Why are some trains delayed, and whether the "ancestor" green leather car can solve the problem …

　　Question 5: The "sleepy" high-speed rail under freezing rain.

　　The snow and ice interweave in Spring Festival travel rush, and the extreme weather makes passengers travel blocked, which also makes some areas bear great passenger pressure.

　　Affected by low temperature, rain, snow and freezing weather, some trains on high-speed rail lines have been delayed to varying degrees recently. At the press conference held by China Meteorological Bureau on February 7th, Zhang Hengde, deputy director of the National Meteorological Center, said that this round of freezing rain and snow weather process is coming to an end, but it still has some impacts on the transportation and energy industries. The overall trend is weakening, but we still need to pay attention to the weather risks in some time periods and areas. At the same time, it is predicted that there will be medium snow along the high-speed railways such as Changsha-Wuhan section and Changsha-Zhangjiajie section in Hunan, Hubei and other places from July 7 to 9, which may lead to train delay and station passengers stranded.

　　In this regard, Professor Cai Guoqiang from the State Key Laboratory of Autonomous Operation of Advanced Rail Transit of Beijing Jiaotong University pointed out to reporters: "Unlike the low temperature, blizzard and strong wind in the past winter, the real problem faced by high-speed rail operations in many places this year is the surprise attack from freezing rain."

　　Question 1

　　What is the "real murderer" of the train being trapped?

　　"The catenary is frozen due to freezing rain, and the train is blocked by electricity and current."

　　What is freezing rain? According to the explanation of China Meteorological Bureau, freezing rain refers to the precipitation that is composed of supercooled water droplets and immediately freezes when it collides with an object with a temperature lower than 0℃. Raindrops below 0℃ remain supercooled in the air below 0℃, and when they fall on objects below 0℃, they immediately freeze into ice layers, which are called rainbows. China Meteorological Bureau pointed out that, by definition, freezing rain is a special type of rainfall and weather phenomenon, and the snow cover is the result of freezing rain, which is a kind of disaster or landscape.

　　It is not the first time that the train stopped due to freezing rain. The reporter checked the information and found that there have been many railway outages caused by freezing rain in China. For example, in January 2008, Nanchang, Jiangxi Province, was blacked out for three hours due to freezing rain, and the train could not leave because of the frozen tracks …

　　But why is it that high-speed rail and motor train can still run in snowstorm, low temperature and windy days, but freezing rain can delay or even stop them? Cai Guoqiang explained that this was due to the rapid formation of snow cover after freezing rain fell into the power grid above the train, which led to the failure of high-speed rail and bullet train to get power input smoothly, so the operation was blocked.

　　"To put it simply, the operation of high-speed rail and bullet train depends on electric energy, and if the train wants to take electricity and receive current, it needs to rub with the catenary at the upper end of the train through the pantograph device above the train, so as to obtain high-voltage current to obtain power. However, freezing rain will freeze the catenary, and the pantograph cannot contact the catenary, so the train loses its power supply. " Cai Guoqiang explained, "If the ice covered on the catenary is weak, the train can melt the ice by the friction heat generated by the pantograph and the catenary. However, if the freezing rain continues or the ice layer is too thick, the friction heat will not work, and the train current will be interrupted. This is also the main reason for the large-scale train delay or shutdown in the two lakes."

　　Question 2

　　Can the bullet train directly hit the ice and open the way?

　　"If it is forced to open, the risk is even greater."

　　Zhao Zhang, who lives in the northeast, has a more intuitive feeling about the threat of freezing rain to the operation of high-speed rail and bullet trains. As the deputy director of the maintenance workshop of Harbin EMU, he worked with his colleagues to fight the railway problems brought by freezing rain last winter.

　　"It is very understandable that everyone wants to go home during the Spring Festival, but the biggest premise for us to transport passengers must be to ensure safety." Zhao Zhang said, as some netizens said, "Forcibly start the train, and break the ice on the catenary and the rails by means of collision or friction to generate heat", which will bring greater risks to passengers.

　　In Zhao Zhang’s view, the test brought by freezing rain to the train trip is not only the loss of power supply for the train. He told reporters that there is a set of high-voltage equipment above the EMU. When freezing rain occurs, the catenary will be covered by ice. If the train is forced to run at this time, it will lead to the "virtual connection" between the catenary and the pantograph under the ice barrier, thus causing the two to generate electric sparks due to friction.

