A leakage current detection circuit, detection system and detection method

Abstract

The present invention provides a leakage current detection circuit, a detection system and a detection method. The leakage current detection circuit includes an input power supply and an RCMU, wherein the input power supply has at least two input power lines, and each of the input power lines is connected in series with a shunt system, and the shunt ratios of the input power lines by the shunt systems are equal; the RCMU is used to measure the sum of the leakage currents of all the shunt systems, which solves the problem that the existing leakage current detection requires connecting multiple leakage protectors in parallel, resulting in increased production costs and inability to accurately detect leakage current. A large current shunt method is used to reduce the detection current, and the structure is simple and easy to install.

Description

Technical Field

[0001] The present invention relates to the technical field of leakage current detection, and in particular to a leakage current detection circuit, a detection system and a detection method applied to high-power equipment. Background Art

[0002] With the development of the electric vehicle industry, the power requirements of charging piles on the market are getting higher and higher, and the input and output currents are also increasing accordingly. In particular, three-phase input power requires the use of four power input lines. As the input current increases, the wire cross-sectional area increases. Therefore, a larger current transformer is required when detecting leakage current. However, the magnetic core used in the current transformer is limited by size and does not have a large enough winding window area, resulting in a large input current wire diameter that cannot be burned, so large currents cannot be detected. The traditional solution is to connect multiple traditional leakage protectors in parallel. Installing multiple traditional leakage protectors increases production costs and cannot accurately detect leakage current. Summary of the invention

[0003] The present invention discloses a leakage current detection circuit, a detection system and a detection method, which solve the problem that the existing leakage current detection requires connecting multiple leakage protectors in parallel, resulting in increased production costs and an inability to accurately detect the leakage current. A large current shunt method is used to reduce the detection current, and the structure is simple and easy to install.

[0004] To achieve the above object, the technical solution of the present invention is specifically implemented as follows:

[0005] On one hand, the present invention discloses a leakage current detection circuit, including an input power supply and an RCMU, wherein the input power supply has at least two input power lines, and each of the input power lines is connected in series with a shunt system, and the resistance current value ratio of the shunt system to the input power line is equal; the RCMU is used to measure the sum of the leakage currents of all the shunt systems.

[0006] Furthermore, the current shunt system includes a first current shunt device and a second current shunt device, the first current shunt device is connected in series to the input power line, and the second current shunt device is connected in parallel to the first current shunt device.

[0007] Furthermore, the first shunting device is a resistor.

[0008] Furthermore, the second current dividing device is a resistor.

[0009] Furthermore, the current resistance value of the second shunt device is n times the current resistance value of the first shunt device, and n>0.

[0010] Another aspect of the present invention discloses a detection system, comprising a leakage current detection circuit as described above.

[0011] Furthermore, the detection system also includes a control unit and a relay, wherein the control unit is used to receive the signal sent by the RCNU and control the relay; the relay is used to receive the control signal of the control unit and connect or disconnect the circuit according to the control signal.

[0012] In another aspect, the present invention discloses a leakage current detection method, comprising the following steps:

[0013] Set the standard leakage current value;

[0014] RCMU measures the leakage current value I' of the shunt system PE , and sent to the control unit;

[0015] The control unit receives the signal sent by the RCMU and calculates the actual leakage current value I PE ;

[0016] Compare the actual leakage current value with the set standard leakage current value;

[0017] If the actual leakage current value is greater than the standard leakage current value, the control unit controls the relay to disconnect the circuit.

[0018] Furthermore, the actual leakage current value I PE The calculation method is:

[0019] I PE =(n+1)I′ PE

[0020] Among them, I PE is the actual leakage current value, I′ PE is the leakage current value measured by RCMU, and n is the resistance proportionality coefficient.

[0021] Beneficial technical effects:

[0022] 1. The present invention discloses a leakage current detection circuit, which includes an input power supply and an RCMU, wherein the input power supply has at least two input power lines, and each of the input power lines is connected in series with a shunt system, and the shunt system has an equal resistance current value ratio to the input power line; the RCMU is used to measure the sum of the leakage currents of all the shunt systems, which solves the problem that the existing leakage current detection requires multiple leakage protectors to be connected in parallel, resulting in increased production costs and inability to accurately detect leakage current. A large current shunt method is used to reduce the detection current, and the structure is simple and easy to install;

[0023] 2. In the present invention, the shunt system is connected in series with the input power line, and the series installation is convenient for modification and has low cost;

[0024] 3. In the present invention, the RCMU only needs to measure the sum of the leakage currents in the shunt system to obtain the actual leakage current, and only needs to detect a small leakage current so that the size of the current transformer can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0026] Figure 1 A leakage current detection circuit according to the first embodiment of the present invention;

[0027] Figure 2 A leakage current detection circuit according to the second embodiment of the present invention;

[0028] Figure 3 The present invention is a flow chart of a leakage current detection method. DETAILED DESCRIPTION

[0029] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0030] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0031] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] On one hand, the present invention discloses a leakage current detection circuit, which includes an input power supply and an RCMU, wherein the input power supply has at least two input power lines, and each of the input power lines is connected in series with a shunt system, and the shunt system has an equal ratio of resistance to current value to the input power line; and the RCMU is used to measure the sum of the leakage currents of all the shunt systems.

