Rail transit direct current traction power supply system residual current protection device

Abstract

The application provides a residual current protection device for a rail transit DC traction power supply system, which comprises a DC shunt, a current transmitter and a residual current protection measurement and control unit. The DC shunt is connected to an overhead ground cable connecting an overhead ground wire and a grounding busbar of a traction substation. The input end of the current transmitter is connected to the DC shunt, and the output end is connected to the residual current protection measurement and control unit. The output end of the residual current protection measurement and control unit is connected to the trip circuit of a line circuit breaker. The residual current protection measurement and control unit collects the residual current on the overhead ground cable. When the residual current increment reaches the setting value, the line circuit breaker is controlled to trip. The application measures the residual current of the overhead ground wire near the grounding busbar of the traction substation. When a sudden current is detected, the protection device acts and trips, thereby removing the line fault, and greatly improving the reliability, speed and sensitivity of the DC power supply line protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of track traffic direct current power supply system line protection, and particularly relates to a track traffic direct current traction power supply system residual current protection device. BACKGROUND

[0002] Based on the advantages of energy saving, environmental protection, convenient travel and promoting the development of urban economy and life, urban rail transit is developing rapidly in more and more cities. In order to meet the increasing passenger transport demand, the train passenger capacity and train dispatching density are also increasing. At the same time, the load current of the direct current power supply line is also greatly increased. When the overhead ground wire is short-circuited at the end of the long and large section line, due to the large line impedance, the overcurrent protection of the traditional direct current system is difficult to distinguish the train running load current and the short-circuit fault current, even if the long delay is set to achieve it, but the speed of protection is lost, so the sensitivity and speed of overcurrent protection will be greatly reduced.

[0003] In order to improve the sensitivity of the above-mentioned direct current overcurrent protection, the existing domestic and foreign track traffic direct current power supply line usually adopts the method of increasing the cross section of the overhead ground wire (double splicing) to reduce the short-circuit path impedance or prolonging the line overcurrent protection setting time, but the above-mentioned method either increases the engineering investment cost or sacrifices the speed of protection, which increases the safety risk before the line fault is removed. At the same time, it also increases the operation and maintenance pressure and the construction difficulty, resulting in high cost of the traction power supply system. SUMMARY

[0004] The present application is aimed at the present situation that the short-circuit current size of the overhead ground wire at the end of the long and large section direct current power supply line is similar to the normal running load current, which makes it difficult for the direct current line overcurrent protection to distinguish, and provides a track traffic direct current traction power supply system residual current protection device. The overhead ground wire is measured for residual current near the grounding busbar of the traction substation. When the sudden increase in current is detected, the protection operates and trips, thereby removing the line fault, greatly improving the reliability, speed and sensitivity of the direct current power supply line protection.

[0005] The technical scheme adopted by the present application is: a track traffic direct current traction power supply system residual current protection device, comprising a direct current shunt, a current transducer and a residual current protection measurement and control unit. The direct current shunt is connected to the overhead ground wire cable connecting the overhead ground wire and the grounding busbar of the traction substation. The input end of the current transducer is connected with the direct current shunt, and the output end is connected with the residual current protection measurement and control unit. The output end of the residual current protection measurement and control unit is connected with the trip loop of the line circuit breaker.

[0006] The direct current shunt matches the current transformer to measure the residual current on the overhead ground cable, the residual current protection measurement and control unit collects the measurement signal of the current transformer, and when the residual current increment reaches the setting value, the line circuit breaker of the overhead ground corresponding contact net is tripped.

[0007] Further, the residual current protection measurement and control unit detects whether the current transformer is faulty, and when the residual current increment reaches the setting value and the current transformer is not faulty, the residual current protection measurement and control unit controls the line circuit breaker to trip.

[0008] Further, the residual current protection measurement and control unit is connected with more than one current transformer.

[0009] Further, the residual current protection measurement and control unit comprises a power module, an input module, a CPU, a memory, an output module and an external interface, the CPU is connected with the input module, the memory, the output module and the external interface respectively, and the power module supplies power for the input module, the CPU and the output module.

[0010] Working principle: Under normal circumstances, there is a small amount of stray current in the overhead ground line, when the contact net is short-circuited to the overhead ground line, the current in the overhead ground line will suddenly increase, when the residual current protection measurement and control unit reaches the setting value of the sudden increase current, the line circuit breaker is controlled to trip, thereby cutting off the line fault.

[0011] Compared with the prior art, the present application has the beneficial effects that:

[0012] 1. The present application increases the line end low voltage judgment logic under the premise of meeting the overcurrent protection function of the DC power supply line of the rail transit, greatly increases the reliability, sensitivity and speed of the protection, and reduces the cost. By detecting the current increment in the overhead ground line, it is judged whether the contact net is short-circuited to the overhead ground line, which is completely independent of other protections, simple, economical and reliable, and the voltage setting value can be set in a very large range, and the protection sensitivity is very high. In order to ensure reliability, the fault judgment function is added in the logic judgment loop, which can obviously improve the safety and reliability of the system operation.