　　Once the electric spark is formed, it will not only cause damage to the motor car itself, but also cause other safety hazards if the electric spark radiates to the high-voltage equipment above the motor car. In addition, the snow cover formed by freezing rain will form an ice cone on the catenary. If the train forcibly passes through, it may cause the ice cone to fall on the train roof equipment, and the falling ice will hit the high-voltage equipment on the EMU roof, which will lead to secondary failures and other high-voltage equipment failures.

　　The threat of freezing rain to train operation is not only reflected in the "ceiling". Zhao Zhang said that when running a train in freezing rain, there are also safety hazards on the tracks and train wheels on the ground.

　　Professor Cai Li, who is engaged in lightning protection research at Wuhan University, also told the reporter that apart from the conduction problems caused by freezing rain, the ice on the rails under the train will also cause inconvenience in changing the turnout, and at the same time, it will also lead to a longer braking distance of the high-speed rail. "The railway side should consider the safety of passengers, and these factors will affect normal driving."

　　"Just like driving in the snow and ice, the tires may get stuck in the snow and ice, and the train may have braking problems on the frozen rails." Zhao Zhang explained that on the one hand, due to snow and ice, the wheel disc brake pads on the train wheels may adhere to the wheels, thus affecting the braking force of the EMU; On the other hand, high-speed trains will also suck snow and ice slag around the tracks into the bogie of the train, which may also affect the braking force of the EMU.

　　Cai Guoqiang also pointed out that because the train can’t directly turn around or turn, it must change the direction by means of turnout conversion. During the operation, it is required that the train wheels and turnouts be switched and attached tightly, and there can be no foreign objects in the middle. Therefore, if there is broken ice or snow in the turnout, it is impossible for the train to turn and change lanes, and there is even a danger of derailment.

　　Question 3

　　Why are the southern trains not designed as "frost fighters"?

　　"Different places focus on different things, not just a piece of paper."

　　During Spring Festival travel rush in 2023, northeast China experienced several cold waves, and the minimum temperature dropped to around -50℃. At that time, Fuxing Alpine Intelligent EMU was able to ride the normal operation of the railway and bear the burden of transporting passengers home in the alpine environment.

　　However, the high-speed rail in the two lakes region was "stopped" due to extreme cold weather. Some netizens also questioned why trains can’t all be designed as "cold intelligence".

　　Cai Li said: "Train design is universal and special. Each railway bureau will strengthen or increase or decrease some functions through the natural environment characteristics of different regions to ensure the safety and convenience of local trains."

　　Generally speaking, the winter temperature in the north is lower than that in the south, so special anti-freezing and warm-keeping materials will be considered in the initial design and operation of trains; Another example is the Hotan-Ruoqiang Railway in Xinjiang, which was put into use in 2022, becoming the world’s first railway line around the desert. In the original design, the railway line has natural advantages in fighting against sandstorms and mobile deserts.

　　Zhao Zhang also said that the train design is not a piece of paper for national use, but is constantly combined with local conditions to improve the progress. Zhao Zhang pointed out that because the temperature in the south is generally higher than that in the north, the requirements for cold resistance and frost resistance will be reduced to some extent, and this cold wave process is rare in the two lakes region, so it is difficult to ensure that every train can run in extreme weather.

　　"On the one hand, it is to consider the design and original cost of the railway. On the other hand, the cost of wear and tear, maintenance and repair is also a large expense." Zhao Zhang pointed out that if all the trains in each city are designed to resist cold and frost in winter, or carry the wind and sand like the railways in Xinjiang, on the one hand, it is not necessary, on the other hand, the economic cost will increase greatly.

　　But even in the snowy city of Harbin, it is also difficult for trains to cope with freezing rain. Zhao Zhang told the reporter, "Because of the freezing rain, the snowstorm disaster is too fast. Even if workers continue to carry out de-icing operations, the ice in the back line has just been removed, and the ice in front has solidified again."

