A method and system for insulation descent line selection using residual current.

Abstract

This invention discloses a method and system for selecting lines with insulation degradation using residual current. The method includes: an insulation monitoring device monitoring the insulation status of a DC system bus in real time; determining whether there is insulation degradation on the DC system bus; if no insulation degradation is found, the insulation monitoring device continues to monitor the insulation status of the DC system bus; otherwise, it further determines the polarity of the DC system bus with insulation degradation; if the degradation is positive, it closes the negative detection switch, grounding the negative terminal through a negative detection resistor; otherwise, it closes the positive detection switch, grounding the positive terminal through a positive detection resistor; after each branch leakage current sensor detects the residual current of its corresponding branch, it processes the data and uploads it to a host computer; after the host computer performs insulation degradation selection and processing, it disconnects the connection between the corresponding electrode and the detection resistor, and the DC system returns to its original operating state, continuing insulation degradation monitoring. This invention achieves rapid line selection based on insulation degradation without affecting system operation.

Description

Technical Field

[0001] This invention relates to DC power supply technology, and in particular to a method and system for selecting lines with insulation degradation using residual current. Background Technology

[0002] Given the DC nature of distributed power sources, DC systems are increasingly being promoted and applied with the continuous development of new energy power generation. Furthermore, the high reliability of DC systems is also applied in power systems; for example, substation relay protection devices often use DC power supply. Currently, there is a relatively mature relay protection scheme for AC systems, but DC system protection has not yet formed a comprehensive protection system. Besides the thermal-magnetic tripping of DC circuit breakers, insulation monitoring is widely used in IT systems. Insulation monitoring currently mostly uses a DC bridge method. This method is simple in structure, but it can only determine the insulation status of the entire system and cannot directly determine the grounding point. It requires disconnecting the DC line and determining the grounding point one by one, which is time-consuming and labor-intensive when detecting fault points. The principle of signal tracing is to detect the AC current of a specific frequency injected into the DC operating power supply, calculate the grounding resistance value of the DC system using the detection results, and determine the faulty line, thereby achieving fault detection and location in the system. However, this injected signal may interfere with the system. Summary of the Invention

[0003] Purpose of the invention: One objective of this invention is to provide a method for selecting lines with decreasing insulation using residual current, enabling rapid line selection based on insulation degradation without affecting system operation.

[0004] Another object of the present invention is to provide a system for insulation drop selection using residual current.

[0005] Technical solution: The present invention provides a method for selecting lines with insulation degradation using residual current, comprising the following steps:

[0006] The insulation monitoring device monitors the insulation status of the DC system busbars in real time.

[0007] To determine if there is insulation degradation in the DC system bus, if there is no insulation degradation, the insulation monitoring device continues to monitor the insulation status of the DC system bus. If there is insulation degradation, the polarity of the DC system bus with the insulation degradation is further determined.

[0008] If the positive terminal drops, close the negative terminal detection switch S2 to ground the negative terminal through the negative terminal detection resistor; if the negative terminal drops, close the positive terminal detection switch S1 to ground the positive terminal through the positive terminal detection resistor.

[0009] After the leakage current sensor of each branch detects the residual current of the corresponding branch, it processes the data and uploads it to the host computer.

[0010] After the host computer selects and processes the line where insulation has decreased, it disconnects the corresponding electrode from the detection resistor, and the DC system returns to its original working state to continue monitoring insulation degradation.

[0011] Preferably, the unbalanced bridge method is used to detect the polarity of the bus insulation degradation in a DC system.

[0012] Furthermore, the unbalanced bridge method specifically refers to:

[0013] Close switch S1, open switch S2, and after the measured value stabilizes, measure the voltage values ​​of the positive and negative terminals of the measuring branch to ground as U and U, respectively. 1+ 、U 1- ,but:

[0014]

[0015] Among them, R + R - These are the positive and negative resistances to ground of the branch, respectively, and R1 is the positive detection resistor;

[0016] Open switch S1, close switch S2, and after the measured value stabilizes, measure the voltage values ​​of the positive and negative terminals of the measuring branch to ground as U and U, respectively. 2+ 、U 2- ,but:

[0017]

[0018] Where R2 is the negative detection resistor, and R1 = R2;

[0019] Combining equations (1) and (2), we get:

[0020]

[0021]

[0022] When R + R - When one of the values ​​deviates from the normal value, the polarity of the insulation drop and the magnitude of the insulation drop resistance are determined.

[0023] Furthermore, the remaining circuit detection method is as follows:

[0024] When the insulation of the positive terminal of the DC system bus decreases, the negative terminal detection switch S2 becomes normally closed. The negative terminal of the DC system bus is grounded through the negative terminal detection resistor R2. Then, the positive terminal of the DC system bus forms a loop through the insulation decrease position of the branch and the negative terminal detection resistor R2. An unbalanced current begins to appear in the branch. The leakage current sensor detects the unbalanced current, which is the residual current.

