Traction network three-terminal differential protection system applied to group cut-through power supply

Abstract

A traction network three-terminal differential protection system applied to group cut-through power supply is composed of intelligent units installed in electrified railway traction substations, parallel stations and subareas, traction network differential protection devices and traction network differential protection channels between the substations, and a downlink line and an uplink line of an electrified railway are each provided with a three-terminal differential protection system. The traction network differential protection channel is composed of optical fiber channels among substations, parallel stations and subareas of an electrified railway, and the traction network three-terminal differential protection device is used for receiving digital voltage, current and switching value signals sent by the intelligent units of the substations. According to the invention, when the traction network fails in a group through power supply mode, the fault power supply unit is accurately positioned and the fault is rapidly removed, the differential current of the same row in the power supply unit is adopted to distinguish the fault from the load, the sensitivity, selectivity and quickness of traction network protection are effectively improved, the protection range is large, the selectivity is good, and the reliability is high. And the reliable operation of the power supply system is supported.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply technology and methods, and in particular to a traction network three-terminal differential protection system applied to group through-power supply. Background Art

[0002] my country has a vast land area and complex terrain conditions. Due to the limitations of terrain conditions, some electrified railway projects have designed railway lines with long and steep slopes. In order to improve the power supply capacity of long and steep slopes and solve the problem of electrical phase separation on steep slopes, the existing technology proposes a solution for connecting the power supply system of traction substation groups to form a grid power supply pattern and realize multi-source power supply. The specific implementation method is as follows: the up and down traction network of the electrified railway double-line is connected to the power supply station in parallel by setting a circuit breaker to realize the interconnection of the up and down traction network of the double-line; the traction network of the power supply arm on both sides of the electrified railway traction substation is realized by adopting a single-phase traction transformer; the traction network on the 27.5kV side of the adjacent traction substation is realized by adopting bilateral power supply to realize the interconnection of the traction network of the adjacent traction substation, and at the same time, the high-voltage side (110kV and above voltage level) of the adjacent traction substation is connected to the same local power substation to realize the interconnection of the high-voltage side of the adjacent traction substation. The above technical solution transforms the traditional single-power supply system into a multi-power bilateral ring power supply by optimizing the system structure. The complex system structure can bring higher power supply flexibility and reliability. In addition, through the adjustment and supplement of loads between interconnected grids, the utilization rate of the entire traction power supply system can be improved, and the space, means and levels for solving the problems of the traction power supply system can be expanded. At the same time, it greatly reduces the electrical phase separation on the contact network under normal operating conditions, reduces important weak links in the traction power supply system, and improves the safety and reliability of the power supply system.

[0003] However, due to the limitations of technical solutions, in actual applications, under the multi-power bilateral ring power supply mode, the current of the traction network load or fault comes from multiple power sources on both sides. If the traction network protection adopts the conventional solution, that is, identifying faults based on the current flowing through the substation feeder circuit breaker and the substation bus voltage, problems such as insufficient protection sensitivity, reduced protection range and poor selectivity will occur, which will cause adverse technical constraints on the effective application of the system. Summary of the invention

[0004] In order to overcome the technical limitations of the existing traction substation group through-power supply system, based on the existing technology, faults are identified according to the current flowing through the substation feeder circuit breaker and the substation bus voltage, which will lead to problems such as insufficient protection sensitivity, reduced protection range and poor selectivity, which has caused adverse technical constraints on the effective application of the system. The present invention provides a traction network differential protection device installed in the traction power supply station booth, collects switch quantity information such as voltage and current information and feeder circuit breaker position in each booth, completes data interaction of differential protection devices between booths with the help of differential protection channels, and realizes operation mode identification and three-terminal differential protection based on the power supply unit by using the interactive information, which provides favorable technical support for the reliable and safe operation of the traction substation group through-power supply system, and a traction network three-terminal differential protection system applied to group through power supply.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] The three-terminal differential protection system of the traction network applied to group through-power supply is characterized in that it is composed of intelligent units installed in the traction substation, parallel station and substation of the electrified railway, traction network differential protection devices and traction network differential protection channels between stations. The downlink and uplink lines of the electrified railway are respectively equipped with three-terminal differential protection systems; the function of the intelligent unit is to sample the voltage and current analog signals in the traction substation connected to the three-terminal differential protection system of the traction network and package them into messages, and output them to the traction network differential protection device in SV digital format, and at the same time, it is connected to the primary equipment by cable and to the traction network differential protection device by optical fiber, converts the switch quantity information of the primary equipment into digital quantity and outputs it to the traction network differential protection device in GOOSE digital format, and drives the switch action after receiving the GOOSE switch closing and opening commands issued by the traction network differential protection device; the traction network differential protection channel is composed of the substation of the electrified railway The three-terminal differential protection device of the traction network is composed of optical fiber channels between the stations, parallel stations and substations. There are two access channels for the traction network differential protection device in the downstream and upstream directions of each station, which are respectively connected to the traction network differential protection channels of the same direction of the other two stations; the traction network three-terminal differential protection device is used to receive the digital voltage, current and switching quantity signals sent by the intelligent unit of this station, and receive the analog quantity and switching quantity signals sent by the traction network differential protection channels of the same row of the other two stations through the traction network differential protection channel, and complete the differential protection function after switching quantity comparison, analog quantity synthesis and protection logic operation; when the three-terminal differential protection device of the traction network is used, when the upstream and downstream traction networks fail, the calculated differential current of the three-terminal differential protection device of the traction network increases, and when the differential current exceeds the setting value, the device will send the tripping and closing commands to the intelligent unit, and the intelligent unit will drive the circuit breaker to trip to complete the fault removal and ensure the safe power supply of the electrified railway.

