Leakage protection method for rail transit power supply system with full negative pole connection

Abstract

The present invention discloses a leakage protection method for a rail transit power supply system with all negative poles connected, which relates to the field of rail transit transportation technology, and includes the following contents: real-time monitoring of the current between the negative pole of the power supply and the grounding wire, when the current value exceeds the set value, the current substation trips; detecting the positive and negative pole difference current of the up-line power supply and the positive and negative pole difference current of the down-line power supply in each substation; when leakage occurs, judging the substation where the leakage occurs according to the difference current direction of the up-line and the difference current direction of the down-line of the substation; judging the contact rail where the leakage occurs according to the difference current polarity of the leakage substation; judging the section where the leakage occurs according to the difference current polarity of the adjacent substations. The leakage protection method of the present invention can accurately and quickly locate the leakage substation and the up-line or down-line of the leakage substation, which is convenient for searching and repairing; and at the same time, the fault section trips, so as not to affect the operation of other sections.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transit transportation, and in particular to a leakage protection method for a rail transit power supply system with full-line negative poles connected. Background Art

[0002] At present, compared with the traditional subway power supply method, the negative pole of the DC traction power supply system of monorail, maglev rail transit, sky rail and subway with four-track return is not returned through the running rail, but a separate negative rail is set for return. The monorail runs on rubber wheels, the maglev train runs in suspension, and the subway uses a four-track dedicated return rail, which makes the monorail and maglev train relatively insulated from the ground. As time goes by, leakage is difficult to avoid. In response to this situation, when a ground leakage fault occurs on the urban rail transit line, the protection device is voltage-based judgment, resulting in tripping of the entire line, affecting operations. At the same time, because the fault section cannot be determined, it brings great trouble to the investigation work. For the rail transit power supply system with the entire line negatively connected, there is currently a lack of power supply system-related leakage protection methods that can quickly locate the leakage section and will not cause the entire line to trip.

[0003] There are currently four methods for leakage protection of the positive pole of the contact network used in the rail transit power supply system, but none of them can provide section protection for the power supply network with the negative pole connected throughout the line. The following is a brief description of the current leakage protection methods:

[0004] 1. DC ground leakage protection device (negative ground unidirectional conduction device)

[0005] The main circuit of the device is as follows Figure 1 As shown. The DC ground leakage protection device cabinet is used in the special rail return system. When a positive pole to ground fault occurs, it provides a path for the fault current and detects the magnitude of the fault current. The DC ground leakage protection device cabinet is connected between the DC negative pole and the grounding busbar, with forward conduction and reverse blocking.

[0006] When the DC power supply system operates normally, ensure that the negative pole dedicated return rail is cut off in the direction to the ground busbar to prevent return current leakage.

[0007] When a ground leakage fault occurs in the DC power supply system, the positive pole is short-circuited with the grounding system, and the current returns to the negative pole through the connection between the DC ground leakage protection device cabinet and the negative pole of the rectifier. The fault current can be detected and an alarm signal can be issued.

[0008] When the positive pole of the DC power supply system is grounded, a short circuit is formed between the positive pole and the negative pole of the contact network indirectly through the diode. At this time, the fault current is large. Then, the fault is removed through the instantaneous overcurrent protection of the DC feeder cabinet or the large current tripping protection of the main body, and the feeder circuit breaker is tripped to protect the power supply system.

[0009] The disadvantages of this device are:

[0010] (1) When the leakage current is less than the action value of the feeder circuit breaker, the leakage fault point cannot be eliminated.

[0011] (2) The diode short-circuit protection method requires the use of multiple diodes in parallel to expand the capacity, and the current sharing coefficient of each diode must be strictly controlled.

[0012] (3) The diode short-circuit protection method uses the overcurrent fault of the DC feeder circuit breaker to trip, which has a great impact on the service life of the DC circuit breaker.

