Insulator flashover under icing conditions

Abstract

Atmospheric ice accretion, combined with pollution, has been recognized as a significant risk factor in the reliability of line and station insulators in cold climate regions. Flashovers occurring on ice-and snow-covered insulators result from combinations of a number of factors and parameters. Electric fields modify the structure of ice, the shape and direction of icicle elongation, the distribution of liquid water and the geometry of air gaps that break up the continuous ice surface. Electric field strength and voltage polarity as well as corona space charge and ionic wind have demonstrable influences on the flashover process. Insulator icing flashover is also affected by changes in air temperature and several other environmental and meteorological conditions including ice type and structure. The presence of surface pollution and the rejection of ions from solid to liquid layers during the freezing and melting process also play a central role in the icing flashover of insulators, which can occur at normal operating voltage under the most adverse conditions. This paper presents an overview of these phenomena and describes the interactions that lead to the initiation and development of discharges on the ice surfaces covering the insulators, as well as their evolution to flashover. The lecture also includes the modeling of these phenomena, leading to successful prediction of the critical flashover voltage as well as to insight into the most practical solutions for improved insulator design and mitigating icing flashovers.

Influence of Fine Metal Particles on Surface Discharge Characteristics of Outdoor Insulators

“…The former means that the conductive particles are evenly scattered on the specimen surface between the electrodes; the latter means that a rectangular area of iron powder close to the HV electrode are Energies 2016, 9, 87 3 of 13 formed, with a width of 2.5 mm and a height of 20 mm. That is to say, the particle density in Figure 2a is 0.2, 0.4, 0.6, 0.8 and 1.0 g/mm 2 , and in Figure 2b it is 0.017, 0.033, 0.05, 0.067 and 0.083 g/mm 2 .…”

“…As concerns the particle parameters of size, amount and distribution, the major results can be summarized as follows: (1) Fine metal particles on the insulator surface under AC voltage conditions show simultaneous behaviors of erratic horizontal movement and vertical lift-off, which cause distortion and intensification of electric stresses inducing surface discharges under a rather low voltage. (2) Flashover voltage shows a decreasing tendency as particle size is reduced and particle amount is increased. An especially significant change occurs when the particle size is smaller than 28 µm, associated with a uniform distribution.…”

“…Outdoor insulators are essential components in the structure and operation of transmission and distribution lines and substations, providing both mechanical connection and electrical insulation for conductors at different voltage levels or for conductors to the ground [1][2][3][4]. From the viewpoint of actual operations, due to direct exposure to atmospheric environments, the variation of aerial components, including both gaseous and solid pollutants, inevitably influences insulator performance.…”

Icing Condition Assessment of In-Service Glass Insulators Based on Graphical Shed Spacing and Graphical Shed Overhang

“…It can also be affected by multiple factors including temperature, humidity, wind velocity, rain and fog, property and quantity of pollution sources, insulator configuration (represented by equivalent salt deposit density (ESDD)), leakage current, and surface pollution layer capacity (SPLC) [5][6][7]. In recent years, there have been many methods to assess the contamination of insulators based on artificial neural networks (ANN) [5], multi model partitioning filter (MMPF) [6], etc.…”

“…In recent years, there have been many methods to assess the contamination of insulators based on artificial neural networks (ANN) [5], multi model partitioning filter (MMPF) [6], etc. Also, insulator icing flashover is affected by meteorological conditions, including ice type and structure [7]. However, there are no appropriate methods to denote and assess icing conditions between insulator sheds.…”