ELECTRICITY TRANSMISSION AND ENVIRONMENT: EFFECT OF WIND LOADS ON LIGHTNING SHIELDING PERFORMANCE OF OVERHEAD POWER LINES

Abstract

In this paper the estimation of wind load effect on the lightning shielding performance of overhead power lines was performed. According to electro-geometrical model any phase conductor has horizontal exposure width where this conductor is not protected against lightning by the overhead ground wire. A typical double circuit 220 kV lattice power transmission line tower was considered. Obtained results demonstrate that in the presence of thundercloud in windy conditions unprotected distance of phase conductor may increase due to deflections of phase conductors. Geometric locations of the conductor attachment points on the suspension insulator string and the lower point of the conductor sagging were calculated in the range of wind pressure from 0 to 800 Pa. This allowed to determine the exposure width values of a 220 kV overhead power line upper phase conductor in the same range of wind pressure values. The results show that for a minimum lightning current of 3 kA, the unprotected distance increases by 4.323 times from 4.167 m to 18.013 m when the wind pressure increases from 0 to 800 Pa (from 0 to 36.140 m/s). For a minimum lightning current of 5 kA, the unprotected distance increases by 7.735 times from 2.825 m to 21.851 m when wind pressure and wind speed vary in the same range. Although the transmission line is reliably protected against lightning strikes with currents greater than 16 kA at wind pressure of up to 200 Pa (18.070 m/s), when the wind pressure increases from 300 Pa to 800 Pa (from 22.131 m/s to 36.140 m/s), the unprotected area increases from 4.752 m to 26.204 m. In Summary, the results show that the influence of wind load must be taken into account in the tasks of calculating lightning protection of overhead power lines. Further efforts should be focused on studying the lightning shielding performance of overhead power lines of higher voltage classes.