[0034] As a preferred embodiment of the present invention, the shunt system includes a first shunt device and a second shunt device, the first shunt device is connected in series to the input power line, and the second shunt device is connected in parallel to the first shunt device. Preferably, the first shunt device is a resistor, and the second shunt device is also a resistor. Of course, the shunt device is not limited to a resistor, as long as the voltage at both ends of the shunt system can be made equal (the ratio of resistance to current value is the same), the resistance current value of the second shunt device is n times the resistance current value of the first shunt device, and n>0.

[0035] Embodiment 1:

[0036] This embodiment takes a single-phase input power supply as an example. Figure 1 The single-phase input power supply includes two input power lines, an incoming line L and an incoming line N. The first input power line, that is, the incoming line L, is connected in series with a first shunt system, and the second input power line, that is, the incoming line N, is connected in series with a second shunt system. The shunt ratio of the first shunt system to the incoming line L is equal to the shunt ratio of the second shunt system to the incoming line N. The first shunt system includes a resistor R1 and a resistor R3. The resistor R1 is connected in series with the incoming line L, and the resistor R3 is connected in parallel with the resistor R1. The second shunt system includes a resistor R2 and a resistor R4. The resistor R2 is connected in series with the incoming line N, and the resistor R4 is connected in parallel with the resistor R2. The resistors satisfy the relationship:

[0037] R3=R4=nR1=nR2

[0038] That is, the resistance value of the resistor R1 connected in series with the incoming line L is equal to the resistance value of the resistor R2 connected in series with the incoming line N, and the resistance value of the resistor R3 connected in parallel with the resistor R1 is equal to the resistance value of the resistor R4 connected in parallel with the resistor R2, and the resistance value of the resistor R3 and the resistance value of the resistor R4 are n times the resistance value of the resistor R1 and the resistance value of the resistor R2 respectively, and n>0.

[0039] RCMU detects leakage current I' PE , and I′ PE =I R3 +I R4 ;

[0040] Actual leakage current:

[0041] I PE =I L +I N

[0042] =I R1 +I R2 +I R3 +I R4

[0043] And because:

[0044] R3=R4=nR1=nR2

[0045] That is:

[0046] I R1 =nI R3

[0047] I R2 =nI R4

[0048] Therefore, the actual leakage current can be obtained:

[0049] I PE =(n+1)I′ PE

[0050] That is, the actual leakage current value can be obtained by multiplying the leakage current measured by RCMU by the resistance coefficient.

[0051] Embodiment 2:

[0052] This embodiment takes a three-phase input power supply as an example. Figure 2 The three-phase input power supply includes four input power lines: an incoming line L1, an incoming line L2, an incoming line L3 and an incoming line N. The first input power line, i.e., the incoming line L1, is connected in series with a first shunt system. The second input power line, i.e., the incoming line N, is connected in series with a second shunt system. The third input power line, i.e., the incoming line L3, is connected in series with a third shunt system. The fourth input power line, i.e., the incoming line L3, is connected in series with a fourth shunt system. The shunt ratio of the first shunt system to the incoming line L1, the shunt ratio of the second shunt system to the incoming line N, the shunt ratio of the third shunt system to the incoming line L3 and the shunt ratio of the fourth shunt system to the incoming line The shunt ratios of L3 are all equal. The first shunt system includes resistors R1 and R8. Resistor R1 is connected in series with the incoming line L1, and resistor R8 is connected in parallel with resistor R1. The second shunt system includes resistors R2 and R7. Resistor R2 is connected in series with the incoming line N, and resistor R7 is connected in parallel with resistor R2. The third shunt system includes resistors R3 and R6. Resistor R3 is connected in series with the incoming line L2, and resistor R6 is connected in parallel with resistor R3. The fourth shunt system includes resistors R4 and R5. Resistor R4 is connected in series with the incoming line L3, and resistor R5 is connected in parallel with resistor R4. The resistors satisfy the following relationship:

[0053] R8=R7=R6=R5=nR1=nR2=nR3=nR4

[0054] That is, the resistance value of the resistor R1 connected in series with the incoming line L1, the resistance value of the resistor R2 connected in series with the incoming line N, the resistance value of the resistor R3 connected in series with the incoming line L2, and the resistance value of the resistor R4 connected in series with the incoming line L3 are all equal, and the resistance value of the resistor R8 connected in parallel with the resistor R1, the resistance value of the resistor R7 connected in parallel with the resistor R2, the resistance value of the resistor R6 connected in parallel with the resistor R3, and the resistance value of the resistor R5 connected in parallel with the resistor R4 are all equal, and the resistance value of the resistor R8, the resistance value of the resistor R7, the resistance value of the resistor R6, and the resistance value of the resistor R5 are n times the resistance value of the resistor R1, the resistance value of the resistor R2, the resistance value of the resistor R3, and the resistance value of the resistor R4, respectively, and n>0.

