Reduction of Magnetic Flux Density of Parallel Overhead Power Lines by Optimization of Phase Wires Hanging Order

Abstract

Overhead power lines are one of the largest sources of the low-frequency magnetic fields. Such magnetic fields occur the harmful effects on human health and other biological objects. The current size of the security zones doesn’t provide a safe level of the magnetic flux density outside them. Therefore, the task of reducing the magnetic flux density value of the overhead power lines outside the security zone is urgent. Some overhead power lines have sections where two lines pass parallel to each other at a short distance. For such lines the method of phase wires hanging order optimization can be applied. For efficiency comparison of different hanging orders was chose two types of electricity pylons: portal (PB330-7) and triangular (P330-3). The cases both lines done by the same pylons were investigated. Analyze of different hanging orders efficiency was performed by mathematical simulation using MATLAB software. The magnetic flux density computation inside the security zone and outside it was done by a specialized simplified methodology of power lines electric and magnetic fields calculation. It is shown that in case of identical phase wires hanging order and the same currents direction of two parallel lines there is a significant increasing of magnetic flux density value at the border of the security zone and outside it for both types of the electricity pylons. It is determined that with a certain hanging order it is possible to achieve a significant reduction of the magnetic flux density value. For lines with electricity pylons of a portal type (PB330-7) the most efficient is the mirror order. It allows to obtain a decreasing of magnetic flux density more than 30 percent at the security zone border and more than 50 percent outside it. For pylons of a triangle type (P330-3) the most efficient is the nonsymmetrical order. It provides the decreasing of magnetic flux density up to 20 percent. In case of opposite currents direction, the most efficient is the same hanging order for both types of electricity pylons. It is shown that optimal phase wires hanging order allows to decrease the magnetic flux density value outside the security zone border, to reduce the distance to border of the area with safe level of the magnetic flux density, to increase the phase current value at which the magnetic flux density value reaches the safe level within the security zone.