The cold wave passed through and the blizzard swept across the country, but it did not reduce people's enthusiasm for returning home for the Spring Festival.
The high-speed rail platform in winter is crowded with travelers who are like arrows. The cold ice rain slapped indiscriminately on your face, and you, like the others, were ready to hold an umbrella to keep out the rain, but unexpectedly, you were stopped by the staff loudly.
Why aren't umbrellas allowed on the high-speed rail platform?
Most high-speed railways use electric traction, and the power passes through the power plant through high-voltage transmission lines, substations, overhead catenary, and pantographs, and finally drives the train [1]. Looking over the track from the platform, one of the dense black lines is an overhead catenary, carrying 20kV-27The operating voltage of 5 kV has long exceeded the 1 kV limit of "high voltage" [2][3].
High-voltage transmission lines are exposed, common insulation materials are furnished in front of ultra-high voltage electricity, and air is the best insulator that can be found.
On weekdays, air is a good insulator and cannot conduct electricity, but high voltage is a special case.
Under high voltage conditions, air can be broken down by electric currents, forming an arc over a certain distance. Once a person enters this danger zone, it can trigger an arc discharge, which instantly releases high temperatures ranging from thousands to tens of thousands of degrees Celsius [4]. It is important to know that the cremation temperature of the remains in the crematorium is only 600 -1200 [5]. Once the human body is hit or penetrated by high-voltage electricity, it is either dead or injured [4].
The yellow cordons on both sides of the platform are one of the measures to eliminate this safety hazard.
According to the provisions of the "Railway Technical Management Regulations (High-speed Railway Part)", the distance between non-professionals (including the objects carried) and the traction live equipment shall not be less than 2 meters. Different types of platforms have different standards for the scope of the cordon, precisely to ensure that passengers are not allowed to enter the danger zone as long as they are outside the cordon[2].
The yellow cordon is paved with all-porcelain braille bricks, using prominent colors and touches to warn passengers of the creativity of picture worms.
In general, the height of the contact line from the top surface of the rail does not exceed 65m；When the passing speed of the train does not exceed 80 km h, the distance between the platform safety marking line and the edge of the platform is 1 m [2].
With a maximum vehicle width of 3For example, the 36 m train CRH380A can be deduced from the limit standard data that electric shock is a false proposition mathematically [6]. As long as the person and the umbrella remain vertically outside the safety line, electrocution is unlikely in the vast majority of cases.
From the Pythagorean theorem, it can be seen that the hypotenuse of a right triangle is longer than the length of any right angle, and the distance between the person outside the safety line and the catenary must be greater than 2 meters The answer is as follows.
The standard resistivity of air is measured in dry conditions, but in rain and snow.
Contrary to common sense, the increase in humidity can increase the breakdown voltage strength of the air to a certain extent, inhibiting the discharge process [7]. But don't be too happy, what is really easy to make high-voltage electricity "break the big defense" is the wind and rain.
Even if it is an insulating material, sleet can form a conductive film when the dirty surface is stained with sticky snow or moisture [8]. The tip, handle or bone of the umbrella, which is made of metal itself, not to mention the ability to conduct electricity.
What's more, the one person and one umbrella on the flat ground are simply the "conspicuous bag" in the high-voltage electric eye. If the rain is connected to the line, it is almost impossible to directly let your umbrella and the catenary "hold hands successfully".
Up to now, there has been no news report in China about the case of high-speed rail umbrella electrocution, after all, to meet all the above conditions, the chance is too great. However, temperature, humidity, rainfall, and the conductivity of rainwater are all uncontrollable, so it is better to be careful.
A sharp object like a lightning rod, with a high charge density at the edge and a high concentration of electric fields, is more susceptible to electric shock[9] Diagram Worm Ideas.
Of course, this is only a very unlikely event. The real danger is the high-speed air flowing by high-speed rail travel, the train wind [10].
Within a certain distance, the speed of the train wind is even comparable to the speed of the train [10]. A 250 km h high-speed train has a wind speed of up to 26 m s on both sides of the train car [11]. The wind speed has reached force 10 and can uproot trees and set off waves up to 9 meters high [12].
When you open an umbrella against the wind, the speed of the vertical fluid is almost entirely applied to the surface of the umbrella, and you will be dragged by the wind like a small boat setting sail, and you will not be able to hold the umbrella at all. A study conducted an umbrella grip test on 9 women with different wind speeds, and when the wind force was 7, the average height of 3 women was 1Female participants who were 62 m and weighed 60 kg were unable to hold an umbrella [13].
The bones and handles are usually made of iron or aluminum, which is stiff and stiff, but not as strong as the storm Unsplash
And once the umbrella falls into orbit, it's a big deal.
The high speed of high-speed rail makes it difficult to brake in time, and foreign objects that suddenly fall into the track will seriously endanger driving safety [14]. In New York, USA, an umbrella fell on the railroad track and damaged the server, and although the conductor discovered it in time, it also caused five trains to be suspended for three hours, and the traffic on the elevated line was interrupted, and thousands of passengers were trapped [15].
In addition to umbrellas, huge aerodynamic forces may also blow your luggage and other items.
From 1972 to 2005, there were 24 wind-related accidents in the UK, which caused instability not only by waiting passengers, but also by wheeled objects such as strollers, wheelchairs, and trolleys on the platform [16]. A gust of wind blows, don't wait until your family has returned, and the gifts you brought to your parents for the New Year have already dispersed.
At present, China mainly relies on manual inspection to remove the snow on the track and the foreign body that fell into the track.
For the safety of passengers, the regulations issued by the railway authority are very strict.
According to the "Railway Technical Management Regulations (High-speed Railway Part)", the maximum speed of the train passing through the platform shall not exceed 250km h. At the same time, according to the speed of train passing, it is necessary to set up safety lines at different distances from the edge of the platform; When the speed is greater than 200 km h, protective equipment such as screen doors will also be added [2].
However, no one can guarantee that accidents will not happen in the midst of wind and snow, and it is always not wrong to keep an eye on it.
It's hard to grab a ticket, but don't delay your journey home because of an umbrella.