Efficiency of the air-termination system of a power transmission line by Electric Field Deflection and fractional Brownian motion model

Abstract

Atmospheric discharges contain random components which the Electrogeometric Model does not take into account, once it is purely geometric and not physical. Some physical models, like the Progressive Leader Model, also do not consider variations in the properties of the air. The Electric Field Deflection (EFD) was recently proposed in literature. This model is sensitive to small variations in the permittivity of the air. To simulate these air variations, a two-dimensional landscape of the electric permittivity was created using fractional Brownian motion (fBm). This technique was combined with EFD to simulate the trajectories of lightning discharges through the Finite Element Method (FEM). This proposed method, called EFD-fBm, was used to analyze the air-termination system of a power transmission line and compared to the Electrogeometric Model. Discharges with current peaks of 2.9, 5.4, 10.1 and 15.7 kA were studied according to the lightning protection standards. The transmission line was analyzed in two transverse planes: a plane with the tower and another one comprising the span between two towers. Landscapes constructed through fBm were used. The proposed model estimated that the efficiency of the air-termination system of the transmission line analyzed was 96.36% for discharges with current peak of 10.1 kA.