Electric leakage detection circuit and method of mining direct current intrinsic safety power supply system and power supply system

Abstract

The invention provides an electric leakage detection circuit of a mining DC intrinsic safety power supply system, the electric leakage detection circuit comprises a switch module and an AC mutual inductor, the switch module is used for converting a DC leakage current generated in a power supply line into a periodic pulse current through periodic on-off, and the AC mutual inductor is used for generating a mutual inductance current for the periodic pulse current. According to the electric leakage detection scheme provided by the invention, an alternating current mutual inductance element with low price can be used in a direct current power supply system, and the electric leakage detection scheme has the beneficial effects of good detection effect, simple structure, low cost and convenience in production, installation and debugging.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power supply, and in particular to a leakage detection circuit, method and power supply system of a DC intrinsically safe power supply system for mines. Background Art

[0002] At present, there are generally two methods for leakage protection of DC power supply systems: the first method is to use the balanced bridge method to detect the insulation strength of the system. When leakage occurs in a circuit somewhere in the system, the insulation strength decreases and an alarm is issued; the second method is to install a DC leakage sensor (Hall current sensor) on the positive and negative lines of the branch, and determine whether there is leakage by comparing whether the input and output currents are consistent.

[0003] In coal mines, DC power equipment for mines is generally powered by flameproof and intrinsically safe lithium-ion battery power supplies and flameproof and intrinsically safe DC regulated power supplies. These two types of power supplies usually have multiple DC intrinsically safe outputs. Since the main body of each DC intrinsically safe circuit power supply is electrically isolated, when its output line leaks to the ground, it cannot form a loop with the ground terminal of the power supply, so that residual current cannot be generated, and the aforementioned method 2 cannot be used for detection. If the aforementioned method 1 is used to detect leakage, the circuit and control process will be too complicated, the cost will be high, and it will be inconvenient to implement.

[0004] Therefore, for the power supply system of DC intrinsically safe power supply for mines, how to perform leakage detection simply and efficiently is a problem that needs to be solved urgently. Summary of the invention

[0005] The invention provides a leakage detection scheme for a mine-used DC intrinsically safe power supply system, which is used to solve the problem of performing simple and efficient leakage detection on the power supply system of the mine-used DC intrinsically safe power supply.

[0006] To solve the above technical problems, the present invention is achieved as follows:

[0007] On the one hand, the present invention provides a leakage detection circuit for a DC intrinsically safe power supply system for a mine, comprising a switch module and an AC transformer, wherein the switch module is used to convert the DC leakage current generated in the power supply line into a periodic pulse current by periodic switching, and the AC transformer is used to generate a mutual inductance current for the periodic pulse current.

[0008] On the other hand, the present invention also provides a leakage detection method for a DC intrinsically safe power supply system for mining, which converts the leakage current generated in the power supply line into a periodic pulse current through a switch module that is periodically turned on and off, and generates a mutual inductance current for the periodic pulse current through an AC transformer.

[0009] On the other hand, the present invention further provides a DC intrinsically safe power supply system for mining, the power supply system comprising the aforementioned leakage detection circuit.

[0010] The leakage detection circuit provided by the present invention has the following advantages:

[0011] 1) It can identify the leakage of positive bus and negative bus, and realize accurate alarm to the line;

[0012] 2) By using the periodic on-off of the switch module, the DC leakage current generated in the power supply line is converted into a periodic pulse current, so that a cheap AC transformer can be used as a current coupling component, eliminating the need to use expensive DC leakage sensors in traditional detection methods, thereby reducing the cost of the detection circuit;

[0013] 3) The circuit uses an AC transformer, and its grounding wire can pass through the heart without passing through the positive and negative busbars, which is more convenient for installation and deployment of multi-channel output mining power supplies;

[0014] 4) The detection circuit is set in the power supply line so that the positive bus and the negative bus are connected through the resistor to form a loop, which will affect the normal operation of the power supply line;

[0015] 5) Since the current of the detection circuit is limited, the detection circuit will not be damaged even if the busbar is metallically grounded.

