power systems]

    Publication Year: 1996 , Page(s): 193 - 199
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    The paper presents modifications to the existing standard decentralised two-level state-estimation approach which imposes conditions on tie power-flow line and boundary-bus power measurements. These conditions are by introducing a modified two-level state-estimation approach which implements modifications to the existing standard approach. The modified approach has no additional requirements at all, except for the observability of the overall system which is an important constraint for any state estimator. A decomposition C-code routine is developed to evaluate the performance of the new concepts associated with the proposed approach. A simple DC power system state estimation network is applied to demonstrate different concepts associated with the proposed approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Assessment of customer outage costs due to electric service interruptions: residential sector

    Publication Year: 1996 , Page(s): 163 - 170
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    The assessment of the benefit or worth of reliability is perceived as being a major contribution in providing the additional detail in the justification of new system facilities and operating reliability levels provided the required information can be obtained in a consistent and coherent manner. The costs incurred by consumers, customer interruption costs (CIC), as a result of interruptions in their electricity supply are considered key indicators of customer expectations and therefore of reliability worth. The assessment of CIC through surveys is considered to yield the most definitive results. Since the worth of these factors is difficult to quantify, consistent convergence of respondents' opinions on issues related to the electricity service can be useful in lending credibility to the interruption costs derived from surveys. The paper is based on extensive surveys conducted at UMIST. It reports on the customer characteristics of the residential respondents and their experience of interruptions, the undesirability of some effects of interruptions and the variation of undesirability of effects with frequency of interruption, season, time of day and weekday/weekend. The customers' ratings of these aspects are also tested for statistical correlation with the customer and experience of interruption variables. Agreement on the opinions is displayed across the RECs leading to the expectation that the corresponding CIC derived from the studies will be comparable as well View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-phase fast decoupled power flow for distribution networks

    Publication Year: 1996 , Page(s): 188 - 192
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Power system single-phase models assume that generation, transmission and distribution systems are perfectly balanced. The great appeal of this type of model is its simplicity, for all the calculations become quite simple, when compared with the three-phase model, and the results obtained are well suited for most applications. There are cases, however, in which its results may not be accurate enough, as may happen with distribution system analysis (unbalanced loads), nontransposed transmission lines, large mutual impedances between lines, etc. These problems require a more accurate three-phase model. The paper extends decoupling theory in order to obtain a fast decoupled three-phase load flow which is suited for distribution power system analysis View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of rotational load shedding on overall power system adequacy indices

    Publication Year: 1996 , Page(s): 181 - 187
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    Reliability evaluation of a complete electric power system including generation, transmission and distribution facilities is an important objective in overall power system planning and operation. Due to the enormity of the problem, reliability analysis is not usually conducted on a complete power system, and reliability evaluations of generating facilities, transmission systems and of distribution system segments are usually conducted independently. There are many benefits in developing the ability to perform overall system reliability evaluation. The most obvious is the allocation of utility resources to optimise the overall system operation. The paper considers the influence of component outages in all parts of an electric power system to obtain a comprehensive appraisal of the overall system adequacy. Different selection procedures for dropping customer loads in the event of energy deficiencies arising from outages in the composite generation and transmission system are included in the calculation of overall power system adequacy indices View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evaluation of reliability worth and value of lost load

    Publication Year: 1996 , Page(s): 171 - 180
    Cited by:  Papers (59)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (984 KB)  

    Customers' perceptions of reliability may not always reflect the level of reliability purported by traditional reliability indices. This has been recognised and efforts have been made by the electricity supply industry (ESI) in the United Kingdom to relate “reliability investment” with customers' marginal benefits obtained from such investment. A difficulty encountered during such earlier and recent efforts has been the lack of appropriate valuation of these benefits. With a view to correcting this paucity, the authors have conducted studies, based on customer surveys, aimed at assessing the customer outage costs (COG) due to electric service interruptions. The incremental values of these costs, ΔCOC, following reliability investment are considered proxies of reliability worth and customers' marginal benefits. The results of these studies have provided a very good insight into customers' concerns regarding supply interruptions, but most importantly a coherent method for evaluating the customer benefits (ΔCOC) has been developed and the required generic data for such evaluation generated. Using these data, a consistent method for calculating the value of lost load (VOLL) is also developed View full abstract»

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