Grounding detection circuit, grounding detection system and detection method of locomotive auxiliary system

Abstract

The invention provides a grounding detection circuit, a grounding detection system and a detection method of a locomotive auxiliary system. The grounding detection circuit of the locomotive auxiliary system comprises an auxiliary transformer, a grounding detection device, a traction charger, an overvoltage protection device and a circuit breaker. When the direct-current side of the traction charger is grounded, the voltage to ground of the alternating-current side of the traction charger is increased, the overvoltage protection device acts, the circuit breaker is disconnected, and the locomotive executes overcurrent protection to isolate the traction charger, so that the safety of the auxiliary load is ensured; at the moment, the locomotive can supply power to the auxiliary load through the auxiliary transformer in the contact network mode to ensure safety of the auxiliary load. According to the invention, the auxiliary system can be ensured to be effectively and safely used under various working conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle auxiliary systems, and particularly relates to a grounding detection circuit, a grounding detection system and a detection method for a locomotive auxiliary system. Background Art

[0002] To ensure the normal function of a locomotive and provide a comfortable driving environment, the locomotive is equipped with corresponding auxiliary units and auxiliary facilities, which constitute an auxiliary system. The auxiliary system of traditional electric locomotives is often powered after stepping down the voltage through an auxiliary transformer, and the auxiliary power supply is 3AC440V, 3AC400V, 3AC380V, etc. The simplified circuit diagram of the auxiliary system power supply is as Figure 1 . The high-voltage traction circuit of the locomotive and the auxiliary circuit are electrically isolated through an auxiliary transformer. The auxiliary circuit continuously monitors the insulation impedance of the auxiliary AC system to the ground through a grounding detection device (also called an insulation detection device). When the insulation of the auxiliary circuit is abnormal, the grounding detection device sends an alarm signal, and the alarm signal will be displayed on the driver's cab display screen for early warning. At this time, the locomotive does not perform protection and waits for maintenance after completing the traction task.

[0003] To make up for the shortcomings of traditional electric locomotives relying on catenary power supply, low traction efficiency and high pollution in non-network areas relying on diesel shunting locomotives, locomotives with traction batteries as energy storage units have emerged. Currently, for high-power locomotives powered by AC catenary, the traction electric drive system generally adopts an AC-DC-AC structure, and the voltage of the intermediate DC link is generally between 1800V and 3600V. For the main-auxiliary integrated structure, the auxiliary power supply is obtained from the intermediate DC link. At present, the power supply voltage of the traction battery pack in mature operation is generally within 1000V. If the traction battery is directly connected to the intermediate DC link, to ensure the power supply demand of the auxiliary load, the DC power of the traction battery can be converted into three-phase AC power through a bidirectional traction charger to supply power to the auxiliary load. This avoids the voltage reduction of the input power supply by the auxiliary transformer, thereby ensuring the normal operation of the auxiliary load, as Figure 2 .

[0004] As Figure 3 shown, in the traction battery power supply mode, the traction charger (also called an AC / DC power conversion module) provides three-phase AC power to the auxiliary load to ensure the normal function of the locomotive auxiliary load. Since this circuit is a non-electrically isolated circuit, when a single-point ground occurs on the DC side of the traction charger, the voltage of the AC side to the ground increases sharply, exceeding the insulation voltage of the auxiliary load. If the locomotive does not perform timely grounding protection at this time, it will cause the burnout of the auxiliary load. However, due to the EMI filtering device of the bidirectional AC / DC, the grounding detection circuit signal cannot form a continuous and reliable loop through the bidirectional AC / DC, that is, when an auxiliary load ground occurs, there is a risk of undetected grounding causing the burnout of the auxiliary load. Summary of the Invention

[0005] The object of the present invention is to provide a grounding detection circuit, a grounding detection system and a detection method for a locomotive auxiliary system in view of the deficiencies of the prior art, and to solve the problem that the grounding detection circuit of the locomotive auxiliary system cannot meet various working conditions.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A grounding detection circuit for a locomotive auxiliary system includes an auxiliary transformer, a grounding detection device, a traction charger, and also includes an overvoltage protection device and a circuit breaker;

[0008] The auxiliary transformer is electrically connected to the grounding detection device and the first end of the circuit breaker respectively;

[0009] The AC side of the traction charger is electrically connected to the grounding detection device and the first end of the circuit breaker respectively;

[0010] The second end of the circuit breaker is electrically connected to the overvoltage protection device;

[0011] The auxiliary transformer, the grounding detection device, the AC side of the traction charger, and the first end of the circuit breaker are all electrically connected to an auxiliary load.