[0016] Therefore, the leakage detection solution provided by the present invention has the beneficial effects of good detection effect, simple structure, low cost, and easy production, installation and debugging. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present disclosure 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 recorded in the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A structural block diagram of a leakage detection circuit provided in an embodiment of the present disclosure;

[0019] Figure 2 A circuit schematic diagram of a leakage detection circuit provided in an embodiment of the present disclosure connected to a power supply line;

[0020] Figure 3 It is a schematic diagram of the current direction in the detection circuit when the positive busbar leaks to the ground;

[0021] Figure 4 It is a schematic diagram of the current direction in the detection circuit when the negative bus leaks to the ground;

[0022] Figure 5 An implementation scheme for a control module;

[0023] Figure 6 It is a photoelectric coupling implementation scheme of the controlled switch K1;

[0024] Figure 7 An implementation scheme for a power module;

[0025] Figure 8 An implementation scheme of the acquisition module;

[0026] Fig. 9 Another implementation scheme of the acquisition module. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present disclosure. In addition, for the sake of clarity, parts that are not related to the description of the exemplary embodiments are omitted in the drawings.

[0028] In this specification, it should be understood that terms such as "including" or "having" are intended to indicate the existence of the features, numbers, steps, behaviors, components, parts or combinations thereof disclosed in the present disclosure, and are not intended to exclude the possibility that one or more other features, numbers, steps, behaviors, components, parts or combinations thereof exist or are added. It should also be noted that the embodiments in the present disclosure and the features in the embodiments may be combined with each other if there is no conflict.

[0029] Figure 1 A structural block diagram of a leakage detection circuit suitable for a DC intrinsically safe power supply system for mines provided in an embodiment of the present disclosure.

[0030] like Figure 1 As shown, the leakage detection circuit includes a switch module 10 and an AC transformer 20. The switch module 10 is used to convert the DC leakage current generated in the power supply line into a periodic pulse current by periodic switching, and the AC transformer 20 is used to generate a mutual inductance current for the periodic pulse current. The AC transformer is a commonly used component in the AC system, including a zero current transformer and a small current multi-turn double-winding current transformer. Compared with the Hall sensor used in the DC system, this type of component has the characteristics of simple structure, low cost and simple wiring.

[0031] like Figure 1As shown, the detection circuit may also include a current limiting resistor 30 and a collection module 40. The switch module 10 has three terminals, the first terminal and the second terminal of which are respectively connected to the positive bus and the negative bus of the power supply line. The third terminal of the switch module 10 is connected to the current limiting resistor 30 and passes through the primary side of the AC transformer 20 and then grounded; the collection module 40 is connected to the secondary side of the AC transformer 20 to convert the mutual inductance current into a leakage alarm signal. The current limiting resistor value is at the KΩ level, which can make the leakage current in the detection circuit very small. For example, the current limiting resistor value is 1KΩ. At this time, the detection circuit can also use a cheaper small current multi-turn double-winding current transformer as a leakage current transformer in series connection, which is not only cheap, but also has higher sensitivity and stronger anti-interference ability.

[0032] like Figure 1 As shown, the switch module 10 further includes a control module 11 and a controlled switch 12. The control module 11 is used to generate a periodic square wave control signal. The controlled switch 12 periodically conducts the loop between the first terminal and the second terminal under the control signal. The controlled switch 11 is a single-pole double-throw switch.

[0033] like Figure 1 As shown, the detection circuit may further include a power module 50, the two input ends of the power module 50 are respectively connected to the positive end and the negative end of the DC bus of the power supply line, and the two output ends of the power module 50 respectively provide working voltages for the switch module 10 and the acquisition module 40. The power module is used to provide working voltages for the switch module and the acquisition module, and local materials are used to simplify the circuit structure.

[0034] Next, the principle of the leakage detection circuit is specifically described through an implementation circuit in a power supply line.

[0035] Figure 2 A circuit schematic diagram of a leakage detection circuit provided in an embodiment of the present disclosure connected to a power supply line.

[0036] exist Figure 2 In the figure, the dotted frame is a leakage detection circuit provided by the embodiment of the present disclosure, and the dotted frame is outside the power supply line and the load to be detected, which is used to illustrate the working principle of the leakage detection circuit.

