Electric leakage detection circuit and method for mining direct-current intrinsically safe power supply system, and power supply system

Abstract

An electric leakage detection circuit for a mining direct-current intrinsically safe power supply system, the circuit comprising a switch module (10) and an alternating-current transformer (20), wherein the switch module (10) is used for converting, by means of periodic on-off switching, a direct-current leakage current generated in a power supply circuit into a periodic pulse current, and the alternating-current transformer (20) is used for generating an induced current on the basis of the periodic pulse current. The electric leakage detection circuit can use a low-cost alternating-current mutual inductance component in a direct-current power supply system, and has the beneficial effects of a good detection effect, a simple structure, a low cost, and convenient production, installation and commissioning.

Description

Leakage detection circuit, method and power supply system for intrinsically safe DC power supply system in mining Technical Field

[0001] This disclosure relates to the field of power supply technology, and in particular to a leakage current detection circuit, method and power supply system for an intrinsically safe DC power supply system for mining applications. Background Technology

[0002] Currently, there are generally two methods for leakage protection in DC power supply systems: Method 1 is to use the balanced bridge method to detect the insulation strength of the system. When leakage occurs in a certain part of the circuit, the insulation strength decreases and an alarm is triggered. Method 2 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 whether the input and output currents are consistent.

[0003] In coal mine environments, mining DC electrical equipment is typically powered by intrinsically safe and explosion-proof lithium-ion batteries and intrinsically safe and explosion-proof DC regulated power supplies. These power supplies usually have multiple intrinsically safe DC outputs. Because each intrinsically safe DC circuit power supply is electrically isolated, when its output line leaks to ground, it cannot form a circuit with the power supply's grounding terminal, thus preventing the generation of residual current and making detection using the aforementioned method two impossible. Using the aforementioned method one to detect leakage would result in overly complex circuitry and control processes, high costs, and inconvenient implementation.

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

[0005] This invention provides a leakage current detection scheme for intrinsically safe DC power supply systems in mines, which solves the problem of simple and efficient leakage current detection for intrinsically safe DC power supply systems in mines.

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

[0007] On one hand, the present invention provides a leakage current detection circuit for a mining DC intrinsically safe power supply system, including a switching module and an AC transformer. The switching module 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, 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 current detection method for a mining DC intrinsically safe power supply system, which converts the leakage current generated in the power supply line into a periodic pulse current through a periodically switching switch module, and generates a mutual inductance current in the periodic pulse current through an AC transformer.

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

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

[0011] 1) It can identify leakage current in both positive and negative busbars, enabling precise alarm down to the line level;

[0012] 2) By using the periodic switching of the switching module, the DC leakage current generated in the power supply line is converted into a periodic pulse current, so that an inexpensive AC transformer can be used as a current coupling component, eliminating the need for expensive DC leakage current sensors in traditional detection methods and reducing the cost of the detection circuit.

[0013] 3) The circuit uses an AC transformer, whose grounding wire only needs to pass through the core and does not need to pass through the positive and negative busbars, making installation more convenient and facilitating the deployment and use of multi-output mining power supplies;

[0014] 4) Installing this detection circuit in the power supply line will not cause the positive busbar and negative busbar to form a loop through a resistor connection, thus affecting the normal operation of the power supply line;

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

[0016] Therefore, the leakage current detection scheme provided by this invention has the advantages of good detection effect, simple structure, low cost, and easy production, installation and debugging. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0019] Figure 2 is a circuit diagram of the leakage current detection circuit connected to the power supply line according to an embodiment of this disclosure;

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

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

[0022] Figure 5 shows one implementation scheme of the control module;

[0023] Figure 6 shows the optocoupler implementation scheme of the controlled switch K1;

[0024] Figure 7 shows one implementation scheme of the power module;

[0025] Figure 8 shows one implementation scheme of the data acquisition module;

[0026] Figure 9 shows another implementation scheme for the data acquisition module. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of this disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this disclosure. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure. Furthermore, for clarity, parts unrelated to the described exemplary embodiments have been omitted from the drawings.

