Calculation Of Magnetic And Electric Field Under Ohl And Its Reduction

This paper describes calculation methods of magnetic and electric field under overhead transmission line (OHL), and a possible way of its reduction. The reduction is obtained by auxiliary shield conductors placed under phase conductors.All aforementioned calculations are derived generally in an analytical form and presented for one example model. The model consists of one tower with one transmission line, and RMS values of magnetic and electric fields are calculated for the control level at a given height above the ground to obtain both the fields profiles under the line. In case the field is too high, auxiliary conductors are placed under the line, and the original field is reduced. Reduction of original field depends on the number and placement of these auxiliary conductors or conductor loops, and a corresponding sensitivity analysis is performed.RMS values of electric and magnetic fields are calculated at control height above the ground and depend directly on the distance from the line. That means RMS values of fields depend directly on the conductors sag which depends on the conductor temperature and hence the current flowing through the line. Thus both the electric and magnetic fields are affected by conductor currents.Aforementioned facts are presented for one example. Sensitivity analysis of the current flowing through the line to magnetic and electric fields is performed, and reduction of fields by addition of auxiliary conductors under the line is calculated.