Leakage detection circuit, method and power supply system for DC intrinsically safe power supply system for mines

Abstract

The present disclosure provides a leakage detection circuit for a DC intrinsically safe power supply system for mines, comprising a switch module and an AC transformer. The switch module is configured to convert DC leakage current generated in the power supply line into a periodic pulse current by periodically switching on and off, and the AC transformer is configured to generate a mutual induction current from the periodic pulse current. The leakage detection solution provided by the present disclosure enables the use of inexpensive AC mutual inductance components in the DC power supply system, resulting in excellent detection performance, a simple structure, low cost, and ease of production, installation, and commissioning.

Description

Technical Field

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

[0002] Currently, there are two common methods for leakage protection in DC power supply systems: the first method uses a 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 DC leakage sensors (Hall current sensors) on the positive and negative lines of the branch circuit. The presence of leakage is determined by comparing the input and output currents.

[0003] In coal mines, DC power equipment is typically 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 typically have multiple intrinsically safe DC outputs. Because each intrinsically safe DC power supply circuit is electrically isolated, if leakage current occurs in the output line, it cannot form a loop with the ground terminal of the power supply, generating residual current and making the aforementioned method 2 unavailable for detection. Using method 1 to detect leakage current would result in overly complex circuitry and control procedures, resulting in high costs and inconvenience.

[0004] Therefore, how to simply and efficiently perform leakage detection on the power supply system of DC intrinsically safe power supply for mines is an urgent problem to be solved. Summary of the Invention

[0005] The present invention provides a leakage detection solution 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 mine-used DC intrinsically safe power supply system.

[0006] To solve the above-mentioned 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 mining, including a switch module and an AC transformer. 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.

[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 periodically switched switch module, and generates a mutual induction current for the periodic pulse current through an AC mutual inductor.

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

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

[0011] 1) It can identify leakage of positive and negative busbars and realize accurate alarm on 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. This allows the use of inexpensive AC transformers as current coupling components, eliminating the need for expensive DC leakage sensors used in traditional detection methods and reducing the cost of the detection circuit.

[0013] 3) The circuit uses an AC transformer, and its ground wire can pass through the center without passing through the positive and negative busbars, which is more convenient for installation and is convenient for the deployment of multi-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 will not be 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any 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 This is a schematic diagram of the current direction in the detection circuit when the positive busbar leaks to the ground;

[0021] Figure 4 This 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 A photoelectric coupling implementation scheme for a controlled switch;

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

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

[0026] Figure 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 of 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, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts 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 presence of the disclosed features, numbers, steps, actions, components, parts, or combinations thereof, and are not intended to exclude the possibility of one or more other features, numbers, steps, actions, components, parts, or combinations thereof being present or added. It should also be noted that, unless there is a conflict, the embodiments of this disclosure and the features therein may be combined with each other.

[0029] Figure 1 This is a structural block diagram of a leakage detection circuit suitable for a mine-used DC intrinsically safe power supply system 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 periodically switching on and off. The AC transformer 20 is used to generate a mutual induction current from the periodic pulse current. AC transformers are commonly used components in AC systems and include zero-current transformers and low-current multi-turn dual-winding current transformers. Compared to Hall sensors used in DC systems, these components have the advantages 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 an acquisition module 40. The switch module 10 has three terminals, with the first and second terminals connected to the positive and negative busbars of the power supply line, respectively. 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 before being grounded. The acquisition module 40 is connected to the secondary side of the AC transformer 20 and is used to convert the mutual inductance current into a leakage alarm signal. A current-limiting resistor value in the kilo-ohm range can minimize leakage current in the detection circuit. For example, if the current-limiting resistor value is 1 kilo-ohm, the detection circuit can also use a cheaper, low-current, multi-turn, dual-winding current transformer connected in series as the leakage current transformer. This is not only cheaper but also more sensitive and has stronger anti-interference capabilities.