[0028] In this specification, it should be understood that terms such as "comprising" or "having" are intended to indicate the presence of features, figures, steps, behaviors, components, portions, or combinations thereof disclosed in this disclosure, and are not intended to exclude the possibility of one or more other features, figures, steps, behaviors, components, portions, or combinations thereof being present or added. It should also be noted that, unless otherwise specified, embodiments and features within embodiments of this disclosure can be combined with each other.

[0029] Figure 1 is a structural block diagram of a leakage current detection circuit suitable for a mining DC intrinsically safe power supply system provided in an embodiment of this disclosure.

[0030] As shown in Figure 1, the leakage current detection circuit includes a switching module 10 and an AC transformer 20. The switching module 10 is used to convert the DC leakage current generated in the power supply line into a periodic pulse current through periodic switching. The AC transformer 20 is used to generate a mutual inductance current from the periodic pulse current. AC transformers are commonly used components in AC systems, including zero-current transformers and small-current multi-turn double-winding current transformers. Compared with Hall sensors used in DC systems, these components have the advantages of simple structure, low cost, and simple wiring.

[0031] As shown in Figure 1, the detection circuit may further include a current-limiting resistor 30 and a data acquisition module 40. The switch module 10 has three terminals. Its first and second terminals are 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 data acquisition module 40 is connected to the secondary side of the AC transformer 20 and is used to convert the current inductance into a leakage current alarm signal. The current-limiting resistor value is in the KΩ range, which makes the leakage current in the detection circuit very small. For example, if the current-limiting resistor value is 1KΩ, the detection circuit can also use a cheaper small-current multi-turn double-winding current transformer as the leakage current transformer connected in series. This not only reduces the price but also increases the sensitivity and strengthens the anti-interference ability.

[0032] As shown in Figure 1, the switch module 10 further includes a control module 11 and a controlled switch 12. The control module 11 generates a periodic square wave control signal, and the controlled switch 12 periodically connects the circuit between the first terminal and the second terminal under the action of the control signal. The controlled switch 11 is a single-pole double-throw switch.

[0033] As shown in Figure 1, this detection circuit may also include a power supply module 50. The two input terminals of the power supply module 50 are connected to the positive and negative terminals of the DC bus of the power supply line, respectively, and the two output terminals of the power supply module 50 provide operating voltages for the switch module 10 and the acquisition module 40, respectively. By providing operating voltages to the switch module and the acquisition module through the power supply module, local materials are used, simplifying the circuit structure.

[0034] The principle of this leakage current detection circuit will be explained in detail below through the implementation circuit in the power supply line.

[0035] Figure 2 is a circuit diagram of the leakage current detection circuit connected to the power supply line according to an embodiment of this disclosure.

[0036] In Figure 2, the area inside the dashed box is the leakage current detection circuit provided in the embodiment of this disclosure, and the area outside the dashed box is the power supply line and load to be detected, which is used to illustrate the working principle of this leakage current detection circuit.

[0037] As shown in Figure 2, the detection circuit includes a control module 01, a zero-current transformer (ZCT) 02, a data acquisition module 03, a DC / DC module 04 (i.e., a power supply module), 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 power supply bus (hereinafter referred to as "positive bus"), and the line from DCI- to DCO- is the negative DC power supply bus (hereinafter referred to as "negative bus"). Resistors Rx+ and Rx- represent the leakage resistance of the positive and negative bus to ground, respectively.

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

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

[0040] As shown in Figure 2, 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 grounding wire. This grounding wire passes through the zero-current transformer 02 and is then connected to the ground wire. The secondary side of the zero-current transformer 02 is connected to the signal input terminals 3 and 4 of the acquisition module 03. On the right side of Figure 2 are two loads connected to the positive busbar and the negative busbar, and the PE terminal of the load is grounded.

