Influence analysis of the shielding grid parameters on right-of-way and on corona effects of an EHV 3-phase transmission line

The use of ever-higher voltages for transmission lines causes many problems in the vicinity thereof, because of the high value of the electric field on the ground which can possibly have an effect on men, animals and plants, while making it impossible to operate apparatus located nearby. The paper shows that a reduction of the electric field on the ground can be obtained by using a grounded shielding grid placed under the line, and that, at the same time, this grid causes a rise of the electric surface gradient on the phase conductors, thus increasing the generated corona effects. An analysis has, therefore, been made of the influence of grid design parameters on the electric field on the ground and on corona effects; the results are reported here. This analysis, performed by reference to two base configurations of an EHV 3-phase transmission line, led to the identification of the shielding-grid parameters, on which action can be taken most readily to reduce the electric field on the ground, while keeping the corona effects within reasonable limits.