Direct current insulation detection device and detection method

Abstract

The application discloses a kind of DC insulation detection device and detection method, device mainly includes microprocessor and insulation monitoring module, insulation monitoring module includes injection module, system test module, broken line detection module and unbalanced bridge module;Injection module is used to inject injection voltage into the equivalent grounding point of neutral point ungrounded power system, and obtains sampling voltage by acquisition system response, then sampling voltage will be sent to microprocessor;System test module is used for system self-checking;Broken line detection module is used to detect the equivalent grounding point access condition of neutral point ungrounded power system;Unbalanced bridge module is used to generate detection loop with the equivalent insulation resistance and capacitance of the neutral point ungrounded power system, and the bridge arm voltage value of single bridge arm is collected and sent to microprocessor for processing;Microprocessor sends detection result to monitoring system, realizes continuous monitoring.The application has capacitance-resistance cooperative monitoring capability, significantly improves the comprehensiveness of fault early warning and diagnosis efficiency of neutral point ungrounded power system, has strong anti-interference, and is suitable for complex electromagnetic environment.

Description

Technical Field

[0001] This invention belongs to the field of insulation testing technology for neutral-point ungrounded power systems, and in particular relates to a DC insulation testing device and testing method. Background Technology

[0002] With the rapid development of industry and the widespread application of power electronic devices, the requirements for power system stability have also increased. The scale of ungrounded neutral power systems is expanding daily, and their power supply safety requirements are significantly higher. As the core of the stability of ungrounded neutral power systems, their insulation state directly determines the safety and economy of their operation. In ungrounded neutral power systems, the voltage to ground of the power supply and distribution busbars is usually high, while the insulation layer is prone to a decrease in insulation resistance due to corrosion, aging, mechanical damage, or human error. If the insulation state is not monitored in real time, long-term operation may lead to single-phase grounding faults, or even short-circuit faults, causing serious safety accidents. Furthermore, leakage capacitance to ground (such as abnormal accumulation due to moisture or pollution) can cause high-frequency harmonic interference, accelerating the insulation degradation process. Therefore, accurate online monitoring of busbar insulation resistance and leakage capacitance to ground is crucial.

[0003] In existing technologies, the bridge method (such as the unbalanced bridge method) has the advantages of high stability and low interference to the tested system, but it is slow in detection speed and cannot accurately calculate the equivalent insulation resistance when the insulation of the positive and negative busbars deteriorates simultaneously. It also neglects real-time monitoring of ground leakage capacitance. The injection method, on the other hand, actively injects a signal into the tested system, obtains the system's response, and then calculates the insulation resistance and leakage capacitance. Although it requires injecting a disturbance signal into the system and has some interference with the system voltage, the injection method has advantages in calculation accuracy and anti-interference. Therefore, how to simultaneously achieve high-precision and rapid detection of insulation resistance and leakage capacitance while minimizing system interference, and eliminate the blind zone of bipolar insulation failure, has become a critical technical bottleneck that urgently needs to be overcome in the field of insulation monitoring of neutral-point ungrounded power systems. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a DC insulation detection device to solve the problem of inaccurate insulation measurement in the field of insulation monitoring of ungrounded neutral power systems in the prior art.

[0005] Another objective of this invention is to provide a DC insulation detection method.

[0006] Technical Solution: The DC insulation detection device of the present invention includes: a microprocessor, a power supply module, a communication module, and an insulation monitoring module; the insulation monitoring module includes an injection module, a system test module, a disconnection detection module, and an unbalanced bridge module; the injection module is used to inject voltage into the equivalent grounding point of the neutral ungrounded power system, and obtain a sampled voltage by acquiring the system response, and then send the sampled voltage to the microprocessor; the system test module is used to perform system self-test; the disconnection detection module is used to detect the connection status of the equivalent grounding point of the neutral ungrounded power system; the unbalanced bridge module is used to generate a detection loop with the equivalent insulation resistance and capacitance of the neutral ungrounded power system, acquire the bridge arm voltage value of a single bridge arm, and send the bridge arm voltage value to the microprocessor for processing; the microprocessor sends the detection results to the monitoring system of the neutral ungrounded power system through the communication module for continuous monitoring of the entire neutral ungrounded power system; the power supply module is used to supply power to the entire device.