[0013] 2. Voltage type leakage protection device

[0014] The main circuit of the device is as follows Figure 2 As shown, SV represents the solenoid valve, C represents the circuit breaker, VD represents the diode, and R represents the resistor. The voltage-type leakage protection device cabinet is used in the dedicated rail return system. When a positive-to-ground grounding fault occurs, the voltage sensor of the protection device detects that the voltage on the leakage resistor reaches 200V and then trips the corresponding feeder circuit breaker.

[0015] The voltage-type leakage protection device cabinet is connected between the DC negative pole and the grounding busbar, and is forward-conducting and reverse-blocking. When the DC power supply system is operating normally, the direction from the negative pole dedicated return rail to the grounding busbar is guaranteed to be blocked to prevent the return current from leaking. When the positive pole of the DC power supply system is short-circuited with the grounding system, the current returns to the negative pole through the connection between the DC grounding leakage protection device cabinet and the negative pole of the rectifier. When the voltage drop of the fault current on the leakage resistor reaches the alarm value, an alarm signal is issued; or when it reaches the trip value, a feeder circuit breaker trip signal is issued to trip the corresponding feeder circuit breaker to eliminate the fault point, thereby protecting the power supply system.

[0016] The disadvantages of this device are:

[0017] The earth's resistance is very small and has almost nothing to do with distance. Therefore, the grounding current of each traction station is similar, and the voltage drop on the leakage resistance is also similar. Therefore, when one of the traction stations reaches the leakage voltage trip value, the other traction stations will also reach it. Therefore, each traction station will trip. Although the leakage fault point is eliminated, the entire line will trip, causing the entire line to stop operating.

[0018] 3. Current type leakage protection device

[0019] The main circuit of the device is as follows Figure 3As shown, KI represents relay, C represents circuit breaker, VD represents diode, and R represents resistor. The current type leakage protection device cabinet is used in the special rail return system. When a positive pole to ground fault occurs, when the leakage current through the protection device reaches 40A, the current relay is activated, and the relay contact jumps the corresponding feeder circuit breaker to eliminate the fault point, thereby protecting the power supply system.

[0020] The disadvantages of this device are:

[0021] The current-type leakage protection device is similar to the voltage-type leakage protection device. Each traction station will trip. Although the leakage fault point is eliminated, the entire line will trip, causing the entire line to stop operating.

[0022] 4. Sectional leakage protection of the positive and negative section power supply network of the contact network

[0023] The main circuit of the device is as follows Figure 4 As shown. On the basis of voltage-type leakage protection device and current-type leakage protection device, the leakage current of positive and negative feeders is checked. The leakage section is determined according to the direction and magnitude of the leakage current of positive and negative feeders, as well as the magnitude and direction of the leakage current of adjacent positive and negative feeders in the section, and then the feeder circuit breaker of the leakage section is disconnected to eliminate the leakage fault point.

[0024] Characteristics of section leakage protection for positive and negative section power supply network of contact network:

[0025] When a leakage fault occurs due to a positive pole short circuit to ground or poor insulation, only the faulty power supply area is protected.

[0026] Rapidly and accurately cut off the leakage fault point without affecting the power supply of the entire line, ensuring the normal operation of DC equipment and the safety of passengers, and narrowing the scope of fault inspection.

[0027] It can detect leakage faults in advance when the leakage current is relatively small and remove the fault point, thus avoiding the need to protect the power supply line after it reaches a high current short-circuit state.

[0028] The disadvantages of this device are:

[0029] For all substations, the negative power supply lines are not divided into sections and are all connected; the power supply system with segmented positive power supply lines cannot achieve segment protection. Because after all substation negative poles are connected, the current flowing out of the positive feeder lines of sections 211, 212, 213, and 214 does not only flow back to the substation from the corresponding negative pole, but from the four negative feeders of the substation, and the leakage current cannot be determined by the current difference between the positive and negative feeders in each section. Summary of the invention

[0030] In response to the above-mentioned technical problems to be solved, the present invention provides a leakage protection method for a rail transit power supply system with the negative pole connected throughout the line, which can accurately and quickly locate the leakage substation and the uplink or downlink line of the leakage substation, making it easy to find and repair; at the same time, it can realize tripping of the faulty section without affecting the operation of other sections.

