Circuit for detecting leakage current of three-phase circuit
By combining hardware and software, and using current transformers and high-precision sampling resistors or Rogowski coils to detect leakage current in three-phase circuits, the problem of high-precision leakage current detection in existing technologies has been solved. This achieves high-precision and flexible detection across the entire current range and reduces hardware costs.
Patent Information
- Application Number
- CN202520080989.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-14
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2035-01-14
AI Technical Summary
Existing technologies struggle to achieve high-precision leakage current detection in industrial applications, ranging from tens of milliamperes to tens of amperes, especially in situations requiring high sensitivity and wide dynamic range. Multi-level hardware protection mechanisms also have limitations.
Using a combination of hardware and software, the voltage signals corresponding to the leakage current of the three-phase circuit are measured by the first and second measurement circuits respectively. The controller calculates the leakage current and uses a current transformer and a high-precision low-temperature drift sampling resistor or Rogowski coil for detection. This enables switching between small and large current ranges and adaptive range to ensure detection accuracy across the entire current range.
It achieves high-precision leakage current detection across the entire current range, reducing hardware space and cost, and improving the flexibility and accuracy of detection.
Smart Images
Figure CN223955779U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to an electrical device, especially to a circuit for detecting leakage current of a three-phase circuit. BACKGROUND
[0002] In industrial applications and power distribution industries, leakage current protection is one of the key measures to ensure safety. Different application scenarios and protection purposes require setting different leakage current protection thresholds. For example, in order to protect personal safety, the leakage current is generally required to be less than 30mA; in the application of charging piles, the leakage current should be less than 100mA; and in the application of motors, the value of leakage current may reach dozens of amperes. However, it is very difficult to use a single hardware circuit to achieve high-precision leakage detection in the range from tens of milliamperes to dozens of amperes.
[0003] Under normal circumstances, professional leakage protection products will adopt multi-level hardware leakage position protection to adapt to different detection requirements and protection levels. Although this multi-level protection mechanism can solve the problem to some extent, it still has limitations in actual application, especially in situations requiring high sensitivity and wide dynamic range. Therefore, developing a software and hardware combined method to detect leakage current in a three-phase system to improve the accuracy and flexibility of detection has become an important research direction. SUMMARY
[0004] The utility model provides a kind of circuit for detecting leakage current of three-phase circuit, it is characterized in that, the circuit includes: first measurement circuit, it is connected to three-phase circuit, and it is configured as the first voltage signal corresponding to the leakage current of three-phase circuit is measured;Second measurement circuit, it is connected to three-phase circuit, and it is configured as the second voltage signal corresponding to the leakage current of each phase line of three-phase circuit is measured respectively;And controller, it is configured as first voltage signal and second voltage signal are received from first measurement circuit and second measurement circuit respectively, and the leakage current of three-phase circuit is detected.
[0005] According to the embodiment of the utility model, the controller is further configured to calculate a first leakage current based on the received first voltage signal and a second leakage current based on the received second voltage signal, and determine a third leakage current based on the calculated first leakage current and second leakage current to detect the leakage current of the three-phase circuit.
[0006] According to the embodiment of the utility model, the first leakage current corresponds to a small current range leakage current detected by the first measurement circuit; and the second leakage current is a vector sum of three-phase currents of the three-phase circuit calculated based on the second voltage signal, corresponding to a large current range leakage current.
[0007] According to the embodiment of the present application, the controller is configured to: compare the calculated first leakage current and second leakage current with a threshold leakage current, determine the second leakage current as the third leakage current when the first leakage current and the second leakage current are both greater than the threshold leakage current, and determine the first leakage current as the third leakage current when at least one of the first leakage current and the second leakage current is not greater than the threshold leakage current.
[0008] According to the embodiment of the present application, the first measurement circuit includes a current transformer and an operational amplifier, wherein the current transformer is configured to be connected to the three-phase circuit and collect a voltage signal corresponding to the leakage current of the three-phase circuit, and wherein the operational amplifier samples and amplifies the collected voltage signal corresponding to the leakage current of the three-phase circuit.
[0009] According to the embodiment of the present application, the current transformer is a zero-sequence current transformer.
[0010] According to the embodiment of the present application, the first voltage signal is proportional to the first leakage current.
[0011] According to the embodiment of the present application, the second measurement circuit includes a plurality of sampling resistors, and the plurality of sampling resistors are configured to be respectively connected to corresponding phase lines in the three-phase circuit.
