Technical Note: Computation of Electric Field Strength Necessary for Eletrostatic Screening of Underground Metallic Gas Pipeline

Abstract

The potential difference between conductors of a transmission line causes them to be charged, so that they become capacitive. Thus the capacitance between the conductors is the charge per unit of potential difference (p.d). Charging current owing in the conductors is the result of alternate charging and discharging of a line due to an alternating voltage impressed on the line. Obviously, electric field is established by this charge. The effects of this field on the objects lying within its vicinity depend on its intensity. In this paper, the electric field of 33kV overhead line is considered. The aim of the paper is to determine the maximum electric field strength or potential gradient, E of the 33kV overhead line at the surface of the ground above an underground metallic gas pipe line located 2 metres away. Computation of E is carried out and if the calculated value of E is higher than the maximum permissible value, corona discharge could occur, and so electrostatic screening or cathodic protection of the pipe line against the electric field will be necessary.

Keywords: transmission line, charge, electric field, potential gradient, electrostatic screening