[0025] Furthermore, the host computer can detect insulation degradation, select the affected line, trigger a grounding alarm, and disconnect the corresponding branch.

[0026] In another embodiment of the present invention, a system for insulation descent line selection using residual current includes:

[0027] An insulation monitoring device is used to monitor the insulation status of the DC system bus in real time and send the data to the host computer.

[0028] The host computer determines the polarity of the insulation drop based on the insulation status of the DC system bus, and controls the closing of the positive or negative detection switch in the insulation monitoring device according to the polarity of the insulation drop.

[0029] The DC circuit breaker and leakage current sensor: After the leakage current sensor of each branch detects the corresponding DC residual current, it is uploaded to the host computer through the signal processing unit. The host computer realizes insulation degradation line selection and grounding alarm according to the branch where the residual current is located, and controls the DC circuit breaker to disconnect the corresponding branch. At the same time, it controls the positive or negative detection switch in the insulation monitoring device to return to its original state, and the DC system returns to its original working state to continue insulation degradation monitoring.

[0030] Preferably, the insulation monitoring device includes a positive detection switch S1, a negative detection switch S2, a positive detection resistor R1, and a negative detection resistor R2. The positive terminal of the DC system bus is grounded sequentially through the positive detection switch S1 and the positive detection resistor R1, and the negative terminal of the DC system bus is grounded sequentially through the negative detection switch S2 and the negative detection resistor R2.

[0031] Preferably, the insulation monitoring device uses the unbalanced bridge method to monitor the insulation status of the DC system bus. When a decrease in insulation is detected on one pole, the detection switch on the opposite pole is closed, forming a residual current loop. The leakage current sensor then detects the corresponding residual current. The residual current signal is processed and uploaded to achieve insulation drop line selection and grounding alarm.

[0032] In one embodiment of the present invention, an apparatus includes a memory and a processor, wherein:

[0033] Memory is used to store computer programs that can run on a processor;

[0034] A processor, configured to execute the steps of the above-described method for insulation drop selection using residual current when running the computer program.

[0035] In one embodiment of the present invention, a storage medium storing a computer program is provided, which, when executed by at least one processor, implements the steps of the above-described method for insulation drop selection using residual current.

[0036] Beneficial effects: Compared with the prior art, the advantages of the present invention are: (1) It combines insulation monitoring and leakage current sensor, which solves the problem of difficult line selection for insulation monitoring on the one hand, and the problem of leakage current sensor being unable to detect residual current in ungrounded systems on the other hand; (2) Without changing the hardware structure of the insulation monitoring device, only the program of the insulation monitoring device needs to be rewritten, and the implementation scheme is simple; (3) The residual current loop is constructed by using grounding resistance, which has stronger anti-interference ability than the detection method of signal injection, and after the line selection and fault elimination are completed, the system is restored to the original ungrounded state, which does not affect the subsequent operation of the system. Attached Figure Description

[0037] Figure 1 This is a flowchart of the method of the present invention;

[0038] Figure 2 This is a schematic diagram of the unbalanced bridge grounding monitoring principle for a branch circuit;

[0039] Figure 3 This is a schematic diagram illustrating the principle of using residual current to select lines with reduced insulation. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, this invention provides a method for insulation degradation selection using residual current. An insulation monitoring device monitors the insulation status of the DC system busbar in real time. When insulation degradation is detected on one pole, the grounding switch on the opposite pole closes, forming a residual current loop. A leakage current sensor detects the corresponding residual current. This residual current signal is processed and uploaded to achieve insulation degradation selection and grounding alarm. Specifically, it includes the following steps:

[0042] S1. The insulation monitoring device monitors the insulation status of the DC system busbar in real time.

[0043] S2. Determine if there is insulation degradation on the DC system bus. If there is no insulation degradation, the insulation monitoring device continues to monitor the insulation status of the DC system bus. If there is insulation degradation, further determine the polarity of the DC system bus with the insulation degradation; specifically:

[0044] First, an unbalanced bridge circuit is used to periodically detect the insulation resistance of the DC system busbar to ground and monitor the grounding status, triggering insulation degradation and grounding alarms. Furthermore, fluctuations and trends in the busbar-to-ground voltage are used to determine if an abnormal voltage connection has occurred in the DC system. The unbalanced bridge grounding monitoring principle diagram is shown below. Figure 2 As shown. Where R + R - R1 and R2 are the positive and negative resistances to ground of the branch, respectively, and the detection resistors of the positive and negative terminals are R1 and R2, respectively.