[0012] According to the embodiment of the present application, the second measurement circuit is configured to measure the voltage across each of the plurality of sampling resistors as a second voltage signal.
[0013] According to the embodiment of the present application, the plurality of sampling resistors are high-precision low-temperature-drift sampling resistors.
[0014] According to the embodiment of the present application, the second measurement circuit includes a plurality of Rogowski coils, and the plurality of Rogowski coils are configured to measure the second voltage signal corresponding to the leakage current of each phase line of the three-phase circuit.
[0015] In the present application, the circuit for detecting the leakage current of the three-phase circuit can realize the use of a current transformer to detect the leakage current in a small current range, and switch to a three-phase vector sum to calculate the leakage current in a large current range, thereby ensuring the detection accuracy of the leakage current in the full current range through adaptive range, and reducing the hardware space and cost. BRIEF DESCRIPTION OF DRAWINGS
[0016] The above and other aspects, features, and advantages of certain embodiments of the present application will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
[0017] Figure 1 is a principle block diagram showing the circuit for detecting the leakage current of the three-phase circuit provided by the embodiment of the present application;
[0018] Figure 2 is a schematic structural diagram illustrating an implementation manner of the circuit for detecting leakage current of a three-phase circuit provided by an embodiment of the utility model;
[0019] Figure 3A is a simulation circuit diagram of the first measurement circuit for detecting leakage current of a three-phase circuit provided by an embodiment of the utility model;
[0020] Figure 3B is a simulation waveform diagram of the first measurement circuit for detecting leakage current of a three-phase circuit provided by an embodiment of the utility model;
[0021] Figure 4A is a simulation circuit diagram of the second measurement circuit for detecting leakage current of a three-phase circuit provided by an embodiment of the utility model;
[0022] Figure 4B is a simulation waveform diagram of the second measurement circuit for detecting leakage current of a three-phase circuit provided by an embodiment of the utility model. DETAILED DESCRIPTION
[0023] Before undertaking the below detailed description, it can be advantageous to set forth definitions of certain words and phrases used throughout this utility model. The terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation. The term "or" is used in the inclusive sense of "and / or" unless it is specifically indicated otherwise. The term "controller" or "control unit" means any device, system or part thereof that controls at least one operation. Such a controller can be implemented in hardware or a combination of hardware and software and / or firmware. For example, a controller can include an application specific integrated circuit (ASIC), a general or special purpose central processing unit (CPU), a digital signal processor (DSP), and a programmable logic device, such as a field programmable gate array (FPGA). A controller can be fabricated as a single printed circuit board (PCB) or distributed among several interconnected PCBs. A controller can contain other processing circuitry, for example, a controller can include two processing circuits such as an FPGA and a CPU interconnected on a PCB. The functions associated with any particular controller can be centralized or distributed, whether locally or remotely. The phrase "at least one of," when used with respect to a list of items, means that different combinations of one or more of the listed items can be used and only one item from the list can be needed. For example, "at least one of A, B, and C" includes any one or any combination of A, B, or C. Also, in the description of the utility model, the terms "first", "second", etc. are used only to distinguish descriptions, and cannot be understood as indicating or implying relative importance or sequence. In the embodiments of the disclosure, unless otherwise explicitly stated, "connection" does not mean "direct connection" or "direct contact", but only requires electrical connection.
[0024] Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.
[0025] The principles of the present application described in the various embodiments herein and illustrated in the accompanying drawings are presented for the purpose of illustration and description only. Those of ordinary skill in the art will understand that the principles of the present application can be implemented in any suitably arranged system or device. In some instances, the actions described herein can be performed in a different order and still achieve desirable results. Additionally, the processes depicted in the figures do not necessarily require the particular order illustrated, or sequential order, to achieve the desired results. In certain implementations, multitasking and parallel processing can be advantageous.
[0026] The text and drawings are provided only as examples to assist in understanding the present application. They should not be construed as limiting the scope of the claims appended hereto. While certain embodiments and examples have been provided, those skilled in the art will understand that modifications can be made without departing from the scope of the present application.
[0027] Figure 1 is a principle block diagram illustrating a circuit for detecting leakage current of a three-phase circuit provided by an embodiment of the present application.
[0028] Reference Figure 1 The circuit 100 for detecting leakage current of the three-phase circuit 200 can include a first measurement circuit 110, a second measurement circuit 120, and a controller 130.
