Alternating-current deicing and anti-icing method for overhead line system of electrified railway

Abstract

The invention discloses an alternating-current deicing and anti-icing method for an overhead line system of an electrified railway, which comprises the following steps: on the basis that a traction substation has two sets of traction transformers (a main transformer and a standby transformer), matching of primary side joints of the two transformers (that is, the main transformer is connected with a main joint and the standby transformer is connected with a tap; or the main transformer is connected with the tap and the standby transformer is connected with the main joint, or the main transformer and the standby transformer are connected with different taps) to change the output voltage, so that a voltage difference exists between the secondary side voltage of the main traction transformer and the secondary side voltage of the standby traction transformer, and ice melting and ice prevention are realized without additionally using ice melting and ice prevention equipment; the investment cost is saved; in addition, the locomotive can also operate in the ice-melting and anti-icing traction network section.

Description

Technical Field

[0001] The invention relates to the technical field of electrified railway traction power supply systems, in particular to an AC ice melting and ice prevention method for an electrified railway contact network. Background Art

[0002] The overhead contact network is the power supply equipment of electric locomotives and plays an important role in driving electric locomotives. As it is an overhead structure exposed to the outside world, it is very easy to be covered with ice in extreme weather conditions (such as freezing rain and snow). Ice on the overhead contact network will bring the following hazards: (1) It causes the conductors to dance, which may seriously cause wire breakage, fracture and deformation of supporting devices such as pillars; (2) It induces "ice flash" accidents, resulting in frequent line tripping and damage to insulators; (3) It affects the normal current collection of the train pantograph, causing arc burns to the pantograph slide and contact wire; (4) It may cause the protection device to malfunction. These hazards will cause long-term power outages on electrified railways, causing serious economic losses and safety hazards. For example, in February 2024, the central China region of my country suffered a severe freezing rain disaster, which caused large-scale damage to the overhead contact network and train pantographs, resulting in large-scale train delays and cancellations, seriously affecting the normal travel of passengers.

[0003] Regarding the problem of contact network icing, the most studied and applied anti-icing technologies at home and abroad are mechanical deicing technology, chemical deicing and thermal deicing technology. Mechanical deicing technology mainly includes methods such as manual knocking, vibration deicing and locomotive pantograph friction. There is no need to add new equipment, but the efficiency is not high and the deicing range is limited; chemical deicing prevents line icing by coating anti-icing materials on the surface of the contact line, but it is limited by the short life and high maintenance cost of anti-icing materials; thermal deicing technology achieves the purpose of anti-icing by circulating a large current on the ice-covered line to increase the temperature of the conductor. Due to its strong operability, it has attracted widespread attention. Thermal deicing can be divided into two types: AC deicing and DC deicing according to the different currents flowing. DC deicing technology has the advantages of not needing to consider line reactance, small system capacity, and high deicing efficiency. However, in AC electrified railways, especially when there are vehicles running in the traction network, it is difficult to directly invest in anti-icing devices. Summary of the invention

[0004] The purpose of the present invention is to provide an AC ice melting and ice prevention method for an electrified railway overhead contact network, which directly utilizes a traction transformer as an ice melting power source to achieve ice melting and ice prevention for the overhead contact network.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] An AC ice-melting method for an electrified railway contact network, the electrified railway contact network comprises a power supply arm, the power supply arm comprises an uplink and a downlink contact wire, and an isolating switch is arranged between the uplink and the downlink contact wires; the secondary side of a main traction transformer is connected to the uplink and the downlink contact wires through a first power supply branch and a second power supply branch, respectively; the secondary side of a standby traction transformer is connected to the uplink and the downlink contact wires through a third power supply branch and a fourth power supply branch, respectively; the primary side of one of the main traction transformer and the standby traction transformer is provided with at least one tap, and the tap is used to change the secondary side voltage of the traction transformer; when the uplink and / or the downlink contact wires are covered with ice, then: a tap is selected so that the secondary side voltage of the main traction transformer has a voltage difference with the secondary side voltage of the standby traction transformer; the isolating switch is closed, the first and the fourth power supply branches are closed and the second and the third power supply branches are disconnected, or the second and the third power supply branches are closed and the first and the fourth power supply branches are disconnected, so that the main traction transformer, the uplink contact wire, the downlink contact wire and the standby traction transformer form an AC circuit for ice melting.

[0007] Furthermore, the primary side of another traction transformer is also provided with at least one tap; and the method also includes selecting the tap of another traction transformer so that the voltage difference between the secondary side voltage of the main traction transformer and the secondary side voltage of the standby traction transformer increases or decreases.

