Electric leakage protection device and rail transit power supply system

Abstract

The application discloses a kind of electric leakage protection device and rail transit power supply system, the device includes: multiple sets of electric leakage protection sub-device, it is set up one-to-one with the multiple traction substations of rail transit power supply system, it includes: ground leakage protection circuit, digital current selective trip protection circuit and switch, digital current selective trip protection circuit is connected with the corresponding switch by tail cable communication, and it is electrically connected with the corresponding ground leakage protection circuit by hard wire, for when receiving the electric leakage warning signal sent by corresponding ground leakage protection circuit, obtain and locate fault interval according to the current vector of all feeder loop inflow, outflow of the power supply interval to which itself belongs, and after positioning, remove fault interval. The switch between the two adjacent traction substations is connected by optical cable communication. Thus, the device can quickly and accurately remove the fault interval, reduce the power outage range, guide the maintenance personnel to carry out targeted maintenance, and maintain the continuity and stability of the power supply system.

Description

Technical Field

[0001] This invention relates to the field of rail transit power supply technology, and in particular to a leakage current protection device and a rail transit power supply system. Background Technology

[0002] In straddle-type monorail transit systems, a segmented grounding leakage current protection scheme based on fiber optic channels has been proposed. This scheme involves installing a segmented grounding leakage current protection device in each traction substation along the entire line. The traction substations are physically connected via single-mode fiber optic cables in a daisy-chain manner, enabling real-time information exchange between different devices. Each traction substation is configured with one segmented grounding leakage current protection device and four differential current detection sensors, with the differential current detection sensors being specially designed products. Its working principle is as follows: it monitors the leakage current of the faulted ground. When the value exceeds the protection setting value, a current relay issues an alarm message. Simultaneously, the CPU (Central Processing Unit) determines whether a grounding short-circuit fault has occurred in the section based on the leakage current magnitude of each feeder circuit, selectively disconnecting the faulty section. In the event of a CPU failure, the segmented grounding leakage current protection devices along the entire line will, after receiving the alarm signal and delaying for 5 seconds, directly issue a circuit breaker trip command via the current relay, causing all traction substations along the line to trip.

[0003] However, when the CPU malfunctions and fails to operate, the current relays of the entire line directly issue a circuit breaker trip command after a delay, causing all traction substations to trip and resulting in a complete power outage on the entire line, thus failing to achieve the "selectivity" of protection operation. Therefore, when the CPU is blocked due to a fault, the CPU cannot distinguish between "faulty sections" and "non-faulty sections," and after a fault occurs, the entire line trips indiscriminately. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the first objective of this invention is to provide a leakage current protection device that can quickly and accurately isolate faulty sections, reduce the scope of power outages, guide maintenance personnel to conduct targeted repairs, and maintain the continuity and stability of the power supply system.

[0005] The second objective of this invention is to provide a power supply system for rail transit.

[0006] To achieve the above objectives, a first aspect of the present invention provides a leakage current protection device, which includes multiple leakage current protection sub-devices. These sub-devices are configured one-to-one with multiple traction substations in a rail transit power supply system. Each leakage current protection sub-device includes a grounding leakage current protection circuit, a digital current selective tripping protection circuit, and a switch. The digital current selective tripping protection circuit is connected to the corresponding switch via a tail cable for communication, and is also connected to the corresponding grounding leakage current protection circuit via a hard wire. Switches in adjacent traction substations are connected via optical fiber for communication. The digital current selective tripping protection circuit, upon receiving a leakage current alarm signal from the corresponding grounding leakage current protection circuit, acquires the current vectors flowing into and out of all feeder circuits in its own power supply section, locates the fault section based on the current vectors, and disconnects the fault section after locating it.

[0007] According to an embodiment of the present invention, the digital current selective trip protection circuit is specifically used to: when the sum of the inflow and outflow current vectors is not zero, determine the power supply section where the feeder circuit where the sum of the inflow and outflow current vectors is not zero is a fault section, and after a first preset time delay, issue a first control command to disconnect the feeder circuit breaker in the fault section.

