摘要:

The analysis of distribution transformers under short-circuit conditions is presented to determine the transient recovery voltage that appears across the poles of the breaking device at the current extinction. The frequency response of the transformer is determined and an equivalent circuit is derived. A simplified circuit, suitable for laboratory tests, is obtained from the equivalent circuit.

DOI:10.1049/ip-c.1991.0031

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Economic loading of medium-sized isolated power systems is considered. Such systems are often characterised by taxing emergency reserve requirements. It is shown how the relevant criteria may be met in a flexible manner through consideration of the cost of any load shedding resulting from possible generation outages. Results are presented which demonstrate that operational savings may be achieved through use of the proposed approach, and that the schedules obtained exhibit less volatility of generator power outputs than is the case when rigid emergency reserve criteria are employed.

DOI:10.1049/ip-c.1991.0032

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A simple and computationally efficient decentralised control design method is introduced for load-frequency control (LFC) in interconnected power systems. The method is based on the use of a reduced-order observer and a proportional-plus-integral controller in each area of the power system, and ensures zero static change in area-frequency and tie-line power. Some of the features of the decentralised scheme are decentralised implementation of a wide choice of feedback controllers, which have been designed off-line to meet the requirements of the global system; a constraint-free structure for the feedback controller; and avoidance of the need for inter-area transfer of data, for the purposes of LFC. The proposed decentralised control algorithms are tested on a computer-based simulation of a two-area interconnected power system. The simulation results demonstrate that the method can give closed-loop performance which is similar to that of the equivalent global control system.

DOI:10.1049/ip-c.1991.0033

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A general methodology for the computation of transients in a nonlinear circuit containing an iron-cored element is presented. Iron-cored elements are a common nonlinear circuit element in power system circuits. The effect of hysteresis has been taken care of by a simple model based on a piecewise linearisation technique. The eddy current effect is simulated by linear modelling. The method can be used for studying circuit phenomena such as inrush current, ferroresonance and subharmonics. Illustrative examples are presented.B/H(or λ/i) excursions and energy losses, separated into individual components of hysteresis and eddy current losses, occurring in the core during the transient state of the circuit are also computed.

DOI:10.1049/ip-c.1991.0034

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A state estimation algorithm is proposed which rejects bad data in the presence of noise. This rejection is accomplished during convergence by means of reweighting, the final solution being the least squares estimate based on the remaining good data. The reweighting is also used to improve convergence with nonlinear measurements. A new 2 × 2 submatrix formulation has been used allowing full active/reactive power coupling of the estimator with greatly reduced computational overheads. Including coupling effects greatly improves bad data detection and identification.

DOI:10.1049/ip-c.1991.0035

出版商:IEE    

年代:1991

数据来源: IET

摘要:

When an unbalanced fault occurs, the fault current in the transmission lines induces an electromotive force in nearby parallel telecommunication circuits, as well as in different metal pipelines. The existence of a earth wire in these cases exerts a favourable influence known as the ‘screening effect’ which is considered in the calculation of the induced electromotive force through the screening factor. An original procedure for obtaining relatively simple analytical expressions for determining the screening factors is presented. The procedure incorporates the fact that the earth wire is galvanically connected to the structures along the line and, at the terminals of the line, to the station frame. The procedure is based on Kirchoff's equations, the principle of superposition and the summing of geometrical series.

DOI:10.1049/ip-c.1991.0036

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper contribution introduces a new method for calculating power system transients based on theZ-transform. The special way the circuit elements can be formulated leads to a simple approach in solving the network equations, especially where a large number of simulation runs have to be performed.

DOI:10.1049/ip-c.1991.0037

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The conventional definition for power-component calculation becomes contentious under nonsinusoidal conditions. In the paper, a definition for power-component calculation, based on the viewpoint of harmonic source and harmonic administration, is presented after the survey of the power-component definitions proposed. In addition, the principles of electro-dynamometer-type meters and digital meters for power-component measurement are discussed, and the performances of these meters are estimated by practical measurement of power components on a simulated harmonic-polluted power circuit. Both the measuring results and the instrumenting principles illustrate that the conventional power-factor meter and the reactive-power meter are sensitive to the voltage and the current harmonics, so they cannot be used under all harmonic-polluted conditions. But the digital meters, especially the microcomputer-based instrument system, are not influenced by the effect of the harmonics within the range of their frequency responses. Therefore they are very suitable to measure the power component, even under the harmonic-polluted conditions.

DOI:10.1049/ip-c.1991.0038

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The effect of steady and transient state responses of a power system on its performance evaluation has been investigated. Retention of all buses from the original power system has been noteworthy along with the modelling of frequency dependent load buses. Inputs to the system are regarded as small perturbations in operational characteristics of transmission lines and system loads. This type of perturbation is modelled by a Gaussian stationary process with constant spectral density. The mean first passage time of a dynamic system from its domain of attraction has been considered the performance index. The sensitivity of this index to the variation of different system parameters has been investigated, and several design criteria have been examined to determine the effect of system configuration on power system performance evaluation.

DOI:10.1049/ip-c.1991.0039

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Ferroresonance can occur in power transformers or reactors fed through capacitive coupling from neighbouring phases or lines. Ritz's method of harmonic balance is used to formulate an analytical solution to the problem of fundamental frequency ferroresonance. A two-term polynomial of order 11 is used to accurately represent the magnetisation characteristic of a typical high-voltage power transformer in the ferroresonance region. The derived closed-form solutions permit construction of a map defining the boundaries between safe and ferroresonant regions as a function of the system parameters. The transformer losses are included in the analysis and are shown to be an important factor in the demarcation of the ferroresonance regions.

DOI:10.1049/ip-c.1991.0040

出版商:IEE    

年代:1991

数据来源: IET