[0007] Optionally, the injection module includes an H-bridge module, a first sampling module, a driving module, and an injection voltage generation module. The driving module will drive the H-bridge module to close or open, and inject the injection voltage generated by the injection voltage generation module into the equivalent grounding point of the neutral-point ungrounded power system. The first sampling module is used to acquire the response of the neutral-point ungrounded power system after the injection voltage signal, and send the response to the microprocessor for processing.

[0008] Optionally, the system test module includes a system test bridge arm and a test bridge arm switch. When the system is tested, the test bridge arm switch will be closed, so that the system test bridge arm is connected to the ungrounded neutral point power system under test.

[0009] Optionally, the disconnection detection module includes a third sampling module and a fourth interface, wherein the fourth interface is connected to the equivalent grounding point of the neutral ungrounded power system; the disconnection detection module is used to cooperate with the system test module; when disconnection is detected, the third sampling module will detect the relevant voltage response value through the fourth interface to determine whether the equivalent grounding point of the neutral ungrounded power system is properly connected.

[0010] Optionally, the unbalanced bridge module includes a second sampling module, an unbalanced bridge arm, an unbalanced bridge arm switch, a balanced bridge arm, and a balanced bridge arm switch. The unbalanced bridge arm is divided into an upper bridge arm and a lower bridge arm. The unbalanced bridge arm switch selects whether the upper and lower bridge arms are closed or open to determine whether to connect to the neutral point ungrounded power system. The balanced bridge arm is also divided into an upper bridge arm and a lower bridge arm. The balanced bridge arm switch selects whether the upper and lower bridge arms are closed or open to determine whether to connect to the neutral point ungrounded power system. If the injection method is working, the detection current will pass through the balanced bridge arm. If the unbalanced bridge method is working, the detection current will selectively pass through the balanced and unbalanced bridge arms according to the working states of the balanced and unbalanced bridge arm switches. The second sampling module collects the bridge arm voltage value of the upper or lower bridge arm through the balanced bridge arm and sends the bridge arm voltage value to the microprocessor for processing.

[0011] Optionally, the communication module includes a CAN communication module and a 485 communication module.

[0012] Optionally, the power supply module includes a first power supply module, a second power supply module, and a third power supply module. The first power supply module is connected to a power supply source obtained from the ungrounded neutral point of the power system under test. The second power supply module is connected to the first power supply module and supplies power to the microprocessor and the third power supply module. The third power supply module supplies power to the insulation monitoring module.

[0013] Optionally, the device also includes buttons and a display screen. The operator inputs detection commands to the microprocessor through the buttons, and the detection results obtained by the microprocessor are displayed on the display screen.

[0014] Optionally, current sensors are installed on the loads of each branch of the ungrounded DC power system to obtain the leakage current of each branch, thereby locating the faulty branch. The sensor data is transmitted to the DC insulation detection device via a communication module, processed, and then further transmitted to the monitoring system of the ungrounded DC power system.

[0015] A DC insulation testing method using the aforementioned insulation testing device includes the following steps:

[0016] S1. When the test begins, the system test and the open circuit test of the neutral point ungrounded power system under test are first performed to determine whether the present invention is working properly and whether the equivalent grounding point and positive and negative busbars of the neutral point ungrounded power system are correctly connected to the insulation test device.

[0017] S2. If the system test and disconnection detection pass, the first round of injection method testing begins. If the insulation resistance value obtained by the injection method is less than the set insulation alarm value, i.e., the insulation level is low, the injection method testing continues. If the insulation level is low multiple times, an insulation level warning is issued. If the insulation resistance value is greater than the insulation alarm value, an unbalanced bridge method test is performed after one injection method test. If the difference between the insulation resistance values ​​obtained by the injection method and the unbalanced bridge method is less than 10%, the unbalanced bridge method is continuously executed. If the difference between the insulation resistance values ​​obtained by the unbalanced bridge method after a set number of tests is greater than 10%, the injection method is switched to perform insulation testing on the system under test.

