摘要:

An algorithm is presented for the determination of loading schedules, for a 24 hour period, for a purely hydro-electric generation system. The scheduling problem is expressed as the minimisation of a nonlinear function subject to nonlinear equality and inequality constraints, and solved by a nonlinear programming procedure based on a gradient search method. The application of this algorithm to an actual system consisting of 44 hydro-electric power stations, containing some 73 turbines, is described. Typical results for this system are presented and the computational requirements discussed. Finally, the use of different objective functions, and the effects of these on power system performance, are considered.

DOI:10.1049/ip-c.1988.0022

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A simulation model for the economic operation of a power system incorporating a reservoir-type hydro-electric plant is presented. An optimum dispatch, based on the Lagrange multipliers method, is used for an hour-by-hour loading of the thermal units. Hydro generation is assigned by means of an optimisation criterion which accounts for plant efficiency variation with output, yielding a realistic and accurate representation of hydro plant operation. Because the expressions involved in the optimisation procedure are explicit, the simulation is highly efficient as well as accurate and is particularly suitable for long range forecasting and parametric studies. A program based on the simulation was used to assist in the optimisation of a proposed hydro-electric plant in Israel. The operating cost of the thermal/hydro power system was evaluated for one-week periods representing different seasons of the year. The results were used to determine the optimal design parameters of the new plant: the generating capacity, number of units and reservoir volume.

DOI:10.1049/ip-c.1988.0023

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Catastrophe theory is a mathematical techique for the qualitative analysis of system equations, defining the jump phenomena and sudden changes caused by smooth alterations in the situation. This theory has been applied previously to the study of steady state stability of power systems. The paper presents a new algorithm to derive the appropriate catastrophe manifold to which the power systems can be fitted. The algorithm is deduced in terms of relevant system parameters that can be helpful for online steady state stability assesment.

DOI:10.1049/ip-c.1988.0024

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Previous analysis of synchronous machines under small pertrubations has been extended. First, the change of the parametersK1–K4describing the system has been expressed in explicit analytical form for different loading. From this a set of curves has been plotted to show variations of such parameters by changing the operating condition, which is an important factor in dynamic stability studies. Secondly, a full-rank pole placer is designed to be robust in the sense that the desired poles do not change much with ‘large’ variations in parametersK1–K4. The solution is based on a nonlinear programming approach. Comparison with a unity-rank controller shows the superiority of the proposed device.

DOI:10.1049/ip-c.1988.0025

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Many power system circuits contain iron cored coils, which are common nonlinear circuit elements. Systems engineers have to model these elements while studying such phenomena as inrush current, ferroresonance, subharmonics etc. The nonlinearity involved in these elements cannot be appropriately taken into account unless due regard is given to the damping effects on account of hysteresis. This paper attempts to simulate digitally the appropriate paths ofB/Hexcursions in a piecewise linear manner when the magnetic core is subjected to random variations of magnetic field intensity and sets up a computer algorithm. The algorithm may be used in digital analysis of systems containing iron cored coils.

DOI:10.1049/ip-c.1988.0026

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A computer model, based upon measured equipment impedances, has been formulated for the prediction of the electromagnetic noise generated by valve firings in HVDC convertor stations. Simple lumped circuit concepts are used so that the model can readily be applied to any convertor station; it can thus be described as generic. It has been used to predict the noise generated in the frequency interval from 5 to 500 kHz at the Dickinson convertor station and validated by comparing the results with RF spectra measured at the station. A key feature is the use of measured impedances of actual equipment in the model, rather than idealised components.

DOI:10.1049/ip-c.1988.0027

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The incorporation of a circuit breaker within an RMU without additional cost and with a reduced volume has been made possible by use of a new interruption technique: autoexpansion. This approach uses the combination of a gas flow created by expansion due to the energy dissipated by the arc itself, and the arc rotation created by a magnetic field. The interruption energy is not therefore taken from the operating mechanism as in the classic puffer principle. The overall device is therefore lightweight, reliable and of reduced dimensions. Interruption is carried out under atmospheric pressure of SF6. Therefore, owing to the use of this interruption principle which allows considerable flexibility of design, the circuitbreaker fulfills three functions: circuit-breaker, isolator and earthing-switch. In addition this approach enables the incorporation of automatic electronic protection systems which give further benefits in terms of flexibility of operation and selectivity.

DOI:10.1049/ip-c.1988.0028

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper presents the design of a digital protection scheme for three-phase power transformers. The design is based on an optimal state observer for estimating the fundamental and harmonic components of the signals. The scheme provides primary protection for internal faults, ground faults and backup protection for external faults. Internal fault protection is provided by means of a percentage differential characteristic, which also includes even- and fifth-harmonic restraints to prevent misoperation during inrush and overexcitation conditions, respectively. Protection for external faults is provided by means of a three-phase digital overcurrent relay. The protection scheme is implemented on a TMS320 digital signal processor and tested in the laboratory using a three-phase transformer. Relay operation times are in the range of ½ to ¾ of a 60 Hz cycle for internal and ground faults. The percentage differential relay provides complete restraint during inrush, overexcitation and external fault conditions.

DOI:10.1049/ip-c.1988.0029

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper outlines the various system conditions which gave rise to low frequency oscillations, including the abnormal operating conditions which were obtained in 1984/85. Operational management of the problem is also described with mention of the oscillation monitors devised to aid the control engineers.

DOI:10.1049/ip-c.1988.0031

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper traces the background, conditions and system study work leading to the development of analytical techniques currently in use for system damping evaluation in England and Wales. The early study work, providing indications of possible low-frequency electromechanical oscillations, is examined together with the early simplified models used for eigenvalue analysis evaluating the damping behaviour of the system during such oscillations. The mechanism producing negative damping of such low frequency electromechanical oscillations is analysed. The development of the detailed eigenvalue analysis program package PRASM currently in use by the CEGB is described in detail. Finally, sample results from the extensive analysis carried out on the CEGB/SSEB oscillation incidents of December 1978-January 1979, utilising the PRASM program package, are given with commentary on likely future developments.

DOI:10.1049/ip-c.1988.0032

出版商:IEE    

年代:1988

数据来源: IET