An Investigation into Magnetic Field Management under Power Transmission Lines using Delta Configurations

Abstract

The increase of power demand has increased the need for transmitting huge amount of power over long dis- tances. Large transmission lines configurations with high voltage and current levels generate large values of electric and magnetic fields stresses which affect the humanbeing and the nearby objects located at ground surfaces. This has in turn prompted increased activity in the documentation of calculation techniques to accurately predict field strengths in isolated conducting bodies coupled to lines of all voltages and design configurations. Overhead transmission systems required strips of land to be designed as right-of-ways (R.O.W.). These strips of land are usually evaluated according to some aspects; the most important one is the operating effects of the energized line includ- ing magnetic and electric field effects. Therefore determination of the maximum value of the magnetic and electric field stress at ground surface is very necessary and important. It is always required to minimize the amount of land set for high voltage (or current) transmission facilities. This can be achieved by the reduction of the field stress at ground level which is also considered as the most object of efforts to minimize the field effects of such high voltage AC transmission lines. This paper investigates the effects of the transmission line towers configurations, on the mitigation of the induced mag- netic fields, around and near the transmission lines, of the 500 kV systems. The magnetic fields of the conventional 500 kV normal horizontal (flat) power transmission line configuration are compared with that of the normal delta, inverted delta, compact normal delta and compact inverted delta configurations, and in turn its effects on the right of way (R.O.W) distance around the transmission line. The obtained results show that, for compact normal delta, and full compact inverted delta configurations, the resultant magnetic fields produced are lower than that produced from the conventional flat line configuration.