Locomotive train supply leakage current detection circuit, detection system and detection method

Abstract

The invention provides a locomotive train supply leakage current detection circuit, system and method. The locomotive train supply leakage current detection circuit comprises a residual current action protection device, a suppression resistor and a contactor. According to the invention, the suppression resistor is added to cut off the grounding access under the condition of short circuit of the two paths of train supply N lines of the carriage, so that the problem that the leakage current of the locomotive exceeds the standard abnormally due to the carriage single-phase load with the short circuit of the two paths of train supply N lines can be solved, and false alarm of the leakage current is avoided. According to the invention, locomotive row supply leakage current detection in different row supply N wire connection modes of a carriage can be realized, the reliability of leakage current detection of a locomotive under different working conditions is improved, and stable and safe operation of the locomotive is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric locomotives, and in particular relates to a locomotive train supply leakage current detection circuit, a detection system and a detection method. Background Art

[0002] With the continuous development of rail transit, the load types of multiplexed vehicles (locomotive + carriage) have also diversified, with most operating in DC600V mode and a few in AC380V mode. To meet the needs of locomotives operating with carriages of different types, locomotives are designed with DC600V and AC380V compatible output modes. However, for carriages in AC380V mode, the connection of the two train-supply N lines (neutral lines) is not uniform: ① The two train-supply N lines are independent; ② The two train-supply N lines are short-circuited (when the two train-supply N lines in one carriage are short-circuited, the train-supply N lines of the entire train are short-circuited). Currently, train-supply leakage current is detected using a residual current operated protection device. When the two train-supply N lines are short-circuited, the two train-supply N lines are connected to the ground wires, forming a shunt, causing the leakage current to exceed the standard and forming a false alarm fault. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies in the existing technology and provide a locomotive train supply leakage current detection circuit, detection system and detection method to improve the reliability of leakage current detection under different locomotive operating conditions.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A locomotive train supply leakage current detection circuit includes a residual current action protection device, a suppression resistor and a contactor;

[0006] The first end of the contactor is grounded, the second end of the contactor is connected to the first end of the residual current operated protection device, the second end of the residual current operated protection device is connected to the first end of the suppression resistor, and the second end of the suppression resistor is connected to the column supply N line.

[0007] The present invention blocks the grounding path when the two train supply N lines are short-circuited in the carriage by adding a suppression resistor. Since the shunt current between the two train supply N lines is suppressed, the problem of abnormal excessive leakage current of the locomotive caused by the single-phase load in the carriage when the two train supply N lines are short-circuited can be solved, thereby avoiding false alarms of leakage current and improving the reliability of leakage current detection.

[0008] Furthermore, the suppression resistor satisfies the following formula:

[0009]

[0010] Among them, R1 is the resistance of the suppression resistor, A1 is the compartment leakage current threshold, V1 is the single-phase output voltage of the three-phase AC power, and K is the deviation.

[0011] Preferably, 0<K≤5%. More preferably, 0<K≤1%.

[0012] Based on the same inventive concept, the present invention also provides a locomotive train supply leakage current detection system, comprising the locomotive train supply leakage current detection circuit, a locomotive control unit and a locomotive display unit;

[0013] The locomotive control unit is used to control the on and off of the contactor, connecting and cutting off the locomotive train power supply;

[0014] The locomotive display unit is used to display the status of the residual current protection device and the train grounding status.

[0015] Based on the same inventive concept, the present invention also provides a method for detecting leakage current of a locomotive train supply, comprising the following steps:

[0016] If the locomotive train power output is DC, the locomotive control unit controls the contactor to open;

[0017] If the locomotive train power output is three-phase AC, the locomotive control unit controls the contactor to close;

[0018] When at least one phase of the three-phase AC power is grounded and the train leakage current is greater than or equal to the train leakage current threshold, the residual current protection device will operate; if the duration of the train leakage current being greater than or equal to the train leakage current threshold is greater than the time threshold, the locomotive control unit will cut off the locomotive train power supply.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention blocks the grounding path when the two train supply N lines are short-circuited by adding a suppression resistor. Since the shunt current between the two train supply N lines is suppressed, the problem of abnormal excessive leakage current of the locomotive caused by the single-phase load of the carriage when the two train supply N lines are short-circuited can be solved, thereby avoiding false leakage current alarms.

[0021] The present invention can realize the locomotive train supply leakage current detection of different carriage train supply N line connection modes, improve the reliability of the locomotive leakage current detection under different working conditions, and realize the smooth and safe operation of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the leakage current detection principle when the two column supply N lines are independent;

[0023] Figure 2 A schematic diagram of the leakage current detection principle when the N lines of two column supplies are shorted;

[0024] Figure 3 Schematic diagram of another leakage current detection principle when the N lines of two column supplies are short-circuited. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below with reference to the following embodiments. It should be noted that the embodiments and features of the embodiments may be combined unless they conflict. For ease of description, the words "upper," "lower," "left," and "right" appearing below merely indicate the directions of upper, lower, left, and right relative to the accompanying drawings and do not limit the structure.