[0037] like Figure 2 As shown, the detection circuit includes a control module 01, a zero current transformer (ZCT) 02, an acquisition module 03, a DC / DC module 04 (i.e., a power module), and also includes a current limiting resistor R1 and a controlled single-pole double-throw switch K1. In the figure, the line from DCI+ to DCO+ is the positive bus of the power supply DC (hereinafter referred to as the "positive bus"), and the line from DCI- to DCO- is the negative bus of the power supply DC (hereinafter referred to as the "negative bus"). The resistors Rx+ and Rx- respectively represent the leakage resistance of the positive bus and the negative bus to the ground.

[0038] like Figure 2 As shown, input terminals 1 and 2 of the DC / DC module 04 are respectively connected to the positive terminal and negative terminal of the DC bus. The DC / DC module 04 converts the bus DC voltage into an appropriate DC voltage and outputs it from output terminals 3 and 4 to power the control module 01 and the acquisition module 03.

[0039] Terminal 1 of control module 01 is the positive power supply terminal of this module, connected to output terminal 3 of DC / DC module 04, terminal 2 of control module 01 is the negative power supply terminal of this module, connected to the negative terminal of DC bus. Terminal 1 of acquisition module 03 is the positive power supply terminal of this module, connected to output terminal 4 of DC / DC module 04, terminal 2 of acquisition module 03 is the negative power supply terminal of this module, connected to the negative terminal of DC bus.

[0040] like Figure 2 As shown, one end of the current limiting resistor R1 is connected to the fixed end 3 of the single-pole double-throw switch K1, and the other end of R1 is a ground line, which passes through the zero current transformer 02 and then connects to the ground line. The secondary side of the zero current transformer 02 is connected to the signal input 3 and 4 terminals of the acquisition module 03. Figure 2 On the middle right side are two loads connected to the positive bus and the negative bus, and the PE end of the load is grounded.

[0041] When the leakage detection circuit is working, the control module 01 generates a periodic square wave signal to control the terminal of the single-pole double-throw switch K1 to periodically switch between positions 1 and 2, thereby periodically connecting the loop connected by the two terminals. The frequency of the square wave signal used for control is close to the frequency of common alternating current, within the frequency range of 40Hz to 60Hz, preferably 50Hz. This square wave signal can make the on-off frequency of the controlled switch close to the leakage signal of common alternating current, so that the zero current transformer can work normally.

[0042] (1) When the power supply line is supplying power normally and there is no leakage in the power supply line, the resistance Rx+ of the positive bus (DCI+-DCO+) to the ground and the resistance Rx- of the negative bus (DCI--DCO-) to the ground are both infinite. At this time, even if the single-pole double-throw switch K1 switches periodically between contacts 1 and 2, it will not form any circuit, generate no leakage signal, and will not affect the power supply circuit.

[0043] (2) When leakage occurs in the power line, the DC leakage current on the ground wire is converted into a periodic pulse square wave signal through the repeated on and off of the controlled switch. The signal flows back through the primary side of the zero current transformer 02, generating a mutual inductance current on the secondary side of the zero current transformer 02. The output signal of the zero current transformer 02 is collected by the acquisition module 03, and then a leakage alarm signal is generated after amplification, comparison and other processing. The leakage alarm signal is transmitted to the monitoring center for corresponding maintenance and control.

[0044] Leakage in power lines can be divided into two types: positive bus leakage and negative bus leakage.

[0045] (a) When the positive bus (DCI+-DCO+) leaks to the ground, the leakage resistance Rx+ becomes smaller. During the periodic switching process of the single-pole double-throw switch K1, when the single-pole double-throw switch K1 is turned to position 2, the negative bus (DCI--DCO-) is connected. The power supply generates leakage current from the DCI+ end of the positive bus through the leakage resistance Rx+, the earth, the grounding wire (through the zero current transformer 2), the current limiting resistor R1 and the controllable single-pole double-throw switch K1. At this time, the current direction passing through the zero current transformer 02 is upward, as shown in FIG. Figure 3 As shown (to make the current direction clear, Figure 3 The power module is omitted).

