Low-voltage direct-current leakage protection device and method

Abstract

The invention belongs to the technical field of electric leakage protection, and particularly discloses a low-voltage direct-current electric leakage protection device and method, and the device comprises the steps: carrying out the current sampling of a direct-current positive loop and a direct-current negative loop through a current sampling circuit, obtaining a current difference value, and comparing the current difference value with a preset leakage current threshold through a logic controller, and if the current difference value is greater than or equal to the leakage current threshold value, the logic controller outputs a trigger signal to the loop on-off controller, so that the loop on-off controller disconnects the direct-current anode loop and the direct-current cathode loop. By performing current sampling and current difference comparison on the direct-current loop, whether an electric leakage phenomenon occurs in the direct-current loop can be accurately judged, and after the electric leakage situation of the direct-current loop is judged, power supply in the direct-current loop can be quickly responded and cut off, so that electric leakage protection on the low-voltage direct-current loop is realized; electric shock accidents or electrical fires caused by electric leakage of direct-current electrical equipment are prevented, and power utilization safety is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of leakage protection, and in particular relates to a low-voltage direct current leakage protection device and method. Background Art

[0002] In recent years, compared with the traditional AC power grid, the low voltage direct current (LVDC) power supply system with a voltage level of 1500V and below has been increasingly used in the fields of power, rail transit, oil drilling, communications, IT, electric vehicles and charging facilities due to its characteristics of no reactive power and frequency requirements. However, with the popularization of low voltage DC power supply systems, the AC leakage protection devices currently on the market can no longer meet the protection requirements of low voltage DC power supply systems. At the same time, there is no matching low voltage DC leakage protection device that can be used to effectively protect low voltage DC power supply systems from leakage, so as to prevent electric shock accidents or electrical fires caused by leakage of DC electrical equipment. Summary of the invention

[0003] The object of the present invention is to provide a low voltage DC leakage protection device and method to solve the above problems existing in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a low-voltage DC leakage protection device, comprising a current sampling circuit, a logic controller and a loop on-off controller, wherein the logic controller is respectively connected to the current sampling circuit and the loop on-off controller, the current sampling circuit is used to perform current sampling on the DC positive loop and the DC negative loop respectively, obtain a positive loop current sampling signal and a negative loop current sampling signal, and obtain a current difference between the DC positive loop and the DC negative loop according to the positive loop current sampling signal and the negative loop current sampling signal, and transmit the current difference to the logic controller, the logic controller is used to compare the current difference with a preset leakage current threshold, and when the current difference is greater than or equal to the leakage current threshold, output a trigger signal to the loop on-off controller, the loop on-off controller is arranged in the DC positive loop and the DC negative loop, and is used to disconnect the DC positive loop and the DC negative loop after receiving the trigger signal.

[0005] When it is used, the current sampling circuit can be used to sample the current of the DC positive circuit and the DC negative circuit respectively, and obtain the positive circuit current sampling signal and the negative circuit current sampling signal. Then, the current difference between the DC positive circuit and the DC negative circuit is obtained according to the positive circuit current sampling signal and the negative circuit current sampling signal, and then the current difference is transmitted to the logic controller. The logic controller compares the current difference with the preset leakage current threshold. If the current difference is greater than or equal to the leakage current threshold, it indicates that leakage occurs in the DC circuit. At this time, the logic controller will output a trigger signal to the circuit on-off controller. The circuit on-off controller is arranged in the DC positive circuit and the DC negative circuit, and is located between the DC power supply and the load. When the circuit on-off controller receives the trigger signal, it immediately disconnects the DC positive circuit and the DC negative circuit, cuts off the power supply between the DC power supply and the load, and achieves the purpose of leakage protection.

[0006] In a possible design, the device also includes a leakage indication circuit, which is connected to the logic controller and is used to obtain a trigger signal from the logic controller and issue leakage indication information according to the trigger signal.

[0007] In one possible design, the leakage indication circuit includes an LED indicator light.

[0008] In a possible design, the apparatus further includes a signal output interface, which is connected to the logic controller and is used to obtain a trigger signal from the logic controller and output the trigger signal to an external device.

[0009] In one possible design, the device further includes a leakage current setting circuit, which is connected to the logic controller and is used to set a leakage current threshold and transmit the leakage current threshold to the logic controller.

[0010] In one possible design, the leakage current threshold is set to 30 mA.

[0011] In one possible design, the current sampling circuit includes a current sensor.

[0012] In a possible design, the logic controller includes a comparator, and the comparator is an operational amplifier.

[0013] In one possible design, the circuit on / off controller includes a DC vacuum contactor.

[0014] In a second aspect, the present invention provides a low-voltage DC leakage protection method, which is applied to the low-voltage DC leakage protection device in the first aspect, and the method comprises: Current sampling is performed on the DC positive loop and the DC negative loop respectively to obtain a positive loop current sampling signal and a negative loop current sampling signal; The current difference between the DC positive loop and the DC negative loop is obtained according to the positive loop current sampling signal and the negative loop current sampling signal; The current difference is compared with a preset leakage current threshold, and when the current difference is greater than or equal to the leakage current threshold, the DC positive circuit and the DC negative circuit are disconnected.

