2015年广西区北部超高压输电线路一次连续覆冰事件的天气学特征

SYNOPTIC CAUSE OF A CONTINUOUS CONDUCTOR ICING EVENT ON ULTRA-HIGH-VOLTAGE TRANSMISSION LINES IN NORTHERN GUANGXI IN 2015

关键词:  电线覆冰  冷空气  暖湿气流  东亚大槽  超高压

Key words:  conductor icing on transmission lines  cold air  warm and humid air flow  the East Asian trough  ultra-high voltage

摘要:

广西区是我国南方电网西电东送输电的重要通道，2015年1月26日—2月8日期间广西区北部桂林地区发生了一次大范围超高压输电线路的连续覆冰事件，其最大覆冰厚度可达24.83 mm。利用ERA5再分析资料和气象观测资料结合南方电网超高压输电线路覆冰观测资料，从天气形势、温湿垂直层结、局地气象要素以及大气环流指数等方面综合分析了此次电线覆冰的天气学成因。结果表明，东亚大槽偏强，阻塞高压引导脊前偏北气流南下，冷空气入境与西太平洋副热带高压带来的暖湿气流汇合，在北方寒潮与南方水汽的共同作用下，地处高海拔的输电线塔杆易出现覆冰。冷暖气团在桂林北部山区上空相互对峙形成准静止锋时出现两种覆冰变化特征：当冷空气强盛且水汽充沛时，过冷却雨滴冻结或者雾滴凝华形成电线积冰；而在暖气团主导下电线覆冰则自然融化。准静止锋的锋区移动在很大程度上影响着电线的覆冰增长过程，特别地，冷暖空气的交替主导是电线反复积冰的主要原因。

Abstract:

Guangxi Province is important for China Southern Power Grid to transmit power from west to east. From January 26 to February 8, 2015, a large scale and continuous conductor icing event of ultra-high-voltage (UHV) transmission lines occurred in Guilin, Guangxi, with a maximum icing thickness of 24.83 mm. Using ERA5 reanalysis data and meteorological observational data combined with the icing observational data of UHV transmission lines from China Southern Power Grid, the current research comprehensively analyzes the synoptic cause of this conductor icing event with a focus on synoptic situation, vertical stratification of temperature and humidity, local meteorological elements, and atmospheric circulation index. Results show that when the East Asian trough is strong, the blocking high pressure guides the northerly cold airflow from the front of the ridge to the south, and the cold air merges with the warm and humid air flow brought by the western Pacific subtropical high. The transmission line towers located in the high altitude are prone to freezing under the joint influence of the cold wave from the north and the water vapor from the south. There are two opposite changes in conductor icing when the cold and warm air confront over the mountainous areas in northern Guilin, forming a quasi-stationary front. When the cold air is strong and moisture is abundant, the supercooled raindrops freeze or the fog droplets condensate to form conductor icing. However, when the warm air dominates, conductor icing melts spontaneously. The movement of the front area significantly affects the growth of the icing of the wire; in particularly, the alternating dominance of the cold and warm air is the main cause of the repeated icing of the wire.