Leakage protection self-checking circuit

Abstract

An electric leakage protection self-checking circuit relates to the technical field of electric leakage detection and comprises a three-phase input circuit, a single-chip microcomputer and a zero sequence current transformer, the three-phase input circuit is connected with the single-chip microcomputer, the single-chip microcomputer is used for detecting voltage change of the three-phase input circuit, and the zero sequence current transformer is connected with the single-chip microcomputer. The zero-sequence current transformer is used for sensing zero-sequence current in the three-phase input circuit, and the zero-sequence current transformer is electrically connected with the single-chip microcomputer. Whether the electric leakage protection device works normally or not is judged through superposition of the zero sequence current transformer and the voltage, misjudgment caused by a single signal can be avoided, and judgment on whether the electric leakage protection device acts or not is more accurate and reliable.

Description

Technical Field

[0001] The utility model relates to the technical field of leakage detection, in particular to a leakage protection self-detection circuit. Background Art

[0002] The underground space in coal mines is small, hot and humid, and power leakage is prone to occur. Leakage will not only cause electric shock to people, but also develop into a phase-to-phase short circuit and cause a gas explosion. Therefore, the power supply must be disconnected in time when a leakage fault occurs. Leakage protection devices have become an important guarantee for continuous and reliable power supply in coal mines. In order to ensure that the leakage protection device of the underground switch can operate reliably, the "Coal Mine Safety Regulations" clearly stipulates that the low-voltage leakage protection must be tripped once a day and a remote leakage test must be performed every month. For example, Chinese patent CN115825713A discloses a leakage test device and method suitable for underground feeder switches in coal mines, which can detect whether the protection action of the feeder switch is sensitive and reliable when cables at different positions are leaking or when electrical equipment is leaking without approaching the feeder switch.

[0003] However, the traditional leakage test method generally only performs a leakage test on the switch itself, and cannot determine whether the leakage protection device at the end of the power supply line is activated.

[0004] Therefore, it is urgent to develop a leakage protection self-detection circuit to solve the problems in the prior art. Utility Model Content

[0005] The purpose of the utility model is to provide a leakage protection self-test circuit, which can determine whether its performance indicators are abnormal when the leakage protection device performs leakage detection action, so as to solve the problem that the traditional leakage test method proposed in the above background technology cannot determine whether the leakage protection device is activated.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] A leakage protection self-check circuit comprises a three-phase input circuit, a single-chip microcomputer and a zero-sequence current transformer, wherein the three-phase input circuit is connected to the single-chip microcomputer, the single-chip microcomputer is used to detect the voltage change of the three-phase input circuit, the zero-sequence current transformer is used to sense the zero-sequence current in the three-phase input circuit, and the zero-sequence current transformer is electrically connected to the single-chip microcomputer.

[0008] Furthermore, the three-phase input circuit includes a first phase input, a second phase input and a third phase input, and at least two phases of the first phase input, the second phase input and the third phase input are connected to the voltage detection pin of the single-chip microcomputer.

[0009] Furthermore, the three-phase input circuit is connected to the voltage detection pin of the single chip microcomputer through at least one transformer.

[0010] Furthermore, the three-phase input circuit is connected to the power supply pin of the single-chip microcomputer through at least one transformer.

[0011] Furthermore, the power supply pin is a pin with a voltage detection function.

[0012] Furthermore, at least one of the first phase input, the second phase input and the third phase input is connected to a zero-sequence current detection circuit, the input end of the zero-sequence current detection circuit is connected to any one of the first phase input, the second phase input and the third phase input, and the zero-sequence current transformer is disposed on the output end.

[0013] Furthermore, the zero-sequence current detection circuit includes a first resistor and a second resistor, one end of the first resistor and the second resistor are simultaneously connected to any one of the first phase input, the second phase input and the third phase input, and the other end of the first resistor and the second resistor are connected to the ground through a selection switch.

[0014] Furthermore, the first resistor and the second resistor have different resistance values.

[0015] Furthermore, a current transmitter is provided on at least one of the first phase input, the second phase input and the third phase input.

[0016] Furthermore, the single chip microcomputer is also connected to a communication module, and is communicatively connected to a host computer via the communication module.

