전력선로에 대한 전자파 전자계의 계산 및 감소대책

Abstract

In this study electromagnetic fields near electric power lines were derived by dipole antenna theory and electromagnetic fields near 3 phase power lines with horizontal and vertical configurations were formulated and could be computed easily using these formula. It seems that those formula could be applicable to the consideration of electromagnetic fields during the design of transmission and distribution lines. And also magnetic fields near electric power lines with branch lines which have a arbitrary angle were derived and formulated by dipole antenna theory and could be calculated easily using the formula. It seems that those formula could be applicable to the consideration of magnetic fields during the design of distribution lines with branch lines .As examples those formulated equations on elements of magnetic fields were applied to models of 3 phase transmssion lines and distribution lines with branch lines and calculated by Matlab programs and the results were presented. And also electromagnetic fields generated by currents of electric wires with finite lengths were induced and formulated to apply to the indoor distribution lines and also using the formula electromagnetic fields were calculated for various configurations of conductors and through analyzing the results mitigation of electromagnetic fields was investigated. Electromagnetic fields were induced by two theories which are Biot Savart's law and dipole antenna theory and the calculated results are same. It could be found that in the case of finite-length electric wires the formula by Biot Savart‘s law are more adaptable than those by dipole antenna theory. Therefore in this study using the formula by Biot Savart's law electromagnetic field distributions were calculated for various configurations of conductors. Reduction effects of magnetic field were analyzed using multi-conductor method(MCM) in analysis of shield. The method can be effective in the analysis because of reducing the amount of allocated memory and the computing time comparative to other methods. Conclusion and results of above study are follows.

(1) Electro magnetic fields near power lines

1) Electromagnetic fields near power lines assumed as ifinite lines (a) In rectangular coordinate system which x-direction is power line's direction, x-components , of electromagnetic fields show very small values ignorbly and reflect only the effects of reflectiion waves in the earth. (b) For variation of horizontal distance profiles of and are same each other, and also those of and are same each other. This means that coupled components of and are perpendicular each other and have the propagation direction of right-hand system such as . (c) Resultant electric field is dominated by the component and resultant magnetic field is dominated by the component . (d) Equations derived in this study are helpful to calculate electromagnetic fields for analyzing the harmful effects of the fields on human and the induction interference of various communication equipments.

2) Electromagnetic fields near power lines with branch lines (a) In case of low observation points if branch angle is small, the resultant magnetic field is directed by , but if become larger and reaches at , is affected by greatly. In case of high observation points (near the power lines), is directed by and this become larger at the position of where branch lines exist. (b) In case of low observation points if branch angle is small, the resultant electric field depends on following the variation of . In case of high observation points, if branch angle is small. is directed by , but if become larger and reaches at , depends on at the position of where branch lines exist.

3) Reduction effects of over-head earth lines in electric fields In case of vertical configuration of 2-phase 2-circuit power lines with two over-head earth lines, electric field is reduced in about 21 %.

4) Electrostatic field and electro magnetic field Electric field under power lines consists of electrostatic field and electric field of electromagnetic fields and the resultant field depends on power factor . The calculation results for a of power lines are follows. (a) Electrostatic field depends on line-voltage and electric field of electromagnetic fields depends on line-current. (b) The lager power factor is, the larger the resultant electric field is.

(2) Electromagnetic fields near indoor distribution power lines with finite lengths

1) Reduction methods of electromagnetic fields by cofigurations of distribution limes (a) The separation between conductors ought to be smaller than smaller as possible. (b) In case of three phase unbalanced currents ought to be reduced as possible. (c) In case of three phase unbalanced currents ought to be reduced as possible. (d) In case of more than two circuits of 3 phase, adequate locations of each phase are more effective 2) Reduction effects of magnetic field by conductive shield. From results calculated by MCM, magnetic field was reduced in about 47 % in case of a flat-shield model and about 55 % in case of a U-shield model.