[0031] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0032] A leakage protection method for a rail transit power supply system with all negative poles connected, comprising the following contents:

[0033] Real-time monitoring of the current between the negative pole of the power supply and the grounding wire. When the current value exceeds the set value, the current substation trips.

[0034] Detect the positive and negative polarity difference current of the uplink power supply and the positive and negative polarity difference current of the downlink power supply in each substation;

[0035] When leakage occurs, the substation where the leakage occurs is determined based on the difference current directions of the up-line and down-line of the substation; the contact rail where the leakage occurs is determined based on the difference current polarity of the leakage substation; and the section where the leakage occurs is determined based on the difference current polarity of adjacent substations.

[0036] As a further improvement of the above technical solution:

[0037] Preferably, a leakage current judgment protection device is provided between the negative power supply electrode and the grounding wire of each substation of the power supply system; the leakage current judgment protection device is used to monitor the current size between the negative power supply electrode and the grounding wire in real time.

[0038] Preferably, the leakage current judgment protection device comprises a unidirectional diode, a current relay and a protection resistor connected in sequence, the protection resistor is connected to the grounding wire, the protection resistor is 1Ω to 10Ω, and one leakage current judgment protection device is installed in each substation.

[0039] Preferably, a first differential current sensor is installed between the upstream positive power supply and the negative power supply of each substation in the power supply system, and a second differential current sensor is installed between the downstream positive power supply and the negative power supply; the first differential current sensor is used to monitor the differential current size and direction between the positive and negative poles of the upstream contact rail of the substation, and the second differential current sensor is used to monitor the differential current size and direction between the positive and negative poles of the downstream contact rail of the substation.

[0040] Preferably, the differential current sensor connects the positive busbar and the negative busbar, and the positive busbar and the negative busbar pass through the differential current sensor window at the same time; each substation is installed with two differential current sensors, namely an up-line differential current sensor and a down-line differential current sensor.

[0041] Preferably, whether leakage occurs is determined based on the current value. If the current value reaches a set value, it is considered that there is leakage in the positive electrode of the upward contact rail or the positive electrode of the downward contact rail between two substations in the power supply system.

[0042] The difference current value determines the two substations with leakage. If the difference current direction of the up line of the same substation is opposite to the difference current direction of the down line, then the substation has leakage and is determined to be leakage substation A.

[0043] If the direction of the differential current of the up-line of the left adjacent substation of substation A is opposite to that of the differential current of the down-line, then the left adjacent substation of substation A has leakage phenomenon, which is defined as leakage substation B; the section between substation A and substation B is the leakage section; the contact rail with positive differential current in substation A and substation B is the leakage contact rail;

[0044] If the direction of the differential current in the up-line of the substation to the right of substation A is opposite to that in the down-line, then the substation to the right of substation A has leakage, which is defined as leakage substation C; the section between substation A and substation C is the leakage section; the contact rail with positive differential current in substation A and substation C is the leakage contact rail.

[0045] The leakage protection method for the rail transit power supply system with the entire line negative pole connected provided by the present invention has the following advantages compared with the prior art:

[0046] The leakage protection method for a rail transit power supply system with the entire line negatively connected of the present invention determines the substation where the leakage occurs according to the difference current direction of the up line and the difference current direction of the down line of the substation, determines the contact rail where the leakage occurs according to the difference current polarity of the leakage substation, and determines the section where the leakage occurs according to the difference current polarity of adjacent substations; when leakage faults occur in different areas, the leakage area can be accurately and quickly located, which is convenient for searching and repairing; at the same time, the faulty section is tripped, so as not to affect the operation of other sections, and the train can resume operation more quickly when encountering leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the main circuit wiring of an existing DC ground leakage protection device.

[0048] Figure 2 This is a schematic diagram of the main circuit wiring of an existing voltage-type leakage protection device.