[0008] An AC anti-icing method for an electrified railway contact network, the electrified railway contact network includes a power supply arm, the power supply arm includes an uplink and a downlink contact wire, and an isolating switch is provided between the uplink and the downlink contact wires; the secondary side of a main traction transformer is connected to the uplink and the downlink contact wires through a first power supply branch and a second power supply branch, respectively; the secondary side of a standby traction transformer is connected to the uplink and the downlink contact wires through a third power supply branch and a fourth power supply branch, respectively; the primary side of one of the main traction transformer and the standby traction transformer is provided with at least one tap, and the tap is used to change the secondary side voltage of the traction transformer; when the uplink and / or downlink contact wires reach the ice growth condition, then: a tap is selected so that the secondary side voltage of the main traction transformer has a voltage difference with the secondary side voltage of the standby traction transformer; the isolating switch is closed, the first and the fourth power supply branches are closed and the second and the third power supply branches are disconnected, or the second and the third power supply branches are closed and the first and the fourth power supply branches are disconnected, so that the main traction transformer, the uplink contact wire, the downlink contact wire and the standby traction transformer form an AC circuit for anti-icing.

[0009] Furthermore, the ice growth conditions are wet growth ice conditions, that is, the wind speed is 3 to 15 m / s, the temperature is -4 to 0°C, and the relative humidity is greater than 80%.

[0010] Furthermore, the primary side of another traction transformer is also provided with at least one tap; and the method also includes selecting the tap of another traction transformer so that the voltage difference between the secondary side voltage of the main traction transformer and the secondary side voltage of the standby traction transformer increases or decreases.

[0011] The beneficial effects of the present invention are as follows: based on the fact that the traction substation itself has two sets of traction transformers (a main transformer and a standby transformer), the output voltage is changed by utilizing the coordination of the primary side connectors of the two transformers (i.e., the main transformer is connected to the main connector and the standby transformer is connected to the tap, or the main transformer is connected to the tap and the standby transformer is connected to the main connector, or the main transformer and the standby transformer are connected to different taps) so that there is a voltage difference between the secondary side voltage of the main traction transformer and the secondary side voltage of the standby traction transformer, thereby achieving ice melting and ice prevention, without the need for additional ice melting and ice prevention equipment, thus saving investment costs; and the locomotive can also operate in the ice melting and ice prevention traction network section. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the traction power supply system structure.

[0013] Figure 2 Schematic diagram of traction transformer tap in an embodiment of the present invention.

[0014] Figure 3 The figure is a flow chart of switching between two working modes in an embodiment of the present invention.

[0015] Figure 4 This is a schematic diagram of system connections in a normal operating mode in an embodiment of the present invention.

[0016] Figure 5 It is a schematic diagram of system connection in ice melting and ice protection operation modes in an embodiment of the present invention.

[0017] Figure 6 It is a schematic diagram of power supply for a locomotive in ice melting and ice protection operation modes in an embodiment of the present invention.

[0018] Figure 7 It is a schematic diagram of the structure of a data processing and control system in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The AC deicing and deicing method for electrified railway overhead line provided by the present invention is based on the structure of the traction substation itself, utilizes the spare transformer in the traction substation, and utilizes the voltage difference to meet the AC deicing and deicing requirements of the overhead line. The deicing device is the main and spare traction transformers in the traction substation, does not require external deicing equipment, is relatively simple to control, can switch working modes, and is put into operation when there is a need for deicing and deicing, which can effectively save investment costs.

[0020] See also Figure 1In the whole traction network, each traction substation has an anti-icing device, that is, two sets of traction transformers, and the overhead line draws power from the busbars on the secondary sides of the two traction transformers. There are substations between the traction substations. When the anti-icing device is started, the isolating switch in the substation is closed to form an anti-icing circuit and reduce the voltage fluctuation at the end of the traction network.

[0021] In a single station, each traction substation has two sets of traction transformers. One set is the main traction transformer, which is put into daily use and is responsible for supplying power to the traction network under normal operating conditions. The other is a backup transformer, which is not put into daily use. It is put into use after the monitoring system issues an instruction to enter the anti-icing mode. Together with the main transformer, it is connected to the upstream and downstream contact lines of the same power supply arm to form an anti-icing power supply and emit anti-icing current.

[0022] Example

[0023] See also Figure 2 , shown is the schematic diagram of the primary side tap of the traction transformer.

