A practical method is developed for selecting the minimal number of lumped elements needed to represent a lossy transmission line if a certain accuracy is desired in a well-defined frequency range. This method, which uses dimensionless transmission line parameters, can be used in a wide range of applications and is also extended to hybrid equivalent circuits, consisting of ideal single lossless lines and resistors. For completeness, a lumped element model for coupled lossy lines is presented which uses the same dimensionless parameters and the same criteria as proposed for single lines. An example of coupled transmission line structure including skin-effect losses illustrates the approach. >

Selection of lumped element models for coupled lossy transmission lines

The special circumstances are considered of an induction motor driven submersible pump supplied from a variable frequency converter which is remote from the pump location, necessitating subsea cables which may be considerably longer than in normal practice. The principal objective of the series of practical tests is to investigate the performance of such systems to evaluate a complete electromechanical system model for use in the prediction of the current and torque requirements of the drive, and to assess the effect of converter switching patterns on the voltage profile of the transmission section. Results of computer studies are presented which are validated by comparison with measurements taken on an ESP system during precommissioning tests. The factors affecting the in-service operational characteristics of the drive are discussed and recommendations made.

Operation of subsea electrical submersible pumps supplied over extended length cable systems

Analysis and selection of transmission line models used in power system transient simulations

In this paper, for solving the problem of simulating the travelling wave phenomena, a method used for determining the number of equivalent /spl Pi/ sections of the transmission line model in accordance with the travelling wave frequency range of interest and the model accuracy required is proposed. By analyzing the fault transients of the multiple /spl Pi/ models and comparing them with those of the distributed-parameter transmission lines, an index to evaluate the accuracy of the transmission line models is proposed. EMTP simulations show that this method is feasible and appropriate.

Transmission line models used in travelling wave studies

This article presents a procedure for the development of a scaled-down laboratory model of a transmission line based on per unit. values of a true line. The X/R ratio of the model is kept same as that of the true line, as then only their performance can be compared. The current-carrying capacity of the scaled-down model is closer to 20 A to enhance its utility with different flexible AC transmission systems devices. A scaled-down model of a true line for which parameters are available in the open literature is fabricated, and a case study of its simulation and validation is presented. These studies show that the laboratory model is able to emulate closely the true line, and therefore, it can be fruitfully used for the dynamic study of the transmission line embedded with flexible AC transmission systems and hardware-in-loop simulation studies.

Design, Analysis, Fabrication, and Testing of Laboratory Model of Transmission Line

The paper is concerned with the representation of transmission circuits used in the evaluation of transient phenomena in power-system networks. The paper proposes general criteria for selecting the number of equivalent ‘T’ or ‘π’ sections that are required to fully represent the circuit over the range of frequency of interest. Emphasis is placed on both the accuracy of representation and economical computation.

W.W. Bell

Papers

Selection of transmission circuit models for power-system transient studies