A ground fault detection device and method for an EDI DC power supply module

Abstract

The present invention discloses an EDI DC power module ground fault detection device and method, comprising a voltage acquisition unit, first and second resistor-capacitor series circuit units, first and second resistor voltage divider units, and first and second voltage comparison units; the voltage acquisition unit is used to acquire the positive output voltage of the DC power module; the first and second resistor-capacitor series circuit units are used to process the acquired voltage and transmit it to the first and second resistor voltage divider units; the first and second resistor voltage divider units are used to divide the processed voltage and output a sampled voltage; the first and second voltage comparison units are used to compare the sampled voltages and trigger a fault signal. The present invention can quickly detect DC power module ground faults, requires fewer components, is low-cost, and can distinguish between positive and negative ground faults. The output trigger signal can be used to alarm or stop system operation.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and relates to a grounding fault detection device and method for an EDI direct current power supply module. Background Art

[0002] Currently, some circulating water and sewage treatment systems in thermal power plants use EDI electro-desalination devices. The positive and negative output poles of the DC power supply module used in the EDI electro-desalination device are directly connected to the EDI electro-desalination module. Due to the humid environment of the circulating water and sewage treatment workshop and the presence of many process water pipelines, the DC power supply module is prone to grounding failure during equipment operation.

[0003] A single-point grounding fault in the DC power module does not affect system operation, and the overcurrent and overload protection of the DC power module cannot provide timely feedback on the fault. However, a two-point grounding fault in the system will cause a short circuit, resulting in system downtime. In more serious cases, the DC power module may be damaged by the short circuit, making it particularly important to detect DC power module grounding faults in a timely manner. Summary of the Invention

[0004] In order to overcome the problems in the prior art, the purpose of the present invention is to provide an EDI DC power supply module grounding fault detection device and method. When a ground fault occurs in the DC power supply module of an EDI electric desalination device, the method can quickly detect the ground fault and give a trigger signal.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An EDI DC power supply module ground fault detection device includes a voltage acquisition unit, a first resistor-capacitor series circuit unit, a second resistor-capacitor series circuit unit, a first resistor voltage divider unit, a second resistor voltage divider unit, a first voltage comparison unit, and a second voltage comparison unit;

[0007] The voltage acquisition unit is used to acquire the positive output voltage of the DC power module;

[0008] The first resistor-capacitor series circuit unit and the second resistor-capacitor series circuit unit are used to process the collected voltage with different time constants and transmit the processed voltage to the first resistor voltage divider unit and the second resistor voltage divider unit;

[0009] The first resistor voltage divider unit and the second resistor voltage divider unit are used to divide the processed voltage and then output the sampling voltage to the first voltage comparison unit and the second voltage comparison unit;

[0010] The first voltage comparison unit and the second voltage comparison unit are used to compare the received sampled voltages and trigger a fault signal.

[0011] A further improvement of the present invention is that the resistance-capacitance coefficient of the first resistor-capacitor series circuit unit is greater than the resistance-capacitance coefficient of the second resistor-capacitor series circuit unit.

[0012] A further improvement of the present invention is that the voltage acquisition unit includes a first resistor and a second resistor;

[0013] The first resistor-capacitor series circuit unit includes a third resistor and a first capacitor;

[0014] The second resistor-capacitor series circuit unit includes a fourth resistor and a second capacitor;

[0015] The first resistor voltage dividing unit includes a fifth resistor and a sixth resistor;

[0016] The second resistor voltage dividing unit includes a seventh resistor and an eighth resistor;

[0017] The first voltage comparison unit includes a first voltage comparator;

[0018] The second voltage comparison unit includes a second voltage comparator;

[0019] One end of the first resistor is connected to the positive pole of the DC module, and the other end is connected to one end of the second resistor, one end of the third resistor and one end of the fourth resistor. The other end of the second resistor is grounded. The other end of the third resistor is connected to the positive pole of the first capacitor, one end of the fifth resistor and the positive end of the first voltage comparator. One end of the fourth resistor is connected to the positive end of the second voltage comparator. One end of the sixth resistor and the negative pole of the second capacitor are both grounded. The other end of the sixth resistor is connected to the negative end of the second voltage comparator. The other end of the seventh resistor is connected to the negative end of the first voltage comparator. The negative pole of the second capacitor and one end of the eighth resistor are both grounded. The other end of the eighth resistor is connected to the negative end of the first voltage comparator.