[0018] S3. Continue step S2 until the detection device receives a stop operation command.

[0019] Beneficial effects: Compared with the prior art, the significant technical effect of the present invention is that by combining the unbalanced bridge method and the injection method, a hybrid detection function of insulation resistance-capacitance of the neutral point ungrounded power system is realized, which minimizes the interference to the neutral point ungrounded power system; after the operator sends a detection signal by pressing the button of the insulation detection device, the insulation detection device starts to automatically and continuously detect the connected neutral point ungrounded power system, thereby improving the detection efficiency and accuracy of the insulation detection of the neutral point ungrounded power system, while ensuring the safety of the operator. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an insulation detection device according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the internal structure and composition of the injection module according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the internal structure and composition of the system testing module according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the internal structure and composition of the wire breakage detection module according to an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the internal structure and composition of the unbalanced bridge module according to an embodiment of the present invention;

[0025] Figure 6 This is a refined internal structure of the injection module in this embodiment of the invention;

[0026] Note: 1-Microprocessor, 2-Second power supply module, 3-CAN communication module, 4-485 communication module, 5-Button, 6-Display screen, 7-First power supply module, 8-First interface, 9-Second interface, 10-Insulation detection module, 101-Injection module, 1011-H-bridge module, 1011A-H-bridge upper left arm switch, 1011B-H-bridge lower left arm switch, 1011C-H-bridge upper right arm switch, 1011D-H-bridge lower right arm switch, 1012-First sampling module, 1013- Drive module, 1014-Injection voltage generation module, 102-System test module, 1021-System test bridge arm, 1022-Test bridge arm switch, 103-Open circuit detection module, 1031-Third sampling module, 1032-Fourth interface, 104-Unbalanced bridge module, 1041-Second sampling module, 1042-Unbalanced bridge arm, 1043-Unbalanced bridge arm switch, 1044-Balanced bridge arm, 1045-Balanced bridge arm switch, 11-Third power supply module, 12-Third interface. Detailed Implementation

[0027] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0028] This invention addresses the problems of slow insulation detection speed and low accuracy in existing technologies by providing a DC insulation detection device; such as... Figure 1 As shown, the insulation detection device in this embodiment includes: a microprocessor 1; a second power supply module 2, a CAN communication module 3, a 485 communication module 4, a button 5, a display screen 6, and an insulation detection module 10, all connected to the microprocessor 1; and a first power supply module 7, a first interface 8, a second interface 9, a third power supply module 11, and a third interface 12. The insulation detection module 10 includes an injection module 101, a system test module 102, a wire breakage detection module 103, and an unbalanced bridge module 104. The 485 communication module 4 and the CAN communication module 3 are connected to the monitoring system of the neutral point ungrounded power system through the third interface 12. The first power supply module 7 is connected to the power supply through the first interface 8, and the power supply is obtained from the neutral point ungrounded power system under test; the first power supply module 7 is connected to the second power supply module 2; the third power supply module 11 is connected to the second power supply module 2, the injection module 101, the system test module 102, the disconnection detection module 103, and the unbalanced bridge module 104; the second interface 9 is connected to the injection module 101, the system test module 102, the disconnection detection module 103, and the unbalanced bridge module 104; the positive and negative buses of the neutral point ungrounded DC power system are connected to the second interface 9, and the second interface 9 does not distinguish between the positive and negative poles of the buses.