[0013] 2. The components and parts used in the installation of the present application are standard types, the direct current shunt, the current transformer and the residual current protection measurement and control unit all have the advantages of small size, simple wiring, convenient installation, easy construction and the like, and the installation position is flexible, which can be installed in the DC switch cabinet of the traction substation or hung on the wall of the cabinet, and does not produce any influence on the civil buildings and other facilities.

[0014] 3. This invention completely solves the problem of blind spots in the overcurrent protection of DC power supply line end faults for overhead ground wires in existing long-distance power supply lines, greatly reducing safety accidents such as equipment damage and electric shock caused by the inability to promptly disconnect line faults. Attached Figure Description

[0015] Fig. 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0016] Fig. 2 This is a structural block diagram of the residual current protection measurement and control unit according to an embodiment of the present invention;

[0017] Fig. 3 This is a logic diagram of an embodiment of the present invention.

[0018] In the diagram, 1-DC shunt, 2-current transmitter, 3-residual current protection and control unit, 4-circuit breaker, and 5-overhead ground cable. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Embodiments of the present invention provide a residual current protection device for a DC traction power supply system for rail transit, such as... Figs. 1-3 As shown, it includes a DC shunt 1, a current transmitter 2, and a residual current protection and control unit 3. The overhead ground wire is connected to the grounding busbar in the traction substation via an overhead ground wire cable 5, and the DC shunt 1 is connected to the overhead ground wire cable 5. The input terminal of the current transmitter 2 is connected to the DC shunt 1, and the output terminal is connected to the residual current protection and control unit 3. The residual current protection and control unit 3 is connected to one or more current transmitters 2, the specific number depending on the actual situation. The output terminal of the residual current protection and control unit 3 is connected to the tripping circuit of the line circuit breaker 4. Each line circuit breaker 4 corresponds to one contact network, and each contact network corresponds to one overhead ground wire; therefore, a one-to-one correspondence can be formed between the line circuit breaker 4 and the current transmitter 2.

[0021] The residual current protection and control unit 3 includes a power supply module, an input module, a CPU, a memory, an output module, and an external interface. The CPU is connected to the input module, the memory, the output module, and the external interface, respectively. The power supply module provides power to the input module, the CPU, and the output module.

[0022] The direct current shunt 1 cooperates with the current transformer 2 to measure the residual current on the overhead ground cable 5, and the current transformer 2 sends a measurement signal of the residual current to the residual current protection control unit 3. The residual current protection control unit 3 performs internal operation and logical judgment on the measurement signal: when the residual current increment of a certain overhead ground line reaches the setting value, and the current transformer 2 for measuring the residual current is not faulty, the line circuit breaker 4 corresponding to the overhead ground line of the overhead contact net is controlled to trip, thereby realizing the protection function.

[0023] The above has been described in detail through examples, but the above is only exemplary embodiments of the present application and cannot be considered as limiting the implementation scope of the present application. The protection scope of the present application is defined by the claims. Any similar technical solution that utilizes the technical solutions of the present application or is inspired by the technical solutions of the present application within the essence and protection scope of the present application, and achieves the above technical effects, or any equivalent changes and improvements to the application scope, shall still belong to the patent coverage and protection scope of the present application.

Claims

1. A residual current protection device for a DC traction power supply system for rail transit, characterized in that: It includes a DC shunt, a current transmitter, and a residual current protection and control unit. The DC shunt is connected to the overhead ground cable that connects the overhead ground wire to the grounding busbar of the traction substation. The input terminal of the current transmitter is connected to the DC shunt, and the output terminal is connected to the residual current protection and control unit. The output terminal of the residual current protection and control unit is connected to the tripping circuit of the line circuit breaker. The DC shunt, in conjunction with the current transmitter, measures the residual current on the overhead ground cable. The residual current protection and control unit acquires the measurement signal from the current transmitter and detects whether the current transmitter is faulty. When the residual current increment reaches the set value and the current transmitter is not faulty, the residual current protection and control unit controls the circuit breaker of the contact network corresponding to the overhead ground cable to trip.

2. The residual current protection device for a DC traction power supply system for rail transit as described in claim 1, characterized in that: The residual current protection and control unit is connected to one or more of the current transmitters.

3. The residual current protection device for a DC traction power supply system for rail transit as described in claim 1, characterized in that: The residual current protection and control unit includes a power supply module, an input module, a CPU, a memory, an output module, and an external interface. The CPU is connected to the input module, the memory, the output module, and the external interface, respectively. The power supply module provides power to the input module, the CPU, and the output module.

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