Why are some trains delayed? Can the "ancestral" green leather car come out to solve the problem...
5 questions about the “trap” of high-speed trains under freezing rain
Ice and snow intersect with the Spring Festival transportation, and the extreme weather has hindered travel for passengers, and also put some areas under huge passenger traffic pressure.
Affected by low temperatures, rain, snow and freezing weather, trains on some high-speed rail lines have been delayed to varying degrees in recent days. At a press conference held by the China Meteorological Administration on February 7, Zhang Hengde, deputy director of the National Meteorological Center, said that this round of rain, snow and freezing weather is coming to an end, but it will still have some impact on the transportation and energy industries. The overall trend is to It has weakened, but we still need to pay attention to weather risks in some periods and areas. At the same time, it is expected that there will be moderate snow along the Changsha-Wuhan section, Changsha-Zhangjiajie section and other high-speed railways in Hunan, Hubei and other places from the 7th to the 9th, which may cause train delays and stranded passengers at stations.
In this regard, Professor Cai Guoqiang of the National Key Laboratory of Advanced Rail Transit Autonomous Operation at Beijing Jiaotong University analyzed and pointed out to reporters: "Unlike the low temperatures, heavy snowfalls, strong winds and other climates in the past cold winters, the real problems faced by high-speed rail operations in many places this year are from freezing rain. surprise attack."
Workers carry out snow and ice removal operations on the line. Photo according to Wuhan Railway Bureau
Question 1
What is the "real culprit" of the train being trapped?
"Freezing rain caused the catenary to freeze, and the train was blocked from receiving power and current flow."
What is freezing rain? According to the China Meteorological Administration, freezing rain refers to precipitation that is composed of supercooled water droplets and freezes immediately upon collision with objects with a temperature below 0°C. Raindrops below 0℃ remain supercooled in air with a temperature below 0℃. When they fall on an object with a temperature below 0℃, they immediately freeze into a layer of ice, which is called raindrops. The China Meteorological Administration pointed out that by definition, freezing rain is a special type of rainfall and weather phenomenon, while rainstorm is the result of freezing rain and is a disaster or landscape.
This is not the first time that trains have been suspended due to freezing rain. The reporter checked the information and found that there have been many railway outages caused by freezing rain in our country. For example, in January 2008, there was a three-hour power outage in Nanchang, Jiangxi due to freezing rain, and trains were unable to leave due to frozen tracks...
But why can high-speed trains and high-speed trains still operate during heavy snowfall, low temperatures, and strong winds, but freezing rain can cause delays or even shutdowns? Cai Guoqiang explained that this was due to the freezing rain falling into the power grid above the train and quickly forming smog. As a result, high-speed trains and high-speed trains were unable to smoothly receive power input, thus hindering their operation.
"To put it simply, the operation of high-speed trains and high-speed trains relies on electric energy. If the train wants to receive electricity and current, it needs to rub the pantograph device above the train with the catenary on the upper end of the train to obtain high-voltage current and obtain power. But freezing rain The catenary will freeze and the pantograph will not be in contact with the catenary, so the train will lose power supply." Cai Guoqiang explained, "If the ice covering the catenary is weak, the friction between the pantograph and the catenary will generate heat. The ice can be melted, but if the freezing rain continues or the ice layer is too thick, frictional heat will not work, and the train current will be interrupted. This is also the main reason for large-scale train delays or suspensions in the two lakes area."
Question 2
Can the train directly hit the ice and move forward?
"If the line is forced to reopen, the risks will be even greater."
Regarding the threat that freezing rain brings to the operation of high-speed rail and high-speed trains, Zhang Zhao, who lives in the Northeast, has a more intuitive feeling. As the deputy director of the maintenance workshop of the Harbin EMU, he worked with his colleagues to fight against the railway problems caused by freezing rain last winter.
"It is very understandable that everyone wants to go home during the Spring Festival, but the biggest prerequisite for us to transport passengers must be to ensure safety." Zhang Zhao said, as some netizens said, "Forcibly start the train and generate heat through impact or friction." "Let the ice on the catenary and railway tracks break", which will bring greater risks to passengers.