[0020] A further improvement of the present invention is that the first capacitor and the second capacitor have equal capacitance values, and the third resistor has a larger resistance value than the fourth resistor.

[0021] A method for detecting a ground fault of an EDI DC power supply module of the device described above is characterized by comprising the following steps:

[0022] Under normal conditions, the positive and negative outputs of the EDI DC power supply module are in a floating state, the voltage acquisition unit measures the voltage in the middle of the output voltage range of the DC power supply module, the first resistor divider unit and the second resistor divider unit output to the first voltage comparison unit and the second voltage comparison unit, the positive terminal voltage of the first voltage comparison unit and the second voltage comparison unit is greater than the negative terminal voltage, and the outputs of the first voltage comparison unit and the second voltage comparison unit are both in a high level state.

[0023] A further improvement of the present invention is that when a ground fault occurs at the negative pole of the EDI DC power supply module, the input voltage of the voltage acquisition unit rises from the middle position of the output voltage range of the DC power supply module to a high potential, the positive terminal voltage input to the first voltage comparison unit is lower than the negative terminal voltage, and the output level of the first voltage comparison unit changes from a high level to a low level. After a period of time, the positive terminal voltage of the first voltage comparison unit is higher than the negative terminal voltage, and the output level of the first voltage comparison unit changes from a low level to a high level. The first voltage comparison unit outputs a negative pulse to trigger the ground fault of the negative pole of the EDI DC power supply module.

[0024] A further improvement of the present invention is that when a ground fault occurs at the positive pole of the EDI DC power supply module, the input voltage of the voltage acquisition unit drops from the middle position of the output voltage range of the DC power supply module to zero potential, the positive terminal voltage input to the second voltage comparison unit is lower than the negative terminal voltage, and the output level of the second voltage comparison unit changes from a high level to a low level. After a period of time, the positive terminal voltage of the second voltage comparison unit is higher than the negative terminal voltage, and the output level of the second voltage comparison unit changes from a low level to a high level. The second voltage comparison unit outputs a negative pulse to trigger the ground fault of the positive pole of the EDI DC power supply module.

[0025] A further improvement of the present invention is that when a ground fault occurs, the voltage across the first capacitor and the second capacitor is calculated according to the following formula:

[0026]

[0027]

[0028] Where U c21 - the voltage across the first capacitor;

[0029] U c31 - the voltage across the second capacitor;

[0030] U 0c21 -The voltage across the first capacitor in a normal state before the ground fault occurs;

[0031] U 0c31 -The voltage across the second capacitor in a normal state before a ground fault occurs;

[0032] U 11 -The voltage acquisition unit outputs voltage when a ground fault occurs.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] In the present invention, under normal conditions, the positive and negative poles of the EDI DC power module are suspended relative to ground, and the measured positive-to-ground voltage value is within the EDI DC power module's output voltage range, close to the middle value. When a positive-pole ground fault occurs in the EDI DC power module, the positive-to-ground voltage drops to near zero potential; when a negative-pole ground fault occurs in the EDI DC power module, the positive-to-ground voltage rises to near the maximum value of the EDI DC power module's voltage range. The sampled voltage is processed by two sets of first and second resistor-capacitor series circuit units with different resistance-capacitance coefficients. When the sampled voltage rises or falls, the voltage response times of the capacitor terminals of the first and second resistor-capacitor series circuit units differ, causing the positive and negative input voltages of the first and second voltage comparison units to shift, resulting in a change in the output levels of the first and second voltage comparison units, triggering a fault signal. Separate trigger signals are generated for positive and negative ground faults in the DC power module, facilitating maintenance. The present invention can quickly detect grounding faults in a DC power supply module, has few components, and is low in cost. It can also distinguish between positive and negative grounding faults. The output trigger signal can be used to alarm or stop system operation, which plays a significant positive role in the safe operation and convenient maintenance of the EDI electric desalination device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention.