[0046] (b) When the negative bus (DCI-—DCO-) leaks to the ground, the leakage resistance Rx- becomes smaller. During the periodic switching process of the single-pole double-throw switch K1, when the single-pole double-throw switch K1 is turned to position 1, the positive bus (DCI+-DCO+) is connected. The power supply generates leakage current from the DCI+ end of the positive bus through the single-pole double-throw switch K1, the current limiting resistor R1, the grounding wire, the earth, the leakage resistance Rx- and the negative bus (DCI-—DCO-). At this time, the current direction through the zero current transformer 2 is downward, as shown in FIG. Figure 4 As shown (to make the current direction clear, Figure 4 The power module is omitted).

[0047] According to the scheme of this embodiment, a single-pole double-throw switch is used to periodically switch the wiring loop. When the switch between the positive bus and the ground is closed, the switch between the negative bus and the ground is disconnected. When the switch between the positive bus and the ground is disconnected, the switch between the negative bus and the ground is closed. Therefore, the leakage detection circuit will not cause the positive bus and the negative bus to form a loop through the resistor connection, that is, the leakage detection circuit has no effect on the power supply line. On the other hand, the detection current does not need to use conventional sensors and detection circuits dedicated to DC detection, but uses a more economical zero current transformer used for AC current, and realizes leakage protection of the DC power supply line with the simplest line structure and the lowest cost, which has good economic benefits.

[0048] The following describes the implementation of each part of the detection current of the present disclosure.

[0049] Figure 5 An implementation scheme of a control module.

[0050] like Figure 5As shown, the control module 01 uses the switch control circuit of the NE555 timer chip. Pin 1 of the NE555 chip is connected to the negative pole of the power supply, pin 2 is connected to pin 6, and connected to the negative pole of the power supply through capacitor Cd1, connected to pin 7 through resistor Rd2, pin 7 is connected to pin 8 through resistor Rd1, pin 4 and pin 8 are connected to the positive pole of the power supply, pin 5 is connected to the negative pole of the power supply through capacitor Cd1, and pin 3 is connected to the positive pole of the power supply through resistor Rd3. By selecting the size of the resistor and capacitor, pin 3 can output a square wave signal with a frequency of about 50Hz.

[0051] The controlled switch K1 can be realized by using a photocoupler. Figure 6 It is an example of photoelectric coupling of the controlled switch K1.

[0052] like Figure 6 As shown, in this embodiment, the controlled switch K1 is composed of resistors Rk1, Rk2, Rk3, Rk4, optocouplers GD1, GD2 and transistor T2. Pin 1 of the optocoupler GD1 is connected to the power supply VCC via the resistor Rk1, pin 2 is the signal input terminal IN, pin 3 is connected to pin 4 of the optocoupler GD2 as the common terminal 3 (connected to PE) of the controlled switch K1, and pin 4 of the optocoupler GD1 is used as pin 1 of the controlled switch K1 (connected to DCI+). Pin 1 of the optocoupler GD2 is connected to the power supply VCC through resistor Rk2, pin 2 is connected to the collector of transistor T2, pin 4 is connected to pin 3 of the optocoupler GD1 and connected to PE, and pin 3 of the optocoupler GD2 serves as pin 2 of the controlled switch K1 (connected to DCI-); resistors Rk3 and Rk4 are connected in series, pin 1 of resistor Rk3 is connected to the signal input end, pin 2 of resistor Rk4 is grounded, the common end of resistors Rk3 and Rk4 is connected to the base of transistor T2, and the emitter of transistor T2 is grounded.

[0053] When working, the square wave control signal output by the control module 01 receives the signal input terminal IN of the control switch K1, and the input signal is divided into two paths, one path controls the optocoupler GD1, and the other path controls the optocoupler GD2 after being inverted by the transistor T2. When the optocoupler GD1 is turned on, the optocoupler GD2 is turned off, and vice versa, when the optocoupler GD1 is turned off, the optocoupler GD2 is turned on, thereby realizing the control effect of the single-pole double-throw switch.

[0054] Figure 7 An implementation scheme of a power module.