[0008] According to an embodiment of the present invention, the grounding leakage protection circuit is further configured to: determine that its own power supply section is a fault section when the leakage alarm signal lasts for a second preset time, and issue a second control command to disconnect the feeder circuit breaker in the fault section, wherein the second preset time is greater than the first preset time.

[0009] According to one embodiment of the present invention, the feeder circuit between two adjacent traction substations forms a power supply section, and the fault section includes a first feeder circuit breaker and a second feeder circuit breaker, which are respectively located in two different traction substations; wherein, disconnecting the feeder circuit breaker in the fault section includes disconnecting the first feeder circuit breaker and the second feeder circuit breaker.

[0010] According to an embodiment of the present invention, when all the digital current selective trip protection circuits in each of the traction substations are operating normally, if the nth power supply section is a fault section, then the digital current selective trip protection circuits in the nth traction substation and the (n+1)th traction substation both issue a first control signal. The first control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the nth traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer.

[0011] According to one embodiment of the present invention, if the digital current selective trip protection circuit in the nth traction substation fails and the nth power supply section is a fault section, the ground leakage protection circuit in the nth power supply section issues a second control signal, wherein the second control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect, the first feeder circuit breaker is installed in the nth traction substation, and the second feeder circuit breaker is installed in the (n+1)th traction substation, where n is a positive integer.

[0012] Furthermore, when the digital current selective trip protection circuit in the nth traction substation fails, the original (n-1)th and nth power supply sections are merged into a new (n-1)'th power supply section. If the (n-1)'th power supply section is a fault section, both the digital current selective trip protection circuit in the (n-1)th traction substation and the digital current selective trip protection circuit in the (n+1)th traction substation issue a first control signal. The first control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the (n-1)th traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer greater than 1.

[0013] According to one embodiment of the present invention, the optical cable is a single-mode optical cable and the pigtail is a multimode pigtail.

[0014] According to the leakage current protection device of the present invention, the fault section can be quickly and accurately cut off, the power outage area can be reduced, and the operation and maintenance personnel can be guided to carry out targeted maintenance to maintain the continuity and stability of the power supply system.

[0015] To achieve the above objectives, a second aspect of the present invention provides a rail transit power supply system, characterized in that it includes: the aforementioned leakage protection device.

[0016] According to the rail transit power supply system of the present invention, the power supply section of the short circuit fault can be quickly and accurately cut off, the power outage area can be reduced, and the operation and maintenance personnel can be guided to carry out targeted maintenance to maintain the continuity and stability of the power supply system.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a leakage current protection device according to an embodiment of the present invention;

[0019] Figure 2This is a network topology diagram of a specific embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the current vector of the upward contact rail-feeder circuit according to a specific embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of digital current selective tripping protection when all digital current selective tripping protection circuits of a specific embodiment of the present invention are activated;

[0022] Figure 5 This is a schematic diagram of the digital current selective tripping protection circuit when it is deactivated, according to a specific embodiment of the present invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] The following is a reference appendix. Figure 1-5 This invention describes a leakage current protection device and a rail transit power supply system according to embodiments of the present invention.

[0025] Figure 1 This is a schematic diagram of the structure of a leakage current protection device according to an embodiment of the present invention.

[0026] In embodiments of the present invention, such as Figure 1 As shown, the leakage current protection device 100 includes multiple leakage current protection sub-devices 10, and the multiple leakage current protection sub-devices 10 are set up one-to-one with the traction substation 20 of the rail transit power supply system 200.

[0027] See Figure 1 The leakage current protection sub-device 10 includes: a grounding leakage current protection circuit 11, a digital current selective tripping protection circuit 12, and a switch 13. The digital current selective tripping protection circuit 12 and the corresponding switch 13 are connected via a tail cable for communication. The digital current selective tripping protection circuit 12 and the corresponding grounding leakage current protection circuit 11 are connected via a hard wire. The switches 13 of two adjacent traction substations are connected via optical fiber for communication. The digital current selective tripping protection circuit 12, upon receiving a leakage current alarm signal from the corresponding grounding leakage current protection circuit 11, acquires the current vectors flowing in and out of all feeder circuits in its power supply section, locates the fault section based on the current vectors, and disconnects the fault section after locating it. The optical fiber can be a single-mode optical fiber, and the tail cable can be a multi-mode tail cable.