[0012] Based on the existing grounding detection circuit of the locomotive auxiliary system, the present invention only adds one overvoltage protection device and one circuit breaker. Compared with adding other grounding detection circuits, such as adding multiple large-value resistors and multiple voltage sensors on the DC side of the traction charger, the present invention can save costs and streamline the layout of locomotive equipment at the same time.

[0013] When the DC side of the traction charger is grounded, the voltage of the AC side of the traction charger to the ground increases, the overvoltage protection device operates, the circuit breaker trips, and the locomotive performs overcurrent protection to isolate the traction charger to ensure the safety of the auxiliary load; at this time, the locomotive can supply power to the auxiliary load through the auxiliary transformer in the catenary mode.

[0014] The present invention can perform grounding protection in time when the DC of the traction charger is grounded, and can ensure that the auxiliary system can be effectively and safely used under various working conditions.

[0015] Furthermore, the protection action value of the overvoltage protection device is less than or equal to the insulation voltage limit value of the auxiliary load. This is to prevent damage to the auxiliary load when the voltage to the ground caused by the grounding of the traction charger is higher than the insulation voltage of the auxiliary load and no protection has been carried out yet.

[0016] Based on the same inventive concept, the present invention also provides a grounding detection system for a locomotive auxiliary system, including the grounding detection circuit of the locomotive auxiliary system, a locomotive control unit, a locomotive display unit, and a locomotive signal transmission unit;

[0017] The locomotive control unit is used to isolate the traction charger;

[0018] The locomotive display unit is used to display the auxiliary load grounding status and alarm signals;

[0019] The locomotive signal transmission unit is used to transmit the load grounding status and alarm signals.

[0020] Based on the same inventive concept, the present invention also provides a grounding detection method for a locomotive auxiliary system, including the following processes:

[0021] When the locomotive is powered by the catenary, the auxiliary transformer supplies power to the auxiliary load. If the grounding detection device determines that the auxiliary load is grounded, the grounding detection device issues an alarm signal;

[0022] When the locomotive is powered by the traction battery, the traction charger supplies power to the auxiliary load. If the AC side of the traction charger is grounded, the grounding detection device determines that the auxiliary load is grounded, and the grounding detection device issues an alarm signal;

[0023] If the DC side of the traction charger is grounded and the AC side voltage of the traction charger does not exceed the protection action value of the overvoltage protection device, the grounding detection device issues an alarm signal; if the DC side of the traction charger is grounded and the AC side voltage of the traction charger exceeds the protection action value of the overvoltage protection device, the overvoltage protection device operates, the circuit breaker disconnects, the locomotive control unit isolates the traction charger, and the grounding detection device issues an alarm signal.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] Based on the existing grounding detection circuit of the locomotive auxiliary system, the present invention only adds 1 overvoltage protection device and 1 circuit breaker, which can save costs and streamline the layout of locomotive equipment at the same time.

[0026] The present invention can perform grounding protection in a timely manner when the DC of the traction charger is grounded, and can ensure the effective and safe operation of the auxiliary system under various working conditions. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the grounding detection circuit of the existing locomotive auxiliary system;

[0028] Figure 2 It is a schematic diagram of the power supply circuit of the locomotive auxiliary system with a traction battery;

[0029] Figure 3 It is a schematic diagram of the grounding detection circuit of the existing locomotive auxiliary system with a traction battery;

[0030] Figure 4It is the grounding detection circuit diagram of the locomotive auxiliary system of the present invention;

[0031] Figure 5 It is the flow schematic diagram of the grounding detection method of the locomotive auxiliary system of the present invention. Specific embodiments

[0032] The present invention will be described in detail below in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. For the convenience of narration, words such as "upper", "lower", "left", and "right" in the following text only indicate the same direction as the upper, lower, left, and right directions of the attached drawings themselves, and do not limit the structure.

[0033] Embodiment

[0034] As Figure 4 , the grounding detection circuit of the locomotive auxiliary system in this embodiment includes an auxiliary transformer, a grounding detection device, a traction charger, an overvoltage protection device, and a circuit breaker; the auxiliary transformer is electrically connected to the grounding detection device and the first end of the circuit breaker respectively; the AC side of the traction charger is electrically connected to the grounding detection device and the first end of the circuit breaker respectively; the second end of the circuit breaker is electrically connected to the overvoltage protection device; the auxiliary transformer, the grounding detection device, the AC side of the traction charger, and the first end of the circuit breaker are all electrically connected to the auxiliary load.