[0029] In the above embodiments of the present invention, the operator inputs a detection command to the microprocessor 1 via the button 5. The detection requirement includes detecting the insulation level of the ungrounded neutral power system under test. The second power supply module 2 provides voltage to the microprocessor 1, enabling it to operate normally. The microprocessor 1 first performs a system self-test via the system test module 102 and then detects the equivalent grounding point connection of the ungrounded neutral power system via the disconnection detection module 103. If both the system self-test and the disconnection detection pass, the display screen 6 indicates normal operation, and the detection of the insulation level of the ungrounded neutral power system begins. After one round of testing is completed, the detection results are displayed on the display screen 6. This avoids the potential danger of manual testing of the insulation performance of the ungrounded neutral power system, improves detection efficiency, and reduces errors from manual testing.

[0030] like Figure 2 As shown, the injection module 101 includes an H-bridge module 1011, a first sampling module 1012, a driving module 1013, and an injection voltage generation module 1014. The power supply for the injection voltage generation module 1014 is provided by a third power supply module 11. The H-bridge module 1011 is used to inject the voltage generated by the injection voltage generation module 1014 into the equivalent grounding point of the neutral-point ungrounded power system, which is the fourth interface 1032 in the open-circuit detection module 103. The driving module 1013 is used to receive the driving signal from the microprocessor 1 and distribute the driving signal to the upper left arm switch 1011A, the lower left arm switch 1011B, the upper right arm switch 1011C, and the lower right arm switch 1011D of the H-bridge. The first sampling module 1012 obtains the sampled voltage through the acquisition system response and sends the sampled voltage to the microprocessor 1 for processing.

[0031] like Figure 3 As shown, the system test module 102 includes a system test bridge arm 1021 and a test bridge arm switch 1022. When the operator controls the button 5 to set the system test, the test bridge arm switch 1022 will close, so that the system test bridge arm 1021 is connected to the ungrounded neutral point power system under test.

[0032] like Figure 4As shown, the disconnection detection module 103 includes a third sampling module 1031 and a fourth interface 1032. The fourth interface 1032 is connected to the equivalent grounding point of the neutral-point ungrounded power system. The disconnection detection module 103 is used in conjunction with the system test module 102. When the operator controls the button 5 to set the disconnection detection, the third sampling module 1031 will obtain the voltage response value through the fourth interface 1032 and the system test bridge arm 1021. The voltage response value is used to determine whether the equivalent grounding point of the neutral-point ungrounded power system is properly connected to the fourth interface 1032.

[0033] like Figure 5 The unbalanced bridge module 104 includes a second sampling module 1041, an unbalanced bridge arm 1042, an unbalanced bridge arm switch 1043, a balanced bridge arm 1044, and a balanced bridge arm switch 1045. The unbalanced bridge arm 1042 is divided into an upper bridge arm and a lower bridge arm. The unbalanced bridge arm switch 1043 selects whether the upper and lower bridge arms are closed or open to determine whether to connect to the neutral point ungrounded power system. The balanced bridge arm 1044 is also divided into an upper bridge arm and a lower bridge arm. The balanced bridge arm switch 1045 selects whether the upper and lower bridge arms are closed or open to determine whether to connect to the neutral point ungrounded power system. The second sampling module 1041 is connected to the balanced bridge arm 1044 and collects the bridge arm voltage value of a single bridge arm through the balanced bridge arm 1044, and sends the bridge arm voltage value to the microprocessor 1 for processing.

[0034] Specifically, if the injection method is working, with the balanced bridge arm switch 1045 closed and the unbalanced bridge arm switch 1043 open, the detection current will pass through the balanced bridge arm 1044; if the unbalanced bridge method is working, when the unbalanced bridge arm switch 1043 and the balanced bridge arm switch 1045 are closed simultaneously, the detection current will pass through both the balanced bridge arm 1044 and the unbalanced bridge arm 1042; when the balanced bridge arm switch 1045 is closed and the unbalanced bridge arm switch 1043 is open, the detection current will only pass through the balanced bridge arm 1044.

[0035] The 485 communication module 4 is connected to the third interface 12 and is used to connect multiple devices that require 485 communication, such as the DC insulation detection device and current sensor of the present invention.