[0015] Beneficial effect: The present invention can accurately determine whether leakage occurs in the DC circuit by sampling the current and comparing the current difference in the DC circuit. After determining that leakage occurs in the DC circuit, the present invention can quickly respond to cut off the power supply in the DC circuit, thereby realizing leakage protection for the low-voltage DC circuit, preventing electric shock accidents or electrical fires caused by leakage of DC electrical equipment, and ensuring electricity safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of a circuit of a device provided in Example 1 of the present invention; Figure 2 Schematic diagram of the circuit of the operational amplifier used in Example 1. DETAILED DESCRIPTION

[0018] It should be noted that the description of these embodiments is intended to help understand the present invention, but does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only intended to describe exemplary embodiments of the present invention. However, the present invention can be embodied in a number of alternative forms, and should not be construed as being limited to the embodiments set forth herein.

[0019] It should be understood that, unless otherwise clearly specified and limited, the corresponding terms should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be an electrical connection, a direct connection, an indirect connection through an intermediate medium, or the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments can be understood according to specific circumstances.

[0020] In the following description, certain details are provided to facilitate a complete understanding of the example embodiments. However, it will be appreciated by those of ordinary skill in the art that the example embodiments may be implemented without these certain details. For example, the system may be shown in a block diagram to avoid obscuring the example with unnecessary details. In other embodiments, well-known processes, structures, and techniques may not be shown in unnecessary detail to avoid obscuring the embodiments.

[0021] Embodiment 1: This embodiment provides a low voltage DC leakage protection device, such as Figure 1 As shown, it includes a current sampling circuit, a logic controller and a loop on-off controller, the logic controller is respectively connected to the current sampling circuit and the loop on-off controller, the current sampling circuit is used to sample the current of the DC positive loop and the DC negative loop respectively, obtain the positive loop current sampling signal and the negative loop current sampling signal, and obtain the current difference between the DC positive loop and the DC negative loop according to the positive loop current sampling signal and the negative loop current sampling signal, and transmit the current difference to the logic controller, the logic controller is used to compare the current difference with a preset leakage current threshold, and when the current difference is greater than or equal to the leakage current threshold, output a trigger signal to the loop on-off controller, the loop on-off controller is arranged in the DC positive loop and the DC negative loop, and is used to disconnect the DC positive loop and the DC negative loop after receiving the trigger signal.

[0022] In specific implementation, the DC circuit includes a DC positive circuit and a DC negative circuit. One end of the DC circuit is connected to a DC power supply, and the other end is connected to a load. A leakage current test button can be set in the DC circuit, and the leakage current test button can be pressed to perform leakage detection. When performing leakage detection, the DC positive circuit and the DC negative circuit can be sampled respectively through the current sampling circuit to obtain the positive circuit current sampling signal and the negative circuit current sampling signal, and then the current difference in1 between the DC positive circuit and the DC negative circuit is obtained according to the positive circuit current sampling signal and the negative circuit current sampling signal (if any electrode leaks to the ground, it will cause the circuit current to be unbalanced, and the current difference in1 is the leakage current value), and then the current difference is transmitted to the logic controller. The logic controller compares the current difference with the preset leakage current threshold. If the current difference is greater than or equal to the leakage current threshold, it indicates that leakage occurs in the DC circuit. At this time, the logic controller will output a trigger signal to the circuit on-off controller. The circuit on-off controller is arranged in the DC positive circuit and the DC negative circuit, between the DC power supply and the load. When the circuit on-off controller receives the trigger signal, it immediately disconnects the DC positive circuit and the DC negative circuit, cuts off the power supply between the DC power supply and the load, and achieves the purpose of leakage protection.

[0023] The current sampling circuit includes a current sensor, which collects the current difference between the positive and negative poles of the loop through a high-precision current sensor and converts it into an analog quantity for output. The logic controller includes a comparator, which can be used as follows Figure 2 The operational amplifier shown. The circuit on-off controller includes a DC vacuum contactor, which can open or close the circuit by controlling the on-off of the electromagnet, thereby realizing the circuit cutting and connecting functions.

[0024] Furthermore, the device also includes a leakage indication circuit and a signal output interface. The leakage indication circuit is connected to the logic controller, and is used to obtain a trigger signal from the logic controller, and to send leakage indication information according to the trigger signal. The leakage indication circuit includes an LED indicator light, through which a leakage indication light signal can be sent, and a buzzer can also be set in the leakage indication circuit to send a leakage indication sound signal through the buzzer. The signal output interface is connected to the logic controller, and is used to obtain a trigger signal from the logic controller, and output the trigger signal to an external device.

[0025] Furthermore, the device also includes a leakage current setting circuit, which is connected to the logic controller and is used to set the leakage current threshold and transmit the leakage current threshold to the logic controller. The leakage current setting circuit can set the leakage current threshold through a knob or switch according to demand. The leakage current threshold can be set to 30mA. The leakage current threshold is the current value that causes the leakage protector device to operate under specified conditions. If the current difference in1 reaches or equals 30mA, the protection device will be activated and the DC power supply will be disconnected. The rated leakage protection action time t of the protection device can be limited to t=0.1s. The rated leakage protection action time refers to the time from the sudden application of the leakage power-off protection action to the time when the protection circuit is cut off.

