Abstract
The cleaning effect of heavy rain (the rainfall reaches 5 mm every day) on surface contamination of insulators is more effective than dew, fog, mist, and other light rain conditions which can initiate leakage currents and increase the likelihood of flashover. It is well understood that heavy rain can wash away contamination from the surface of high voltage (HV) insulators and thereby reduce the risk of pollution flashover. This study examines the cleaning effect of natural wetting conditions on HV insulators on four 500 kV transmission lines in Hunan Province, China. Historical meteorological data, monthly equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) measurements taken over a period of five years were analyzed to investigate the relationship between rainfall intensity and insulator cleaning. The measured data show that the ESDD/NSDD changes with the seasonal variation, which accumulates in dry season (January–April, about 117–122 days) and is washed off in the wet season (June–October, about 118–127 days). According to the measured data, the ESDD and NSDD on the surface of insulators were affected by the rainfall intensity (in the dry season it is about 1 mm/day and in the wet season it is about 5 mm/day). Based on a comparison of the four study sites, we propose a mathematical model to show the functional relationship between rainfall intensity and insulator self-cleaning capability. The mathematical model’s coefficient of determination (R2) is greater than 0.9 and the effective rate of self-cleaning capability reaches 80%.
Highlights
It is well understood that airborne contamination can strongly influence the voltage thathigh voltage (HV) insulators can withstand [1,2,3]
The average values of the measured equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) between 2011 and 2015 show seasonal variation: contamination accumulates andisiswashed washed in the season
On the basis of the ESDD and NSDD test data, the results show that different areas have different cumulative contamination features
Summary
It is well understood that airborne contamination can strongly influence the voltage thatHV insulators can withstand [1,2,3]. Accurate measurement and prediction of natural contamination on insulator surfaces is important for taking the appropriate measures to prevent pollution flashover in power systems. Some examples of typical pollution environments are defined as follows: marine environments, industrial environments, agricultural environments, and desert environments, since there is the release of some pollution, like marine salts, inert dust, and high degrees of salt. The winter environment, especially concerning the period with low absolute humidity, dusty, windy and exposure to sand and salt (from road salting) is most similar to the desert environment.
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