[0007] Furthermore, in the application of the intelligent unit, one intelligent unit is installed in the downstream direction of the traction substation, parallel station and substation, each intelligent unit is connected to the corresponding downstream voltage, current and switch quantity, and each station is connected to analog quantity and switch quantity.

[0008] Furthermore, the traction network three-terminal differential protection device has two optical fiber channel interfaces, which are respectively connected to the other two sides of the traction network three-terminal differential protection devices in accordance with the optical fiber channel loop connection method, that is, channel one of the traction network three-terminal differential protection device on one side is connected to channel two of the traction network three-terminal differential protection device on the other side, channel one of the substation traction network three-terminal differential protection device is connected to channel two of the substation traction network three-terminal differential protection device, channel one of the substation traction network three-terminal differential protection device is connected to channel two of the parallel station traction network three-terminal differential protection device, and channel one of the parallel station traction network three-terminal differential protection device is connected to channel two of the substation traction network three-terminal differential protection device.

[0009] Furthermore, in the application of the intelligent unit, the intelligent unit of each station will input the collected analog quantities and switch quantities into the three-terminal differential protection device of the traction network of the station in the form of digital signals. The three-terminal differential protection devices of the traction networks of the three station booths are connected and exchange information through the traction network differential protection channel. The three-terminal differential protection devices of the three traction networks of each station calculate the differential and braking currents and incremental currents according to the different differential zones of the power supply units.

[0010] Further, the differential current calculation formula is as follows: The braking current calculation formula is as follows: Incremental differential current: The incremental current calculation formula is as follows:

[0011] Furthermore, in the fault identification of the three-terminal differential protection device of the traction network, when the differential current is within the differential protection action area or the incremental differential current is greater than the incremental differential set value, it is identified as a traction network fault. When the differential current, braking current and voltage satisfy the formula When the differential current satisfies the ratio differential element action condition, the ratio differential element acts. When the differential current satisfies the formula I CD >I CD>> When the differential current meets the differential quick-break element action condition, the incremental differential current satisfies the formula ΔI CD >I set When , the incremental differential current meets the incremental differential protection element action conditions, and the incremental differential protection is activated.

[0012] Furthermore, in the application of the three-terminal differential protection device for the traction network, when any one of the ratio differential protection element, the differential quick-break element and the incremental differential element of the three-terminal differential protection device for the traction network is actuated, the three-terminal differential protection device for the traction network sends a tripping signal to the intelligent unit in a GOOSE message format through the optical fiber connected to the intelligent unit. After the intelligent unit receives the GOOSE tripping command sent by the three-terminal differential protection device for the traction network, it drives the circuit breaker to open the circuit breaker via the cable connected to the circuit breaker to cut off the fault.

[0013] The beneficial effects of the present invention are as follows: the present invention installs a traction network differential protection device in the traction power supply station booth, and through its synchronous sampling technology, protects the traction network differential protection device between stations in the power supply unit by using differential protection channel information interaction, thereby realizing accurate positioning of the faulty power supply unit and rapid fault removal when a traction network fault occurs under the group through-power supply mode, and adopts the differential current of the same line in the power supply unit to distinguish between faults and loads, thereby effectively improving the sensitivity, selectivity and speed of traction network protection, with a large protection range and good selectivity, and providing favorable technical support for the reliable and safe operation of the traction substation group through-power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a topological diagram of the through-connected power supply system of traction substation groups;

[0015] Figure 2 It is the structural diagram of the three-terminal differential protection system of the traction network;

[0016] Figure 3 It is a connection scheme for the three-terminal differential protection channels of the traction network;

[0017] Figure 4 This is a schematic diagram of the differential partitioning of the power supply unit.