In Zhang Zhao's view, the test brought by freezing rain to train travel is not just the loss of power supply to 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 move at this time, it will cause the catenary to "break" with the pantograph under the ice barrier. "Virtual connection", causing the two to generate sparks due to friction.
Once an electric spark is formed, in addition to causing damage to the train itself, if the spark radiates to the high-voltage equipment above the train, it may cause other safety hazards. In addition, the smog caused by freezing rain will form ice picks on the contact wire. If the train passes by force, the ice picks may fall on the train roof equipment. The falling ice will impact the high-voltage equipment on the roof of the train unit, causing secondary faults and causing Other high-voltage equipment failed.
The threat of freezing rain to train operation is not only reflected in the "ceiling". Zhang Zhao said that when driving trains in freezing rain, the rails and train wheels on the ground also pose safety risks.
Professor Cai Li, who is engaged in lightning protection research at Wuhan University, also told reporters that apart from the conductive problems caused by freezing rain, icing on the rails under the train will also cause inconvenience for trains to change track, and will also cause the braking distance of high-speed trains to become longer. "Railway The party must consider the safety of passengers, as these factors will affect normal driving."
"Just like driving in ice and snow, the tires may get stuck in the ice and snow and become unable to move, trains may also have braking problems on icy rails." Zhang Zhao explained that on the one hand, due to ice and snow, the discs on the train wheels brake The brake pads may adhere to the wheels, thus affecting the braking force of the EMU. On the other hand, high-speed trains will also suck snow, ice slag, etc. around the rails into the bogie of the train, which may also affect the braking force of the EMU. .
Cai Guoqiang also pointed out that since the train cannot turn around or turn directly, it must use switches to change the direction of travel. During operation, the train wheels and the switches are required to be in close contact with each other, and there should be no foreign matter in between. Therefore, if there is broken ice or snow in the switch, the train will not be able to turn and change lanes, and there may even be a risk of derailment.
Question 3
Why aren't Southern Trains designed as "anti-freeze warriors"?
"Each place has different priorities, and one picture does not rule the world."
During the Spring Festival travel period in 2023, Northeastern my country experienced multiple cold waves, with the lowest temperature dropping to around -50°C. At that time, the "Fuxing High-Cold Intelligent EMU" was able to operate the railway normally and shoulder the heavy responsibility of transporting passengers home in the high-cold environment.
However, this time the high-speed rail in the Lianghu area was "suspended" due to the extreme cold wave weather. Some netizens also asked, why can’t all trains be designed to be “cold-smart”?
Cai Li said: "Train design is both universal and specific. Each railway bureau will strengthen or add or delete some functions based on the natural environment characteristics of different areas to ensure the safety and convenience of local train travel."
Generally speaking, the winter temperature in the north is lower than that in the south, so in the initial design and operation of trains, special anti-freeze and thermal insulation materials will be considered; another example is the Xinjiang Hotan-Ruoqiang Railway, which will be put into use in 2022 and will become the world's first railway around the desert. Railway. In its original design, the railway line had natural advantages in combating sandstorms and mobile deserts.
Zhang Zhao also said that the train design is not a blueprint that can be used nationwide, but is constantly improved and promoted based on local realities. Zhang Zhao’s analysis pointed out that since 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 a certain extent. This cold wave process is rare in the two lakes areas, so it is difficult to ensure that every train can Operate in extreme weather.
"On the one hand, we need to consider the design and original cost of the railway. On the other hand, the cost of wear, maintenance, and repairs is also a large expense." Zhang Zhao pointed out that if all trains in each city are designed to withstand cold and frost in winter, Or it can withstand sandstorms like the railways running in Xinjiang. On the one hand, there is no such necessity. On the other hand, the economic cost will be greatly increased.
But even in the ice and snow city of Harbin, there are still difficulties when trains deal with freezing rain. Zhang Zhao told reporters, "Due to the freezing rain, the rainstorm disaster occurred too quickly. Even if workers continued to carry out de-icing operations, in the end, the ice on the rear lines had just been removed, and the ice in front formed again."
