Power engineering education and the Internet: motivation andinstructional tools

Alternatives in the application of the Internet are applied to power engineering education. Because the student perception of power engineering is often that this is an old technology, new ways to effectively present the challenges, and the opportunities as well, are needed. The Internet and innovative graphic and textural materials are suggested to effectively present the case for power engineering as a valuable career. This is suggested to build on student interest in these computer technologies. The contents of web sites for this purpose are described, and the educational pedagogy of the method is discussed     

A nondiverging polar-form Newton-based power flow

The design of a mine electric power system requires that power-flow studies be conducted to guarantee that all motor operating and starting loads can be met while acceptable bus voltage levels are maintained. If future loads are overestimated, then the iterative techniques used to solve the system voltage profile will often diverge, leaving no clue for the designer as to the cause of the divergence. A nondiverging power flow formulation based on Newton's method is presented that is applicable to power flow programs that use the polar form of the bus voltage variables. The method is effective in guaranteeing nondivergence of the power flow solution and in indicating where erroneous system data exist for nonconvergent cases     

Precedence relationship performance of an indirect matrix solver

A highly parallel truncated accelerated Neuman series preconditioner is presented. Results from using this preconditioner are compared with those obtained using a traditional truncated Neumann series preconditioner and the Jacobi method on matrices whose numerical content is characteristic of the bus admittance matrices used in the analysis of faulted power system problems. These results show that the number of precedence relationships experienced by this technique are of the same order of magnitude as the number encountered when using direct methods     

Comments, with reply, on `Electric field of a transmission lineover a multilayered media'

The commenter points out that the general solution for the electric field of a current line source of alternating current over a stratified earth of any number of layers published in the above letter (see ibid., vol.75, no.1, p.170-171, 1987) was obtained by him in a paper that he published 24 years ago. The authors acknowledge Wait's prior claim, observing that parallel research of this sort is too often encountered     

Prediction of top-oil temperature for transformers using neuralnetworks

Artificial neural networks represent a growing new technology as indicated by a wide range of proposed applications. At a substation, when the transformer's windings get too hot, either load has to be reduced as a short-term solution, or another transformer bay has to be installed as a long-term plan. To decide on whether to deploy either of these two strategies, one should be able to predict the transformer temperature accurately. This paper explores the possibility of using artificial neural networks for predicting the top-oil temperature of transformers. Static neural networks, temporal processing networks and recurrent networks are explored for predicting the top-oil temperature of transformers. The results using different networks are compared with the auto regression linear model     

Transformer top-oil temperature modeling and simulation

Improving the utilization of transformers requires that the hot-spot temperatures and top-oil temperatures (TOTs) be predicted accurately. The authors' experimentation with various discretization schemes and models proved that many of the linear and nonlinear semiphysical and nonphysical models they were using to predict transformer TOT were correctly modeling the TOT behavior. Their experience convinced them that noisy input data and the absence of data on significant driving variables, not model deficiencies, were frustrating their attempts to reduce the prediction error further. In this paper, they discuss the body of research that led them to these conclusions     

The Newton?Raphson Load Flow Applied to AC/DC Systems with Commutation Impedance

Existing conditions in industrial ac-dc power systems may result in significant commutation resistances. If the resistance to reactance ratio of the commutation impedance is high, significant errors can result in load-flow studies which neglect the resistive portion. A method is presented for inclusion of a resistance-inductance fed bridge rectifier in a Newton-Raphson (N-R) load flow program. Polar form of the power flow equations is assumed. An example problem is provided for comparison.     

Track/trolley system transients

A simple yet effective method is presented for modeling a track/trolley/earth conductor system. The results from this approach can used to predict more accurately the system resistance, inductance, time constant, and transient current division between track and earth which can be used in the fuse protection of mine DC power systems. The agreement of the predicted values with measure values is shown to be better than that obtained with previously used methods for three reasons. First, the more accurate two-frequency model for the internal impedance of the track/trolley system conductors is used. Second, the external impedance model used is superior to an earlier model since the tunnel-type characteristics of the underground environment are taken into account. Third, a more accurate method is used to account for the conductor/conductor and earth/conductor interaction     

Frequency domain transient stability simulation of power systems:implementation by supercomputer

Results of performing transient stability simulations of a power system using frequency-domain methods are reported, and comparisons are made with a standard time-domain simulation of the same events. Each simulation was run on both a VAX and a CRAY machine. Because of their inherent structure, it is necessary to implement time domain simulations by serial techniques that are not capable of effectively exploiting parallel and vector processing capabilities. Frequency domain techniques are more likely to give rise to vector and matrix operations which are amenable to parallel and vector processing, and they are generally less efficient in dealing with nonlinearities. The relative benefits of the simulation methods are evaluated     

Complete Analysis of the Operating Modes of the Resistance?Inductance-Fed Bridge Rectifier

Equations describing the ac-dc terminal relationships of the resistance-inductance-fed three-phase full-wave bridge converter from no load to short circuit are provided. Modal boundaries are plotted in the μ-? plane showing the limits within which these equations are valid. Results show the resistance to have a significant effect on the terminal characteristics. Modal boundaries are shown to be nonlinear functions of the commutation resistance-direct current product.