[0026] Example

[0027] like Figure 3 The locomotive train supply leakage current detection circuit of this embodiment includes a residual current operated protection device, a suppression resistor and a contactor; the first end of the contactor is grounded, the second end of the contactor is connected to the first end of the residual current operated protection device, the second end of the residual current operated protection device is connected to the first end of the suppression resistor, and the second end of the suppression resistor is connected to the train supply N line.

[0028] The locomotive is designed with two train power output modes: DC600V mode (direct current) and AC380V mode (three-phase alternating current).

[0029] (1) DC600V mode

[0030] When the locomotive selects the train supply output mode as DC600V, the locomotive control unit controls the contactor KM7 to disconnect and the leakage current detection circuit is cut off.

[0031] (2) AC380V mode

[0032] When the locomotive selects the train power output mode as AC380V, the locomotive control unit controls the contactor KM7 to close and the leakage current detection circuit is activated.

[0033] In addition, a leakage current detection circuit activation / deactivation interface is provided on the locomotive display unit so that the driver can manually control it.

[0034] The leakage current detection and judgment method in the AC380V mode is as follows:

[0035] (1) Leakage current detection principle:

[0036] like Figure 1When the train supply output selects AC380V mode, contactor KM7 is closed and the leakage current detection circuit is put into operation. Under normal circumstances, the current forms a loop through the U line, V line, W line and N line, and the current detected by the residual current protection device RCD is relatively small. If one or more phases of the three-phase AC power are grounded, the current forms a loop with the car body and rails through the grounding point, forming a large current, causing the leakage current to exceed the standard (the train supply leakage current is greater than or equal to 2A). The residual current protection device RCD will be activated and the leakage current exceeding the standard fault will be reported to the locomotive control unit. After the locomotive control unit determines that the RCD action lasts for more than 1s, it will report "A train supply grounding fault" or "B train supply grounding fault" on the computer display to prompt the driver and perform subsequent operations.

[0037] (2) The principle of independent leakage current detection of the carriage N line is the same as described in (1).

[0038] (3) Principle of leakage current detection of carriage N line short circuit:

[0039] 1) No suppression resistor added

[0040] like Figure 2 When the suppression resistor is not added and the two train supply N lines of the carriage are short-circuited, the two train supply N lines are connected to the ground wire to form a shunt, and the current flows as follows Figure 2 Path 2 (blue arrow) shows the load current as the sum of the leakage currents in paths 1 and 2. Since the impedance difference between the two paths is small, the difference between the two currents is minimal. As the single-phase load power increases, the current in path 2 increases, ultimately causing an abnormally high leakage current fault, resulting in a false alarm of "Line A ground fault" or "Line B ground fault."

[0041] 2) Adding suppression resistance

[0042] like Figure 3 When a suppression resistor is added, regardless of whether the two train supply N lines are shorted or disconnected, due to the low line impedance (milliohm level), adding a suppression resistor of a certain value in path 2 ensures that the current in path 2 is suppressed under normal leakage current detection conditions. This solution suppresses the shunt current between the two train supply N lines, thus resolving the problem of excessive locomotive leakage current caused by single-phase loads in trains with the two train supply N lines shorted.

[0043] Selection requirements for suppression resistors: The resistance of the suppression resistor cannot be too large, and the insulation resistance value for carriage leakage current detection must not exceed 5% of its design deviation. Preferably, the insulation resistance value deviation for carriage leakage current detection is controlled below 1%, which has no effect on carriage leakage current detection.

[0044] The suppression resistor satisfies the following formula:

[0045]

[0046] Wherein, R1 is the resistance of the suppression resistor, A1 is the compartment leakage current threshold, V1 is the single-phase output voltage, and K is the deviation. Preferably, 0<K≤5%; more preferably, 0<K≤1%.

[0047] For example, the compartment leakage current threshold is 50mA, and the insulation resistance for compartment leakage current detection is 230 / 0.05 = 4600Ω. After adding a 30Ω suppression resistor, when the two neutral lines are independent, the insulation resistance corresponding to 50mA is 4600-30 = 4570Ω. When the two neutral lines are short-circuited, the insulation resistance corresponding to 50mA is 4600-15 (two 30Ω resistors in parallel) = 4585Ω. This meets the requirement that the insulation resistance deviation for compartment leakage current detection is within 5%. According to industry experience, the design fluctuation of various parameters is generally ±5%, and fluctuations within ±5% generally do not affect related performance.