[0041] When the leakage current detection circuit is working, the control module 01 generates a periodic square wave signal to control the terminals of the single-pole double-throw switch K1 to periodically switch between positions 1 and 2, thereby periodically connecting the circuits connected by the two terminals. The frequency of the square wave signal used for control is close to the frequency of common AC power, preferably 50Hz, within the frequency range of 40Hz to 60Hz. This square wave signal enables the switching of the controlled switch to generate a leakage current signal with a frequency close to that of common AC power, thus ensuring the normal operation of the zero-current transformer.

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

[0043] (2) When leakage current occurs in the power line, the DC leakage current on the ground wire is converted into a periodic pulse square wave signal by the repeated switching of the controlled switch. This 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 amplified, compared and processed to generate a leakage current alarm signal. This leakage current alarm signal is transmitted to the monitoring center for corresponding maintenance and control.

[0044] Leakage in electrical circuits can be categorized into two types: positive busbar leakage and negative busbar leakage.

[0045] (a) When the positive busbar (DCI+-DCO+) leaks to ground, the leakage resistance Rx+ decreases. During the periodic switching of the single-pole double-throw switch K1, when the single-pole double-throw switch K1 is switched to position 2, the negative busbar (DCI--DCO-) is connected. The power supply generates leakage current from the DCI+ terminal of the positive busbar through the leakage resistance Rx+, the ground, the grounding wire (passing 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 through the zero current transformer 02 is upward, as shown in Figure 3 (the power supply module is omitted in Figure 3 to make the current direction clear).

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

[0047] According to the scheme of this embodiment, a single-pole double-throw switch is used to periodically switch the connection circuit. When the switch between the positive bus and the ground wire is closed, the switch between the negative bus and the ground wire is open; when the switch between the positive bus and the ground wire is open, the switch between the negative bus and the ground wire is closed. Therefore, the leakage current detection circuit will not cause the positive and negative bus to form a loop through a resistor connection, meaning that the leakage current detection circuit does not have any impact on the power supply line. On the other hand, the detection current does not require the use of conventional sensors and detection circuits specifically designed for DC detection, but instead uses a more economical zero-current transformer for AC current. This achieves leakage protection for DC power supply lines with the simplest circuit structure and the lowest cost, resulting in good economic benefits.

[0048] The following describes the implementation schemes for the various parts of the current detection current disclosed in this invention.

[0049] Figure 5 shows one implementation scheme of the control module.

[0050] As shown in Figure 5, control module 01 uses the switching 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 together and then connected to the negative power supply through capacitor Cd1. Pin 7 is connected through resistor Rd2, and pin 7 is then connected to pin 8 through resistor Rd1. Pins 4 and 8 are connected to the positive power supply. Pin 5 is connected to the negative power supply through capacitor Cd1, and pin 3 is connected to the positive power supply through resistor Rd3. By selecting the values ​​of the resistors and capacitors, a square wave signal with a frequency of approximately 50Hz can be output from pin 3.

[0051] The controlled switch K1 can be implemented using an optocoupler. Figure 6 shows an example of an optocoupler for the controlled switch K1.

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

[0053] During operation, the square wave control signal output by control module 01 receives the signal input terminal IN of control switch K1. The input signal is split into two paths: one path controls optocoupler GD1, and the other path, after being inverted by transistor T2, controls optocoupler GD2. 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 a single-pole double-throw switch.

[0054] Figure 7 shows one implementation scheme of the power module.

[0055] The core component of power module 04, U1, is the DC / DC chip SCT2400. 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 supplying power to U1. Pin 4 is the enable pin, connected to VCC through resistor R4 to enable the chip. Pin 1 of power inductor L1 is connected to pin 6 of U1, and pin 2 of power inductor L1 is connected to the power output. Resistors R5 and R6 are connected in series between the output terminal VOUT and ground, and the voltage is divided and connected to pin 3 of U1. Adjusting the voltage division ratio of R5 and R6 controls the output voltage. Capacitor C7 is connected in parallel with R6 to eliminate output overshoot voltage. C4 and C5 are output filter capacitors, connected in parallel at the voltage output terminal for output filtering.