[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 configured to generate a periodic square wave control signal. Under the control signal, the controlled switch 12 periodically conducts the circuit between the first terminal and the second terminal. The controlled switch 12 is a single-pole double-throw switch.

[0033] like Figure 1 As shown, the detection circuit may further include a power supply module 50. The two input terminals of the power supply module 50 are respectively connected to the positive and negative terminals of the DC bus of the power supply circuit, and the two output terminals of the power supply module 50 respectively provide operating voltages for the switch module 10 and the acquisition module 40. Providing operating voltages to the switch module and the acquisition module through the power supply module 50 simplifies the circuit structure by using local materials.

[0034] The principle of the leakage detection circuit is described in detail below through an implementation circuit in a power supply line.

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

[0036] exist Figure 2 In the figure, the dotted box is the leakage detection circuit provided by the embodiment of the present disclosure, and the power supply line and load to be detected are outside the dotted box, which is used to illustrate the working principle of this 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. Figure 1The power module in the circuit 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 DC bus (hereafter referred to as the "positive bus"), and the line from DCI- to DCO- is the negative DC bus (hereafter referred to as the "negative bus"). Resistors Rx+ and Rx- represent the leakage resistance of the positive and negative buses to ground, respectively.

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

[0040] like Figure 2 As shown, one end of the current-limiting resistor R1 is connected to the fixed terminal 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 terminals 3 and 4 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 terminals of the loads are grounded.

[0041] When the leakage detection circuit is operating, control module O1 generates a periodic square wave signal to control the terminals of single-pole double-throw switch K1 to periodically switch between positions 1 and 2, thereby periodically connecting the circuit connected by the two terminals. The frequency of this control square wave signal is close to that of common alternating current (AC), within the 40Hz to 60Hz range, preferably 50Hz. This square wave signal ensures that the switching of the controlled switch generates a leakage signal with a frequency close to that of common AC power, ensuring proper operation of the zero-current transformer.

[0042] (1) When the power supply circuit is operating normally and there is no leakage in the power supply circuit, the resistance Rx+ of the positive busbar (DCI+-DCO+) to ground and the resistance Rx- of the negative busbar (DCI--DCO-) to 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, will not generate leakage signals, 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. This signal flows back through the primary side of the zero current transformer 02, generating a mutual induction 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 amplified, compared, and processed to generate a leakage alarm signal. This 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+ decreases. 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 single-pole double-throw switch K1. At this time, the current direction through the zero current transformer 02 is upward, as shown in Figure 2. Figure 3 As shown (to make the current direction clear, Figure 3 Power supply module 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 controlled 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 Figure 2. Figure 4 As shown (to make the current direction clear, Figure 4 Power supply module omitted).

[0047] According to the solution of this embodiment, a single-pole double-throw switch is used to periodically switch the wiring circuit. When the switch between the positive busbar and the ground line is closed, the switch between the negative busbar and the ground line is open. When the switch between the positive busbar and the ground line is open, the switch between the negative busbar and the ground line is closed. As a result, the leakage detection circuit does not form a loop by connecting the positive and negative busbars via a resistor. In other words, this leakage detection circuit has no impact on the power supply line. Furthermore, this detection current does not require conventional sensors and detection circuits dedicated to DC detection, but instead uses a more economical zero current transformer used for AC current. This achieves leakage protection for the DC power supply line with the simplest circuit structure and the lowest cost, achieving excellent economic benefits.

[0048] The following explains Figure 2 Implementation plan of each part of the detection circuit.

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

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

[0051] The single-pole double-throw switch K1 can be realized by using a photocoupler. Figure 6 It is an example of optocoupler of SPDT switch K1.

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

[0053] During operation, the square wave control signal output by control module 01 is connected to the signal input terminal IN of single-pole double-throw switch K1. The input signal is split into two paths: one path controls optocoupler GD1, and the other path controls optocoupler GD2 after being inverted by transistor T2. When optocoupler GD1 is on, optocoupler GD2 is off. Conversely, when optocoupler GD1 is off, optocoupler GD2 is on, thus achieving the control effect of the single-pole double-throw switch.