[0045] Close the positive detection switch S1 and open the negative detection switch S2. Set a certain time delay and wait for the measured value to stabilize before taking the measurement. The measured values ​​of the busbar positive and negative voltages to ground are U and U, respectively. 1+ 、U 1- ,but:

[0046]

[0047] Disconnect the positive detection switch S1 and close the negative detection switch S2. Set a certain time delay and wait for the measured value to stabilize before taking the measurement. The measured values ​​of the busbar positive and negative voltages to ground are U and U, respectively. 2+ 、U 2- ,but:

[0048]

[0049] Combining equations (1) and (2), we can obtain:

[0050]

[0051]

[0052] When R + R - When one of the values ​​deviates from the normal value, the polarity of the insulation drop and the magnitude of the insulation drop resistance can be determined.

[0053] S3. If the positive terminal drops, close the negative terminal detection switch S2 to ground the negative terminal through the negative terminal detection resistor. If the negative terminal drops, close the positive terminal detection switch S1 to ground the positive terminal through the positive terminal detection resistor.

[0054] S4. After the leakage current sensor of each branch detects the residual current of the corresponding branch, it processes the data and uploads it to the host computer. After the host computer selects and processes the line with insulation drop, it disconnects the connection between the corresponding electrode and the detection resistor. The DC system returns to its original working state and continues to monitor the insulation drop.

[0055] The method for detecting remaining circuits is as follows:

[0056] When the insulation of the positive terminal of the DC system bus decreases, the negative terminal detection switch S2 becomes normally closed. The negative terminal of the DC system bus is grounded through the negative terminal detection resistor R2. Then, the positive terminal of the DC system bus forms a loop through the insulation decrease position of the branch and the negative terminal detection resistor R2. An unbalanced current begins to appear in the branch. The leakage current sensor detects the unbalanced current, which is the residual current.

[0057] After the host computer detects the line where the insulation has decreased, it will trigger a grounding alarm, disconnect the corresponding branch, and handle the fault.

[0058] like Figure 3 As shown, the specific workflow is illustrated using the example of insulation degradation at the positive terminal of branch 1. After determining the polarity of the insulation degradation, the insulation monitoring device changes its grounding state. When the insulation degradation at the positive terminal of branch 1 occurs, the insulation monitoring device detects the degradation at the positive terminal of the busbar, and the negative terminal detection switch S2 becomes normally closed. The negative terminal of the DC system busbar is grounded through the negative terminal detection resistor R2. Thus, the positive terminal of the DC system busbar forms a loop through the insulation degradation location of branch 1 and the negative terminal detection resistor R2, and an unbalanced current begins to appear in branch 1. At this time, the leakage current sensor can detect the unbalanced current (i.e., the residual current). The line selection based on insulation degradation can be achieved through signal acquisition by the host computer.

[0059] After the insulation degradation is detected and processed, the negative pole detection switch S2 is opened from the normally closed state, and the DC system returns to its original working state to continue monitoring the insulation degradation.

[0060] The present invention provides a system for insulation descent line selection using residual current, comprising:

[0061] An insulation monitoring device is used to monitor the insulation status of the DC system bus in real time and send the data to the host computer.

[0062] The host computer determines the polarity of the insulation drop based on the insulation status of the DC system bus, and controls the closing of the positive or negative detection switch in the insulation monitoring device according to the polarity of the insulation drop.

[0063] The DC circuit breaker and leakage current sensor: After the leakage current sensor of each branch detects the corresponding DC residual current, it is uploaded to the host computer through the signal processing unit. The host computer realizes insulation degradation line selection and grounding alarm according to the branch where the residual current is located, and controls the DC circuit breaker to disconnect the corresponding branch. At the same time, it controls the positive or negative detection switch in the insulation monitoring device to return to its original state, and the DC system returns to its original working state to continue insulation degradation monitoring.

[0064] The insulation monitoring device includes a positive detection switch S1, a negative detection switch S2, a positive detection resistor R1, and a negative detection resistor R2. The positive terminal of the DC system bus is grounded sequentially through the positive detection switch S1 and the positive detection resistor R1, and the negative terminal of the DC system bus is grounded sequentially through the negative detection switch S2 and the negative detection resistor R2.

[0065] The insulation monitoring device uses the unbalanced bridge method to monitor the insulation status of the DC system bus. When the insulation of one pole decreases, the detection switch of the other opposite pole closes, forming a residual current loop. The leakage current sensor then detects the corresponding residual current. The residual current signal is processed and uploaded to realize insulation decrease line selection and grounding alarm.