[0028] As an example, this invention provides a protection scheme for information exchange between the digital current selective tripping protection circuit 12 and GOOSE (Generic Object Oriented SubstationEvent) network communication. See also... Figure 2 This scheme requires one grounding leakage protection circuit 11 (also known as 64D), one digital current selective tripping protection circuit 12, and one switch 13 (such as an Ethernet switch) to be installed in each traction substation 20 along the entire line. The digital current selective tripping protection circuit 12 in each traction substation 20 is connected to the switch 13 via a multimode tail cable. The switches 13 of adjacent traction substations are connected in a "daisy-chain" manner via optical fiber. The digital current selective tripping protection circuit 12 can perform real-time information exchange using the IEC61850 communication protocol. Its working principle is as follows: when the digital current selective tripping protection circuit 12 receives the negative ground voltage rise alarm signal from the grounding leakage protection circuit 11, it quickly locates the fault section by judging whether the vector sum of the current flowing in and out of all feeder circuits in its own power supply section is zero, thereby "selectively" cutting off the fault section.

[0029] It should be noted that when using this scheme in a straddle-type monorail DC traction power supply system, the following conditions must be met:

[0030] 1) In the system design, each power supply section is separated from the others;

[0031] 2) A shunt is installed in both the positive and negative circuits of each feedback line;

[0032] 3) Each traction substation 20 is equipped with at least one grounding leakage protection circuit 11, one digital current selective trip protection circuit 12, and one switch 13;

[0033] 4) Form a GOOSE network with the communication protocol IEC61850. Broadcast the real-time current and voltage signals of the feeder circuit and the grounding leakage protection circuit 11, as well as the status information of the feeder circuit breaker, to the digital current selective trip protection circuit 12 of the left and right adjacent stations or the entire line in the form of broadcast.

[0034] In one embodiment of the present invention, the grounding leakage protection circuit 11 can be used to send a leakage alarm signal to the corresponding digital current selective trip protection circuit 12 when a negative ground voltage is detected to be greater than or equal to a preset alarm setting value and continues to be a preset alarm delay setting value.

[0035] The preset alarm setting value and the preset alarm delay setting value can be calibrated according to actual needs.

[0036] Specifically, when a short circuit fault occurs between the positive contact rail and ground, the grounding leakage protection circuit 11 can detect the increase in the negative ground voltage value. When the value reaches the alarm setting value and continues to the preset alarm delay setting value, the grounding leakage protection circuit 11 issues a leakage alarm signal. The leakage alarm signal contact can be connected to the digital current protection circuit 12 through a hard wire.

[0037] In one embodiment of the present invention, the digital current selective trip protection circuit 12 can be specifically used to: determine the power supply section where the feeder circuit where the sum of the inflow and outflow current vectors is not zero as the fault section when the sum of the inflow and outflow current vectors is not zero, and issue a first control command after a delay t1 (i.e., a first preset time) to disconnect the feeder circuit breaker in the fault section.

[0038] Specifically, the fault region can be determined according to Kirchhoff's Current Law: at any node in a circuit, at any given moment, the sum of the currents flowing into the node equals the sum of the currents flowing out of the node. See also... Figure 3 Taking the upstream contact rail as an example, assuming any node in any power supply section is a detection node, when the digital current selective trip protection circuit 12 receives the leakage alarm signal sent by the corresponding grounding leakage protection circuit 11, it can obtain the current vectors of each feeder circuit in the left and right adjacent stations through the GOOSE network. Under normal operating conditions (no short circuit point K1), the sum of the current vectors flowing into and out of all feeder circuits at this node at any given time is zero; under short circuit fault conditions, the sum of the current vectors flowing into and out of all feeder circuits at this node at any given time is not zero. Similarly, determining whether a short circuit fault has occurred in any power supply section of the downstream contact rail can also be performed using the above method. Thus, the power supply section with a short circuit fault can be quickly and accurately determined, guiding maintenance personnel to carry out targeted repairs. After locating the fault section, after determining the feeder circuit with a non-zero sum of the current vectors flowing into and out of the fault section, a first control command is issued to disconnect the feeder circuit breaker in the fault section after a first preset time. It should be noted that a digital current selective trip protection circuit 12 can belong to two power supply zones. When it belongs to the first power supply zone, it controls the first feeder circuit breaker; otherwise, it controls the second feeder circuit breaker.