[0036] Figure 2 This is the change diagram of the output voltage U11 of the voltage acquisition unit when a ground fault occurs on the negative pole of the EDI DC power supply module;

[0037] Figure 3 Graph showing changes in the positive input voltage U41 of the first voltage comparison unit and the negative output voltage U52 of the first voltage comparison unit when a ground fault occurs at the negative terminal of the EDI DC power supply module;

[0038] Figure 4 This is a diagram showing changes in the output level U61 of the first voltage comparison unit when a ground fault occurs at the negative pole of the EDI DC power supply module;

[0039] Figure 5 This is the change diagram of the output voltage U11 of the voltage acquisition unit when a ground fault occurs on the positive pole of the EDI DC power module;

[0040] Figure 6 This is a diagram showing changes in the output voltage of the voltage acquisition unit and the positive terminal input voltage U42 of the second voltage comparison unit and the negative terminal output voltage U51 of the second voltage comparison unit when a ground fault occurs on the positive terminal of the EDI DC power supply module;

[0041] Figure 7This is a diagram showing the change in the output level U71 of the second voltage comparison unit when a ground fault occurs on the positive electrode of the EDI DC power supply module;

[0042] Among them, 1 is a voltage acquisition unit; 2 is a first resistor-capacitor series circuit unit; 3 is a second resistor-capacitor series circuit unit; 4 is a first resistor voltage divider unit; 5 is a second resistor voltage divider unit; 6 is a first voltage comparison unit; and 7 is a second voltage comparison unit. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the accompanying drawings.

[0044] See also Figure 1 The present invention includes a voltage acquisition unit 1, two sets of resistor-capacitor series circuit units, namely a first resistor-capacitor series circuit unit 2 and a second resistor-capacitor series circuit unit 3, two sets of resistor voltage divider units, namely a first resistor voltage divider unit 4 and a second resistor voltage divider unit 5, and two sets of voltage comparison units, namely a first voltage comparison unit 6 and a second voltage comparison unit 7.

[0045] Specifically, the voltage acquisition unit 1 includes a first resistor R1 and a second resistor R2.

[0046] The first resistor-capacitor series circuit unit 2 includes a third resistor R21 and a first capacitor C21.

[0047] The second resistor-capacitor series circuit unit 3 includes a fourth resistor R31 and a second capacitor C31.

[0048] The first resistor voltage dividing unit 4 includes a fifth resistor R22 and a sixth resistor R23 .

[0049] The second resistor voltage dividing unit 5 includes a seventh resistor R32 and an eighth resistor R33 .

[0050] The first voltage comparison unit 6 includes a first voltage comparator.

[0051] The second voltage comparison unit 7 includes a second voltage comparator.

[0052] One end of the first resistor R1 is connected to the positive electrode of the DC module, and the other end is connected to one end of the second resistor R2, one end of the third resistor R21, and one end of the fourth resistor R31. The other end of the second resistor R2 is grounded. The other end of the third resistor R21 is connected to the positive electrode of the first capacitor C21, one end of the fifth resistor R22, and the positive terminal of the first voltage comparator. The other end of the fourth resistor R31 is connected to the positive electrode of the second capacitor C31, one end of the seventh resistor R32, and the positive terminal of the second voltage comparator. One end of the sixth resistor R23 and the negative electrode of the second capacitor C31 are both grounded. The other end of the sixth resistor R23 is connected to the negative terminal of the second voltage comparator. The other end of the seventh resistor R32 is connected to the negative terminal of the first voltage comparator. The negative electrode of the second capacitor C31 and one end of the eighth resistor R33 are both grounded. The other end of the eighth resistor R33 is connected to the negative terminal of the first voltage comparator.