[0049] Figure 3 This is a schematic diagram of the main circuit wiring of an existing current-type leakage protection device.

[0050] Figure 4 It is a schematic diagram of the segmented leakage protection of the existing contact network positive and negative segmented power supply network.

[0051] Figure 5 It is a circuit principle diagram of the present invention. DETAILED DESCRIPTION

[0052] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0053] The power supply system of the entire line is divided into upstream contact rail power supply and downstream contact rail power supply. The upstream and downstream contact rails are divided into positive contact rails and negative contact rails. The positive contact rails of the upstream and downstream contact rails are divided into several power supply sections, and the negative contact rails of the upstream and downstream contact rails are connected throughout the line regardless of power supply sections.

[0054] The present invention provides a leakage protection method for a rail transit power supply system with the entire line negatively connected, wherein a leakage current judgment protection device is arranged between the negative power supply electrode and the grounding wire of each substation in the power supply system, and the leakage current judgment protection device is used to monitor the leakage current between the negative power supply electrode and the grounding wire.

[0055] The leakage current judgment protection device includes a unidirectional diode, a current relay and a protection resistor connected in sequence, and the protection resistor is connected to the ground wire. The protection resistor is a selectable resistor of 1Ω to 10Ω; each substation is equipped with one leakage current judgment protection device.

[0056] A first differential current sensor is installed between the upstream positive power supply and the negative power supply of each substation in the power supply system, and a second differential current sensor is installed between the downstream positive power supply and the negative power supply; the first differential current sensor is used to monitor the differential current size and direction between the positive and negative poles of the upstream contact rail of the substation, and the second differential current sensor is used to monitor the differential current size and direction between the positive and negative poles of the downstream contact rail of the substation.

[0057] The differential current sensor connects the positive busbar and the negative busbar, and the positive busbar and the negative busbar pass through the differential current sensor window at the same time; each substation is equipped with two differential current sensors, one for the uplink line and the other for the downlink line. The two differential current sensors are installed between the output side of the circuit breaker and the Internet access line, preferably in the Internet isolation switch cabinet, or a separate differential current sensor box is set up.

[0058] The present invention provides a leakage protection method for a rail transit power supply system with all-line negative poles connected, comprising the following contents:

[0059] The leakage current judgment protection device is used to monitor the leakage current magnitude I between the negative power supply electrode and the grounding wire. D , when the leakage current exceeds the set value, it is confirmed that there is leakage in the current substation, and the leakage substation circuit breaker needs to be tripped;

[0060] Real-time detection of the difference in current size and direction used to connect all upstream positive busbars and all upstream negative busbars in each substation, using I SC1 Indicates the difference in current size and direction between all downstream positive busbars and all downstream negative busbars, expressed as I SC2 express.

[0061] The direction of the differential current is defined as: the differential current flowing from the substation to the contact rail is positive, and the differential current flowing from the contact rail to the substation is negative.

[0062] According to I D The size determines whether there is leakage in the power supply system; according to the I SC1 and I SC2 Directionally determine the substation and leakage section where leakage occurs in the power supply system.

[0063] I D When it is greater than the set value, it means that there is leakage in the power supply system; in the same substation, I SC1 and I SC2 When the direction is opposite, it means that the leakage occurs in this substation, and the contact rail with positive differential current in this substation is the leakage contact rail; this substation obtains the I SC1 and I SC2 Direction information, left or right neighboring substation I SC1 and I SC2 The one in the opposite direction is the second leakage substation; the area between the two leakage substations is the leakage section.

[0064] In this embodiment, four substations are used to illustrate the leakage protection method of the present invention.

[0065] like Figure 5 As shown, 4 substations are set up, each substation supplies power to 2 upstream sections and 2 downstream sections, 1SCD~4SCD are current sensors of leakage current judgment protection devices of each substation, nKM1~nKM4 are positive bus circuit breakers of each substation, and SC1~SC8 are differential current sensors of upstream and downstream lines of each substation.