[0056] In Figure 7, VIN and ground are connected to the positive and negative busbars respectively, and are converted into appropriate voltages (5V in Figure 7) by the power supply module 04 to provide working power to the control module 01, the controlled switch K1 and the acquisition module 03.

[0057] There are two implementation schemes for the data acquisition module. Figure 8 shows the first implementation scheme for the data acquisition module.

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

[0059] Figure 9 shows the second implementation scheme of the data acquisition module.

[0060] The scheme is implemented by a bipolar to unipolar circuit 031, a filter circuit 032, and a leakage current 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 the reference voltage. The filter circuit 032 is used to filter the positive polarity pulse signal to obtain a leakage current DC level signal. The leakage current comparison circuit 033 generates corresponding positive bus and negative bus leakage current alarm signals according to the level of the leakage current DC level signal.

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

[0062] Op-amp A2 is connected between the positive terminal of the power supply and ground through a voltage divider circuit. Resistors R8 and R9 are of equal value. After voltage division, the voltage at point B is VCC / 2, which is then buffered by a follower and used as the reference voltage VCC / 2.

[0063] Resistor R1 is connected to pin 2 of operational amplifier 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 operational amplifier A1; one pin of resistor R3 is connected to pin 3 of operational amplifier 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 operational amplifier A1, and the other pin is connected to the boost voltage (connected to pin 1 of operational amplifier A2, i.e., the reference voltage). The leakage current signal acquired by zero-current transformer 02 is converted into a positive pulse signal centered on voltage VCC / 2 by bipolar-to-unipolar circuit 031.

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

[0065] (c) The leakage current comparison circuit 033 consists of operational amplifiers A3 and 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, where VR is the leakage current detection threshold.

[0067] Operational amplifier A3 and resistors R10, R11, and R12 form a positive busbar leakage detection circuit. R10 is connected to point C and pin 2 of operational amplifier A3, R11 is connected to point E and pin 3 of operational amplifier A3, and R12 is connected to pin 3 and pin 1 of operational amplifier A3. When there is a positive busbar leakage, the voltage at point E is higher than VCC / 2. When the leakage is severe, the voltage at point E is higher than VCC / 2 + VR. At this point, pin 1 of operational amplifier A3 outputs a high level, generating a positive busbar alarm signal.

[0068] Operational amplifier A4 and resistors R13, R14, and R15 form a negative bus leakage detection circuit. R13 is connected between point E and pin 2 of operational amplifier A4, R14 is connected between point D and pin 3 of operational amplifier A4, and R15 is connected between pin 3 and pin 1 of operational amplifier A4. When there is a leakage in the negative bus, the voltage at point E is lower than VCC / 2. When the leakage is severe, and the voltage at point E is lower than VCC / 2-VR, pin 1 of operational amplifier A4 outputs a high level, generating a negative bus alarm signal.

[0069] The positive and negative busbar alarm signals are connected to the monitoring system to detect leakage current in the DC circuit's positive and negative busbars. This solution not only provides leakage current alarms but also identifies whether the leakage occurred on the positive or negative busbar.

[0070] Because 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 used as leakage current transformers connected in series. This not only makes them cheaper but also provides higher sensitivity and stronger anti-interference capabilities.

[0071] The structure and principle of the leakage current detection circuit provided in the embodiments of this disclosure have been described above. This leakage current detection circuit has the following advantages:

[0072] 1) It can identify leakage current in both positive and negative busbars, enabling precise alarm down to the line level;

[0073] 2) By using the periodic switching of the switching module, the DC leakage current generated in the power supply line is converted into a periodic pulse current, so that an inexpensive AC transformer can be used as a current coupling component, eliminating the need for expensive DC leakage current sensors in traditional detection methods and reducing the cost of the detection circuit.