　　In Cai Guoqiang’s view, train design really needs to consider many factors, such as driving speed, safety and comfort, combined with the geographical location of the driving area, weather factors and input costs. "From the past experience, it is really not necessary to put trains suitable for alpine regions in non-alpine regions." However, he also pointed out that the blocked railway operation caused by the snowstorm and freezing rain in Hubei also reminded us that we should further transform and optimize the train design, such as transforming the train structure and adding deicing function to cope with the extreme weather of rain and snow.

　　Question 4

　　How does the northern railway solve the freezing rain crisis?

　　"Harbin’s experience is three steps"

　　How to deal with the snowstorm and freezing rain, and how to deal with the icing of railway catenary? Cai Guoqiang told reporters that the main method adopted at present in China is still manual tapping, or unmanned aerial vehicles hanging popsicles for tapping. If the rain and snow weather is cold and humid, it is often knocked behind on the ice layer, and the catenary will freeze again soon.

　　As a railway worker in northern cities, Zhao Zhang has accumulated experience in dealing with freezing rain crisis. Taking the freezing rain problem solved by Harbin Railway Bureau last year as an example, he introduced the local "freezing rain coping process"-

　　The first step is to open the way with the help of the past locomotive head, that is, the "green leather train head" that netizens said. Zhao Zhang explained that because the locomotive uses diesel engine to generate electricity by itself, it does not need external power drainage, so before the first high-speed train EMU set off, it was cleared by the locomotive, and the carbon skateboard on the locomotive roof was used to touch the catenary, which played the role of scraping ice for the first time.

　　In the second step, when the locomotive is cleared, Harbin Railway Bureau will also open a hot-sliding EMU with a "copper-based carbon skateboard", and scrape the residual broken ice of the catenary back and forth by using the double-sided copper bars above the roof. In this way, after scraping the ice twice in a row, the passenger EMU will drive smoothly.

　　Thirdly, during the non-operation of the train at night, Harbin Railway Bureau will also organize a large number of manpower to the site to carry out manual snow sweeping and deicing operations. Zhao Zhang said: "Because of the frequent occurrence of snowstorm hazards in Harbin, the above-mentioned echelon deicing operation mode was formed in the exploration to ensure the safe travel of passengers in extreme weather."

　　Question 5

　　Is the green leather train "stronger" than the high-speed train?

　　"The two cannot be mentioned in the same breath"

　　Under the threat of freezing rain, high-speed trains and bullet trains that use electric energy pressed the pause button. However, the green leather train, dubbed by netizens as the "ancestor", entered the stage.

　　Why can the green leather train "go fast" in extreme weather? Cai Guoqiang explained that the green leather train, also known as the ordinary speed train, relies on the first locomotive to drive the rear carriage forward. Generally speaking, ordinary speed trains are divided into two kinds of locomotives, one is electric locomotive and the other is diesel locomotive. In the snowstorm weather, the ordinary speed trains driven by electric locomotives will still be affected, but diesel locomotives can still slow down in the ice and snow because they use diesel without external power supply.

　　"It is an emergency measure of our railway department to let the locomotive head pull the bullet train or the high-speed train forward, with the purpose of helping the EMU leave the emergency area and let the bullet train run safely in the area without ice and snow." Zhao Zhang doesn’t support some netizens’ suggestion that "instead of stopping the train, the locomotive head should be pulled all the time". He said that this can be achieved in theory, but the speed of travel will be greatly affected. Therefore, the usual practice of the railway department is to take the EMU to a safe area with the help of the locomotive head, so that the EMU can run normally, or make up for the time loss caused by the delay of the train as much as possible by means of transfer.

　　As for the sound that green leather cars are "stronger" than high-speed trains, Zhao Zhang doesn’t agree: "Because green leather cars rely on diesel to get kinetic energy, they are more adaptable to snow weather. However, from the perspective of travel speed and ride comfort, green leather cars are far less than the current high-speed trains. " Zhao Zhang told reporters that at present, the fastest green leather car runs at a maximum speed of 120km/h, while the running speed of the motor train can even reach 350km/h, which cannot be mentioned in the same breath.

　　Chengdu Business Daily-Red Star Journalist Yang Yuqi Luo Mengjie Hu Yiwen Intern Zhang Junjie Guan Liubo