[0066] In this embodiment, the main hardware environment for the application of the leakage protection method for the rail transit power supply system with the entire line negatively connected is: 4 positive bus circuit breakers for 4 lines in each substation, 1 upstream positive and negative bus differential current sensor, 1 downstream positive and negative bus differential current sensor, and 1 leakage current judgment protection device.

[0067] In this embodiment, the leakage current judgment protection device is used to detect the leakage current. When the leakage current reaches the set value, the leakage section is judged according to the following method:

[0068] The upstream positive and negative bus differential current sensor and the downstream positive and negative bus differential current sensor are used to determine the leakage section. If the upstream positive and negative bus differential current and the downstream positive and negative bus differential current of the same substation are in opposite directions, that is, one is positive and the other is negative, then this substation is a leakage substation; the power supply line with positive differential current in this leakage substation is a leakage line, if the differential current of the upstream line is positive, then the leakage position is on the upstream line, if the differential current of the downstream line is positive, then the leakage position is on the downstream line; the section between this leakage substation and the adjacent leakage substation is the leakage section.

[0069] Furthermore, a circuit breaker is used as a leakage protection execution device. When leakage occurs, the circuit breaker corresponding to the leakage section is tripped to disconnect the leakage power supply and eliminate the leakage fault point.

[0070] The following is a detailed Figure 5 The leakage of the middle and up line section 2 is taken as an example to illustrate the leakage protection method of the present invention.

[0071] If there is leakage current in the up line section 2, the leakage current will go from the 213 busbar of substation 2 and the 211 busbar of substation 3 to the leakage point; then from the leakage point through the 1SCD of substation 1, the 2SCD of substation 2, the 3SCD of substation 3 and the 4SCD of substation 4 to the negative poles of each substation; the negative pole of substation 1 goes to the negative poles of the up and down contact rails through SC1 and SC2, and the negative pole of substation 4 goes to the negative poles of the up and down contact rails through SC7 and SC8; the negative poles of the up and down contact rails go to the negative pole of substation 2 through SC3 and SC4 of substation 2, and the negative poles of the up and down contact rails go to the negative pole of substation 2 through SC5 and SC6 of substation 3.

[0072] Step 1: Determine if leakage fault occurs

[0073] From the above, it can be seen that if the leakage current of 1SCD of substation 1, 2SCD of substation 2, 3SCD of substation 3 and 4SCD of substation 4 reaches the set value, it means that there is a leakage fault in the power supply system and protective measures need to be taken.

[0074] Step 2: Identify the substation and contact rail where the leakage fault occurred

[0075] The current flowing from line 213 in substation 2 to point 2B flows from 2SCD, 2I-up, and 2I-down to the negative pole of substation 2, and the current passing through SC3 is: the difference between 2I2 and 2I-up, which is downward and defined as positive. Similarly, it can be concluded that the difference current direction in SC4 is negative; the difference current directions in SC1 and SC2 are both downward, which is positive; the difference current direction in SC5 is downward, which is positive; the difference current direction in SC6 is upward, which is negative; the difference current direction in SC7 and SC8 is both downward, which is positive.

[0076] The difference currents in SC1 and SC2 in substation 1 are both positive and in the same direction, indicating that there is no leakage fault in substation 1.

[0077] The difference currents in SC7 and SC8 in substation 4 are both positive and in the same direction, indicating that substation 4 has no leakage fault.

[0078] The SC3 differential current in substation 2 is positive, and the SC4 differential current is negative; the differential current directions of the uplink and downlink in substation 2 are opposite, indicating that there is a leakage fault in substation 2. The uplink 213 with a positive differential current is a leakage line.

[0079] The SC5 differential current in substation 3 is positive, and the SC6 differential current is negative; the differential current directions of the upline and downline in substation 3 are opposite, indicating that there is a leakage fault in substation 3. The upline 211 with a positive differential current is a leakage line.

