Where does the electricity for high speed rail come from? Is it DC or AC?

The power supply line is actually called contact network

The contact network of high-speed railroad is the power transmission line erected along the railroad line to supply electricity to the electric locomotive. The electric current on which the high-speed railway train runs is delivered through the contact network at the upper end of the locomotive, and once the contact network is out of power or the train’s electric bow has poor contact with the contact network, the power supply to the train will be affected.

This year, a high-speed railroad in Beijing was delayed because of a temporary power failure caused by a farmer’s mulch, which is an unforeseeable factor. This is an unforeseeable factor. Because the film meets with high wind, the film hangs on the top of the contact network, and the contact network can’t supply power normally, which causes the temporary failure of power supply of the high-speed railroad.

Voltage level

Industrial frequency single-phase AC system: 25kV, 50Hz or 60Hz, alternating current, international generally to 60Hz, China to 50Hz, due to resistance plus transmission factors, the actual voltage is 27.5kV.

50hz means action, speed frequency, that is, 1 second movement 50 times, our national electricity 220V is 50 Hz, the period is 0.2 seconds, that is to say, 220V positive and negative polarity in 0.2 seconds to change once a second, a second change of 50 times, that is, 50 Hz.

The actual voltage is transmitted by the power plant, which will produce certain loss because of the distance and various reasons.

In the process of power transmission from power plant to contact network of high-speed railroad, there are several parts of power loss as follows:

Self-supply and self-use power of the power plant (the power used to meet the needs of power generation, mainly related to what power plant), transmission line loss from the outlet of the power plant to the substation, and the loss of the substation (mainly including the loss of the substation busbar and transformer);

Losses from substation line outlet to distribution transformer (mainly including losses of distribution line and distribution transformer), losses from distribution transformer to contact network (mainly including losses of low-voltage distribution line and meter losses).

In general, from the power plant to the high-speed railroad, it includes the loss of lines, transformers and meters, etc. The contact network line loss is related to the length of the line, the cross-sectional area of the line, the voltage level, the power conveyed and the temperature;

Transformer loss is divided into transformer copper loss and iron loss, which is related to the transformer model, transformer capacity and power delivered; meter loss is related to the model and internal structure of the meter (meter loss is very low), and it can also be generalized as consumed power.

Power supply level

There are unilateral, bilateral power supply and trans-area power supply in contact network, and unilateral and bilateral power supply are normal power supply.

Unilateral power supply: The power supply arm obtains current only from the substation at one end. This refers to the fact that power can only be obtained from a single power plant, and the HSR will not be able to operate if the equipment fails to transmit power.

At 17:43 on April 2, 2021, due to the equipment failure caused by the cloudy and rainy weather, which led to the emergency braking of train G6968 during the operation stage, Jebao used the DF11-0393 internal combustion engine to haul the train to Daming Lake Station. During the whole period of the train can only use oxygen cylinders for oxygen supply, no lighting in the carriage, visible is the circuit failure can not be repaired for a short period of time, if it is a bilateral power supply method is good.

Bilateral power supply: power supply arm from the two ends of the neighboring substation to obtain the current power supply. Cross-area power supply is a kind of abnormal power supply method (also called accidental power supply method).

Cross-area power supply is when a traction substation due to failure can not be normal power supply, the fault substation bear the power supply arm, through the switching equipment component area kiosk with the neighboring power supply arm connection, by the neighboring traction substation to carry out temporary power supply.

The power supply situation in the section of compound line is similar to the above, but there are four feeder lines from the traction substation, which supply power to the upward and downward contact grids on both sides respectively. The traction substation realizes parallel power supply on the same side of the upstream and downstream to improve the voltage at the end of the power supply arm. Cross-area power supply is realized through the switchgear in the zoning kiosk.


Of course, the bilateral power supply requires twice as many contact grids in order to meet the emergency power supply preparations, i.e. in the event of a failure of the normal power supply lines, the alternative accidental power supply will come in handy;

Especially in winter and summer, if it is not particularly cold or hot, the consequence of power failure in the train will be unimaginable, if all the power supply lines of high-speed railways adopt the bilateral power supply method, there is no need to worry about the power failure at all.

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