[0039] In one embodiment of the present invention, the grounding leakage protection circuit 11 can also be used to: determine that the power supply section in which it is located is a fault section when the leakage alarm signal lasts for a second preset time, and issue a second control command to disconnect the feeder circuit breaker in the fault section, wherein the second preset time is greater than the first preset time.

[0040] Specifically, when a GOOSE network segment or a digital current selective trip protection circuit 12 fails, the digital current selective trip protection circuit 12 is locked out, and the grounding leakage protection circuit 11 of that traction substation provides backup protection, while the digital current selective trip protection circuits of other traction substations are normally engaged. The grounding leakage protection circuit 11 can directly determine its own power supply section as the fault section after a leakage alarm signal delay t2 (i.e., the second preset time) and issue a second control command (e.g., a protection trip command) to trip the feeder circuit breaker in the fault section. Therefore, when a positive contact rail short circuit to ground occurs in a power supply section, the digital current selective trip protection circuit based on GOOSE network communication can still accurately identify the fault section.

[0041] In an embodiment of the present invention, see Figure 4 , Figure 5 The feeder circuits between two adjacent traction substations 20 form a power supply section. The fault section includes a first feeder circuit breaker and a second feeder circuit breaker, which are respectively located in two different traction substations 20. Disconnecting the feeder circuit breakers in the fault section includes disconnecting both the first and second feeder circuit breakers.

[0042] Specifically, when the digital current selective trip protection circuit 12 issues the second control command, it disconnects the first and second feeder circuit breakers in two adjacent and different traction substations 20. After the feeder circuit breakers trip and are locked, the faulty section is disconnected, and other non-faulty sections are powered normally.

[0043] Therefore, this leakage current protection device can quickly and accurately cut off the fault area, reduce the power outage range, guide maintenance personnel to carry out targeted maintenance, and maintain the continuity and stability of the power supply system.

[0044] In one specific embodiment of the present invention, based on the convenience of the GOOSE channel, digital current selective tripping protection can be established for all power supply sections along the entire line, allowing all digital current selective tripping protection circuits to participate in current selective tripping. This can be divided into two operating conditions: "all digital current selective tripping protection circuits are engaged" and "a certain digital current selective tripping protection circuit is deactivated" for "dual-sided power supply," and "all digital current selective tripping protection circuits are engaged" and "a certain digital current selective tripping protection circuit is deactivated" for "large dual-sided power supply." Since the digital current selective tripping protection scheme for short-circuit faults in the upstream and downstream contact rail sections is the same, this invention only uses the upstream contact rail as an example.

[0045] As an example, when all the digital current selective trip protection circuits 12 in each traction substation are working normally, if the nth power supply section is a fault section, then the digital current selective trip protection circuits 12 in the nth traction substation and the (n+1)th traction substation will both issue a first control signal. The first control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is set in the nth traction substation, and the second feeder circuit breaker is set in the (n+1)th traction substation, where n is a positive integer.

[0046] Specifically, see Figure 4 For straddle-type monorail projects, a comprehensive grounding system can be adopted. (1) When both sides are powered and all digital current selective trip protection devices are in operation, if a positive contact rail short circuit to ground occurs in the nth power supply section, all grounding leakage protection circuits 11 along the entire line will detect the same negative ground voltage ΔU. n .

[0047] a) When △U n <△U d When the preset alarm setting value is reached, the ground leakage protection circuit 11 will not issue an alarm signal, and the digital current selective trip protection circuit 12 will be locked and will not start.