[0053] Voltage acquisition unit 1 samples the positive output voltage of the DC power module, processes the sampled voltage with different time constants through first and second resistor-capacitor series circuit units 2 and 3, and then divides it through first and second resistor-capacitor series circuit units 4 and 5. Four sampled voltages are then output to first and second voltage comparison units 6 and 7 for comparison. The resistance-capacitance coefficient of first resistor-capacitor series circuit unit 2 is larger than that of second resistor-capacitor series circuit unit 3. Under normal conditions, the positive and negative outputs of the EDI DC power module are suspended, and the voltage measured by voltage acquisition unit 1 is generally in the middle of the DC power module's output voltage range. The voltages output by first and second resistor-capacitor series circuit units 4 and 5 to first and second voltage comparison units 6 and 7 are both higher at the positive end than at the negative end, and the outputs of both first and second voltage comparison units 6 and 7 are in a high-level state.

[0054] The principle of the present invention is:

[0055] In a normal state, the positive and negative poles of the EDI DC power module are suspended relative to the ground. The measured voltage of the positive pole to the ground is within the output voltage range of the EDI DC power module and is close to the middle value.

[0056] When a positive ground fault occurs in the EDI DC power module, the voltage of the positive electrode to the ground drops close to zero potential;

[0057] When a negative ground fault occurs in the EDI DC power module, the positive-to-ground voltage rises, approaching the maximum voltage range of the EDI DC power module. The sampled voltage is processed by two sets of first and second resistor-capacitor series circuit units 2 and 3, each with different resistance-capacitance coefficients. When the sampled voltage rises or falls, the voltage response times of the capacitor terminals of the first and second resistor-capacitor series circuit units 2 and 3 are inconsistent, causing the positive and negative input voltages of the first and second voltage comparison units 6 and 7 to shift, causing the output levels of the first and second voltage comparison units 6 and 7 to change, triggering a fault signal.

[0058] The working process of the present invention:

[0059] In this method, the first resistor-capacitor series circuit unit 2 and the second resistor-capacitor series circuit unit 3 are equivalent to a first-order RC charging circuit. When a ground fault occurs, the voltage across the first capacitor C21 and the second capacitor C31 can be approximately solved according to the following formula:

[0060]

[0061]

[0062] Where U c21 - voltage across the first capacitor C21;

[0063] U c31 - the voltage across the second capacitor C31;

[0064] U 0c21 -The voltage across the first capacitor C21 in a normal state before a ground fault occurs;

[0065] U 0c31 -The voltage across the second capacitor C31 in a normal state before a ground fault occurs;

[0066] U 11 -When a ground fault occurs, the voltage acquisition unit 1 outputs the voltage.

[0067] In this method, the first capacitor C21 and the second capacitor C31 have the same capacitance value, and the third resistor R21 has an order of magnitude greater resistance than the fourth resistor R31. According to (Formula-1) and (Formula-2), it can be concluded that the time constant of the first-order RC charging circuit is equal to the product of resistance and capacitance. 21 C 21 Greater than R 31 C 31 Therefore, the voltage change speed of the first capacitor C21 in the resistor-capacitor series unit 2 is slower than the voltage change speed of the second capacitor C31 in the resistor-capacitor series unit 3.

[0068] Under normal conditions, the positive terminal voltage U41 of the first voltage comparison unit 6 and the positive terminal voltage U51 of the second voltage comparison unit 7 are equal. Due to the resistor voltage divider, the positive terminal voltage U41 connected to the first voltage comparison unit 6 is higher than the negative terminal voltage U52, and the first voltage comparison unit 6 outputs a high level. When the positive terminal voltage U51 connected to the second voltage comparison unit 7 is higher than the negative terminal voltage U42, the second voltage comparison unit 7 outputs a high level.

[0069] Take R1 = 9 × 10 4 Ω, R2=1×10 4 Ω, R21=10 5 Ω, C21=0.1uF, R22=1×10 6 Ω, R23=9×10 6 Ω, R31=10 4 Ω, C21=0.1uF, R22=1×10 6 Ω, R23=9×10 6 Ω.

