Analysis Of The Causes For High-voltage Wire Icing Cases

Using the real-time observation data of ice thickness, comprehensive strength, environmental temperature, relative humidity, wind speed,and wind direction on 500 kV high voltage transmission lines in Hubei Province in February 2008 and January 2009, along with the MICAPS data and NCEP reanalysis data, two icing processes on #307 tower, Zhangen line and two icing processes on #115 tower, Xiaoshi line were analyzed.Using the MICAPS data and NCEP reanalysis data, circulation characteristics and icing processes of air-to-surface layer were analyzed.The results are as follows. There were two troughs and a ridge in high latitudes, a short-wave trough in low latitudes on 500 hPa, a low-level jet on 700 hPa, a shear line on 850 hPa, and a surface cold front during the icing process. In the surface layer, there were also air from the sea during the icing process. The circulation prompted changes in temperature of air flow over the intersection of Hubei Province, and the whole atmosphere was under high humidity condition, which provided moisture and dynamic conditions for the formation of ice.Data collected on the transmission line was used to calculate ice weight and ice growth rate, to analyze the growth process of ice accretion, to discuss the influence of environmental temperature, relative humidity, wind speed, wind direction, precipitation, and other meteorological conditions on the icing process. The results showed that the icing processes were related to environmental temperature, relative humidity, wind speed, wind direction, and precipitation. By using linear analysis, canonical correlation analysis, grey relational analysis method, and nonlinear fitting method, statistical analysis was made on the relationship between ice thickness and meteorological elements. The results showed that the change of meteorological elements had a great influence on ice thickness, and the influence of temperature dominated. Fitting was carried out on ice thickness and temperature, and the higher correlation coefficient of fitting equation was obtained。We analyzed four icing process comprehensively, and summarized the mechanism for the formation of the icing processes:inversion system existed in the four icing processes, but the atmospheric vertical temperature structures were different. There were cold-warm-cold atmospheric temperature vertical structures in the icing processes on February 25-26,2008, February 26-28,2009 and November 12-13,2009. Temperature of the inversion layer was less than 0℃, and there was no cold-warm-cold vertical structure of atmospheric temperature in the icing process on January 5-9,2009. Differences among atmospheric temperature vertical structures led to obvious differences in the formation mechanism of icing process. The existence of a warm layer resulted in the differences in formation mechanism.