[0018] Figure 5 It is a schematic diagram of the action characteristics of the steady-state differential protection. DETAILED DESCRIPTION

[0019] Figure 1 , 2As shown, the traction network three-terminal differential protection system applied to group through-power supply is composed of intelligent units installed in traction substations, parallel stations and substations of electrified railways, traction network differential protection devices and traction network differential protection channels between stations. The traction network three-terminal differential protection system is configured for the downlink line and the uplink line respectively. The function of the intelligent unit is to sample the voltage and current analog signals in the traction station connected to the three-terminal differential protection system of the traction network and package them into messages, which are output to the traction network differential protection device in SV digital format. At the same time, it is connected to the primary equipment (electrical equipment that is directly used to produce and use electric energy and has a higher voltage than the control circuit (secondary equipment) is called primary equipment, such as transformers, disconnectors, circuit breakers, etc.) by cables, and connected to the traction network differential protection device by optical fibers. The switch quantity information of the primary equipment is converted into digital quantity and output to the traction network differential protection device in GOOSE digital format, and the switch is driven after receiving the GOOSE switch closing and opening commands issued by the traction network differential protection device (here it means that the intelligent unit collects the status information of the primary equipment and sends the status information to the differential protection device through the GOOSE signal. When the differential protection device determines that the system has a fault and needs to be opened and closed, the switch information that needs to be opened and closed is transmitted to the corresponding intelligent unit through the GOOSE signal, and the intelligent unit parses and controls the corresponding switch to perform opening and closing operations). The traction network differential protection channel is composed of optical fiber channels between substations, parallel stations and substations. Each substation has two access channels for the traction network differential protection device in the downstream and upstream directions, which are respectively connected to the traction network differential protection devices in the same direction of the other two substations. The connection method of the traction network differential protection device is as follows: Figure 3 The traction network differential protection device is used to receive the digital voltage, current and switch quantity signals sent by the intelligent unit of the station, and receive the analog quantity and switch quantity signals sent by the traction network differential protection channels of the same line of the other two stations through the traction network differential protection channel. After the switch quantity comparison, analog quantity synthesis and protection logic operation, the differential protection function is completed. Specifically, the differential partition of the power supply unit in the power supply area is as follows Figure 4 When a fault occurs in the uplink (downlink) traction network, the calculated differential current of the three-terminal differential protection device of the traction network increases. When the differential current exceeds the setting value, the device sends the tripping and closing commands to the intelligent unit, and the intelligent unit drives the circuit breaker in the power supply area to trip and complete the fault removal. Specifically, the steady-state differential protection action characteristics of the three-terminal differential protection device of the traction network are as follows: Figure 5 shown.

[0020] Figure 1 , 2As shown, the three-terminal differential protection system of the traction network applied to group through power supply is configured based on the downstream (upstream) of the power supply unit in the relevant area. As shown below, this embodiment introduces the specific implementation method according to the downstream direction of the power supply unit. The first step is to install intelligent units in the traction substation, parallel station and substation and connect analog and switch quantities; one intelligent unit is installed in the downstream direction of the intelligent unit of the traction substation, parallel station and substation, and each intelligent unit is connected to the voltage, current and switch quantity of the corresponding line (downstream). The analog quantities and switch quantities connected to each station are shown in Table 1.

[0021] Table 1 Statistics of analog and switch quantity access to downstream intelligent units

[0022]

[0023]

[0024] Figure 3 As shown, the second step is to connect the traction network differential protection device. The traction network differential protection device has two optical fiber channel interfaces, which are respectively connected to the traction network differential protection devices on the other two sides in an optical fiber channel loop connection mode, that is, channel 1 of the traction network differential protection device on one side is connected to channel 2 of the traction network differential protection device on the other side. Channel 1 of the traction network differential protection device of the substation is connected to channel 2 of the traction network differential protection device of the substation, channel 1 of the traction network differential protection device of the substation is connected to channel 2 of the traction network differential protection device of the parallel station, and channel 1 of the traction network differential protection device of the parallel station is connected to channel 2 of the traction network differential protection device of the substation.