[0036] The CAN communication module 3 is used to connect to the monitoring system of the neutral point ungrounded power system and send the results of the DC insulation detection device back to the monitoring system for continuous monitoring of the neutral point ungrounded power system.

[0037] Specifically, taking the injection method as an example, the purpose of the injection module 101 will be explained. Figure 6When the operator activates the injection method, the balance arm switch 1045 is closed first, the balance arm 1044 is connected to the ungrounded neutral point power system under test, and the second sampling module 1041 obtains the arm voltage and then obtains the bus voltage of the ungrounded neutral point power system under test. During the first round of testing, the drive module 1013 will drive the upper left arm switch 1011A and the lower right arm switch 1011D of the H-bridge module 1011 to close, causing the H-bridge module 1011 to generate a first injection voltage under this condition. The first injection voltage will be injected into the fourth interface 1032. When there is insulation resistance and insulation capacitance, the sampling resistor in the first sampling module 1012 will generate a response voltage, which will be sent to the microprocessor 1. During the second round of testing, the drive module 1013 will drive the lower left arm switch 1011B and the upper right arm switch 1011C of the H-bridge module 1011 to close, causing the H-bridge module 1011 to generate a second injection voltage, which will be injected into the fourth interface 1032. The responses generated by the first and second injection voltages are used together as calculation data to generate insulation resistance and insulation capacitance values, which are displayed on the display screen 6 and transmitted to the third interface 12.

[0038] Specifically, taking the unbalanced bridge method as an example, the purpose of the unbalanced bridge module 104 is explained. Figure 3When the operator starts the unbalanced bridge method, the drive module 1013 will first drive the H-bridge left upper arm switch 1011A and H-bridge right upper arm switch 1011C inside the H-bridge module 1011 to close, which is used to lock the injection method; the balance bridge arm switch 1045 closes, and the balance bridge arm 1044 is connected to the ungrounded power system of the neutral point under test. The second sampling module 1041 acquires the bridge arm voltage to obtain the bus voltage of the ungrounded neutral point power system under test. During the first round of testing, the unbalanced bridge arm switch 1043 closes the upper bridge arm of the unbalanced bridge arm 1042, connecting it to the ungrounded neutral point power system under test. The unbalanced bridge arm switch 1043 disconnects the lower bridge arm of the unbalanced bridge arm 1042, preventing it from connecting to the ungrounded neutral point power system under test. The second sampling module 1041 acquires the first bridge arm voltage under this condition. During the second round of testing, the unbalanced bridge arm switch 1043 closes the lower bridge arm of the unbalanced bridge arm 1042, connecting it to the ungrounded neutral point power system under test. The unbalanced bridge arm switch 1043 disconnects the upper bridge arm of the unbalanced bridge arm 1042, preventing it from connecting to the ungrounded neutral point power system under test. The second sampling module 1041 acquires the second bridge arm voltage under this condition. The first bridge arm voltage and the second bridge arm voltage are sent together as calculation data to the microprocessor 1. The microprocessor 1 calculates and displays the obtained insulation resistance value on the display screen 6, and also transmits the insulation resistance value to the third interface 12.

[0039] It should be noted that, in this embodiment of the invention, current sensors can also be installed on the loads of each power branch of the ungrounded neutral point power system under test. The current sensor data is transmitted to the insulation detection device of the present invention through the third interface 12 connected to the 485 communication module 4. After processing the current sensor data, the insulation detection device further transmits it to the monitoring system through the third interface 12. When the insulation detection device determines that an insulation fault has occurred in the ungrounded neutral point power system, the current sensor is used to obtain the leakage current of each power branch to locate the problematic branch, and transmits it to the insulation detection device through the third interface 12. After processing the problematic branch data located by the current sensor, the insulation detection device reports it to the monitoring system.

[0040] The insulation testing method for the DC insulation testing device includes the following steps:

[0041] S1. When the present invention is connected to the power supply, and the operator selects to start testing the ungrounded neutral power system under test by pressing button 5, the system test and disconnection test of the present invention will be performed automatically first to determine whether the present invention is working properly and whether the equivalent grounding point and positive and negative busbars of the ungrounded neutral power system are correctly connected to the insulation detection device of the present invention.

