A model for calculating deviation angle of icicle buildup on insulators and its experimental validation

SUMMARY A physical model for the growth of icicle buildup on insulator is presented, and a mathematical analysis equation is obtained by analysing the moment balance of the unfrozen water droplet at icicle tip in this article. The equation reveals the influences of wind velocity, ambient temperature, air pressure and sizes of water droplets on icicle deviation angle. The constraint conditions of this equation are also obtained. The influential factors to icicle deviation angle and critical wind velocity of icicle growth are analysed in this article, respectively. The model is validated on the basis of the field test results in the Xuefeng Mountain Natural Icing Station and the laboratory test results in the large multifunction artificial climate chamber in Chongqing University. The experiment results are basically in agreement with the calculated results. The results show that icicle deviation angle is influenced by wind velocity, air pressure, ambient temperature and sizes of water droplet at icicle tip. Among these factors, the wind velocity is the strongest one. When wind velocity increases to a certain degree, icicle will stop growing. In addition, the transmission lines through high altitude regions tend to be confronted with more serious icing and ice flashover problems compared with the plain areas, which is proved by the previous experiment results. Copyright © 2011 John Wiley & Sons, Ltd.