[0066] An apparatus of the present invention includes a memory and a processor, wherein:

[0067] Memory is used to store computer programs that can run on a processor;

[0068] A processor, configured to execute the steps of the above-described method for insulation drop selection using residual current when running the computer program.

[0069] The present invention provides a storage medium storing a computer program, which, when executed by at least one processor, implements the steps of the above-described method for insulation drop selection using residual current.

Claims

1. A method for selecting lines based on insulation degradation using residual current, characterized in that: The insulation monitoring device monitors the insulation status of the DC system busbars in real time. To determine if there is insulation degradation in the DC system bus, if there is no insulation degradation, the insulation monitoring device continues to monitor the insulation status of the DC system bus. If there is insulation degradation, the unbalanced bridge method is further used to determine the polarity of the DC system bus with insulation degradation. If the positive terminal drops, close the negative terminal detection switch S2 to ground the negative terminal through the negative terminal detection resistor; if the negative terminal drops, close the positive terminal detection switch S1 to ground the positive terminal through the positive terminal detection resistor. After the leakage current sensor detects the residual current in the corresponding branch, it processes the data and uploads it to the host computer; the residual current detection method is as follows: If the insulation of the positive pole of the DC system bus drops, the negative pole detection switch S2 becomes normally closed. The negative pole of the DC system bus is grounded through the negative pole detection resistor R2. Then, the positive pole of the DC system bus forms a loop through the insulation drop position of the branch and the negative pole detection resistor R2. An unbalanced current begins to appear in the branch. The leakage current sensor detects the unbalanced current, which is the residual current. After the host computer selects and processes the line where insulation has decreased, it disconnects the corresponding electrode from the detection resistor, and the DC system returns to its original working state to continue monitoring insulation degradation.

2. The method for selecting lines by utilizing residual current to achieve insulation degradation according to claim 1, characterized in that: The unbalanced bridge method is specifically as follows: Close switch S1, open switch S2, and after the measured value stabilizes, measure the voltage values ​​of the positive and negative terminals of the measuring branch to ground as U and U, respectively. 1+ U 1- ,but: Among them, R + R - These are the positive and negative resistances to ground of the branch, respectively, and R1 is the positive detection resistor; Open switch S1, close switch S2, and after the measured value stabilizes, measure the voltage values ​​of the positive and negative terminals of the measuring branch to ground as U and U, respectively. 2+ U 2- ,but: Where R2 is the negative detection resistor, and R1 = R2; Combining equations (1) and (2), we get: When R + R - When one of the values ​​deviates from the normal value, the polarity of the insulation drop and the magnitude of the insulation drop resistance are determined.

3. The method for selecting lines by utilizing residual current to achieve insulation degradation according to claim 1, characterized in that: After the host computer detects the line where the insulation has decreased, it will trigger a grounding alarm and disconnect the corresponding branch.

4. A system for insulation descent line selection using residual current, characterized in that, include: An insulation monitoring device is used to monitor the insulation status of the DC system bus in real time and send the data to a host computer. The insulation monitoring device includes a positive detection switch S1, a negative detection switch S2, a positive detection resistor R1, and a negative detection resistor R2. The positive terminal of the DC system bus is grounded sequentially through the positive detection switch S1 and the positive detection resistor R1, and the negative terminal of the DC system bus is grounded sequentially through the negative detection switch S2 and the negative detection resistor R2. The insulation monitoring device uses an unbalanced bridge method to monitor the insulation status of the DC system bus. When a decrease in insulation is detected in one pole, the detection switch of the opposite pole is closed, forming a residual current loop. The leakage current sensor detects the corresponding residual current, and the residual current signal is processed and uploaded to achieve insulation drop selection and grounding alarm. The host computer determines the polarity of the insulation drop based on the insulation status of the DC system bus, and controls the closing of the positive or negative detection switch in the insulation monitoring device according to the polarity of the insulation drop. The DC circuit breaker and leakage current sensor: After the leakage current sensor of each branch detects the corresponding DC residual current, it is uploaded to the host computer through the signal processing unit. The host computer realizes insulation degradation line selection and grounding alarm according to the branch where the residual current is located, and controls the DC circuit breaker to disconnect the corresponding branch. At the same time, it controls the positive or negative detection switch in the insulation monitoring device to return to its original state, and the DC system returns to its original working state to continue insulation degradation monitoring.

5. A device, characterized in that, Includes memory and processor, wherein: Memory is used to store computer programs that can run on a processor; A processor, configured to, while running the computer program, perform the steps of a method for insulation drop selection using residual current as described in any one of claims 1-3.

6. A storage medium, characterized in that, The storage medium stores a computer program that, when executed by at least one processor, implements the steps of the method for insulation drop selection using residual current as described in any one of claims 1-3.

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