[0042] S2. If the system test and disconnection detection pass, the first round of injection method testing begins. If the insulation resistance value obtained by the injection method is less than the insulation alarm value set by the operator, the injection method testing continues. If low insulation level is detected multiple times, the insulation detection device of this invention will issue a low insulation level warning. If the insulation resistance value is greater than the insulation alarm value, an unbalanced bridge method test will be performed after one injection method test. If the difference between the detected resistance values ​​obtained by the injection method and the unbalanced bridge method is less than 10%, the unbalanced bridge method will continue to be executed. If the difference between the resistance values ​​obtained by the unbalanced bridge method after a set number of tests is greater than 10%, the injection method will be switched to perform insulation testing on the system under test.

[0043] S3. Continue the above steps until the operator actively shuts down the insulation detection device of the present invention by pressing button 5 or stops the operation of the insulation detection device of the present invention by the control signal of the third interface through the monitoring system of the ungrounded neutral point of the power system under test. Then all operations will stop.

[0044] This invention addresses the shortcomings of existing bridge methods, such as slow detection speed and insufficient accuracy in detecting simultaneous insulation faults on both positive and negative busbars. It proposes a fusion of the bridge and injection methods: stable insulation monitoring is achieved through the bridge method, while the injection method injects a low-frequency signal into the equivalent grounding point of the neutral-point ungrounded power grid, simultaneously calculating the insulation resistance of both positive and negative poles and the leakage capacitance to ground. This solves the comprehensive detection challenge of bipolar insulation degradation and abnormal capacitance parameters. This invention possesses capacitance-resistance coordinated monitoring capabilities, significantly improving the comprehensiveness and diagnostic efficiency of fault early warning in neutral-point ungrounded power systems. It also exhibits strong anti-interference capabilities and is suitable for complex electromagnetic environments.

[0045] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A DC insulation testing device, characterized in that, include: The system comprises a microprocessor (1), a power supply module, a communication module, and an insulation monitoring module (10). The insulation monitoring module (10) includes an injection module (101), a system test module (102), a disconnection detection module (103), and an unbalanced bridge module (104). The injection module (101) injects the voltage into the equivalent grounding point of the ungrounded neutral power system and obtains the sampled voltage by acquiring the system response. The sampled voltage is then sent to the microprocessor (1). The system test module (102) performs a system self-test. The disconnection detection module (103) detects the connection status of the equivalent grounding point of the ungrounded neutral power system. The unbalanced bridge module (104) generates a detection loop with the equivalent insulation resistance and equivalent capacitance of the ungrounded neutral power system, acquires the bridge arm voltage value of a single bridge arm, and sends the bridge arm voltage value to the microprocessor (1) for processing. The microprocessor (1) sends the detection results to the monitoring system of the ungrounded neutral power system through the communication module for continuous monitoring of the entire ungrounded neutral power system. The power supply module supplies power to the entire device. The unbalanced bridge module (104) includes a second sampling module (1041), an unbalanced bridge arm (1042), an unbalanced bridge arm switch (1043), a balanced bridge arm (1044), and a balanced bridge arm switch (1045). The unbalanced bridge arm (1042) is divided into an upper bridge arm and a lower bridge arm. The unbalanced bridge arm switch (1043) selects whether the upper and lower bridge arms are closed or open to determine whether to connect to the neutral point ungrounded power system. The balanced bridge arm (1044) is divided into an upper bridge arm and a lower bridge arm. The balanced bridge arm switch (1045) selects whether the upper and lower bridge arms are closed or open to determine whether to connect to the neutral point ungrounded power system. The arm is closed or open to determine whether to connect to the neutral point ungrounded power system; if the injection method is working, the detection current will pass through the balanced bridge arm (1044); if the unbalanced bridge method is working, the detection current will selectively pass through the balanced bridge arm (1044) and the unbalanced bridge arm (1042) according to the working state of the balanced bridge arm switch (1045) and the unbalanced bridge arm switch (1043); the second sampling module (1041) collects the bridge arm voltage values ​​of the upper and lower bridge arms through the balanced bridge arm (1044), and the microprocessor (1) processes the bridge arm voltage values.