[0070] When a ground fault occurs at the negative pole of the EDI DC power supply module, the input voltage of the voltage acquisition unit 1 rises from the middle position of the output voltage range of the DC power supply module to a high potential. Since the positive terminal voltage U41 of the first voltage comparison unit 6 rises slower than the negative terminal voltage U52, the positive terminal voltage input to the first voltage comparison unit 6 is lower than the negative terminal voltage, and the output level of the first voltage comparison unit 6 changes from a high level to a low level. After a period of time, the positive terminal voltage of the first voltage comparison unit 6 is higher than the negative terminal voltage, and the output level of the first voltage comparison unit 6 changes from a low level to a high level. In this process, the first voltage comparison unit 6 outputs a negative pulse to trigger a ground fault at the negative pole of the EDI DC power supply module. The voltage curve in the specific process is as follows: Figure 2 、 Figure 3 and Figure 4 shown.

[0071] In the figure, U11 is the output voltage of the voltage acquisition unit; U41 is the positive input voltage of the first voltage comparison unit; U52 is the negative output voltage of the first voltage comparison unit; and U61 is the output level of the first voltage comparison unit.

[0072] When a ground fault occurs at the positive pole of the EDI DC power module, the input voltage of the voltage acquisition unit 1 drops from the middle of the output voltage range of the DC power module to zero potential. Since the positive terminal voltage U51 of the second voltage comparison unit 7 drops faster than the negative terminal voltage U42, the positive terminal voltage input to the second voltage comparison unit 7 is lower than the negative terminal voltage, and the output level of the second voltage comparison unit 7 changes from a high level to a low level. After a period of time, the positive terminal voltage of the second voltage comparison unit 7 is higher than the negative terminal voltage, and the output level of the second voltage comparison unit 7 changes from a low level to a high level. In this process, the voltage comparison unit outputs a negative pulse to trigger a ground fault at the positive pole of the EDI DC power module. The voltage curve in the specific process is as follows: Figure 5 、 Figure 6 and Figure 7 shown.

[0073] In the figure, U11 is the output voltage of the voltage acquisition unit; U42 is the positive input voltage of the second voltage comparison unit; U51 is the negative output voltage of the second voltage comparison unit; and U71 is the output level of the second voltage comparison unit.

[0074] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An EDI DC power supply module grounding fault detection device, characterized in that: It comprises a voltage acquisition unit (1), a first resistor-capacitor series circuit unit (2), a second resistor-capacitor series circuit unit (3), a first resistor voltage dividing unit (4), a second resistor voltage dividing unit (5), a first voltage comparison unit (6) and a second voltage comparison unit (7); The voltage acquisition unit (1) is used to acquire the positive output voltage of the DC power supply module; The first resistor-capacitor series circuit unit (2) and the second resistor-capacitor series circuit unit (3) are used to process the collected voltage with different time constants and transmit the processed voltage to the first resistor voltage divider unit (4) and the second resistor voltage divider unit (5); The first resistor voltage divider unit (4) and the second resistor voltage divider unit (5) are used to divide the processed voltage and then output four sampling voltages to the first voltage comparison unit (6) and the second voltage comparison unit (7); The first voltage comparison unit (6) and the second voltage comparison unit (7) are used to compare the received sampled voltages and trigger a fault signal; The resistance-capacitance coefficient of the first resistor-capacitor series circuit unit (2) is greater than the resistance-capacitance coefficient of the second resistor-capacitor series circuit unit (3).