[0025] Figure 3 As shown in the figure, in the third step, the intelligent unit of each station will input the collected analog and switch quantities into the traction network differential protection device of the station using digital signals. The traction network differential protection devices of the three stations are connected and exchange information through the traction network differential protection device. The traction network differential protection device of each station calculates the differential and braking current according to the different differential zones of the power supply unit. The differential zones of the power supply unit are as follows: Figure 4 The differential and braking currents and incremental (incremental differential protection is a protection formed by the difference between the current after the fault and the load component, i.e. the fault component current) of the traction network differential protection device are calculated as follows: In differential zone 1, (e.g. Figure 4 The protection range is divided into three zones: Zone 1 refers to the range from the 1QF down-circuit breaker of the substation to the 5QF up-circuit breaker of the substation; Zone 2 refers to the range from the 2QF up-circuit breaker of the substation to the 6QF down-circuit breaker of the substation; Zone 3 refers to the range from the 3QF and 4QF of the parallel station circuit breakers. In the calculation of differential and braking currents, the differential current formula is: The braking current formula is: The incremental differential current formula is: In differential zone 3, in the calculation of differential and braking current, the differential current formula is, The braking current formula is: The incremental differential current formula is, In the above formulas (1) to (6), I CD ,I r , ΔI CD , They represent differential current, braking current, incremental differential current, substation downstream feeder current, parallel station downstream feeder current, substation downstream feeder incremental current, parallel station downstream feeder incremental current, substation downstream feeder incremental current, parallel station upstream feeder incremental current, parallel station upstream feeder incremental current. Specifically, the incremental current calculation formulas in formulas (3) and (6) are: in, They are the current protection current and the two-wave front protection current respectively.

[0026] Figure 5 As shown in the figure, the fourth step is to identify the fault of the traction network. Specifically, the three-terminal differential protection device of the traction network sets the steady-state differential protection element and the incremental differential protection element to identify the fault. The steady-state differential protection action (steady-state differential protection uses the current phasor after the line fault, according to the pre-set protection action, so that the equipment affected by the fault is disconnected from the power system to avoid greater losses.) The characteristics are as follows Figure 5 As shown, when the differential current of the three-terminal differential protection device of the traction network is within its differential protection action zone or the incremental differential current is greater than the incremental differential setting, it is identified as a traction network fault. The specific method is that the three-terminal differential protection device of the traction network sets the working parameters of the steady-state differential protection element, including the fast action zone and the ratio differential action zone, in which the ratio differential action zone considers the low-voltage lockout, and the fast action zone only judges the differential current size. When the differential current, braking current and voltage meet the formula When the differential current meets the ratio differential element action condition, the ratio differential element of the traction network three-terminal differential protection device will act. In the formula, I CD is the differential current, I CD> is the ratio differential protection action current setting value, k is the ratio braking coefficient, I r is the braking current, U is the protection voltage, U set Low voltage starting setting. When the differential current satisfies the formula I CD >I CD>> (8), the differential current meets the action condition of the differential quick-break element, and the differential quick-break action of the three-terminal differential protection device of the traction network is performed. In the formula, I CD>> The three-terminal differential protection device sets the incremental differential protection element parameters. When the incremental differential current satisfies the formula ΔI CD>I set (9), the incremental differential current meets the incremental differential protection element action condition, and the incremental differential protection of the traction network three-terminal differential protection device is actuated. In the formula, ΔI CD is the incremental differential current, I set It is the setting value of the incremental differential protection operating current.

[0027] Figure 5 As shown, the fifth step is to remove the traction network fault. When any of the ratio differential protection elements, differential quick-break elements and incremental differential elements of the three-terminal differential protection device of the traction network is activated, the three-terminal differential protection device sends a trip signal to the intelligent unit through the optical fiber connected to the intelligent unit in the GOOSE message format. After receiving the GOOSE trip command sent by the three-terminal differential protection device, the intelligent unit drives the circuit breaker to open and remove the fault through the cable connected to the circuit breaker. Through all the above technical schemes, the present invention uses the traction network differential protection device installed in the traction power supply station booth, and through its synchronous sampling technology, the traction network differential protection device between the power supply units uses the differential protection channel information interaction to achieve the accurate positioning of the faulty power supply unit and the rapid removal of the fault when the traction network fails in the group through power supply mode, and uses the differential current of the same line in the power supply unit to distinguish the fault from the load, which effectively improves the sensitivity, selectivity and speed of the traction network protection, has a large protection range and good selectivity, and provides favorable technical support for the reliable and safe operation of the group through power supply system of the traction substation.

