Study On The Causes,Characteristics And Simulation Of Ice Cover On Power Transmission Lines In The Southern Region

Power Transmission line ice as an important factor affecting the operation of China’s power transmission lines in winter,a serious threat to the smooth operation of society and the safety of people’s property.In this paper,we analyze and summarize the causes,characteristics and simulations of ice cover from the perspectives of large-scale weather circulation,microtopography-micrometeorology and ice cover algorithms for power transmission lines in five southern provinces from winter 2014 to winter 2020.Firstly,from the perspective of weather science,using ERA5 atmospheric reanalysis data to analyze the mid-altitude circulation situation,mid-level and low-level water vapor channels and the vertical distribution characteristics of meteorological elements,the weather circulation situation corresponding to a typical ice-covering event is derived as follows: The presence of the "two troughs and one ridge" stable circulation in Eurasia,the cooperation of the low-level southwestern rapids and the collapse of the blocking high pressure in the Ural Mountains have combined to cause severe ice cover events.Secondly,from the perspective of microtopography-micro-meteorology,the spatial and temporal distribution characteristics of power transmission line ice cover and the changing characteristics of wind and air pressure fields in mountainous areas are analyzed by using the data from the southern regional power transmission line ice cover monitoring system and topographic elevation data.The monthly variation of ice cover is obvious,the annual variation is not obvious,the main ice cover area is located in northeastern Yunnan to northeastern Guangxi.In terms of terrain,windward slopes and canyon terrain have a significant acceleration effect on the wind(2-3m/s),and the surface static pressure increases by 10-20 Pa near the mountain area.Finally,from the perspective of ice-cover algorithm,the Makkonen ice-cover algorithm and Jones ice-cover algorithm are used to analyze the causes of inaccurate ice-cover simulation of power transmission lines in typical micro-terrain and micro-meteorological regions,and the influence of the distribution characteristics of meteorological elements on ice-cover results under different terrain is given quantitatively by using ice-cover monitoring system data and terrain elevation data: In terms of temperature and liquid water content,temperature was negatively correlated with altitude,with lower altitudes having 20-30% less liquid water content than higher altitudes.In terms of wind speed,the simulated wind speed is consistent with the actual wind speed(0.7-5.1 m/s)when the slope is less than 20° due to the combined effect of the guided airflow behind the slot and the narrow tube effect.When the slope is greater than 20°,the wind speed is overestimated due to significant near-ground friction.In terms of pass orientation,wind speeds are overestimated for power transmission lines on southwest and southeast facing passes.This study is important for the power sector to accurately grasp the spatial and temporal distribution and intensity of ice cover,and to carry out anti-ice mitigation work such as DC ice melting and line protection.