[0024] There are 6 different taps for traction transformers, including ±2.5%, ±5%, and ±7.5%. Since the high-voltage winding of the transformer is usually on the outside, it is convenient to connect the taps, so the taps are usually distributed on the high-voltage side of the traction transformer, that is, the primary side. By adjusting the tap position of the power supply access, the number of turns of the traction transformer winding can be changed, and then the transformation ratio can be changed, thereby adjusting the output voltage of the secondary side. Figure 2 The voltage marked on each tap corresponds to the number of turns of the primary winding connected to the terminal, not the input voltage. For example, when the traction transformer ratio is 110 / 27.5 when the main tap is connected, the output voltage is 27.5kV when the input voltage is 110kV; if the tap is connected at -7.5%, the actual transformer ratio becomes 110*(1-7.5%) / 27.5=101.75 / 27.5, and the input voltage remains unchanged at 110kV, so the secondary output voltage can be changed.

[0025] The secondary side output voltage calculation formula is as follows:

[0026]

[0027] Among them, U1 is the primary input voltage of the traction transformer, and U2 is the secondary output voltage, both in kV; since the rated voltage of the primary side of the traction transformer is 110kV and the rated voltage of the secondary side is 27.5kV, here 110 represents the number of turns of the primary winding, and 27.5 represents the number of turns of the secondary winding; k represents the different taps of the traction transformer.

[0028] When the primary input voltage is 110kV, the secondary output voltage formula can be converted into the following formula:

[0029]

[0030] See also Figure 3 , which is a flow chart of the device switching between two working modes. The specific implementation steps are:

[0031] Step 1: The AC ice melting device is not put into operation temporarily. Initialize each circuit breaker and disconnector first to make the traction power supply system work in normal operation mode. The specific process of the switching operation is as follows:

[0032] 1.1 Close the output feeder circuit breakers QF1, QF2, QF3 and QF4 of the main traction transformer;

[0033] 1.2 Disconnect the output feeder circuit breakers QF5, QF6, QF7, and QF8 of the standby traction transformer;

[0034] 1.3 Disconnect the isolating switches QS11 and QS12, and use electrical phase separation to separate the α power supply arm and the β power supply arm;

[0035] 1.4 The disconnectors QS9 and QS10 in the partition can be selectively closed to make the upstream and downstream lines of the same power supply arm run in parallel, so as to minimize the voltage fluctuation at the end of the traction network.

[0036] Step 2: Start the overhead line environmental parameter monitoring unit.

[0037] Step three, the overhead line environmental parameter monitoring unit monitors the ambient temperature, humidity, wind speed and other parameters and the icing condition of the overhead line, and converts the monitoring parameters into a specified signal and feeds it back to the data processing center, which calculates the icing intensity and icing growth rate under the environmental conditions. When the line has been iced or it is judged that the environment in which the overhead line is located reaches the wet growth icing conditions, the system switches to the AC anti-icing working mode; otherwise, it continues to compare the external environmental parameters.

[0038] Step 4: The system switches to AC anti-icing mode. The specific process of the switching operation is as follows:

[0039] 5.1 The electrical phase isolating switches QS11 and QS12 remain disconnected;

[0040] 5.2 Main traction transformer α-phase and β-phase upstream output feeder circuit breakers QF1 and QF3 remain closed, and downstream output feeder circuit breakers QF2 and QF4 are disconnected;

[0041] 5.3 The standby traction transformer is put into use, the standby traction transformer α-phase and β-phase downstream output feeder circuit breakers QF5 and QF7 are closed, and the upstream output feeder circuit breakers QF6 and QF8 are opened;

[0042] 5.4 Close the disconnectors QS9 and QS10 to form an AC ice-melting circuit in series with the upstream and downstream contact networks;

[0043] 5.5 Start the data processing and control system, provide the de-icing voltage reference value U, and adjust the tap positions of the primary sides of the two traction transformers according to the reference value to make the anti-de-icing voltage at a suitable level;

[0044] 5.6 After the buffer time t, the disconnectors QS1, QS3, QS5 and QS7 are closed and the system operates in the contact network AC anti-icing mode.

[0045] Step 5: judging the contact network icing condition according to the sensor feedback signal in the contact network environmental parameter monitoring unit, combined with meteorological data information and contact network monitoring equipment;

[0046] If the contact network is covered with ice, the status of each circuit breaker and disconnector remains unchanged, and the device continues to work in the AC anti-ice melting mode; otherwise, it ends.

