Surface roughness effects on the corona discharge intensity of long-term operating conductors

Abstract

An investigation into the effect of surface roughness on corona discharge intensity of long-term operating conductors is presented. The electric field distortion level was found to increase linearly with surface average roughness Ra. At the corona inception voltages, the ionization intensity ξ in the ionization zone was calculated, it would increase exponentially with the raise of Ra. As a result, the corona discharge intensity of long-term operating conductors was stronger, and the corona inception voltages were lower than those of the new conductors. The deviation of radio noise and audible noise was found to increase linearly with the raise of Ra.

Micro discharges in HVDC gas insulated systems

“…For example, two electrodes with the same arithmetic average roughness R a , one with slim and sharp micro protrusions will show discharges at much lower field strengths than an electrode with the same measured roughness but broader and rounder shaped micro protrusions [14]. However, a correlation between surface roughness R a and the local field enhancement factor eff can be observed if the surface roughening process is the same [14,20]. At low field stress, ionization is confined to the high field region near the rough electrode surface, where impact ionization increases locally the density of gas ions.…”

“…The test samples are made of PTFE, because it has a high bulk resistivity of >10 20 Ωm and surface resistivity of >10 18 Ωsquare [35]. The permittivity of the PTFE used is ε r = 2.1.…”

Influence on voltage distribution of composite insulator by inserting metal electrodes in weather sheds

“…However, the voltage and electric field are unevenly distributed along the composite insulator, which means particular positions of the insulator may suffer from extreme electric filed stress and could cause deterioration of the insulation material. Operation reports indicated several problems when using composite insulator: tracking and erosion of the shed material; chalking and crazing of insulator surface; reduction of contamination flashover strength; deterioration of mechanical strength [6], and decreased corona inception voltage [7][8][9][10]. These defects in composite insulators may result in power failure which threatened the safety of power systems.…”

Surface aging effects of long-term energized conductors on spectrum characteristics of audible noise

“…The intensity of corona discharge pronouncedly strengthens with surface aging degree, namely surface roughness level, which is consistent with the conclusion of related literature. 14 Due to the enhancement of corona discharge intensity, the collisions between the ions, electrons and neutral particles become more severe and the more energy is transferred to the heat and momentum, which generate a stronger air perturbation and lead to a plasma acoustic field.…”

“…12,13 Recent years, scanning electron microscopy (SEM) and three-dimensional phase shift MicroXam have been employed to measure the surface morphology of the aged conductors which had been energized for about 12, 15 and 20 years in 500 kV and 220 kV alternating current (AC) power grid. 14,15 The aging degree of the longterm operating conductors of power transmission lines are different from that of the new ones, a Author to whom correspondence should be addressed, e-mail: yiyongshanxi@126.con; wanglm@sz.tsinghua.edu.cn 2158-3226/2017/7(9)/095020/6 7, 095020-1 © Author(s) 2017 095020-2…”