[0055] The core U1 of the power module 04 is the DC / DC chip SCT2400. Pins 1 and 6 of U1 are connected to the bootstrap capacitor C6, pin 2 is grounded, and pin 5 is connected to the power input VIN. The power input is filtered by capacitors C1, C2, and C3 to supply power to U1; pin 4 is the enable terminal, which is connected to VCC through resistor R4 to enable the chip to work. Pin 1 of the power inductor L1 is connected to pin 6 of U1, and pin 2 of the power inductor L1 is connected to the power output. Resistors R5 and R6 are connected in series between the output terminal VOUT and the ground, and connected to pin 3 of U1 after voltage division. The output voltage can be controlled by adjusting the voltage division ratio of R5 and R6. Capacitors C7 and R6 are connected in parallel to eliminate output overshoot voltage. C4 and C5 are output filter capacitors, which are connected to the voltage output terminal to play the role of output filtering.

[0056] Figure 7 The VIN and ground in the circuit are connected to the positive and negative busbars respectively, and then converted into an appropriate voltage by the power module 04 ( Figure 7 5V in the example), providing working power to the control module 01, the controlled switch K1 and the acquisition module 03.

[0057] There are two implementation schemes for the acquisition module. Figure 8 This is the first implementation scheme of the acquisition module.

[0058] In this implementation scheme, the acquisition module 03 is implemented by the leakage chip SS4129, whose 8th pin is the positive pole of the power supply, the 3rd pin is the negative pole of the power supply, and the capacitor filter CL6 is connected in parallel between the 3rd and 8th pins; the 1st and 2nd pins are signal input terminals; the 4th pin is the filter and integral output pin, which is grounded through the capacitor CL4; the 5th pin is the overvoltage input pin, but the overvoltage protection function is not used, and the 5th pin is directly grounded. The output signal of the zero current transformer 02 is sampled by the sampling resistor RL1, and BAV99 is a bidirectional diode connected in parallel with RL1 to play a clamping protection role. The capacitors CL1, CL2, CL3, and the resistors RL2 and RL3 form a filtering circuit, wherein the capacitor CL1 is connected between the 1st pin of the leakage chip SS4129 and the ground, the capacitor CL1 is connected between the 2nd pin of the leakage chip SS4129 and the ground, the capacitor CL1 is connected between the 1st pin and the 2nd pin of the leakage chip, the resistor RL2 is connected to the 1st pin of the leakage chip and one end of the sampling signal, and the resistor RL3 is connected to the 2nd pin of the leakage chip and the other end of the sampling signal. Pin 6 of the leakage chip is a large drive current output pin, and pin 7 is a small drive current output pin. When the leakage current value is greater than the specified rated current threshold, the leakage chip output pin (i.e. pin 6 or pin 7) quickly outputs a high-level leakage alarm signal for the monitoring system to read.

[0059] Fig. 9 This is the second implementation scheme of the acquisition module.

[0060] The scheme is implemented by a bipolar-to-unipolar circuit 031, a filter circuit 032 and a leakage comparison circuit 033. The bipolar-to-unipolar circuit 031 is used to convert the mutual inductance current collected from the zero current transformer into a positive polarity pulse signal centered on a reference voltage; the filter circuit 032 is used to filter the positive polarity pulse signal to obtain a leakage DC level signal; the leakage comparison circuit 033 generates corresponding positive bus and negative bus leakage alarm signals according to the level of the leakage DC level signal.

[0061] (a) The bipolar-to-unipolar conversion circuit 031 is composed of operational amplifiers A1, A2, resistors R1, R2, R3, R4 and resistors R8, R9.

[0062] Operational amplifier A2 is connected between the positive pole of the power supply and the ground through a voltage divider circuit. Resistors R8 and R9 are equal in value. After voltage division, the voltage at point B is VCC / 2, which is used as the reference voltage VCC / 2 after being buffered by the follower.

[0063] Resistor R1 is connected to pin 2 of op amp A1, and the other pin is connected to the opposite-name terminal of zero current transformer 02; resistor R2 is connected to pins 1 and 2 of op amp A1, one pin of resistor R3 is connected to pin 3 of op amp A1, and the other pin is connected to the same-name terminal of zero current transformer 02; one pin of resistor R4 is connected to pin 3 of op amp A1, and the other pin is connected to the lifting voltage (connected to pin 1 of op amp A2, i.e., the reference voltage). The leakage signal collected from zero current transformer 02 is converted into a positive polarity pulse signal centered on voltage VCC / 2 through bipolar to unipolar circuit 031.