[0080] Step 3: Determine the section where the leakage fault occurs

[0081] The up and down differential currents in substation 2 and substation 3 are opposite in direction, and the differential currents in the up line are both positive. Therefore, the up line between substation 2 and substation 3 is a leakage section. The circuit breaker 213 of the up line of substation 2 and the circuit breaker 211 of the up line of substation 3 are disconnected, and the power supply of the up line of section 2 is stopped, and the leakage phenomenon is eliminated. The down line and other sections of the up line are powered normally, which does not affect the operation of the vehicle.

[0082] If there are only leakage current judgment protection devices in substations 1 to 4, and there is no method to judge the leakage section, when the leakage current detected by 1SCD, 2SCD, 3SCD and 4SCD reaches the set value, all circuit breakers of the corresponding substations will be tripped; because each substation is equipped with a leakage current judgment protection device, the positive circuit breakers of all substations will be tripped, causing a power outage in the entire line, seriously affecting vehicle operation.

[0083] The above implementation cases are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, they are not intended to limit the present invention. Therefore, any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A leakage protection method for a rail transit power supply system with all negative poles connected, characterized in that: Includes the following: Real-time monitoring of the current between the negative pole of the power supply and the grounding wire. When the current value exceeds the set value, the current substation trips. Detect the positive and negative polarity difference current of the up-line power supply and the positive and negative polarity difference current of the down-line power supply in each substation; When leakage occurs, the substation where leakage occurs is determined according to the difference current direction of the up-line and the difference current direction of the down-line of the substation; Determine the contact rail where leakage occurs based on the polarity of the differential current in the leakage substation; determine the section where leakage occurs based on the polarity of the differential current in the adjacent substation; A leakage current judgment protection device is installed between the negative power supply pole and the grounding wire of each substation in the power supply system; The leakage current judgment protection device is used to monitor the current between the negative power supply electrode and the grounding wire in real time; Judging whether there is leakage according to the current value, if the current value reaches a set value, it is considered that there is leakage in the positive pole of the upward contact rail or the positive pole of the downward contact rail between two substations in the power supply system; The difference current value determines the two substations with leakage. If the difference current direction of the up line of the same substation is opposite to the difference current direction of the down line, then the substation has leakage and is determined to be leakage substation A. If the direction of the differential current of the up-line of the left adjacent substation of substation A is opposite to that of the differential current of the down-line, then the left adjacent substation of substation A has leakage phenomenon, which is defined as leakage substation B; the section between substation A and substation B is the leakage section; the contact rail with positive differential current in substation A and substation B is the leakage contact rail; If the direction of the differential current in the up-line of the substation to the right of substation A is opposite to that in the down-line, then the substation to the right of substation A has leakage, which is defined as leakage substation C; the section between substation A and substation C is the leakage section; the contact rail with positive differential current in substation A and substation C is the leakage contact rail.

2. The method for leakage protection of rail transit power supply system with full negative pole connection according to claim 1 is characterized in that: The leakage current judgment protection device comprises a unidirectional diode, a current relay and a protection resistor connected in sequence. The protection resistor is connected to the grounding wire. The protection resistor is 1Ω to 10Ω. Each substation is equipped with one leakage current judgment protection device.

3. The method for leakage protection of rail transit power supply system with full negative pole connection according to claim 1 is characterized in that: A first differential current sensor is installed between the upstream positive power supply and the negative power supply of each substation in the power supply system, and a second differential current sensor is installed between the downstream positive power supply and the negative power supply; the first differential current sensor is used to monitor the differential current size and direction between the positive and negative poles of the upstream contact rail of the substation, and the second differential current sensor is used to monitor the differential current size and direction between the positive and negative poles of the downstream contact rail of the substation.

4. The method for leakage protection of a rail transit power supply system with all negative poles connected according to claim 3 is characterized in that: The differential current sensor is connected to the positive busbar and the negative busbar, and the positive busbar and the negative busbar pass through the differential current sensor window at the same time; each substation is equipped with two differential current sensors, namely, an up-line differential current sensor and a down-line differential current sensor.

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