[0029] The first measurement circuit 110 can be connected to the three-phase circuit 200, and can be configured to measure a first voltage signal corresponding to the leakage current of the three-phase circuit. The first voltage signal can be a single-ended voltage signal proportional to the leakage current of the three-phase circuit.
[0030] In some embodiments, the first measurement circuit 110 can further include a current transformer and an operational amplifier. In some embodiments, the current transformer can be configured to be connected to the three-phase circuit 200, and to collect a voltage signal corresponding to the leakage current of the three-phase circuit. In some embodiments, the operational amplifier can sample and amplify the collected voltage signal corresponding to the leakage current of the three-phase circuit. The specific schematic structure of the first measurement circuit 110 including the current transformer and the operational amplifier is shown in subsequent Figure 3A
[0031] In some embodiments, the current transformer in the first measurement circuit 110 can be a zero sequence current transformer. Each phase line of the three-phase circuit can be connected to a zero sequence current transformer, so that the zero sequence current transformer can detect the vector sum of the three-phase current.
[0032] In some embodiments, the first measurement circuit 110 including the current transformer is used to measure the leakage current of a small current range (e.g., tens of milliamperes), and therefore the current transformer can be implemented with a small volume. Further, when detecting the leakage current of the small current range by using the current transformer, a detection accuracy of ±1% can be achieved after calibration.
[0033] The second measurement circuit 120 can be connected to the three-phase circuit 200 and can be configured to measure second voltage signals corresponding to the leakage currents of each phase line of the three-phase circuit, respectively. The second voltage signals can include respective voltage signals corresponding to the leakage currents of each phase line of the three-phase circuit, respectively.
[0034] In some embodiments, the second measurement circuit 120 can include a plurality of sampling resistors, and the plurality of sampling resistors can be configured to be connected to corresponding phase lines in the three-phase circuit, respectively. In some embodiments, the second measurement circuit 120 can be configured to measure the voltage across each of the plurality of sampling resistors as the second voltage signals, respectively. The specific schematic structure of the second measurement circuit 120 is shown in subsequent Figure 4A
[0035] In some embodiments, the plurality of sampling resistors in the second measurement circuit 120 can be high-precision low-temperature drift sampling resistors.
[0036] In some embodiments, the second measurement circuit 120 can include a plurality of Rogowski coils, which can be configured to measure voltage signals corresponding to the leakage currents of each phase line of the three-phase circuit as the second voltage signals, respectively.
[0037] Further, when the second measurement circuit 120 detects the leakage current of the large current range by vector sum calculation, a detection accuracy of ±1% can be achieved after calibration.
[0038] The controller 130 can be configured to receive the first voltage signals and the second voltage signals from the first measurement circuit 110 and the second measurement circuit 120, respectively, and calculate the first leakage current based on the received first voltage signals and the second leakage current based on the received second voltage signals. Further, the controller 130 can be configured to determine the third leakage current based on the calculated first leakage current and the second leakage current to detect the leakage current of the three-phase circuit.
[0039] In some embodiments, the first leakage current may correspond to the low-current leakage current detected by the first measuring circuit. In some embodiments, the second leakage current may be the vector sum of the three-phase currents of the three-phase circuit calculated based on the second voltage signal, and may correspond to the high-current leakage current. Specific waveforms of the first and second leakage currents will be described later. Figure 3B and Figure 4B As shown in the image.
[0040] In some embodiments, the process by which the controller 130 determines a third leakage current based on the calculated first and second leakage currents may include: comparing the calculated first and second leakage currents with a threshold leakage current; determining the second leakage current as the third leakage current when both the first and second leakage currents are greater than the threshold leakage current; and determining the first leakage current as the third leakage current when at least one of the first and second leakage currents is not greater than the threshold leakage current. In some embodiments, the threshold leakage current may be a value preset according to actual industrial applications and equipment limitations. For example, in some embodiments, the threshold leakage current may be 3.3 A. Here, "greater than" means within a certain tolerance range compared to the threshold leakage current, rather than strictly greater than the threshold leakage current.
[0041] pass Figure 1 The circuit 100 shown in the diagram for detecting leakage current in a three-phase circuit can realize software monitoring of hardware leakage current and calculation of leakage current through current vector summation, and automatically switch leakage current range to adaptively adapt the range to ensure the detection accuracy of leakage current in the full current range, while reducing hardware space and cost.
