Electrostatic fields underneath power lines operated at very high voltages

The intensity of the electrostatic field at ground level due to transmission lines operating at 765, 1100 and 1500kV have been calculated as a function of lateral distance under the line. These results showed that the maximum field varied between 15 and 20kV/m. It was found that this field could be reduced significantly by interposing earth shield wires between the line conductors and earth; the intensities being most affected by the number of wires. It was also shown that a nonuniform distribution of these wires is essential to ensure maximum effectiveness. However, because these shield wires add nothing to the operation of lines, but will add to their cost, it is necessary to define values of fields that can be tolerated at ground level.