[0048] b) When △U n ≥△U d (i.e., the preset alarm setting value) and the duration △T≥△T d When the preset alarm delay setting value is reached, all grounding leakage protection circuits 11 along the entire line send alarm signals to the digital current selective tripping protection circuit 12 in this traction substation. After receiving the alarm signals, the digital current selective tripping protection circuits 12 of both traction substations on the left and right sides of all power supply sections begin to calculate the vector sum of the feeder currents within their respective power supply sections. The fault section is located by determining whether the sum is not zero. Because the corresponding digital current selective tripping protection circuit 12, i.e., BH... n BH (n+1) Confirm i n3 i ’ n3 i (n+1)1 i ’ (n+1)1 The vector sum is not zero (e.g.) Figure 3 and Figure 4 As shown), the short circuit point is in the nth power supply interval. After a delay of t1, the corresponding digital current selective trip protection circuit 12, i.e., BH, will activate. n BH (n+1) Simultaneously, a command is issued to disconnect the feeder circuit breaker in this traction substation and the feeder circuit breaker in the adjacent traction substation (i.e., the first control signal); QF n3 (i.e., the first feeder circuit breaker), QF(n+1)1 After the second feeder circuit breaker trips, it is locked out, cutting off the power supply section with the short circuit fault. In other power supply sections, since the current vector sum is zero, the digital current selective trip protection circuit 12 judges them to be normal and locks out without operating.

[0049] (2) When both sides of the power supply are engaged and all digital current selective trip protection circuits 12 are activated, assuming the nth traction substation fails and is taken out of operation, the DC traction system can be changed from "both sides of the power supply" mode to "large both sides of the power supply" mode through a "switching" operation. That is, the original (n-1)th and nth power supply sections are merged into a new (n-1)'th power supply section. When a positive contact rail to ground short circuit occurs in this section, all grounding leakage protection circuits 11 on the entire line detect the same negative ground voltage ΔU. (n-1) Similarly:

[0050] a) When △U (n-1) <△U d When the preset alarm setting value is reached, the ground leakage protection circuit 11 will not issue an alarm signal, and the digital current selective trip protection circuit 12 will be locked and will not start.

[0051] b) When △U (n-1) ≥△U d (i.e., the preset alarm setting value) and the duration △T≥△T d When the preset alarm delay setting value is reached, all grounding and leakage protection circuits 11 along the entire line send alarm signals to the digital current selective tripping protection circuit 12 in this traction substation. The corresponding digital current selective tripping protection circuit 12, i.e., BH... (n-1) BH (n+1) Simultaneously, a command is issued to disconnect the feeder circuit breaker in this traction substation and the feeder circuit breaker in the adjacent traction substation (i.e., the first control signal); QF (n-1)3 (i.e., the first feeder circuit breaker), QF (n+1)1 After the second feeder circuit breaker trips, it is locked out, cutting off the (n-1)'th power supply section. Since the current vector sum is zero in the other power supply sections, the digital current selective trip protection circuit 12 judges them to be normal and locks out without operating.

[0052] As an example, if the digital current selective trip protection circuit 12 in the nth traction substation fails and the nth power supply section is a fault section, then the ground leakage protection circuit 11 in the nth power supply section issues a second control signal, wherein the second control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the nth traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer.

[0053] Specifically, see Figure 5 When dual-side power supply is in effect and a digital current selective trip protection circuit 12 is deactivated, if the inter-station fiber optic channel of a certain power supply section fails or the digital current selective trip protection circuit 12 fails, the digital current selective trip protection of that section will fail to lock out, and the grounding leakage protection circuit 11 will serve as its backup protection. To avoid erroneous disconnection of normal power supply sections, the protection trip action (i.e., the second control signal) delay t2 of the grounding leakage protection circuit 11 must be greater than t1 to meet the requirements.