[0064] After the positive pulse signal output by the bipolar to unipolar circuit 031 is filtered by the filter circuit 032, a leakage DC level signal is generated at point E. When the positive bus of the power supply circuit is grounded, the level is greater than VCC / 2, and when the negative bus is grounded, the level is less than VCC / 2.

[0065] (c) The leakage comparison circuit 033 is composed of operational amplifiers A3, A4, and resistors R5, R6, R7, R10, R11, R12, R13, R14, and R15.

[0066] Resistors R5, R6, and R7 form a series circuit connected between voltage VCC and ground. The voltage division values ​​at points C and D are set to VCC / 2+VR and VCC / 2-VR respectively, and VR is a leakage judgment threshold value.

[0067] The op amp A3 and resistors R10, R11, and R12 form a positive bus leakage detection circuit. R10 is connected to point C and pin 2 of op amp A3, R11 is connected to point E and pin 3 of op amp A3, and R12 is connected to pin 3 and pin 1 of op amp A3. When the positive bus leaks, the voltage at point E is higher than VCC / 2. When the leakage is serious and the voltage at point E is higher than VCC / 2+VR, pin 1 of op amp A3 outputs a high level, generating a positive bus alarm signal.

[0068] Op amp A4 and resistors R13, R14, and R15 form a negative bus leakage detection circuit. R13 is connected to point E and pin 2 of op amp A4, R14 is connected to point D and pin 3 of op amp A4, and R15 is connected to pin 3 and pin 1 of op amp A4. When the negative bus leaks, the voltage at point E is lower than VCC / 2. When the leakage is serious and the voltage at point E is lower than VCC / 2-VR, pin 1 of op amp A4 outputs a high level, generating a negative bus alarm signal.

[0069] The positive bus alarm signal and the negative bus alarm signal will be connected to the monitoring system to complete the leakage detection of the positive bus and negative bus of the DC circuit. This solution can not only complete the leakage alarm, but also detect whether the leakage occurs in the positive bus or the negative bus.

[0070] Since a current limiting resistor with a resistance value of 1KΩ is set in the detection circuit, the leakage current in the circuit is very small. Ordinary, lower-cost, low-current multi-turn double-winding current transformers can also be selected as leakage current transformers for series connection. This is not only cheaper, but also more sensitive and has stronger anti-interference ability.

[0071] The structure and principle of the leakage detection circuit provided by the embodiment of the present disclosure are described above. The leakage detection circuit has the following advantages:

[0072] 1) It can identify the leakage of positive bus and negative bus, and realize accurate alarm to the line;

[0073] 2) By using the periodic on-off of the switch module, the DC leakage current generated in the power supply line is converted into a periodic pulse current, so that a cheap AC transformer can be used as a current coupling component, eliminating the need to use expensive DC leakage sensors in traditional detection methods, thereby reducing the cost of the detection circuit;

[0074] 3) The circuit uses an AC transformer, and its grounding wire can pass through the heart without passing through the positive and negative busbars, which is more convenient for installation and deployment of multi-channel output mining power supplies;

[0075] 4) The detection circuit is set in the power supply line so that the positive bus and the negative bus are connected through the resistor to form a loop, which will affect the normal operation of the power supply line;

[0076] 5) Since the current of the detection circuit is limited, the detection circuit will not be damaged even if the busbar is metallically grounded.

[0077] Therefore, the leakage detection solution provided by the present invention has the beneficial effects of good detection effect, simple structure, low cost, and easy production, installation and debugging.

[0078] Based on the same inventive concept, the specification of the present disclosure also provides a leakage detection method for a DC intrinsically safe power supply system for mining. This method converts the leakage current generated in the power supply line into a periodic pulse current through a switch module that is periodically turned on and off, and generates a mutual inductance current for the periodic pulse current through an AC transformer.

[0079] Based on the same inventive concept, the specification of the present disclosure also provides a DC intrinsically safe power supply system for mining, which power supply system includes the leakage detection circuit of the DC intrinsically safe power supply system for mining as described above.