[0028] The main features and advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0029] In addition, it should be understood that although the present specification is described according to the implementation mode, the implementation mode does not only include an independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A three-terminal differential protection system for traction network used for group through power supply, characterized in that: It is composed of intelligent units installed in traction substations, parallel stations and substations of electrified railways, traction network differential protection devices and traction network differential protection channels between stations. The downlink and uplink lines of electrified railways are respectively equipped with three-terminal differential protection systems; the function of the intelligent unit is to sample the voltage and current analog signals in the traction substation pavilion connected to the three-terminal differential protection system of the traction network and pack them into messages, and output them to the traction network differential protection device in SV digital format. At the same time, it is connected to the primary equipment by cables and to the traction network differential protection device by optical fibers, converts the switch quantity information of the primary equipment into digital quantities and outputs them to the traction network differential protection device in GOOSE digital format, and drives the switch action after receiving the GOOSE switch closing and opening commands issued by the traction network differential protection device; The traction network differential protection channel is composed of optical fiber channels between substations, parallel stations and substations of the electrified railway. Each station has two access channels for the traction network differential protection device in the downstream and upstream directions, which are respectively connected to the traction network differential protection channels of the same direction of the other two stations; the traction network three-terminal differential protection device is used to receive the digital voltage, current and switch quantity signals sent by the intelligent unit of the station, and receive the analog quantity and switch quantity signals sent by the traction network differential protection channels of the same row of the other two stations through the traction network differential protection channel, and complete the differential protection function after switch quantity comparison, analog quantity synthesis and protection logic operation; when the traction network three-terminal differential protection device is used, when the upstream and downstream traction networks fail, the calculated differential current of the traction network three-terminal differential protection device increases, and when the differential current exceeds the setting value, the device will send the tripping and closing commands to the intelligent unit, and the intelligent unit will drive the circuit breaker to trip to complete the fault removal and ensure the safe power supply of the electrified railway.

2. The traction network three-terminal differential protection system for group through power supply according to claim 1 is characterized in that: In the application of intelligent units, one intelligent unit is installed in the downstream direction of the traction substation, parallel station and substation. Each intelligent unit is connected to the corresponding downstream voltage, current and switch quantity, and each station is connected to analog quantity and switch quantity.

3. The traction network three-terminal differential protection system for group through power supply according to claim 1 is characterized in that: The traction network three-terminal differential protection device has two optical fiber channel interfaces, which are respectively connected to the other two sides of the traction network three-terminal differential protection devices in accordance with the optical fiber channel loop connection method, that is, channel one of the traction network three-terminal differential protection device on one side is connected to channel two of the traction network three-terminal differential protection device on the other side, channel one of the substation traction network three-terminal differential protection device is connected to channel two of the substation traction network three-terminal differential protection device, channel one of the substation traction network three-terminal differential protection device is connected to channel two of the parallel station traction network three-terminal differential protection device, and channel one of the parallel station traction network three-terminal differential protection device is connected to channel two of the substation traction network three-terminal differential protection device.

4. The traction network three-terminal differential protection system for group through power supply according to claim 1 is characterized in that: In the application of intelligent units, the intelligent units of each station will input the collected analog and switch quantities into the three-terminal differential protection device of the traction network of the station in the form of digital signals. The three-terminal differential protection devices of the traction networks of the three station booths are connected and exchange information through the traction network differential protection channel. The three-terminal differential protection devices of the three traction networks of each station calculate the differential and braking currents and incremental currents according to the different differential zones of the power supply units.

5. The traction network three-terminal differential protection system for group through power supply according to claim 1 is characterized in that: The differential current calculation formula is as follows, The braking current calculation formula is as follows: Incremental differential current: The incremental current calculation formula is as follows:

6. The traction network three-terminal differential protection system for group through power supply according to claim 1 is characterized in that: In the fault identification of the three-terminal differential protection device of the traction network, when the differential current is within the differential protection action area or the incremental differential current is greater than the incremental differential setting, it is identified as a traction network fault. When the differential current, braking current and voltage satisfy the formula When the differential current satisfies the ratio differential element action condition, the ratio differential element acts. When the differential current satisfies the formula I CD >I CD》 When the differential current meets the differential quick-break element action condition, the incremental differential current satisfies the formula ΔI CD >I set When , the incremental differential current meets the incremental differential protection element action conditions, and the incremental differential protection is activated.

7. The traction network three-terminal differential protection system for group through power supply according to claim 1 is characterized in that: In the application of the three-terminal differential protection device of the traction network, when any one of the ratio differential protection element, differential quick-break element and incremental differential element of the three-terminal differential protection device of the traction network is actuated, the three-terminal differential protection device of the traction network sends a tripping signal to the intelligent unit in the GOOSE message format through the optical fiber connected to the intelligent unit. After the intelligent unit receives the GOOSE tripping command sent by the three-terminal differential protection device of the traction network, it drives the circuit breaker to open the circuit breaker through the cable connected to the circuit breaker to cut off the fault.

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