摘要:

The reduction of fault current is one of the oldest problems of power systems engineering. Fault current reduction permits the interconnection of large networks without replacing circuit breakers, improves transient stability, and reduces the cost of equipment. The paper investigates the reduction of fault current by the insertion of a resonant LC circuit into the transmission line. The device consists of a capacitor and a thyristor-switched inductance, tuned to the supply frequency. The thyristor switches are operated at zero-current-crossing to eliminate the generation of harmonics. The system operation is analysed using analytic methods and transient simulation techniques. A parametric study determines the effect of components and network parameters on the current limiter operation. Design methods and component selection criteria are developed. The results demonstrate that the device can reduce both transient and steady-state fault current significantly. It can be built with commercially available components. The significant operation improvement is expected to justify the cost of the new device.

DOI:10.1049/ip-c.1992.0001

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper presents a fast and accurate technique for power system state estimation. The proposed technique is based on the exact linearisation of the Cartesian co-ordinate formulation of nodal load flow equations. The complete Taylor series expansion is used to solve these equations while retaining the nonlinearity. In this technique, the Jacobian and Hessian matrices are kept constant, and hence need to be computed once only, at the beginning of the solution, and then stored in the computer memory using the sparsity storage procedure. Because, in this technique the active and reactive power problems are attempted simultaneously, not sequentially, there is no need to use decomposition into two subproblems, namelyP–Θ andQ–V. The linear programming (LP) technique is used to solve the state estimation problem without any approximation for the load flow equations. For small changes in active and reactive power, the right-hand side of the LP is compensated only when the state estimation solution of the real component of the bus voltages is obtained with a minimum number of iterations compared with the fast decoupled state estimation (FDSE). For large band-data points, however, the imaginary components of the bus voltages must be computed, in addition to the real components. The proposed technique is more suitable than FDSE for solving ill-conditioned networks which have large bad-data points. An extensive study was carried out on a standard 23-bus test system to demonstrate the capability of the proposed technique for solving the state estimation problems.

DOI:10.1049/ip-c.1992.0002

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A constant matrix loadflow method is presented along with its fast version leading to the proposed fast super decoupled loadflow (FSDL) method. Gain matrices of the FSDL method are defined independent of rotation angles, and they differ only in their diagonal terms. Rotation angles are limited to the maximum value of −36°. The slack-start procedure for efficiency is also suggested. These along with a simple modification of real power mismatches at PV-nodes yield a robust and fast loadflow method. The method is tested and compared with the recent general-purpose version of the fast decoupled loadflow (GFDL) method under a wide range of simulated system operating conditions and network parameters. The proposed method has good convergence and can be more than twice as fast as the GFDL method for systems of largeR/Xratio branches.

DOI:10.1049/ip-c.1992.0003

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Results are given of circuit-breaker restrike waveforms during no-load, live-line switching operations on a 362 kV network, together with laboratory tests of the early dielectric recovery of the circuit breaker. It is shown that the tendency to restrike is assisted by the excellent interrupting ability of the breaker when the initial transient recovery voltage rises at the very slow rate typical of ‘stiff’ networks.

DOI:10.1049/ip-c.1992.0004

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Methods for on-line calculation of the phasors of symmetrical components from the complex space-phasor are presented. In this way the number of numerical operations can be cut by one third. The methods combine the suppression of higher frequencies and the separation of symmetrical components. Transfer functions obtained from the developed filter algorithms for the complex input and output signals are investigated and compared. The proposed approach with a variable sampling window enables a faster estimation of the desired components under transient conditions compared to the method using a constant sampling window.

DOI:10.1049/ip-c.1992.0005

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Starting from the motion of a charged particle in the electric field set up by the conductor system of a power transmission line, the paper develops a model for the streamers released when the voltage stress at the surfaces of conductors leads to corona discharges from them. The frequency content of streamer pulses defines the frequency spectrum of radio noise-fields radiated from transmission lines in corona. This is a definition which is achieved for the first time in analytical form in the present paper. From the basis which the waveshape of a single streamer pulse in the time domain provides, multiple point discharges are interpreted as random uncorrelated noise sources in power spectral density form. Comparisons are made between this frequency domain function and previously published corona excitation functions derived from measurement. Further validation studies are reported in which noise-interfering fields found from the streamer model which the paper develops are correlated with the results of recent measurements on a 500 kV double-circuit line energised for test purposes to 522 kV.

DOI:10.1049/ip-c.1992.0006

出版商:IEE    

年代:1992

数据来源: IET

摘要:

An innovative algorithm based on a set of modified co-ordination equations has been developed, which is claimed to be the fastest algorithm for the solution of the economic load dispatch (ELD) problem. Penalty factors involved in modified co-ordination equations are realised very elegantly with little computational effort from the knowledge of a base case fast decoupled load flow (FDLF) solution using a perturbation technique. An attempt has been made to account for line flow constraints in an innovative manner in the proposed ELD model. The ELD algorithm is tested on IEEE 14 and IEEE 30 bus test systems and the results are compared with those obtained with a classical technique based on exact co-ordination equations and with some rigorous mathematical programming techniques. Analysis reveals that the proposed ELD algorithm based on modified co-ordination equations is much faster than the one based on classical technique using exact co-ordination equations, particularly for large systems, and hence can be justified to be the fastest among other algorithms based on mathematical programming techniques or ELD solution.

DOI:10.1049/ip-c.1992.0007

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Use of the wind for electric power generation is increasingly being considered as a possible generation alternative due to the rising interest in sources of energy that are renewable and without harmful environmental effects. Furthermore, difficult global economic and political conditions are tending to make countries depend more on their own resources and rely less on imported fuels. Wind is, however, not always available, and conventional generation sources must provide power to meet demands in these calm periods. It is therefore necessary to include energy limitations in the reliability evaluation of wind energy conversation systems (WECS). The paper presents energy-based models that permit the assimilation of wind energy sources in conventional generation system adequacy evaluation.

DOI:10.1049/ip-c.1992.0008

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Reliability evaluation of a complete electric power system, including generation, transmission and distribution facilities, is normally not conducted because of the enormity of the problem. Instead, reliability evaluations of generating facilities, of composite generation and transmission systems, and of distribution system segments alone are conducted independently and the reliability indices obtained for each segment are used to make decisions. These assessments, however, often assume the other parts of the system to be fully reliable and capable of performing their intended function. This kind of analysis therefore gives an optimistic appraisal of the system performance. The paper considers the influence of outages of elements in all parts of an electric power system to obtain a more comprehensive appraisal of the overall system. Some of the factors that affect the overall system performance are highlighted. The relative contributions to overall system indices from composite generation and transmission failures and distribution zone failures are also illustrated. The concepts involved in the reliability evaluation of a complete power network are presented using an educational test system developed at the University of Saskatchewan.

DOI:10.1049/ip-c.1992.0009

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A neural-network-aided solution to the problem of static-security assessment of a large scale power system is proposed. It is based on a pattern-recognition technique where a group of neural networks is trained to classify the secure/insecure status of the power system for specific contingencies based on the precontingency system variables. The large dimensionality of the input data is reduced by partitioning the problem into smaller subproblems at different stages. When each trained NN is queried online, it can provide the power-system operator with the security status of the current operating point for a specified contingency. Parallel network architecture and the adaptive capability of the neural networks can be combined to achieve high speeds of execution and good classification accuracy.

DOI:10.1049/ip-c.1992.0010

出版商:IEE    

年代:1992

数据来源: IET