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

[0055] The core of the power module, or DC / DC module 04, U1, is the SCT2400 DC / DC chip. Pins 1 and 6 of U1 are connected to 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 before powering U1. Pin 4 is the enable pin, connected to VCC through resistor R4 to enable the chip. 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 ground, dividing the voltage and connecting them to pin 3 of U1. Adjusting the voltage divider ratio of R5 and R6 controls the output voltage. Capacitor C7 and resistor R6 are connected in parallel to eliminate output overshoot voltage. C4 and C5 are output filter capacitors, connected to the voltage output terminal to provide output filtering.

[0056] Figure 7 The VIN and ground in the circuit are connected to the positive and negative busbars respectively, and converted into appropriate voltage by DC / DC module 04 ( Figure 7 5V in the example), provides working power to the control module 01, the single-pole double-throw switch K1 and the acquisition module 03.

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

[0058] In this implementation, acquisition module 03 is implemented using a leakage current chip SS4129. Pin 8 is the positive power supply, pin 3 is the negative power supply, and a filter capacitor CL6 is connected in parallel between pins 3 and 8. Pins 1 and 2 are signal inputs. Pin 4 is the filter and integration output pin, connected to ground via capacitor CL4. Pin 5 is the overvoltage input pin, but the overvoltage protection function is not used and is directly grounded. The output signal of zero current transformer 02 is sampled by sampling resistor RL1. A bidirectional diode BAV99 is connected in parallel with RL1 to provide clamping protection. Capacitors CL1, CL2, CL3, and resistors RL2 and RL3 form the filter circuit. Capacitor CL1 is connected between pin 1 of the leakage current chip SS4129 and ground, capacitor CL1 is connected between pin 2 of the leakage current chip SS4129 and ground, capacitor CL1 is connected between pins 1 and 2 of the leakage current chip, resistor RL2 is connected between pin 1 of the leakage current chip and one end of the sampling signal, and resistor RL3 is connected between pin 2 of the leakage current chip and the other end of the sampling signal. Pin 6 of the leakage chip is a high-drive current output pin, and pin 7 is a low-drive current output pin. When the leakage current exceeds the specified rated current threshold, the leakage chip output pin (i.e., pin 6 or 7) quickly outputs a high-level leakage alarm signal for the monitoring system to read.

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

[0060] The scheme is implemented by a bipolar-to-unipolar circuit 031, a filtering 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 filtering 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) Bipolar-to-unipolar conversion circuit 031 consists of operational amplifiers A1 and A2, resistors R1, R2, R3, R4, and resistors R8 and 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 buffered by the follower and used as the reference voltage VCC / 2.

[0063] Resistor R1 is connected to pin 2 of op amp A1, with its other pin connected to the opposite-polarity terminal of zero current transformer 02. Resistor R2 is connected to pins 1 and 2 of op amp A1. Resistor R3 has one pin connected to pin 3 of op amp A1, with its other pin connected to the same-polarity terminal of zero current transformer 02. Resistor R4 has one pin connected to pin 3 of op amp A1, with its other pin connected to the boost 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 at voltage VCC / 2 via bipolar-to-unipolar circuit 031.

[0064] The positive pulse signal output by bipolar-to-unipolar converter 031 is filtered by filter circuit 032, generating a leakage DC level signal at point E. When the positive busbar of the power supply circuit is grounded, this level is greater than VCC / 2; when the negative busbar is grounded, this level is less than VCC / 2.

[0065] (c) Leakage comparator circuit 033 consists 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 divider values ​​at points C and D are set to VCC / 2+VR and VCC / 2-VR respectively, where VR is the leakage judgment threshold value.

