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Generation, Transmission and Distribution, IEE Proceedings C

Issue 4 • Date Jul 1992

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Displaying Results 1 - 8 of 8
  • Digital model for transient studies of a three-phase five-legged transformer

    Publication Year: 1992 , Page(s): 351 - 358
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A flux linkage model for a three-phase five-legged transformer is derived for the first time. The effects of mutual and leakage inductances, saturation, eddy current loss, hysteresis and residual fluxes of the nonlinear iron core are included. A straightforward and novel method for determining both the apparent and incremental inductance matrices for a loaded two-winding five-legged transformer is derived. Simulations presented are based on apparent inductance (λ/i) rather than incremental inductance (dλ/di) because this approach was found to be preferable for predicting the behaviour of the laboratory transformer used. Eddy current and hysteresis losses are combined into one core loss term which is accounted for by a voltage-dependence resistance load on the secondary. The model thus yields a completely detailed description of the transformer's behaviour. A predictor-corrector algorithm written in FORTRAN is used to solve the set of nonlinear differential equations View full abstract»

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  • Contribution of single-phase motors to system fault level

    Publication Year: 1992 , Page(s): 359 - 364
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    System designers need to know the maximum current which may flow in any system component to ensure that otherwise healthy plant is not put at risk due to a fault in other equipment. This is particularly the case for switchgear. Large three-phase induction motors make a contribution to both break and make duty. Due to the rapid decrement of their contribution, the 2.55 factor is inadequate. It is shown by means of calculation and test results that even small single-phase induction motors make a contribution to switchgear make duty. It is necessary to calculate both the make and break duty, but it is suggested that, for the longer term, the relationship between break and make should be raised, possibly to a factor of 3. Failure to allow for the higher make duty may lead to dangerous conditions on a system View full abstract»

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  • Applying pattern recognition in distance relaying. II. Feasibility

    Publication Year: 1992 , Page(s): 306 - 314
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    For part I see ibid., vol.139, no.4, p.301-5 (1992). In part I, the limitations of the existing operating characteristic of distance relays were mentioned. With increasing interconnection between power systems, it has become necessary to avoid relay maloperation and obtain operating characteristics adaptive to an operation of the overhead line being protected by it. In part II, the result of applying pattern recognition in designing distance relays with adaptive operating characteristics is reported. In proposing this approach, the stochastic nature of the power system is acknowledged. The purpose is to obtain a near-optimal operating characteristic matching the performance characteristic of the overhead line the distance relay is to protect. A further advantage obtained by this approach is that the distance relay can be organised to generate an online database or learning set which can be further used to tune the operating characteristic and prevent maloperation under stringent duty conditions View full abstract»

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  • Effects of frequency dependence and line parameters on single ended travelling wave based fault location schemes

    Publication Year: 1992 , Page(s): 332 - 342
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    The effects of frequency dependence, line asymmetry, and varying ground conductivity on ultrahigh speed, travelling wave based, single ended, protection schemes are investigated. Typical schemes assume the transmission lines to be balanced and frequency independent which simplifies the analysis of the fault transients. Investigation of a single circuit vertically configured transmission line reveals that better results can be obtained by using modal parameters based on the configuration of the transmission line. The problem of modal mixing at discontinuities on the transmission line is demonstrated in the case of an unbalanced line to ground fault. The results described have applications in both protection and fault location schemes View full abstract»

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  • Unified power-flow control concept for flexible AC transmission systems

    Publication Year: 1992 , Page(s): 323 - 331
    Cited by:  Papers (43)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    The author outlines the technical and economic factors which characterise the uniform, all solid-state power-flow controller approach for real-time controlled, flexible AC transmission systems. The unified power-flow controller in its general form can provide simultaneous, real-time control of all basic power system parameters (transmission voltage, impedance, and phase angle), or any combinations thereof, determining the transmitted power. The parameters selected for control can be changed without hardware alterations, e.g. the function of the controller can be changed from that of a phase-shifter to that of a series line compensator, or vice versa, with or without additional terminal voltage regulation and shunt VAr compensation, to adapt to particular short term contingencies or future system modifications View full abstract»

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  • Adaptive analogue network for real-time estimation of basic waveforms of voltages and currents

    Publication Year: 1992 , Page(s): 343 - 350
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A new parallel algorithm for estimation of parameters of sinewave, distorted by DC exponential signal and contaminated by noise, is proposed. The method may be seen as an extension and generalisation of the standard least-squares (L2-norm) optimisation approach. The advantage of the developed algorithm is that it is more robust with respect to the modelling error and impulsive (wild) noise than when a standard least-squares criterion is employed. The implementation of the algorithm by a suitable adaptive analogue network is also given. Computer simulation results are presented to confirm the validity and performance of the proposed network. The proposed method seems to be particularly useful for real-time high-speed and low-cost estimation of parameters of sinusoidal signals View full abstract»

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  • Consumer rationality assumptions in the real-time pricing of electricity

    Publication Year: 1992 , Page(s): 315 - 322
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    Dynamic tariffs such as RTP (real-time pricing) and day-ahead pricing function as load management tools because they interact with consumer behaviour. Hence analytical models for an electricity supply system with RTP would need to incorporate behavioural models for consumers. These models have to be logically and mathematically consistent and empirically meaningful. The model developed by the authors relies on the concepts of demand elasticity across time, degree of consumer economic rationality and, on the supply side, on the price formation model. The authors explore a range of assumptions in respect of these matters View full abstract»

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  • Applying pattern recognition in distance relaying. I. Concept

    Publication Year: 1992 , Page(s): 301 - 305
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The principal application of distance relays is for the protection of essential subtransmission networks and transmission lines operating at EHV and UHV, whose performance depends on various factors. The task of selecting a universal operating characteristic for distance relays is difficult. Although, over the years, different characteristics have been in use, there is a general agreement that the quadrilateral characteristic is superior to other characteristics. This agreement is largely based on application successes. Authors introduce the concept of obtaining the operating characteristics by applying the method of pattern recognition. The principle provides a meaningful approach for generating an operating characteristic that is natural for the overhead line, i.e. by the reason that all possible factors that can affect the overhead lines performance, can be considered View full abstract»

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