[0047] See also Figure 4 , shown is a schematic diagram of system connections when the device operates in normal operating mode.

[0048] In the figure, the main traction transformer is put into operation to supply power to the upstream and downstream lines of the two power supply arms, and the standby traction transformer is not put into operation.

[0049] See also Figure 5 , which is a schematic diagram of system connection when the device works in AC anti-icing mode.

[0050] In the figure, the feeder circuit breakers of the main traction transformer connecting the α and β power supply arms' uplink lines and the feeder circuit breakers of the standby traction transformer connecting the α and β power supply arms' downlink lines are all closed, and the tap positions of the two transformers are set at different positions to form a potential difference at the head end of the traction network.

[0051] See also Figure 6 , which is the topology diagram of the system anti-icing circuit. C1 and C2 are the up and down contact wires, and the 110kV voltage of the power grid is connected to different taps of the two transformers. If the tap k1 of the main traction transformer is negative, the tap k2 of the standby traction transformer is positive, and the input voltage is 110kV, the voltage U at the head end of the two contact wires can be calculated by the above formula. C1 , U C2 The difference between the two is the ice melting voltage U. The calculation results are shown in Table 1.

[0052] Table 1 Calculation results of anti-icing voltage under different taps

[0053] Tap Location <![CDATA[U C1 (kV)]]> <![CDATA[U C2 (kV)]]> U(kV) <![CDATA[k1=-2.5%,k2=+2.5%]]> 28.205 26.829 1.376 <![CDATA[k1=-2.5%,k2=+5%]]> 28.205 26.190 2.015 <![CDATA[k1=-2.5%,k2=+7.5%]]> 28.205 25.581 2.624 <![CDATA[k1=-5%,k2=+2.5%]]> 28.947 26.829 2.118 <![CDATA[k1=-5%,k2=+5%]]> 28.947 26.190 2.757 <![CDATA[k1=-5%,k2=+7.5%]]> 28.947 25.581 3.366 <![CDATA[k1=-7.5%,k2=+2.5%]]> 29.730 26.829 2.901 <![CDATA[k1=-7.5%,k2=+5%]]> 29.730 26.190 3.540 <![CDATA[k1=-7.5%,k2=+7.5%]]> 29.730 25.581 4.149

[0054] As can be seen from Table 1, there are 9 adjustable voltage gears. Taking the CTMH-150 contact wire and JTMH-120 load-bearing cable as an example, calculated based on a single power supply arm length of 25km, when the up and down contact wires are connected in series as the ice-melting circuit, the line equivalent impedance is about 15Ω. When the line is unloaded, the anti-icing device can provide an anti-icing current of up to 276.6A; when the line is running with an electric locomotive, the anti-icing current provided by the device can be superimposed on the locomotive current and used together as the anti-icing current of the line. After the accumulation of time, online anti-icing is achieved. In the actual operation process, the data center establishes a thermal balance equation based on the parameters measured by the monitoring device. It can calculate the critical anti-icing current when the line is not covered with ice but reaches the ice growth conditions and the critical ice-melting current when the line is covered with ice, so as to select different tap positions to adjust the voltage gear and output the corresponding anti-icing current. The specific gear selection method is as follows:

[0055] Taking the overhead contact network with CTMH-150 contact wire and JTMH-120 catenary as an example, when the line is not covered with ice but needs to be protected from ice, if the monitoring device detects that the ambient temperature is -2°C and the liquid water content in the air is 0.25g / m 3 , the wind speed is 3m / s, and the critical anti-icing current of the contact line in this case is calculated to be 154.45A. According to the line equivalent impedance of about 15Ω, the required anti-icing voltage is about 2.317kV, so k1=-5%, k2=+5% can be selected, and the corresponding anti-icing voltage is 2.757kV; when the line needs to melt ice, if the monitoring device monitors the ambient temperature to be -2℃, the liquid water content in the air is 0.25g / m3, the wind speed is 10m / s, and the ice thickness is 8mm, it is calculated that the critical anti-icing current of the contact line in this case is 225.87A. According to the line equivalent impedance of about 15Ω, the required anti-icing voltage is about 3.388kV, so k1=-7.5%, k2=+5% can be selected, and the corresponding melting ice voltage is 3.540kV.

[0056] Figure 7 It is a structural diagram of the device data processing and control system.

