Electromagnetic Unbalance Research Articles

Electromagnetic Unbalance in Untransposed Overhead Transmission Lines.(Dept.E)

This paper presents a complete analysis for the unbalance problem in O.H.T.L. which arises due to T.L untransposition. Derivations for the electromagnetic unbalance factors by the application of symmetrical component analysis are introduced. The main factors affecting electro-magnetic unbalance factors are discussed with special regard to double circuit T.L. Numerical application is made to clarify the degree of effectiveness for each factor.

Analysis of the structure‐dynamic behaviour of an induction machine with balancing kerfs

PurposeTo present results of research closely linked with real life applications. It resumes work of a period of about two years.Design/methodology/approachApplying the finite‐element method (FEM) the impact of balancing kerfs in the bars of squirrel‐cage rotors of a small scale, mass series induction machine (IM) is studied. For the analysis and design optimization of the IM both, 2D electromagnetic, multi‐slice and 3D structure‐dynamic models are considered. Introducing and applying a novel 2D‐3D force‐transformation scheme, all possible balancing variants of the IM are studied in terms of electromagnetic and mechanical behaviour.FindingsThe obtained results lead to a significant improvement of the studied IM. In fact, it is found, that the method of balancing the rotor by carving the rotor bars results in higher unbalanced pull rather than reducing it. This is due to electromagnetic unbalance caused by balancing. Hence, the IM is no longer balanced in series production. This again leads to a major economic benefit.Research limitations/implicationsUsing the FEM for simulation of structure dynamic problems is often limited to how the boundary layers are handled. In real life materials are not “connected” but glued or clamped. Therefore, the behaviour can only be adopted by manipulating the material parameters derived from iterative parameter adoption by measurement.Practical implicationsOwing to the findings the IM is no longer balanced in series production, leading to a significant reduction of costs. In general, the applied methods can be used for the analysis and optimization of any kind of manufacturing or tolerance problem of electrical machines such as various kinds of eccentricity, punching kerfs, broken bars, magnetization errors in permanent‐magnet machines, etc.Originality/valueThis contribution gives a close insight of how to study the impact of manufacturing and tolerance problems of electric machinery, applying the method to an IM with balancing kerfs.

Electromagnetic unbalances of six-phase transmission lines

In this paper, the electromagnetic unbalance factors of six-phase transmission lines with compact and conventional tower-top configurations, with and without two overhead ground wires, are reviewed and the results presented.

ELECTROMAGNETIC UNBALANCE OF UNTRANSPOSED AND TRANSPOSED TRANSMISSION LINES WITH “N” OVERHEAD GROUND WIRES

This paper discusses the electromagnetic unbalances of transmission lines caused by mutual impedances. The unbalance factors of 27 different transmission line configurations have been studied by using a digital computer. The impacts of transposition, phase arrangement, additions of transformer, and capacitors to the lines in terms of circulating currents, sequence impedances, and net through and circulatory unbalance factors have been investigated extensively. Furthermore, the impact of “n” overhead ground wires on the electromagnetic unbalance factors of untransposed single‐ and double‐circuit transmission lines have been studied and the results have been tabulated and plotted.

Electromagnetic unbalance in power systems with untransposed transmission lines

Transposition of power transmission lines represents high costs due to the required transposition towers and also results in low mechanical and electrical strengths. These disadvantages make it desirable not to transpose lines if the resulting unbalances are not adverse. This paper proposes a method to predict the electromagnetic (combination of inductive and capacitive) unbalance of untransposed lines. The method is validated by its application to typical lines under various load conditions and various geometric mean radii.

Electromagnetic unbalance of transmission lines

A SIMPLE but satisfactorily approximate method of computing electromagnetic unbalances1 for double circuit lines, either with or without ground wires, results if the following simplifying assumptions are made: 1. The two circuits are symmetrically arranged on the transmission tower. 2. Line currents in each of the two circuits are balanced and equal. 3. External impedances Z ext terminating the lines are balanced. 4. Mutual impedances are small compared to self-impedances, and voltages induced through mutual impedance by small (negative- or zero-sequence) currents are negligible.

Electromagnetic Unbalance of Untransposed Transmission Lines; II. Single Lines With Horizontal Conductor Arrangement [includes discussion

Various configurations of single-circuit overhead lines without and with ground wires have been considered in a previous investigation of unbalance factors mo and m2.1 In this part of the study, electromagnetic unbalance has been calculated and balance factors plotted for single-circuit overhead transmission lines with horizontal conductor arrangement and two ground wires, so located in many different positions that the protective angle differs from the 30 degrees of the earlier analysis. Since many new lines have been built with a smaller protective angle, the arrangements covered in the investigation may become valuable for application considerations. All computations have been made on an International Business Machines card program calculator, and the basic procedure is given in the Appendix.

Unbalance of single circuit lines

IN RECENT YEARS, many new overhead lines have been built without transpositions in the individual line section and experience has indicated that transpositions are rarely necessary. The elimination of transposition structures leads to geometrical unsymmetry of the phases along the line section, and consequently to small electrostatic and electromagnetic unbalances. In this study are investigated characteristic electromagnetic unbalance factors of various configurations of single circuit lines, i.e., various triangular and flat arrangements without and with ground wires.

Electromagnetic Unbalance of Untransposed Transmission Lines [includes discussion

Electromagnetic Unbalance of Untransposed Transmission Lines [includes discussion