The Transmission of Bulk Power Over Long Distances

Active and Passive Electronic Components, Jul 2018

Circular, plate, radial and coaxial arrangements for phases of double circuit transmission lines are proposed. Power transmission over long distances depends on the mutual effect between each two respective phases. A theoretical analysis for voltage, power and current along such lines is presented. The general constants for each configuration are evaluated, as well as the maximum power limit for long distance double circuit transmission lines. Different voltage levels of 500 and 1000 kV are considered for a length of 1000 km. An external impedance is suggested to be connected at various points of coaxial arrangement with separate phases. The capacitive effect for such an external impedance is studied.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

http://downloads.hindawi.com/journals/apec/1990/027680.pdf

The Transmission of Bulk Power Over Long Distances

International Journal of THE TRANSMISSION OF BULK POWER OVER LONG DISTANCES 0 Faculty of Engineering, Suez Canal University , Port Said , Egypt Circular, plate, radial and coaxial arrangements for phases of double circuit transmission lines are proposed. Power transmission over long distances depends on the mutual effect between each two respective phases. A theoretical analysis for voltage, power and current along such lines is presented. The general constants for each configuration are evaluated, as well as the maximum power limit for long distance double circuit transmission lines. Different voltage levels of 500 and 1000 kV are considered for a length of 1000 km. An external impedance is suggested to be connected at various points of coaxial arrangement with separate phases. The capacitive effect for such an external impedance is studied. - INTRODUCTION UHV transmission up to 1600 kV appears to offer particular advantage principally to those countries where large generation sites are located far from load centers. Such sites will undoubtedly utilize coal, hydro or nuclear fuels. A very important factor in the future of UHV, which has not been presented in the past, will be the need to move large blocks of energy over long distances because of changes in the world’s fuel situation. An advantage of UHV transmission stems from the fact that, by its use, it may be possible to utilize existing concentrated energy sources, or even to concentrate energy sources in a few areas particularly suitable for safety or environmental reasons. This would avoid spreading generation plants all over the territory. The use of UHV may be more influenced by special requirements (environmental, nuisance) than by purely economic choice so that the future of UHV will depend on the development of proper technical solutions to match these requirements. Although it has been concluded that UHV DC transmission represents an alternative for very long distances (1000-1500 km), the AC transmission appears as the main tool for such a transmission. LINE CONNECTION As blocks of power are generated at a long distance from load centers, a new idea for power transmission will be necessary. This has been tried previously [ 2 ]. The single line diagram for the proposed connection is given in Fig. 1. The phases of the first circuit A, B and C are connected only to the generating end while phases of the second circuit a, b and c are connected to the load at the receiving end. For such circuits the mutual effect 25 between the group of phases (A-a), (B-b) and (C-c) is not the same. Also, the power limit for natural transmitted power through such a line may be varied according to configurations of phases (Fig. 2). The effect of mutual capacitance Cnm and mutual inductance Mnm between phases n and m is accounted. For accurate representation, the equivalent circuit for the shown line should be given for an incremental distance dx (see Fig. 3). This representation leads to an exact analysis for steady state performance. GENERAL CONSTANTS The telegraphic equations of a line for voltage V(x) and current I(x) at a distance x as a function of main parameters (resistance R, inductance L, conductance G and capacitance C) may be expressed in the form: -dVn(x)/dx (Rnn + jwLnn)In(X) + jWMnm Ira(X) dIn(x)/dx ann + jwCnn + (Grim + jwCnrn) (1) 6 m=l mn m-’l 6 m=l mn Vn(x) + (Grim + jwCnm) Vm(x) where w is the angular frequency. The general expression for voltage and current at a point x of a line may be formulated as:6 The integration constants A1,2,3,4, B 1,2,3,4, C 1,2.3,4 and 91,2,3,4 can be determined in terms of current and voltage at the generating end using the terminal conditions.2 The main parameters such as admittance Y, impedance Z, and, propagation coefficient a can be estimated.2 If the mutual effect between the two circuits is disappeared, the deduced equations will be the same as an ordinary line. This can be considered as a check for the obtained expressions. As the general constants depend on the main parameters of a line, they must be investigated for different configurations of phases. For circular arrangement of conductors (Fig. 2a) as well as for radial configuration (Fig. 2b), the general constants are estimated. Although mathematical expressions for constants Ao and Do are not identical, calculations prove that their values are the same. Also, the angle of constants Ao and Do is close to Equivalent circuit for a section dx of a line. x uo length , km 1500 that of ordinary line.2 The general constant Bo in resistive coordinates is obtained as shown in Fig. 4. The magnitude of constant Ao for radial arrangement as well as for ordinary double circuit transmission line is decreased by increasing the line length up to 1200 km, after which its value is increased (see Fig. 4). This means that the mutual reactance between conductors is capacitive with a minimum magnitude of constant Bo while shunt admittance is capacitive up to (...truncated)


This is a preview of a remote PDF: http://downloads.hindawi.com/journals/apec/1990/027680.pdf

M. Hamed. The Transmission of Bulk Power Over Long Distances, Active and Passive Electronic Components, 14, DOI: 10.1155/1990/27680