[0054] When the digital current selective tripping protection circuit 12 of the (n-1)th power supply section is locked out, a positive contact rail to ground short circuit occurs in the nth power supply section (e.g. Figure 4 (As shown). All grounding leakage protection circuits 11 along the entire line detected the same negative ground voltage ΔU. n All power supply sections except the (n-1)th power supply section are protected selectively by the digital current selective tripping protection circuit 12, meaning only the nth power supply section is tripped, and the other sections are not protected. Since t2 is greater than t1, when the protection of the nth power supply section trips, the grounding leakage protection circuit 11 of the (n-1)th power supply section only alarms but does not trip. After the protection of the nth power supply section completes, the fault is cleared, and the alarm signal of the grounding leakage protection circuit 11 for the entire line disappears.

[0055] When both the digital current selective trip protection circuit 12 locks out and a positive contact rail short circuit to ground occurs in the nth power supply section, the digital current selective trip protection circuit 12 in all normal power supply sections will not activate and will lock out the feeder circuit breaker. Simultaneously, after a leakage alarm signal delay t2, the grounding leakage protection circuit 11 in the nth power supply section will disconnect the first and second feeder circuit breakers in that faulty section to clear the fault.

[0056] As an example, when the digital current selective trip protection circuit 12 in the nth traction substation fails, the original (n-1)th and nth power supply sections are merged into a new (n-1)'th power supply section. If the (n-1)'th power supply section is a fault section, both the digital current selective trip protection circuit 12 in the (n-1)th traction substation and the digital current selective trip protection circuit 12 in the (n+1)th traction substation issue a first control signal. The first control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the (n-1)th traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer greater than 1.

[0057] Specifically, when the large dual-sided power supply is in operation and a certain digital current selective trip protection circuit 12 is deactivated, the DC traction system can be changed from the "dual-sided power supply" mode to the "large dual-sided power supply" mode through a "switching" operation. That is, the original (n-1)th and nth power supply sections are merged into a new (n-1)'th power supply section. If the digital current selective trip protection circuit 12 of the (n-1)'th power supply section fails to be blocked due to "fiber optic channel failure" or "digital current selective trip protection circuit 12 failure", then the ground leakage protection circuit 11 is used as its backup protection.

[0058] If a short circuit occurs between the positive contact rail and ground in any power supply section within the (n-1)'th power supply section, all grounding leakage protection circuits 11 along the entire line will detect the same negative ground voltage ΔU. (n-1) The digital current selective tripping protection circuit 12 of the traction substations on both sides of the fault section simultaneously issues a command (i.e., the first control signal) to disconnect the first and second feeder circuit breakers, thus isolating the fault section. The protection devices in other power supply sections are locked and do not operate.

[0059] If a short circuit to ground occurs simultaneously in the positive contact rail of the (n-1)'th power supply section, the digital current selective tripping protection circuit 12 of all normal power supply sections will not activate and will lock the feeder circuit breaker. At the same time, the grounding leakage protection circuit 11 of the traction substations on both sides of the (n-1)'th power supply section will disconnect the first feeder circuit breaker and the second feeder circuit breaker after a leakage alarm signal delay t2 to achieve the purpose of clearing the fault.

[0060] Therefore, based on the four operating conditions described above, it can be seen that the digital current selective tripping protection scheme based on GOOSE communication can accurately cut off the fault section and reduce the power outage area.

[0061] In summary, this leakage current protection device uses digital current selective tripping as the main protection, supplemented by voltage-type grounding leakage protection as backup protection. It first determines whether a negative ground voltage rise has occurred in the entire power supply section. Then, by analyzing the current vectors of all feeder circuits within each power supply section, it quickly locates the faulty section and accurately disconnects it, thus narrowing the power outage area. Therefore, this leakage current protection device satisfies the requirements of "speed," "selectivity," and "sensitivity" in disconnecting the faulty section by the main protection, while also improving its "reliability" under the protection of backup protection.

[0062] See Figure 1 The present invention also provides a rail transit power supply system 200, including the above-mentioned leakage protection device 100.

[0063] The rail transit power supply system of this invention uses a leakage current protection device, with digital current selective tripping as the main protection and voltage-type grounding leakage current protection as backup protection. It first determines whether a negative ground voltage rise has occurred in the entire power supply section, and then quickly locates the fault section by judging the current vector of all feeder circuits in each power supply section, thereby accurately isolating the fault section and narrowing the power outage area. Therefore, this leakage current protection device can satisfy the "speed," "selectivity," and "sensitivity" of the main protection in isolating the fault section, and also improve its "reliability" under the protection of backup protection.