[0042] Figure 2 This is a schematic structural diagram illustrating the implementation of a circuit for detecting leakage current in a three-phase circuit according to an embodiment of the present invention.
[0043] refer to Figure 2 The circuit 100' for detecting leakage current in the three-phase circuit 200 may include a first measuring circuit 110, a second measuring circuit 120, and a controller 130. L1, L2, and L3 correspond to the respective phase lines of the three-phase circuit 200. Figure 2 In China, the adoption of and Figure 1 The same reference mark in the reference mark to indicate the same reference mark as in the reference mark ... Figure 1 The same or similar elements.
[0044] The first measurement circuit 110 may include a current transformer 111 and an operational amplifier (not shown). Figure 2 As shown, the current transformer 111 can be configured to connect to each phase line L1, L2, L3 of the three-phase circuit 200 and acquire voltage signals corresponding to the leakage current of the three-phase circuit.
[0045] The second measurement circuit 120 can include sampling resistors R1, R2, R3. As shown in Figure 2 , the sampling resistors R1, R2, R3 can be configured to be connected to corresponding phase lines in the three-phase circuit respectively. The second measurement circuit 120 can be configured to measure the voltage across each of the sampling resistors R1, R2, R3 respectively as a second voltage signal. In some embodiments, the sampling resistors R1, R2, R3 can be high-precision low-temperature drift sampling resistors.
[0046] Figure 3A is a simulation circuit diagram illustrating the first measurement circuit for detecting the leakage current of the three-phase circuit provided by the embodiments of the present application.
[0047] Referring to Figure 3A , the part shown by the dashed box in the figure can be the first measurement circuit, and I1 shown in the figure can be the simulated leakage current. Among them, the part shown by the solid box in the figure can be a current transformer. The output waveform of the simulation circuit of the first measurement circuit is as shown in Figure 3B .
[0048] Figure 3B is a simulation waveform diagram illustrating the first measurement circuit for detecting the leakage current of the three-phase circuit provided by the embodiments of the present application.
[0049] Referring to Figure 3B , the first waveform 301 shown in the figure can be the waveform of the simulated leakage current I1 as shown in Figure 3A . The simulated leakage current I1 can be a sinusoidal 3.3 ARMS (effective value of alternating current) leakage current. The second waveform 302 shown in the figure can be the current at the secondary side of the current transformer as shown in Figure 3A . The third waveform 303 shown in the figure can be a single-ended voltage signal proportional to the leakage current of the three-phase circuit after sampling and amplification processing.
[0050] The voltage signal corresponding to the third waveform 303 shown in Figure 3B may be the first voltage signal received by the controller. Since the first voltage signal is proportional to the leakage current of the three-phase circuit, the controller can calculate the first leakage current based on the received first voltage signal.
[0051] Figure 4A is a simulation circuit diagram illustrating the second measurement circuit for detecting the leakage current of the three-phase circuit provided by the embodiments of the present application.
[0052] Referring to Figure 4AIn the diagram, L1, L2, and L3 correspond to the respective phase lines of the three-phase circuit, and R1, R2, and R3 are sampling resistors connected to the corresponding phase lines in the three-phase circuit. Rload1, Rload2, and Rload3 represent the load resistors in the three-phase circuit, and Rleak simulates the leakage resistance caused by leakage current in phase line L3. The output waveform of the simulation circuit of this second measurement circuit is shown below. Figure 4B As shown in the image.
[0053] Figure 4B This is a simulation waveform diagram showing the second measuring circuit for detecting leakage current in a three-phase circuit provided in an embodiment of the present invention.
[0054] refer to Figure 4B The first waveform 401 shown in the figure can be flowing through Figure 4A The diagram shows the current waveforms of sampling resistors R1, R2, and R3. Waveform 401-1 represents the current flowing through sampling resistor R1 in phase L1 of the three-phase circuit; waveform 401-2 represents the current flowing through sampling resistor R1 in phase L2; and waveform 401-3 represents the current flowing through sampling resistor R1 in phase L3. Due to leakage current in phase L3, the amplitude of waveform 401-3 is significantly greater than that of waveforms 401-1 and 401-2. The current in each phase of the three-phase circuit can be calculated by the controller based on the second voltage signal received from the second measurement circuit.