[0067] Op amp A3 and resistors R10, R11, and R12 form the positive busbar leakage detection circuit. R10 is connected between point C and pin 2 of op amp A3, R11 is connected between point E and pin 3 of op amp A3, and R12 is connected between pins 3 and 1 of op amp A3. When the positive busbar leaks, the voltage at point E exceeds VCC / 2. If the leakage is severe and the voltage at point E exceeds VCC / 2 + VR, pin 1 of op amp A3 outputs a high level, generating a positive busbar alarm signal.

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

[0069] The positive and negative busbar alarm signals are fed into the monitoring system to detect leakage on the DC circuit's positive and negative busbars. This solution not only provides leakage alarms but also identifies the specific location of the leakage on the positive or negative busbar.

[0070] Since a current limiting resistor with a resistance 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 used as leakage current transformers in series connection. This is not only cheaper, but also more sensitive and has stronger anti-interference capabilities.

[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 leakage of positive and negative busbars and realize accurate alarm on 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. This allows the use of inexpensive AC transformers as current coupling components, eliminating the need for expensive DC leakage sensors used in traditional detection methods and reducing the cost of the detection circuit.

[0074] 3) The circuit uses an AC transformer, and its ground wire can pass through the center without passing through the positive and negative busbars, which is more convenient for installation and is convenient for the deployment of multi-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 will not be 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 includes the leakage detection circuit of the DC intrinsically safe power supply system for mining as described above.

[0080] The foregoing describes specific embodiments of the present disclosure. Other embodiments are within the scope of the appended claims. The detection method and power supply system provided in the embodiments of the present disclosure correspond to the detection circuit. 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 foregoing is merely an embodiment of the present disclosure and is not intended to limit the present disclosure. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure are intended to be included within the scope of the claims of the present disclosure.

Claims

1. A leakage detection circuit for a DC intrinsically safe power supply system for mines, characterized in that: It includes 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; In which, the switch module has three terminals, the first terminal and the second terminal are respectively connected to the positive bus and the negative bus of the power supply line, and the switch module includes a control module and a controlled switch. The control module is used to generate a periodic square wave control signal, and the controlled switch periodically turns on the circuit connected to the first terminal and the second terminal under the action of the control signal.

2. The detection circuit according to claim 1, characterized in that The detection circuit also includes a current limiting resistor and an acquisition module. 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 acquisition 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 detection circuit also includes a power supply module, the 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 the two output terminals of the power supply module respectively provide working voltage for the switch module and the acquisition module.

4. The detection circuit according to claim 1, characterized in that: The frequency of the periodic square wave control signal generated by the control module is between 40 and 60 Hz.

5. The detection circuit according to claim 1, characterized in that: The controlled switch is implemented using a photoelectric coupling circuit, which includes an optocoupler GD1, an optocoupler GD2, and a transistor T2. One output end of the optocoupler GD1 serves as the first terminal of the switch module, one output end of the optocoupler GD2 serves as the second terminal of the switch module, and a common end of the optocoupler GD1 and the optocoupler GD2 serves as the third terminal of the switch module. The input end of the optocoupler GD1 is connected to the signal output end of the control module to obtain the control signal, and the input end of the optocoupler 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.

6. 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.

7. 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 filtering 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, the positive bus leakage detection branch of the leakage comparison circuit outputs a high level, and a positive bus leakage alarm signal is generated; when the negative bus of the power supply line leaks, the level of the DC level signal is less than the reference voltage, the negative bus leakage detection branch of the leakage comparison circuit outputs a high level, and a negative bus leakage alarm signal is generated.

8. A leakage detection method for a DC intrinsically safe power supply system for mines, 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 induction current is generated from the periodic pulse current through a mutual inductor; In which, the switch module has three terminals, the first terminal and the second terminal are respectively connected to the positive bus and the negative bus of the power supply line, and the switch module includes a control module and a controlled switch. The control module is used to generate a periodic square wave control signal, and the controlled switch periodically turns on the circuit connected to the first terminal and the second terminal under the action of the control signal.

9. A DC intrinsically safe power supply system for mining, characterized in that: The power supply system includes the leakage detection circuit according to any one of claims 1 to 7.

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