[0017] Compared with the prior art, the beneficial effects of the utility model are: by setting a three-phase input circuit for connecting to an upstream feeding system, a single-chip microcomputer that can detect voltage changes in the three-phase input circuit, and a zero-sequence current transformer for sensing the zero-sequence current in the three-phase input circuit and sending the signal of the zero-sequence current to the single-chip microcomputer, the single-chip microcomputer can detect whether the leakage test is started normally through the zero-sequence current transformer, and judge whether the leakage protection device is working normally through the voltage.

[0018] At the same time, the present application determines whether the leakage protection device is working normally through the superposition of the zero-sequence current transformer and the voltage, which can avoid the misjudgment caused by a single signal, and the judgment of whether the leakage protection device is operating is more accurate and reliable.

[0019] Other features and advantages of the present invention will be disclosed in detail in the following specific implementations and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the overall circuit principle diagram of the utility model. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0022] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] Leakage protection self-test circuit, such as Figure 1 As shown, it includes a three-phase input circuit for connecting to an upstream feeding system, a zero-sequence current transformer for sensing the zero-sequence current in the three-phase input circuit and sending the signal of the zero-sequence current to a single-chip microcomputer, and a single-chip microcomputer for detecting the voltage change of the three-phase input circuit and receiving the zero-sequence current signal of the zero-sequence current transformer, the three-phase input circuit is connected to the single-chip microcomputer, and the zero-sequence current transformer is electrically connected to the single-chip microcomputer.

[0024] When in use, after all circuits are connected, the single-chip microcomputer can detect whether the leakage test starts normally through the zero-sequence current transformer. If the leakage test starts normally, before the upstream feed switch is actuated, there will be leakage current in the circuit where the zero-sequence current transformer L4 is located. If the upstream feed switch works normally, the system voltage of the three-phase input circuit that supplies power to the single-chip microcomputer drops rapidly; if the remote feed switch does not actuate, the system voltage does not change. Specifically, the model of the single-chip microcomputer is CH32V307VCT6.

[0025] The connection mode between the three-phase input circuit and the upstream power feeding system is specifically parallel wiring. In this embodiment, the power supply circuit between the upstream power feeding system and the AC motor is directly selected. Figure 1 As shown, the three-phase input circuit includes a first phase input X1, a second phase input X2 and a third phase input X3, and the first phase input X1, the second phase input X2 and the third phase input X3 are respectively connected to the D1, D2 and D3 interfaces of the AC motor in the leakage protection system through a switch KM. At least two phases of the first phase input X1, the second phase input X2 and the third phase input X3 are connected to the voltage detection pin of the single-chip microcomputer.

[0026] In this embodiment, at least two of the first phase input, the second phase input and the third phase input are respectively connected to the two ends of the primary side of the first transformer T1. In this embodiment, a second transformer T2 is also included, and the two ends of the secondary side of the first transformer T1 are connected to the two ends of the primary side of the second transformer T2, and the two ends of the secondary side of the second transformer T2 are respectively connected to the second pin and the third pin of the single-chip microcomputer. The single-chip microcomputer detects the voltage of the secondary side of the second transformer T2 through the second pin and the third pin, and detects the voltage change of at least two of the first phase input, the second phase input and the third phase input according to the voltage change of the secondary side of the second transformer T2.

[0027] In this embodiment, the second pin and the third pin of the single-chip microcomputer can also be power pins at the same time, so as to realize the power supply of the single-chip microcomputer by the three-phase input circuit.

[0028] Optionally, as another implementation, the three-phase input circuit can be connected to the power supply pin of the single-chip microcomputer through a power module to power the single-chip microcomputer. The power module includes a step-down chip, an AC-to-DC chip, and a voltage stabilizing chip, etc., which are prior art and will not be described in detail in this application. Optionally, the single-chip microcomputer can also be powered by a rechargeable battery, and can still maintain normal operation for 3-5 minutes after the low-voltage AC power is disconnected, ensuring that the leakage test results are reported to the host computer.

[0029] The single-chip microcomputer is also connected to a communication module, and is connected to the host computer through the communication module. The communication module is used to receive control instructions from the host computer and report the leakage detection result. Communication is carried out through RS485, Ethernet, WiFi or 4G / 5G, etc., and is flexibly configured according to the underground power environment. This is a prior art and will not be repeated in this application.