[0055] The second waveform 402 shown in the figure can be the vector sum of the three-phase currents of the three-phase circuit calculated by the controller, that is, the vector sum of the currents of each phase line in the three-phase circuit corresponding to waveforms 401-1, 401-2 and 401-3 respectively.
[0056] The third waveform 403 shown in the figure can be a flow through Figure 4A The simulated leakage current of Rleak is shown. According to... Figure 4B As shown, flowing through Figure 4A The third waveform 403 of the simulated Rleak leakage current shown is the same as the waveform of the vector sum of the three-phase currents in the calculated three-phase circuit. Therefore, leakage current detection at high current levels can be achieved through vector sum calculation.
[0057] In some embodiments, the present invention also provides an electronic device, which includes a load circuit and a circuit for detecting leakage current in a three-phase circuit. The circuit for detecting leakage current in the three-phase circuit is connected to the load circuit to detect leakage current in the circuit.
[0058] As described above, the circuit for detecting the leakage current of the three-phase circuit includes: a first measurement circuit connected to the three-phase circuit and configured to measure a first voltage signal corresponding to the leakage current of the three-phase circuit; a second measurement circuit connected to the three-phase circuit and configured to measure a second voltage signal corresponding to the leakage current of each phase line of the three-phase circuit, respectively; and a controller configured to receive the first voltage signal and the second voltage signal from the first measurement circuit and the second measurement circuit, respectively, and detect the leakage current of the three-phase circuit.
[0059] Although the present application has been described with an example embodiment, various changes and modifications can be suggested to one skilled in the art. It is intended that the present application cover the modifications and changes as fall within the scope of the appended claims.
[0060] No description in the present application should be interpreted as implying any particular element, step or function is an essential element that must be included in the scope of the claims. The scope of the patent subject matter is only limited by the claims.
Claims
1. A circuit for detecting leakage current in a three-phase circuit, characterized by The circuit comprises: a first measurement circuit connected to the three-phase circuit and configured to measure a first voltage signal corresponding to a leakage current of the three-phase circuit; a second measurement circuit connected to the three-phase circuit and configured to measure a second voltage signal corresponding to a leakage current of each phase line of the three-phase circuit, respectively; and a controller configured to receive the first voltage signal and the second voltage signal from the first measurement circuit and the second measurement circuit, respectively, and detect the leakage current of the three-phase circuit.
2. The circuit of claim 1, wherein, The controller is further configured to calculate a first leakage current based on the received first voltage signal and a second leakage current based on the received second voltage signal, and determine a third leakage current based on the calculated first leakage current and the second leakage current, to detect the leakage current of the three-phase circuit.
3. The circuit of claim 2, wherein the first leakage current corresponds to a small current range leakage current detected by the first measurement circuit; and the second leakage current is a vector sum of three-phase currents of the three-phase circuit calculated based on the second voltage signal, corresponding to a large current range leakage current.
4. The circuit of claim 2, wherein, The controller is configured to: compare the calculated first leakage current and the second leakage current with a threshold leakage current, when both the first leakage current and the second leakage current are greater than the threshold leakage current, determine the second leakage current as the third leakage current, and when at least one of the first leakage current and the second leakage current is not greater than the threshold leakage current, determine the first leakage current as the third leakage current.
5. The circuit of claim 1, wherein, The first measurement circuit comprises a current transformer and an operational amplifier, wherein the current transformer is configured to be connected to the three-phase circuit and collect a voltage signal corresponding to the leakage current of the three-phase circuit, and wherein the operational amplifier is configured to sample and amplify the collected voltage signal corresponding to the leakage current of the three-phase circuit.
6. The circuit of claim 5, wherein, The current transformer is a zero sequence current transformer.
7. The circuit of claim 2, wherein, The first voltage signal is proportional to the first leakage current.
8. The circuit of claim 1, wherein, The second measurement circuit comprises a plurality of sampling resistors configured to be connected to corresponding phase lines in the three-phase circuit, respectively.
9. The circuit of claim 8, wherein, The second measurement circuit is configured to measure a voltage across each of the plurality of sampling resistors as the second voltage signal, respectively.
10. The circuit of claim 8, wherein, The plurality of sampling resistors are high-precision low-temperature drift sampling resistors.
11. The circuit of claim 1, wherein, The second measurement circuit comprises a plurality of Rogowski coils configured to measure the second voltage signal corresponding to the leakage current of each phase line of the three-phase circuit, respectively.