[0074] 3) The circuit uses an AC transformer, whose grounding wire only needs to pass through the core and does not need to pass through the positive and negative busbars, making installation more convenient and facilitating the deployment and use of multi-output mining power supplies;

[0075] 4) Installing this detection circuit in the power supply line will not cause the positive busbar and negative busbar to form a loop through a resistor connection, thus affecting the normal operation of the power supply line;

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

[0077] Therefore, the leakage current detection scheme provided by this invention has the advantages of good detection effect, simple structure, low cost, and easy production, installation and debugging.

[0078] Based on the same inventive concept, the present disclosure also provides a leakage current detection method for a mining DC intrinsically safe power supply system. This method uses a periodically switching switch module to convert the leakage current generated in the power supply line into a periodic pulse current, and uses an AC transformer to generate a mutual inductance current for the periodic pulse current.

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

[0080] The specific embodiments of this disclosure have been described above. Other embodiments are within the scope of the appended claims. The detection method and power supply system provided in the embodiments of this disclosure correspond to the detection circuit; therefore, the detection method and power supply system also have similar beneficial technical effects to 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 merely an embodiment of this disclosure and is not intended to limit the scope of this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of the claims of this disclosure.

Claims

1. A leakage current detection circuit for a mining intrinsically safe DC power supply system, characterized in that, It includes a switching module and an AC transformer. The switching module 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 is used to generate a mutual inductance 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 data acquisition module. The first and second terminals of the switch module are respectively connected to the positive and negative busbars of the power supply line. The third terminal of the switch module is connected to the current-limiting resistor and passes through the primary side of the AC transformer before being grounded. The data acquisition module is connected to the secondary side of the AC transformer and is used to convert the current inductance into a leakage alarm signal.

3. The detection circuit according to claim 2, characterized in that, The switching 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 connects the circuit connected to the first terminal and the second terminal under the action of the control signal.

4. The detection circuit according to claim 2, characterized in that, The detection circuit also includes a power supply module, the two input terminals of which are respectively connected to the positive and negative terminals of the DC bus of the power supply line, and the two output terminals of which provide operating voltage to the switching 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 using an optocoupler circuit, which includes optocoupler GD1, optocoupler GD2, and transistor T2. One output terminal of optocoupler GD1 serves as the first terminal of the controlled switch, one output terminal of optocoupler GD2 serves as the second terminal of the controlled switch, and the common terminal of optocoupler GD1 and optocoupler GD2 serves as the third terminal of the controlled switch. The input terminal of optocoupler GD1 is connected to the signal output terminal of the control module to obtain the control signal, and the input terminal of optocoupler GD2 is connected to the signal output terminal of the control module via transistor T2 to obtain an inverse 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 current chip. The input terminal of the leakage current chip is connected to the secondary side of the AC current transformer through a filter circuit, a bidirectional diode and a sampling resistor. When the sampled current exceeds the rated current threshold, the output terminal of the leakage current chip outputs a high-level leakage current 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 filtering circuit, and a leakage current comparison circuit, wherein... The bipolar-to-unipolar circuit is used to convert the current collected from the AC transformer into a positive pulse signal centered on the reference voltage; the filtering circuit is used to filter the positive pulse signal to obtain a leakage DC level signal. When the positive busbar of the power supply line leaks current, the level of the DC level signal is greater than the reference voltage, and the positive busbar leakage detection branch of the leakage current comparison circuit outputs a high level, generating a positive busbar leakage alarm signal; when the negative busbar of the power supply line leaks current, the level of the DC level signal is less than the reference voltage, and the negative busbar leakage detection branch of the leakage current comparison circuit outputs a high level, generating a negative busbar leakage alarm signal.

9. A method for detecting leakage current in a mining intrinsically safe DC power supply system, characterized in that, The leakage current generated in the power supply line is converted into a periodic pulse current by a switching module that is periodically switched on and off, and a mutual inductance current is generated by the periodic pulse current through an interactive inductor.

10. A mining DC intrinsically safe power supply system, characterized in that, The power supply system includes a leakage current detection circuit as described in any one of claims 1 to 9.

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