[0055] RCMU detects leakage current I' PE , and I′ PE =I R5 +I R6 +I R7 +I R8 ;

[0056] Actual leakage current:

[0057] I PE =I L1 +I N +I L2 +I L3

[0058] =I R1 +I R2 +I R3 +I R4 +I R5 +I R6 +I R7 +I R8

[0059] And because:

[0060] R8=R7=R6=R5=nR1=nR2=nR3=nR4

[0061] That is:

[0062] I R1 =nI R8

[0063] I R2 =nI R7

[0064] I R3 =nI R6

[0065] I R4 =nI R5

[0066] Therefore, the actual leakage current can be obtained:

[0067] I PE =(n+1)I′ PE

[0068] That is, the actual leakage current value can be obtained by multiplying the leakage current measured by RCMU by the resistance coefficient.

[0069] On the other hand, the present invention discloses a detection system, which includes the leakage current detection circuit as described above, and also includes a control unit and a relay. The control unit is used to receive the signal sent by the RCNU and control the relay. Preferably, the control unit includes a charging pile end controller; the relay is used to receive the control signal of the control unit and connect or disconnect the circuit according to the control signal.

[0070] Another aspect of the present invention discloses a leakage current detection method. Figure 3 , specifically including the following steps: S1: setting the standard leakage current value; S2: RCMU measuring the leakage current value I' of the shunt system PE , and sends it to the control unit; S3: The control unit receives the signal sent by the RCMU and calculates the actual leakage current value I PE ; S4: Compare the actual leakage current value with the set standard leakage current value; S5: If the actual leakage current value is greater than the standard leakage current value, the control unit controls the relay to disconnect the circuit.

[0071] The working principle of the detection system disclosed in the present invention is:

[0072] When in use, first set a standard leakage current, and RCMU measures the leakage current value I' of the shunt system. PE The leakage current value is sent to the control unit through the communication signal, and the control unit receives the leakage current value I′ sent by RCMU. PE Calculate the actual leakage current value I PE =(n+1)I′ PE The actual leakage current value is compared with the standard leakage current value. If the actual leakage current value is greater than the standard leakage current value, the control unit controls the relay to disconnect the circuit, which solves the problem that the existing leakage current detection requires multiple leakage protectors to be connected in parallel, resulting in increased production costs and inability to accurately detect leakage current. A large current shunt method is used to reduce the detection current, and the structure is simple and easy to install.

[0073] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0074] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0075] The above embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A leakage current detection circuit, It is characterized in that include: An input power supply, wherein the input power supply has at least two input power lines, and each of the input power lines is connected in series with a shunt system, and the shunt system has an equal ratio of resistance to current of the input power lines; RCMU, for measuring the sum of leakage currents of all the shunt systems; The current shunting system comprises a first current shunting device and a second current shunting device, the first current shunting device is connected in series on the input power line, and the second current shunting device is connected in parallel with the first current shunting device; The first current dividing device is a resistor; The second current dividing device is a resistor; The current resistance value of the second shunt device is n times the current resistance value of the first shunt device, and n>0.

2. A detection system, It is characterized in that The invention comprises a leakage current detection circuit as claimed in claim 1.

3. A detection system according to claim 2, It is characterized in that Also includes: A control unit, for receiving a signal sent by the RCMU and controlling a relay; The relay is used to receive the control signal of the control unit and connect or disconnect the circuit according to the control signal.

4. A leakage current detection method of the detection system as claimed in claim 3, It is characterized in that The following steps are involved: Set the standard leakage current value; RCMU measures the leakage current value I' of the shunt system PE , and sent to the control unit; The control unit receives the signal sent by the RCMU and calculates the actual leakage current value I PE ; Compare the actual leakage current value with the set standard leakage current value; If the actual leakage current value is greater than the standard leakage current value, the control unit controls the relay to disconnect the circuit.

5. A leakage current detection method according to claim 4, It is characterized in that The actual leakage current value I PE The calculation method is: I PE =(n+1)I′ PE Among them, I PE is the actual leakage current value, I′ PE is the leakage current value measured by RCMU, and n is the resistance proportionality coefficient.

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