[0048] The suppression resistor value is selected to be 30Ω, and after field tests and operational assessments, the overall grounding detection status is good.

[0049] Taking into account the possibility that the carriage train supply N line may be connected in parallel, and combined with the performance of the locomotive train supply itself, the train supply leakage current threshold is selected to be 2A and the duration is 1s to stop the power output, and verification is carried out. After field tests and operation assessments, the field application is in good condition.

[0050] This embodiment provides a locomotive train supply leakage current detection circuit and detection control method that meet the different train supply N line connection modes of the carriages, ensure the normal detection and judgment of the leakage current when the two train supply N lines are independent / short-circuited, and realize the normal operation of the locomotive compatible with the carriage formations with different train supply N line connection modes: (1) the locomotive meets the leakage current detection and judgment when the train supply is in AC380V output mode and the two train supply N lines of the carriage are independent; (2) the locomotive meets the leakage current detection and judgment when the train supply is in AC380V output mode and the two train supply N lines of the carriage are short-circuited; (3) the two train supply leakage current detection of the locomotive is realized.

[0051] This embodiment connects suppression resistors and residual current operated protective devices to the locomotive's two train supply N lines. This allows for leakage current detection and determination when the locomotive train supply is in AC380V output mode and the two train supply N lines in the carriages are independent or short-circuited. This improves the reliability of grounding detection in the locomotive's AC380V train supply output mode to meet market application requirements. By adding suppression resistors in the AC380V train supply output mode, the method for detecting train supply output leakage current between the locomotive and the carriage is optimized, ensuring smooth and safe operation of the locomotive.

[0052] Train-based power supply refers to a method of powering each carriage directly from a generator car at the rear of a train. Train-based power supply systems are primarily used in scenarios where locomotives require centralized power supply. In particular, in long-train operations, the train-based power supply management cabinet connects two train-based power supply units in parallel to power the carriages.

[0053] A residual current operated device (RCD) is an important electrical safety device, primarily consisting of a detection element (such as a zero-sequence current transformer), intermediate circuitry (including amplifiers, comparators, trip units, etc.), and an actuator (main switch). When the residual current (leakage current) generated by a fault in a live conductor to ground in a circuit exceeds a specified value, the RCD issues an alarm. Its operating principle is based on detecting the difference between the supply current and the loop current in the circuit, thereby achieving protection. Examples of RCDs include the GSH200 and DS201.

[0054] A contactor is an industrial electrical device whose main function is to generate a magnetic field by flowing current through a coil, thereby closing the contacts and controlling the load. Contactors include the CJX2-1210 and CJX2-6511.

[0055] The contents illustrated in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications of the present invention by those skilled in the art shall fall within the scope defined by the claims attached to this application.

Claims

1. A locomotive train supply leakage current detection circuit, including a residual current operated protection device, characterized in that: Also includes suppression resistors and contactors; The first end of the contactor is grounded, the second end of the contactor is connected to the first end of the residual current operated protection device, the second end of the residual current operated protection device is connected to the first end of the suppression resistor, and the second end of the suppression resistor is connected to the column supply N line.

2. The locomotive train supply leakage current detection circuit according to claim 1, characterized in that: The suppression resistor satisfies the following formula: Among them, R1 is the resistance of the suppression resistor, A1 is the compartment leakage current threshold, V1 is the single-phase output voltage of the three-phase AC power, and K is the deviation.

3. The locomotive train supply leakage current detection circuit according to claim 2, characterized in that: 0＜K≤5％。 4. The locomotive train supply leakage current detection circuit according to claim 3, characterized in that: 0＜K≤1％。 5. A locomotive train leakage current detection system, characterized in that: It comprises the locomotive train supply leakage current detection circuit, locomotive control unit and locomotive display unit according to any one of claims 1 to 4; The locomotive control unit is used to control the on and off of the contactor, connecting and cutting off the locomotive train power supply; The locomotive display unit is used to display the status of the residual current protection device and the train grounding status.

6. A method for detecting leakage current of a locomotive train supply, characterized in that: The locomotive train leakage current detection system according to claim 5 is used, and the process includes the following steps: If the locomotive train power output is DC, the locomotive control unit controls the contactor to open; If the locomotive train power output is three-phase AC, the locomotive control unit controls the contactor to close; When at least one phase of the three-phase AC power is grounded and the train leakage current is greater than or equal to the train leakage current threshold, the residual current protection device will operate; if the duration of the train leakage current being greater than or equal to the train leakage current threshold is greater than the time threshold, the locomotive control unit will cut off the locomotive train power supply.

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