[0064] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0065] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0069] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A leakage current protection device, characterized in that, The leakage current protection device includes multiple sets of leakage current protection sub-devices, and each set of leakage current protection sub-devices is installed in a one-to-one correspondence with multiple traction substations of the rail transit power supply system. Each leakage current protection sub-device includes: The system includes a grounding leakage protection circuit, a digital current selective trip protection circuit, and a switch. The digital current selective trip protection circuit and the corresponding switch are connected via a tail cable for communication. The digital current selective trip protection circuit and the corresponding grounding leakage protection circuit are connected via a hard wire. The switches of two adjacent traction substations are connected via an optical fiber for communication. The digital current selective trip protection circuit is used to obtain the current vectors flowing into and out of all feeder circuits in its own power supply section when it receives a leakage alarm signal sent by the corresponding ground leakage protection circuit, locate the fault section according to the current vectors flowing into and out of the circuit, and disconnect the fault section after locating the fault section. The feeder circuit between two adjacent traction substations forms a power supply section. The fault section includes a first feeder circuit breaker and a second feeder circuit breaker. The first feeder circuit breaker and the second feeder circuit breaker are respectively installed in two different traction substations. When the digital current selective trip protection circuit in the nth traction substation fails, the original (n-1)th and nth power supply sections are merged into a new (n-1)'th power supply section, where, If the (n-1)'th power supply section is a fault section, then the digital current selective trip protection circuit in the (n-1)th traction substation and the digital current selective trip protection circuit in the (n+1)th traction substation both issue a first control signal. The first control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the (n-1)th traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer greater than 1.

2. The leakage current protection device according to claim 1, characterized in that, The grounding leakage protection circuit is used for: When a negative ground voltage is detected to be greater than or equal to a preset alarm setting value and continues for a preset alarm delay setting value, a leakage current alarm signal is sent to the corresponding digital current selective trip protection circuit.

3. The leakage current protection device according to claim 1, characterized in that, The digital current selective tripping protection circuit is specifically used for: When the sum of the inflow and outflow current vectors is not zero, the power supply section where the feeder circuit with the sum of the inflow and outflow current vectors is not zero is determined as the fault section, and after a first preset time delay, a first control command is issued to disconnect the feeder circuit breaker in the fault section.

4. The leakage current protection device according to claim 3, characterized in that, The grounding leakage protection circuit is also used for: When the leakage current alarm signal lasts for a second preset time, the power supply section where it is located is determined to be a fault section, and a second control command is issued to disconnect the feeder circuit breaker in the fault section, wherein the second preset time is greater than the first preset time.

5. The leakage current protection device according to claim 3 or 4, characterized in that, Disconnecting the feeder circuit breaker in the fault section includes: disconnecting the first feeder circuit breaker and the second feeder circuit breaker.

6. The leakage current protection device according to claim 5, characterized in that, When the digital current selective trip protection circuits in each of the aforementioned traction substations are all operating normally. If the nth power supply section is a fault section, the digital current selective trip protection circuit in the nth traction substation and the digital current selective trip protection circuit in the (n+1)th traction substation both issue a first control signal. The first control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the nth traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer.

7. The leakage current protection device according to claim 5, characterized in that, If the digital current selective trip protection circuit in the nth traction substation fails and the nth power supply section is a fault section, then the ground leakage protection circuit in the nth power supply section issues a second control signal. The second control signal is used to control the first feeder circuit breaker and the second feeder circuit breaker to disconnect. The first feeder circuit breaker is located in the nth traction substation, and the second feeder circuit breaker is located in the (n+1)th traction substation, where n is a positive integer.

8. The leakage current protection device according to claim 1, characterized in that, The optical cable is a single-mode optical cable, and the pigtail is a multimode pigtail.

9. A power supply system for rail transit, characterized in that, include: The leakage current protection device as described in any one of claims 1-8.

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