On 15 December, with dozens of warnings issued from the central to provincial stations, the first cold wave of this winter finally ran into Zhejiang. Temperatures plummeted 13-20 degrees Celsius in the biting north wind in the mountains of Wuyue, and many mountainous areas experienced 7-9 gusts of wind, sleet and ice, which had an impact on people's lives and industrial production.

The cold wave will not only lead to the above mentioned severe weather that we commonly see, but will also cause a disaster phenomenon: power grid over ice, which brings great threat to the operation of the power grid.

资料来源：网络

Ice-covered power grids can cause conductors, ground wires, and tower fittings to be subjected to abnormal tensions, resulting in mechanical damage such as twisting and collapsing. In addition, because of the insulator ice cover or melting process will cause the insulation coefficient to drop, forming a flashover, also known as ice flash.In the winter of 2008, an ice overlay caused part of the power system in 13 provinces in southern China's power system to be unlinked from the main grid. Nationwide, 36,740 power lines were out of service due to the disaster, 2018 substations were out of service, and 8,381 towers of 110 kV and above power lines fell due to the disaster. As many as 170 counties (cities) were without power nationwide, and some areas were without power for more than 10 days. The disaster also caused some railway traction substations to lose power, and the operation of electrified railways such as Beijing-Guangzhou, Hukun and Yingxia was interrupted.

In the ice disaster in January 2016, although the two networks have improved the level of disaster prevention, the State Grid statistics still caused 2,615,000 users to be without power, and the South Grid statistics showed that 2 35kV lines tripped, and 122 10KV lines tripped, which had a huge impact on people's life and production.

Before the arrival of this winter's cold wave, the State Grid Corporation of Zhejiang Province, Shaoxing Power Supply Company has made all kinds of preparations. Among them, Shaoxing Shengzhou Ya Juan Township fog danggang part of the power grid is located in the mountainous area, special geographical conditions and climatic characteristics make this area of the line often become the earliest occurrence of ice-covered risk points in the whole of Zhejiang. This area is also highly susceptible to extreme weather such as ice-covered roads, rain and snow, making it difficult for manual inspections. Low temperatures can also cause lithium battery drones to plummet in airtime and performance.

The hydrogen-powered UAV jointly developed by the State Grid's Zhejiang Shuangchuang Centre and Hydrogen Air Science and Technology took on the important task of inspecting ice-covered mountain areas at this critical moment.In the early hours of December 16, the temperature in mountainous areas had dropped below zero, and the probability of ice-covered disasters had increased dramatically. Shaoxing power transmission operation and inspection centre inspectors, in the snow and ice covered mountain road to the target line, the car anti-skid chain are broken a few. After the inspectors assessed the difficulty and risk, the team planned to fly a hydrogen fuel cell-powered drone called "Hydrogen Thunder". The Hydrogen Thunder UAV can withstand temperatures as low as -20°C and has a maximum operating radius of 30 kilometres. Taking off from this position can cover all the risky lines.

Another challenge in the mountainous area is the complex and turbulent airflow, and the wind resistance of the Hydrogen Timing is fully tested in 6-7 level gusts plus updrafts. After 2 hours of inspection, the drone used a visible light pod to inspect 16 kilometres of lines, 53 towers, and took about 3,600 photos.

The Shaoxing Transmission Operation and Inspection Centre also tested for the first time the use of a hydrogen-powered drone plus LIDAR for ice-covered scanning. The UAV carries the LIDAR pod of the Airwing Intelligence Core, generates a 3D point cloud model in real time, and calculates the distance between the arc droop and the crossings online. The curvature of the collected ice-covered arcs combined with the type of conductor and span parameters can quickly calculate the weight of the conductor ice-covered, and assess the degree of risk.