[0057] The method determines whether the device is operating in a normal operation mode or an AC anti-icing mode according to a sensor feedback signal in a contact network environmental parameter monitoring unit, specifically:

[0058] 1) The overhead line environmental parameter monitoring unit includes a temperature sensor, a humidity sensor, and a wind speed sensor. The three sensors respectively detect the temperature, humidity, and wind speed conditions of the overhead line environment. At the same time, the monitoring device monitors the icing condition of the overhead line.

[0059] 2) The parameters monitored by the sensor are converted into specified signals and fed back to the data processing and control center. The data processing and control center first observes whether the line is covered with ice through monitoring equipment. If ice is present, the anti-ice melting mode is entered. If there is no ice, the meteorological parameters are combined to determine whether the contact network has reached the ice growth conditions. If the conditions are not met, the system operates normally. If the wet growth ice conditions are reached, that is, the wind speed is 3 to 15 m / s, the temperature is -4 to 0°C, and the relative humidity is greater than 80%, the control center issues a corresponding command to put the system into the anti-ice melting working mode.

Claims

1. An AC de-icing method for an electrified railway contact network, wherein the electrified railway contact network comprises a power supply arm, the power supply arm comprises an uplink contact wire and a downlink contact wire, and an isolating switch is arranged between the uplink contact wire and the downlink contact wire; the secondary side of a main traction transformer is connected to the uplink contact wire and the downlink contact wire through a first power supply branch and a second power supply branch, respectively; the secondary side of a standby traction transformer is connected to the uplink contact wire and the downlink contact wire through a third power supply branch and a fourth power supply branch, respectively; It is characterized in that The main traction transformer and the standby traction transformer, wherein the primary side of one of the traction transformers is provided with at least one tap, and the tap is used to change the secondary side voltage of the traction transformer; When the uplink and / or downlink contact wires are covered with ice, then: Selecting a tap so that the secondary voltage of the main traction transformer has a voltage difference with the secondary voltage of the standby traction transformer; Close the disconnector, close the first and fourth power supply branches and disconnect the second and third power supply branches, or close the second and third power supply branches and disconnect the first and fourth power supply branches, so that the main traction transformer, the up contact wire, the down contact wire and the standby traction transformer form an AC circuit for ice melting.

2. The AC deicing method for electrified railway contact network according to claim 1, characterized in that: The primary side of another traction transformer is also provided with at least one tap; and the method further includes selecting the tap of another traction transformer so that the voltage difference between the secondary side voltage of the main traction transformer and the secondary side voltage of the standby traction transformer increases or decreases.

3. The AC deicing method for electrified railway contact network according to claim 1, characterized in that: The power supply arm is an α power supply arm or a β power supply arm.

4. An AC anti-icing method for an electrified railway overhead contact network, the electrified railway overhead contact network comprising a power supply arm, the power supply arm comprising an uplink and a downlink contact wire, an isolating switch being arranged between the uplink and the downlink contact wires; a secondary side of a main traction transformer being connected to the uplink and the downlink contact wires through a first power supply branch and a second power supply branch, respectively; a secondary side of a standby traction transformer being connected to the uplink and the downlink contact wires through a third power supply branch and a fourth power supply branch, respectively; It is characterized in that The main traction transformer and the standby traction transformer, wherein the primary side of one of the traction transformers is provided with at least one tap, and the tap is used to change the secondary side voltage of the traction transformer; When the uplink and / or downlink contact lines reach ice growth conditions, then: Selecting a tap so that the secondary voltage of the main traction transformer has a voltage difference with the secondary voltage of the standby traction transformer; Close the disconnector, close the first and fourth power supply branches and disconnect the second and third power supply branches, or close the second and third power supply branches and disconnect the first and fourth power supply branches, so that the main traction transformer, the up contact wire, the down contact wire and the standby traction transformer form an AC circuit for anti-icing.

5. The AC anti-icing method for electrified railway overhead contact network according to claim 4, characterized in that: The ice growth conditions are wet growth ice conditions, that is, the wind speed is 3 to 15 m / s, the temperature is -4 to 0° C., and the relative humidity is greater than 80%.

6. The AC anti-icing method for electrified railway overhead contact network according to claim 4, characterized in that: The primary side of another traction transformer is also provided with at least one tap; and the method further includes selecting the tap of another traction transformer so that the voltage difference between the secondary side voltage of the main traction transformer and the secondary side voltage of the standby traction transformer increases or decreases.

7. The AC anti-icing method for electrified railway overhead contact network according to claim 4, characterized in that: The power supply arm is an α power supply arm or a β power supply arm.

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