In Cai Guoqiang’s view, train design does need to consider many factors, such as driving speed, safety, and comfort, as well as the geographical location, weather factors, and investment costs of the driving area. "Judging from past experience, it is really not necessary to launch trains suitable for high-cold areas in non-alpine areas." However, he also pointed out that the obstruction of railway operations caused by heavy snowfall and freezing rain in Hubei also reminded us that we should further transform and optimize Train design, such as modifying the train structure and adding de-icing functions to cope with extreme weather such as rain and snow.
Question 4
How does Northern Railway resolve the freezing rain crisis?
“Harbin’s experience is three steps”
How to deal with blizzard, freezing rain and icing on railway catenaries? Cai Guoqiang told reporters that the main method currently adopted in China is still manual knocking or knocking with deicing sticks suspended from drones. If the weather is cold and humid due to rain or snow, the catenary will often freeze again soon after the ice is knocked off.
As a railway worker in a northern city, Zhang Zhao has accumulated experience in dealing with freezing rain crises. Taking the Harbin Railway Bureau's solution to the freezing rain problem last year as an example, he introduced the local "freezing rain response process" -
The first step is to use the locomotive locomotive of the past, which is what netizens call the "green locomotive" to open the road. Zhang Zhao explained that since the locomotive uses a diesel engine to generate electricity without the need for external power diversion, before the first high-speed rail EMU set off, the locomotive cleared the way and used the carbon skateboard on the roof of the locomotive to contact the catenary. Ice scraping effect.
In the second step, after the locomotive clears the way, the Harbin Railway Bureau will also add a hot sliding train unit equipped with a "copper-based carbon skateboard" to use the bilateral copper bars above the roof to scrape back and forth the remaining crushed ice on the catenary. First, the EMU carrying passengers can drive smoothly only after the ice is scraped twice in a row.
The third step is that when trains are not running at night, the Harbin Railway Bureau will also organize a large number of manpower to the site to carry out manual snow removal and ice removal operations. Zhang Zhao said: "Since Harbin also often suffers from rainstorm hazards, the above-mentioned echelon de-icing operation model has been formed through exploration to ensure the safe travel of passengers in extreme weather."
Question 5
Are green trains “better” than high-speed trains?
“The two cannot be the same”
Under the threat of freezing rain, high-speed trains and high-speed trains that use electric energy have pressed the pause button. But the green train, dubbed the "ancestor" by netizens, took the stage.
Why can green trains run so fast in extreme weather? Cai Guoqiang explained that green trains are also called regular-speed trains, relying on the first locomotive to drive the carriages behind. Generally speaking, general-speed trains are divided into two types of locomotives, one is electric locomotives, and the other is diesel locomotives. During heavy snowfall, normal-speed trains pulled by electric locomotives will still be affected, but diesel locomotives do not need external power supply because they use diesel, so they can still travel at reduced speed in ice and snow.
"Letting the locomotive pull the EMU or high-speed train forward is an emergency measure of our railway department. The purpose is to help the EMU leave the emergency area and allow the EMU to operate safely in areas without ice and snow." Regarding the question raised by some netizens "Instead of It is better to stop the train than to let the locomotive pull it along." Zhang Zhao does not support it. He said that in theory this is achievable, but the speed of travel will be greatly affected. Therefore, the usual approach of the railway department is to use The locomotive brings the EMU to a safe area, allowing the EMU to run normally, or making up for the time loss caused by train delays as much as possible through transfers and other methods.
Zhang Zhao disagrees with the idea that green vehicles are "stronger" than high-speed trains: "Because green vehicles rely on diesel to obtain kinetic energy, they are more adaptable to wind and snow. But from the perspective of travel speed and ride comfort, "The green trains are far inferior to the current high-speed trains." Zhang Zhao told reporters that the current fastest green trains have a maximum speed of 120 kilometers per hour, and the current speed of the EMUs can even reach around 350 kilometers per hour. The two are incompatible.
Chengdu Commercial Daily-Red Star News reporter Yang Yuqi, Luo Mengjie, Hu Yiwen, intern Zhang Junjie, Guan Liubo