[0080] The above describes a specific embodiment of the present disclosure. Other embodiments are within the scope of the attached claims. The detection method and power supply system provided in the embodiments of the present disclosure correspond to the detection circuit, and therefore, the detection method and power supply system also have similar beneficial technical effects as the corresponding circuit. Since the beneficial technical effects of the detection circuit have been described in detail above, they will not be repeated here.

[0081] The above description is only an embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various changes and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the scope of the claims of the present disclosure.

Claims

1. A leakage detection circuit for a DC intrinsically safe power supply system for a mine, characterized in that: It comprises a switch module and an AC transformer, wherein the switch module is used to convert the DC leakage current generated in the power supply line into a periodic pulse current by periodic switching, and the AC transformer is used to generate a mutual induction current for the periodic pulse current.

2. The detection circuit according to claim 1, characterized in that: The detection circuit also includes a current limiting resistor and a collection module. The first terminal and the second terminal of the switch module are respectively connected to the positive bus and the negative bus of the power supply line. The wiring of the third terminal of the switch module is connected to the current limiting resistor and passes through the primary side of the AC transformer and then grounded; the collection module is connected to the secondary side of the AC transformer and is used to convert the mutual inductance current into a leakage alarm signal.

3. The detection circuit according to claim 2, characterized in that: The switch module includes a control module and a controlled switch. The control module is used to generate a periodic square wave control signal. Under the action of the control signal, the controlled switch periodically conducts the loop connected to the first terminal and the second terminal.

4. The detection circuit according to claim 2, characterized in that: The detection circuit also includes a power supply module, two input terminals of the power supply module are respectively connected to the positive terminal and the negative terminal of the DC bus of the power supply circuit, and two output terminals of the power supply module provide working voltage for the switch module and the acquisition module respectively.

5. The detection circuit according to claim 3, characterized in that: The frequency of the periodic square wave control signal generated by the control module is between 40 and 60 Hz.

6. The detection circuit according to claim 3, characterized in that: The controlled switch is implemented by a photoelectric coupling circuit, which includes a photocoupler GD1, a photocoupler GD2 and a transistor T2. An output end of the photocoupler GD1 serves as the first terminal of the controlled switch, an output end of the photocoupler GD2 serves as the second terminal of the controlled switch, and a common end of the photocoupler GD1 and the photocoupler GD2 serves as the third terminal of the controlled switch. The input end of the photocoupler GD1 is connected to the signal output end of the control module to obtain the control signal, and the input end of the photocoupler GD2 is connected to the signal output end of the control module via the transistor T2 to obtain an inverted control signal opposite to the control signal.

7. The detection circuit according to claim 2, characterized in that: The acquisition module is implemented using a leakage chip. The input end of the leakage chip is connected to the secondary side of the AC transformer through a filtering circuit, a bidirectional diode and a sampling resistor. When the sampled mutual inductance current exceeds the rated current threshold, the output end of the leakage chip outputs a high-level leakage alarm signal.

8. The detection circuit according to claim 2, characterized in that: The acquisition module is implemented by a bipolar to unipolar circuit, a filter circuit and a leakage comparison circuit, wherein: The bipolar-to-unipolar circuit is used to convert the mutual inductance current collected from the AC mutual inductor into a positive polarity pulse signal centered on a reference voltage; the filter circuit is used to filter the positive polarity pulse signal to obtain a leakage DC level signal; When the positive bus of the power supply line leaks, the level of the DC level signal is greater than the reference voltage, and the positive bus leakage detection branch of the leakage comparison circuit outputs a high level, generating a positive bus leakage alarm signal; when the negative bus of the power supply line leaks, the level of the DC level signal is less than the reference voltage, and the negative bus leakage detection branch of the leakage comparison circuit outputs a high level, generating a negative bus leakage alarm signal.

9. A leakage detection method for a DC intrinsically safe power supply system for a mine, characterized in that: The leakage current generated in the power supply line is converted into a periodic pulse current through a periodically switched switch module, and a mutual inductance current is generated for the periodic pulse current through a mutual inductor.

10. A DC intrinsically safe power supply system for mining, characterized in that: The power supply system comprises the leakage detection circuit according to any one of claims 1 to 9.

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