Abstract
In this paper, the interrelation between temperature distribution and dry band on wet contaminated insulators is studied by theoretical analysis, numerical simulation, and a high-voltage artificial contamination experiment. The influences of the composition of the contaminant and the relative humidity of the environment on the moisture absorption of the contamination layer are studied. It is indicated that the critical relative humidity (CRH) of the soluble mixture in the contamination layer decreases with the increase of the variety of soluble substances. This can be considered as a previously neglected reason for the inconsistency between the result of an artificial contamination test and that of a natural contamination test. Furthermore, the influences of the maximum temperature, wind speed, altitude, relative humidity, and the composition of the contamination on the water evaporation rate of the contaminated layer are also studied. The formation of dry band is predicted by studying the law of water transport in the contamination layer. The influence of the location, width, drying degree, and quantity of dry bands on the insulator surface temperature are studied by numerical simulation. An infrared thermal imager and ultraviolet camera are adopted to measure the temperature distribution and the discharge phenomenon on the insulator surface separately, which verifies the above numerical simulation. The study results deepen the research on the moisture absorption characteristics, the law of temperature distribution, the formation of dry bands, and the influence of dry bands on the temperature distribution of wet contaminated insulators.
Highlights
With the expansion of the power-grid scale and environmental pollution, insulator flashover accidents caused by contamination pose a serious threat to the safety and stability of power systems.Taking China’s electric power system as an example, large-scale contamination flashovers have occurred in six major domestic power grids, resulting in huge economic losses
From the 1980s to the beginning of the 21st century, there have been about 60 regional and large-scale blackouts in China, 29 blackouts caused by line contamination flashovers, and three blackouts caused by contamination flashovers in the substation and booster station of power plants
At the same relative humidity (RH), even if the artificially contaminated water-soluble component in a naturally contaminated insulator is a mixture of a variety of soluble substances, its critical relative humidity (CRH) is quite low
Summary
With the expansion of the power-grid scale and environmental pollution, insulator flashover accidents caused by contamination pose a serious threat to the safety and stability of power systems. A wetted and polluted insulator generates and dissipates heat under the influence of voltage. The research on the heat generation mechanism of wetted and polluted insulators, the distribution of temperature fields, and the conditions for the formation of dry bands or dry band arcs is still imperfect. An infrared thermal imager and ultraviolet camera are applied to a high-voltage artificial contamination experiment to study the temperature distribution on an insulator surface and discharge characteristics. Based on the results obtained, the hygroscopicity and water evaporation rate of the pollution layer on different areas of insulators are further investigated, and the conditions for dry band formation are obtained. Surface Temperature Distribution of Wet Contaminated Insulators in High Voltage Operation
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