[0030] The zero-sequence current transformer detects the zero-sequence current in the three-phase input circuit through a zero-sequence current detection circuit.

[0031] At least one of the first phase input, the second phase input and the third phase input is connected to a zero-sequence current detection circuit, the input end of the zero-sequence current detection circuit is connected to any one of the first phase input, the second phase input and the third phase input, and the zero-sequence current transformer is disposed on the output end.

[0032] The zero-sequence current detection circuit includes a first resistor and a second resistor, one end of the first resistor and the second resistor is simultaneously connected to any one of the first phase input, the second phase input and the third phase input, and the other end of the first resistor and the second resistor is connected to the ground through a selection switch K. In this embodiment, a first resistor R1 and a second resistor R2 are included, the resistance of the first resistor R1 is 11kΩ, and the resistance of the second resistor R2 is 20kΩ. The resistor selection is selected by selecting the switch K according to the system voltage. Optionally, the selection switch can be an ordinary switch, which is adjusted manually, or a relay, which is adjusted by a single-chip microcomputer. This is a prior art and will not be repeated in this application. If a 2kΩ resistor is used when the current voltage is 127V, 3.5kΩ is used for 380V, 11kΩ is used for 660V, 20kΩ is used for 1140V, etc., the adaptability is better.

[0033] It also includes a current transmitter DL, which is used to detect the current values ​​of the first phase input, the second phase input and the third phase input, and input the detection results to the single chip microcomputer.

[0034] The device further comprises a leakage test button, the leakage test button is connected to the 29th pin and the 30th pin of the single chip microcomputer, and when pressed, the single chip microcomputer starts the leakage test. Optionally, in this embodiment, the leakage test button may include a normally open relay, and when the button is pressed, the normally open relay is closed, and the leakage test starts.

[0035] The utility model provides a leakage protection self-checking circuit with simple structure, convenient use and high reliability.

[0036] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A leakage protection self-test circuit, characterized in that: It includes a three-phase input circuit, a single-chip microcomputer and a zero-sequence current transformer. The three-phase input circuit is connected to the single-chip microcomputer. The single-chip microcomputer is used to detect the voltage change of the three-phase input circuit. The zero-sequence current transformer is used to sense the zero-sequence current in the three-phase input circuit. The zero-sequence current transformer is electrically connected to the single-chip microcomputer.

2. The leakage protection self-detection circuit according to claim 1, characterized in that: The three-phase input circuit includes a first phase input, a second phase input and a third phase input, and at least two phases of the first phase input, the second phase input and the third phase input are connected to the voltage detection pin of the single-chip microcomputer.

3. The leakage protection self-detection circuit according to claim 2, characterized in that: The three-phase input circuit is connected to the voltage detection pin of the single chip microcomputer through at least one transformer.

4. The leakage protection self-detection circuit according to claim 3, characterized in that: The three-phase input circuit is connected to the power supply pin of the single chip microcomputer through at least one transformer.

5. The leakage protection self-detection circuit according to claim 4, characterized in that: The power supply pin is a pin with a voltage detection function.

6. The leakage protection self-detection circuit according to claim 2, characterized in that: At least one of the first phase input, the second phase input and the third phase input is connected to a zero-sequence current detection circuit, the input end of the zero-sequence current detection circuit is connected to any one of the first phase input, the second phase input and the third phase input, and the zero-sequence current transformer is disposed on the output end.

7. The leakage protection self-checking circuit according to claim 6, characterized in that: The zero-sequence current detection circuit includes a first resistor and a second resistor, one end of the first resistor and the second resistor are simultaneously connected to any one of the first phase input, the second phase input and the third phase input, and the other end of the first resistor and the second resistor are connected to the ground through a selection switch.

8. The leakage protection self-checking circuit according to claim 7, characterized in that: The first resistor and the second resistor have different resistance values.

9. The leakage protection self-detection circuit according to claim 7, characterized in that: A current transmitter is provided on at least one of the first phase input, the second phase input and the third phase input.

10. The leakage protection self-detection circuit according to any one of claims 1 to 9, characterized in that: The single chip microcomputer is also connected to a communication module, and is connected to a host computer through the communication module.

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