2. The DC insulation testing device according to claim 1, characterized in that, The injection module (101) includes an H-bridge module (1011), a first sampling module (1012), a driving module (1013), and an injection voltage generation module (1014). The driving module (1013) will drive the H-bridge module (1011) to close or open, so as to inject the injection voltage generated by the injection voltage generation module (1014) into the equivalent grounding point of the neutral ungrounded power system. The first sampling module (1012) is used to acquire the response of the neutral point ungrounded power system after the injected voltage signal, and the microprocessor (1) processes the response.

3. The DC insulation testing device according to claim 1, characterized in that, The system test module (102) includes a system test bridge arm (1021) and a test bridge arm switch (1022). When the system is tested, the test bridge arm switch (1022) will be closed, so that the system test bridge arm (1021) is connected to the ungrounded neutral point power system under test.

4. The DC insulation testing device according to claim 1, characterized in that, The disconnection detection module (103) includes a third sampling module (1031) and a fourth interface (1032). The fourth interface (1032) is connected to the equivalent grounding point of the neutral ungrounded power system. The disconnection detection module (103) is used in conjunction with the system test module (102). When a disconnection is detected, the third sampling module (1031) will detect the relevant voltage response value through the fourth interface (1032) to determine whether the equivalent grounding point of the neutral ungrounded power system is properly connected.

5. The DC insulation testing device according to claim 1, characterized in that, The communication modules include a CAN communication module (3) and a 485 communication module (4).

6. The DC insulation testing device according to claim 1, characterized in that, The power supply module includes a first power supply module (7), a second power supply module (2) and a third power supply module (11). The first power supply module (7) is connected to the power supply source, which is obtained from the ungrounded neutral point power system under test. The second power supply module (2) is connected to the first power supply module (7) and supplies power to the microprocessor (1) and the third power supply module (11). The third power supply module (11) supplies power to the insulation monitoring module (10).

7. The DC insulation testing device according to claim 1, characterized in that, The device also includes a button (5) and a display screen (6). The operator inputs detection commands to the microprocessor (1) through the button (5), and the detection results obtained by the microprocessor (1) are displayed on the display screen (6).

8. The DC insulation testing device according to claim 1, characterized in that, Current sensors are installed on the loads of each branch of the ungrounded DC power system to obtain the leakage current of each branch load, thereby locating the faulty branch. The sensor data is transmitted to the DC insulation detection device through the communication module, processed, and then further transmitted to the monitoring system of the ungrounded DC power system.

9. A DC insulation testing method, characterized in that, Includes the following steps: S1. When the test begins, a system test and a disconnection test are first performed on the ungrounded neutral power system under test. This is used to determine whether the insulation testing device described in any one of claims 1 to 8 is working properly and whether the equivalent grounding point and positive and negative busbars of the ungrounded neutral power system are correctly connected to the insulation testing device. S2. If the system test and disconnection detection pass, the first round of injection method testing begins. If the insulation resistance value obtained by the injection method is less than the set insulation alarm value, i.e., the insulation level is low, the injection method testing continues. If the insulation level is detected multiple times, a low insulation level warning is issued. If the insulation resistance value is greater than the insulation alarm value, an unbalanced bridge method test is performed after one injection method test. If the difference between the insulation resistance values ​​obtained by the injection method and the unbalanced bridge method is less than 10%, the unbalanced bridge method is continuously executed. If the difference between the insulation resistance values ​​obtained by the unbalanced bridge method after a set number of tests is greater than 10%, the injection method is switched to perform insulation testing on the system under test. S3. Continue step S2 until the detection device receives a stop operation command.

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