Optical investigation methods for determining the impact of rain drops on HVDC corona

Abstract

a b s t r a c tCorona behavior of HVDC overhead lines plays a significant role when dimensioning transmission lines. Rain constitutes an important study case since corona effects (e.g. losses, discharge amplitudes) are considerably affected. In this paper, imaging methods are introduced to investigate the impact of rain on corona behavior. Geometrical properties of rain drops on a stranded conductor were extracted. UVimages were used to precisely locate discharges. The methods' capabilities are demonstrated using data from an indoor test line during a simulated rain shower. Optical and electrical data were correlated. These methods aim to support the development of surfaces with favorable corona properties.

Minimum steady corona inception voltage calculation method under rain condition

“…There only exists an unknown parameter in (8), eccentricity e, ranging from zero to unit. Through calculating the minimal value of W in the data range of e, the eccentricity e of steady state can be obtained, and then corresponding value of the semi-major axis and semi-minor axis are calculated, which determine the morphology of droplet.…”

“…On the one hand, the deformation of liquid droplet has been studied in various research fields. Droplet is considered as a cone, and the cone angle of pendent droplet is employed to describe the deformation degree of water droplet in [8], which shows a characteristic minimum at around 99.5°. The geometrical properties and electrical performance of rain droplets corona are extracted by optical investigation method, and the droplet on stranded conductor is energised with positive high-voltage DC.…”

Influence of Surface Wettability on Discharges from Water Drops in Electric Fields

“…The behavior of liquids inside electric fields has been studied extensively in the literature for a range of applications such as electrospinning of nanofibers, nanoprinting, and electro-hydrodynamic spraying. , It has been shown experimentally and computationally that a droplet deposited on a surface deforms under a homogeneous dc electric field perpendicular to the surface. , With increasing field strength the drop elongates in the direction of the field, and its surface eventually becomes unstable. − For a droplet on a superhydrophobic surface, however, it has been observed that it may lift off due to electrostatic forces before reaching instability. ,, A deformed droplet acting as an electrode perturbs the electric field and can lead to the onset of an electric discharge from its tip by assuming a specific shape called a Taylor cone. − An electric discharge is a current flow from an electrode into a dielectric medium that surrounds it. Free electrons are accelerated by an electric field and ionize neutral gas molecules through collisions.…”

“…Therefore, understanding the mechanism that lies behind discharge inception from a water droplet is of vital importance. Even though a broad range of studies has focused on the deformation of droplets in electric fields before ,,− and after − surface instability occurs, only a limited number of works have investigated the correlation between this deformation and discharge inception. , To the best of our knowledge, the effect of different surface wettabilities , and respective drop deformation on discharge onset has not been explored for dc fields perpendicular to the surface in a combined computational and experimental study. Here, we report that surface wettability has a direct effect on the droplet deformation in an electric field as well as on the discharge inception.…”

Superhydrophobic Coatings for Improved Performance of Electrical Insulators

“…Under dry conditions (i.e., absence of water), as the electric field applied across a dielectric material increases, there is an onset of corona discharge due to leakage currents. The corona discharge results in insulator surface damage . This surface damage propagates through the material layer by layer causing considerable material loss and expediting the degradation of the material .…”