2. The EDI DC power module grounding fault detection device according to claim 1, characterized in that: The voltage acquisition unit (1) comprises a first resistor (R1) and a second resistor (R2); The first resistor-capacitor series circuit unit (2) comprises a third resistor (R21) and a first capacitor (C21); The second resistor-capacitor series circuit unit (3) comprises a fourth resistor (R31) and a second capacitor (C31); The first resistor voltage dividing unit (4) includes a fifth resistor (R22) and a sixth resistor (R23); The second resistor voltage dividing unit (5) includes a seventh resistor (R32) and an eighth resistor (R33); The first voltage comparison unit (6) includes a first voltage comparator; The second voltage comparison unit (7) includes a second voltage comparator; One end of the first resistor (R1) is connected to the positive electrode of the DC module, and the other end is connected to one end of the second resistor (R2), one end of the third resistor (R21) and one end of the fourth resistor (R31); the other end of the second resistor (R2) is grounded; the other end of the third resistor (R21) is connected to the positive electrode of the first capacitor (C21), one end of the fifth resistor (R22) and the positive end of the first voltage comparator; the other end of the fifth resistor (R22) is connected to the other end of the sixth resistor (R23); the other end of the fourth resistor (R31) is connected to the positive electrode of the second capacitor (C31), one end of the seventh resistor (R21) and the positive end of the first voltage comparator. One end of the sixth resistor (R23) and the positive end of the second voltage comparator are connected, one end of the sixth resistor (R23) and the negative end of the first capacitor (C21) are both grounded, the other end of the sixth resistor (R23) is connected to the negative end of the second voltage comparator, the other end of the seventh resistor (R32) is connected to the negative end of the first voltage comparator, the negative end of the second capacitor (C31) and one end of the eighth resistor (R33) are both grounded, the other end of the eighth resistor (R33) is connected to the negative end of the first voltage comparator, and the other end of the seventh resistor (R32) is connected to the other end of the eighth resistor (R33).

3. The EDI DC power module grounding fault detection device according to claim 2, characterized in that: The capacitance values ​​of the first capacitor (C21) and the second capacitor (C31) are equal, and the resistance value of the third resistor (R21) is greater than that of the fourth resistor (R31).

4. A method for detecting a ground fault of an EDI DC power module of the device according to claim 2, characterized in that: The following steps are involved: In a normal state, the positive and negative outputs of the EDI DC power module are in a suspended state, the voltage value measured by the voltage acquisition unit (1) is in the middle of the output voltage range of the DC power module, the first resistor voltage divider unit (4) and the second resistor voltage divider unit (5) output to the first voltage comparison unit (6) and the second voltage comparison unit (7), the positive terminal voltage of the first voltage comparison unit (6) and the second voltage comparison unit (7) is greater than the negative terminal voltage, and the outputs of the first voltage comparison unit (6) and the second voltage comparison unit (7) are both in a high level state; When a ground fault occurs, the voltage across the first capacitor (C21) and the second capacitor (C31) is calculated according to the following formula: (Formula 1) (Formula 2) Where U c21 - the voltage across the first capacitor; U c31 - the voltage across the second capacitor; U 0c21 -The voltage across the first capacitor in a normal state before the ground fault occurs; U 0c31 -The voltage across the second capacitor in a normal state before a ground fault occurs; U 11 -The voltage acquisition unit outputs voltage when a ground fault occurs.

5. A method for detecting a ground fault of an EDI DC power supply module according to claim 4, characterized in that: When a ground fault occurs at the negative pole of the EDI DC power module, the input voltage of the voltage acquisition unit (1) rises from the middle position of the output voltage range of the DC power module to a high potential, the positive terminal voltage input to the first voltage comparison unit (6) is lower than the negative terminal voltage, and the output level of the first voltage comparison unit (6) changes from a high level to a low level. After a period of time, the positive terminal voltage of the first voltage comparison unit (6) is higher than the negative terminal voltage, and the output level of the first voltage comparison unit (6) changes from a low level to a high level. The first voltage comparison unit (6) outputs a negative pulse to trigger a ground fault at the negative pole of the EDI DC power module.

6. A method for detecting a ground fault in an EDI DC power supply module of the device according to claim 4, characterized in that: When a ground fault occurs at the positive pole of the EDI DC power module, the input voltage of the voltage acquisition unit (1) drops from the middle position of the output voltage range of the DC power module to zero potential, the positive terminal voltage input to the second voltage comparison unit (7) is lower than the negative terminal voltage, and the output level of the second voltage comparison unit (7) changes from a high level to a low level. After a period of time, the positive terminal voltage of the second voltage comparison unit (7) is higher than the negative terminal voltage, and the output level of the second voltage comparison unit (7) changes from a low level to a high level. The second voltage comparison unit (7) outputs a negative pulse to trigger the ground fault of the positive pole of the EDI DC power module.

Images