[0035] The grounding detection system of the locomotive auxiliary system in this embodiment includes the grounding detection circuit of the motor vehicle auxiliary system, a locomotive control unit, a locomotive display unit, and a locomotive signal transmission unit. The locomotive control unit is used to perform overcurrent protection to isolate the traction charger; the locomotive display unit is used to display the grounding state of the auxiliary load and the alarm signal; the locomotive signal transmission unit is used to transmit the grounding state of the load and the alarm signal.

[0036] The protection action value of the overvoltage protection device is set to be less than or equal to the insulation voltage limit value T of the auxiliary load, to prevent damage to the auxiliary load when the system is not protected yet when the ground voltage T1 caused by system grounding is higher than the auxiliary load insulation voltage T.

[0037] The circuit breaker QF1 is used to protect the overvoltage protection device.

[0038] When the locomotive is operating normally, the circuit breaker QF1 is in the closed state, and the opening and closing state of the circuit breaker QF1 is collected through the locomotive control unit to determine whether the overvoltage protection device operates.

[0039] As Figure 5 , the grounding detection method of the locomotive auxiliary system in this embodiment includes the following processes:

[0040] When the locomotive is powered by the catenary, the auxiliary transformer supplies power to the auxiliary loads. The grounding detection device judges the grounding of the auxiliary system, and the grounding detection device sends out an alarm signal. The grounding status of the auxiliary loads and the alarm signal are displayed on the locomotive display unit, and the locomotive maintains operation and returns to the depot for maintenance;

[0041] When the locomotive is powered by the traction battery, the auxiliary loads are powered by the traction charger. When the AC side of the traction charger is grounded, the grounding detection device judges the grounding of the auxiliary system. When the voltage of the AC side to the ground does not exceed the insulation voltage of the auxiliary loads, the grounding detection device only sends out an alarm signal, and the grounding status of the auxiliary loads and the alarm signal will be displayed on the locomotive display unit in the driver's cab for early warning. The locomotive maintains operation and returns to the depot for maintenance;

[0042] When the DC side of the traction charger is grounded, the phenomenon that the voltage of the AC side to the ground increases sharply caused by the grounding of the DC side of the traction charger is utilized. When the circuit of the DC side of the traction charger is grounded, if the voltage of the AC side of the traction charger does not exceed the protection action value of the overvoltage protection device, the grounding detection device sends out an alarm signal; if the voltage of the AC side of the traction charger exceeds the protection action value of the overvoltage protection device, the overvoltage protection device operates, the circuit breaker QF1 disconnects, and at the same time the locomotive control unit executes overcurrent protection to isolate the traction charger. The locomotive control unit judges the grounding of the DC side of the traction charger in combination with the disconnection state of the circuit breaker QF1 and the overcurrent protection state of the traction charger, and the grounding status of the auxiliary loads and the alarm signal will be displayed on the locomotive display unit in the driver's cab. At this time, the traction battery cannot supply power to the auxiliary loads through the traction charger, and the locomotive can switch to the catenary mode to supply power to the auxiliary loads through the auxiliary transformer.

[0043] The grounding detection device, also known as the insulation detection device, is an on-line real-time monitoring device specially used to detect the insulation status of the busbar and branches of the DC power supply system. Through a series of technical means, it ensures the safety and reliability of the power system, especially in the industrial field, it has a wide range of applications. The grounding detection device can monitor the insulation resistance of the system to the ground in real time and start the fault early warning or alarm function when the resistance is lower than the set value. The grounding detection device injects specific pulse signals (such as +20V and -20V) into the system and calculates the resistance of the system to the ground and the leakage capacitance by detecting the feedback of these signals in the system. This design enables the device to work reliably in both AC and DC ungrounded systems. Grounding detection devices such as ACPD200 type, AIM-D100-CA type, etc. are selected according to requirements.

[0044] The overvoltage protection device is an electrical component, and its core components are voltage-dependent resistors (varistors, suppression diodes) and / or gas discharge devices. The overvoltage protection device is mainly used to protect the insulation of electrical equipment such as generators, transformers, vacuum switches, busbars, and motors from being damaged by overvoltages. The main operating principle of the overvoltage protection is to use a discharge gap to divide the voltage of the zinc oxide varistor to reduce the switching impulse, protect the residual voltage, and achieve the protection of switching overvoltages. It has been widely used in industries such as power, chemical, coal, construction, and electrified railways. Overvoltage protection devices such as KYT27.5-47 / 800 type, BY-2A type, etc. are selected according to requirements.

[0045] A circuit breaker is a switching device that can close, carry, and interrupt current under normal or abnormal conditions. Circuit breakers such as DZ15 type, DZ20 type, DZ20l type, DZL25 type, etc. are selected according to requirements.