[0026] The working parameters of the low voltage DC leakage protection device can be set as: Applicable DC voltage range: DC100V~DC1000V. Rated working current: <1000A. Auxiliary control voltage: DC5V~DC48V. Leakage action current: 5mA-30mA. Leakage protection action time: 0.1S-0.3S. Signal output: switch signal output. Ambient temperature: -35℃~60℃. Ambient humidity: <98%.

[0027] Embodiment 2: This embodiment provides a low-voltage DC leakage protection method, which is applied to the low-voltage DC leakage protection device in Embodiment 1. The method includes the following steps: Current sampling is performed on the DC positive loop and the DC negative loop respectively to obtain a positive loop current sampling signal and a negative loop current sampling signal; The current difference between the DC positive loop and the DC negative loop is obtained according to the positive loop current sampling signal and the negative loop current sampling signal; The current difference is compared with a preset leakage current threshold, and when the current difference is greater than or equal to the leakage current threshold, the DC positive circuit and the DC negative circuit are disconnected.

[0028] Embodiment 3: This embodiment provides a logic controller, the logic controller comprising: Data interface, used to establish signal connection between the processor and the current sampling circuit and the loop on-off controller; A memory for storing instructions; The processor is used to read the instructions stored in the memory and implement the functions of the logic controller in Example 1 according to the instructions.

[0029] Optionally, the logic controller further includes an internal bus, through which the processor, the memory and the data interface can be interconnected, and the internal bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory can include, but is not limited to, a random access memory (Random Access Memory, RAM), a read-only memory (Read Only Memory, ROM), a flash memory (Flash Memory), a first-in first-out memory (First Input First Output, FIFO) and / or a first-in last-out memory (First In Last Out, FILO), etc. The processor may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0030] This embodiment also provides a readable storage medium, which stores instructions. When the instructions are executed on the logic controller, the logic controller implements the functions of the logic controller in Embodiment 1. The readable storage medium refers to a carrier for storing data, which may include but is not limited to a floppy disk, an optical disk, a hard disk, a flash memory, a USB flash drive and / or a memory stick, etc. The computer may be a general-purpose computer, a special-purpose computer, a computer network or other programmable device. This embodiment also provides a program product, which, when executed on the logic controller, implements the functions of the logic controller in Embodiment 1.

[0031] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low voltage DC leakage protection device, characterized in that: It includes a current sampling circuit, a logic controller and a loop on-off controller. The logic controller is connected to the current sampling circuit and the loop on-off controller respectively. The current sampling circuit is used to sample the current of the DC positive loop and the DC negative loop respectively to obtain the positive loop current sampling signal and the negative loop current sampling signal, and obtain the current difference between the DC positive loop and the DC negative loop according to the positive loop current sampling signal and the negative loop current sampling signal, and transmit the current difference to the logic controller. The logic controller is used to compare the current difference with a preset leakage current threshold, and when the current difference is greater than or equal to the leakage current threshold, output a trigger signal to the loop on-off controller. The loop on-off controller is arranged in the DC positive loop and the DC negative loop, and is used to disconnect the DC positive loop and the DC negative loop after receiving the trigger signal.

2. A low voltage DC leakage protection device according to claim 1, characterized in that: The device also includes a leakage indication circuit, which is connected to the logic controller and is used to obtain a trigger signal from the logic controller and send leakage indication information according to the trigger signal.

3. A low voltage DC leakage protection device according to claim 2, characterized in that: The leakage indication circuit includes an LED indicator light.

4. A low voltage DC leakage protection device according to claim 1, characterized in that: The device also includes a signal output interface, which is connected to the logic controller and is used to obtain a trigger signal from the logic controller and output the trigger signal to an external device.

5. A low voltage DC leakage protection device according to claim 1, characterized in that: The device further comprises a leakage current setting circuit, which is connected to the logic controller and is used for setting a leakage current threshold and transmitting the leakage current threshold to the logic controller.

6. A low voltage DC leakage protection device according to claim 5, characterized in that: The leakage current threshold is set to 30 mA.

7. A low voltage DC leakage protection device according to claim 1, characterized in that: The current sampling circuit includes a current sensor.

8. A low voltage DC leakage protection device according to claim 1, characterized in that: The logic controller includes a comparator, and the comparator adopts an operational amplifier.

9. A low voltage DC leakage protection device according to claim 1, characterized in that: The circuit on-off controller includes a DC vacuum contactor.

10. A low voltage DC leakage protection method, applied to the low voltage DC leakage protection device according to any one of claims 1 to 9, characterized in that: include: Current sampling is performed on the DC positive loop and the DC negative loop respectively to obtain a positive loop current sampling signal and a negative loop current sampling signal; The current difference between the DC positive loop and the DC negative loop is obtained according to the positive loop current sampling signal and the negative loop current sampling signal; The current difference is compared with a preset leakage current threshold, and when the current difference is greater than or equal to the leakage current threshold, the DC positive circuit and the DC negative circuit are disconnected.

Images