摘要:

The effect of slight discontinuities within the measuring arm of a wall-loss bridge is investigated, and it is shown that erroneous values of attenuation coefficient may arise, owing to the presence of such discontinuities. A method is proposed by means of which such errors may be eliminated. Experimental results are presented, demonstrating that significant errors do arise owing to imperfections in the apparatus and that these errors may be removed using the technique described.

DOI:10.1049/piee.1977.0125

出版商:IEE    

年代:1977

数据来源: IET

摘要:

This paper describes the circuitry, construction and performance of an analogue multiplier which achieves an accuracy within 0.03%. The technique employed involves splitting one analogue input signal into two parts, one in digital form and the other in analogue form. The two parts are separately multiplied by the other input signal, the results summed together to obtain the required product. Here, particular emphasis is laid on the circuitry and construction necessary to achieve high accuracy while minimising the effects of the inevitable switching involved with this method.

DOI:10.1049/piee.1977.0126

出版商:IEE    

年代:1977

数据来源: IET

DOI:10.1049/piee.1977.0127

出版商:IEE    

年代:1977

数据来源: IET

摘要:

Systematical construction of Lyapunov functions for studying power-system transient-stability problems are investigated. Lyapunov functions that are quadratic in the state variables, are constructed by a direct-search technique involving the maximisation of the volume of the region of asymptotic stability. Single, as well as multimachine, problems have been studied.

DOI:10.1049/piee.1977.0128

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper presents the implementation of the fast-decoupled load-flow technique for real-time monitoring of power systems in the presence of metering inaccuracies and data-acquisition failures. The real-time load-flow solution with mode injections and redundant line flows, using the fast-decoupled load flow, is much faster and requires less computer storage than that using conventional Newton-Raphson method, but still provides the same accuracy. Results of this analysis for a.e.p. 30-busbar test system are included for illustration.

DOI:10.1049/piee.1977.0129

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper deals with the study of self-excitation phenomenon of dual-excited synchronous machines connected to highly series-compensated transmission lines having low resistance, particularly in the case of e.h.v. long transmission lines using bundled conductors. Analysis for self-excitation for a typical system is carried out through the Routh-Hurwitz and a simpler approach for the unregulated case, whereas the parameter-plane approach is effectively used for the regulated case. The effect of the transformer (pψ) terms in the mathematical model on self-excitation has been highlighted. A comparison between the performance of dual-excited and equivalent conventional machines has been brought out.Dual-excited turbogenerators exhibit instability due to fast self-excitation only, whereas dual-excited hydroelectric generators exhibit instability due to both slow and fast self excitation. While the performances of both dual-excited and equivalent conventional turbogenerators are found to be nearly therome, the performance of a dual-excited hydroelectric generator is found to be decidedly better than that of an equivalent conventional one. In general, slow self excitation can be completely suppressed, but not fast self excitation, even with dual excitation. Complete elimination of self excitation seems to be feasible with a suitable resistanceRcin parallel with the capacitor. Another interesting conclusion is that the omission of thepψ terms for the regulated case leads to highly optimistic results.

DOI:10.1049/piee.1977.0130

出版商:IEE    

年代:1977

数据来源: IET

摘要:

It has been recognised that the dynamic-stability margin of synchronous generators can be improved by the damping effect of the speed-stabilising signal in the excitation control system. The dynamic-stability analysis is extended to account for the effect of loads modelled as a nonlinear function of voltage. In order to make the analysis realistic, a conventional load-frequency control system is also considered to be regulating the power-system frequency and tie-line power. The load voltage is considered to be undergoing changes in the dynamic period in response to speed signal in the excitation system which establishes a coupling betweenQVand p.f. control loops. The damping effect on frequency and tie-line power oscillations is studied by varying the load characteristics and excitation stabiliser parameters.

DOI:10.1049/piee.1977.0131

出版商:IEE    

年代:1977

数据来源: IET

DOI:10.1049/piee.1977.0132

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The performance of a single gas-blast interrupter, when switching low amplitude inductive currents, has been examined in detail. The effect of local circuit-component variation has been studied, and the factors which dominate the arc-instability condition established. It has been shown that circuit voltage and rate of change of current are of less significance than instantaneous current in determining the point of arc instability, though they can influence arc-restriking performance during the current chopping period. Where the dominant capacitance is separated from the interrupter by some inductance, both instability and chopped-current levels are increased.The nature of the arc-instability oscillation has been studied and related to earlier work. A new technique for predicting instability and hence estimating chopped current level for different circuit arrangements based on a single series of tests is proposed. This, when coupled with a frequency impedance characteristic for the connected circuit, would enable more precise prediction of current chopping levels in a given system application.

DOI:10.1049/piee.1977.0133

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper describes a technique for the optimisation of the parameter settings of the excitation controller of a synchronous machine which is suitable for on-site use. The optimisation method is based on an integral squarederror criterion, and involves the use of parameter sensitivity functions to estimate the parameter changes needed to alter system responses to approach some predetermined or desirable form. The computation of the parameter sensitivity functions is achieved by a direct method, which does not demand explicit identification of the controlled system and which yields the sensitivity functions of all output variables to all adjustable parameters from the results of a single-step test. The technique may be implemented using a small digital computer. The paper includes the results of simulation studies on unsynchronised and on loaded generators, together with results of micromachine experiments.

DOI:10.1049/piee.1977.0135

出版商:IEE    

年代:1977

数据来源: IET