[0046] The auxiliary transformer is mainly used to improve the power output of the power supply and ensure the stable power supply of high-power equipment. It can convert low-voltage direct current into high-voltage direct current to meet the needs of specific equipment. Auxiliary transformers such as RM type transformers, EPEFDEPC type transformers, EF type transformers, etc. are selected according to requirements.

[0047] The insulation voltage limit refers to the standard voltage value used to measure the insulation strength, electrical clearance, and creepage distance of different potential parts of electrical appliances and their components under specified conditions.

[0048] The protection action value of the overvoltage protection device refers to that when the system voltage exceeds a certain set value, the overvoltage protection device will start to prevent the equipment or system from being damaged. The protection action value can be found in the instruction manual or technical specifications of the overvoltage protection device.

[0049] For the grounding detection circuit of the locomotive auxiliary system in this embodiment, when the catenary power supply mode is adopted, the auxiliary system can maintain operation with single-point grounding of the locomotive; when the traction battery power supply mode is adopted, after the DC side of the traction charger is grounded, the system automatically protects and isolates the traction charger, and then the catenary mode can be switched to maintain the normal operation of the auxiliary system. The grounding detection circuit of the locomotive auxiliary system has high redundancy and reliability.

[0050] For the grounding detection circuit of the locomotive auxiliary system in this embodiment, based on the existing grounding detection circuit of the locomotive auxiliary system, only one overvoltage protection device and one circuit breaker are added. Compared with adding other grounding detection devices, such as adding a half-voltage detection device (multiple large-value resistors and multiple voltage sensors) on the DC side, it can save costs and streamline the layout of locomotive equipment at the same time.

[0051] The locomotive auxiliary circuit grounding detection method of this embodiment adds the status feedback of the overvoltage protection device. That is, under normal circumstances, the circuit breaker QF1 is in the closed state. When the circuit breaker QF1 of the overvoltage protection device is disconnected and the traction charger overcurrent protection acts simultaneously, the DC side grounding fault of the traction charger can be located, with fast protection and timely and accurate location.

[0052] The content clarified in the above embodiments should be understood that these embodiments are only used to illustrate the present invention more clearly, rather than to limit the scope of the present invention. After reading the present invention, various equivalent forms of modification of the present invention by those skilled in the art all fall within the scope defined by the appended claims of this application.

Claims

1. A grounding detection circuit of a locomotive auxiliary system, comprising an auxiliary transformer, a grounding detection device, and a traction charger, characterized in that: It also includes overvoltage protection devices and circuit breakers; The auxiliary transformer is electrically connected to the grounding detection device and the first end of the circuit breaker respectively; The AC side of the traction charger is electrically connected to the ground detection device and the first end of the circuit breaker respectively; The second end of the circuit breaker is electrically connected to the overvoltage protection device; The auxiliary transformer, the grounding detection device, the AC side of the traction charger, and the first end of the circuit breaker are all electrically connected to the auxiliary load.

2. The ground detection circuit of the locomotive auxiliary system according to claim 1, characterized in that: The protection action value of the overvoltage protection device is less than or equal to the insulation voltage limit of the auxiliary load.

3. A ground detection system for a locomotive auxiliary system, characterized in that: A locomotive auxiliary system comprising a ground detection circuit, a locomotive control unit, a locomotive display unit, and a locomotive signal transmission unit according to any one of claims 1 to 2; The locomotive control unit is used to isolate the traction charger; The locomotive display unit is used to display the auxiliary load grounding status and alarm signal; The locomotive signal transmission unit is used to transmit the auxiliary load grounding state and alarm signal.

4. A grounding detection method for a locomotive auxiliary system, characterized in that: The ground detection system of the locomotive auxiliary system according to claim 3 is used, and the process includes the following steps: When the locomotive is powered by the overhead line, the auxiliary load is powered by the auxiliary transformer. If the grounding detection device determines that the auxiliary load is grounded, the grounding detection device sends an alarm signal; When the locomotive is powered by the traction battery, the auxiliary load is powered by the traction charger. If the AC side of the traction charger is grounded, the grounding detection device determines that the auxiliary load is grounded, and the grounding detection device sends an alarm signal; If the DC side of the traction charger is grounded and the voltage on the AC side of the traction charger does not exceed the protection action value of the overvoltage protection device, the grounding detection device sends an alarm signal; if the DC side of the traction charger is grounded and the voltage on the AC side of the traction charger exceeds the protection action value of the overvoltage protection device, the overvoltage protection device is activated, the circuit breaker is disconnected, the locomotive control unit isolates the traction charger, and the grounding detection device sends an alarm signal.

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