A cable insulation test circuit and a test method thereof

Abstract

The application provides a cable insulation test circuit and a test method thereof. The circuit comprises a main control module, a line state checking module, an insulation test module, a discharge module, a signal indication module, a touch screen module and a line control module. The input end of the main control module is connected with the touch screen module, and the output end of the main control module is connected with the line state checking module, the insulation test module, the discharge module, the signal indication module, the touch screen module and the line control module respectively. The main control module is used for sending control instructions to the line state checking module, the insulation test module, the discharge module, the signal indication module, the touch screen module and the line control module. The main control module receives test data and state information of the line state checking module, the insulation test module, the discharge module, the signal indication module, the touch screen module and the line control module, and processes the data. The line state checking module is used for checking the state of the line.

Description

Technical Field

[0001] This invention belongs to the field of cable insulation testing technology, specifically relating to a cable insulation testing circuit and its testing method. Background Technology

[0002] After the aircraft cables have been installed and wired as planned, their electrical performance must be tested in accordance with relevant standards (HB6438-2005 "General Requirements for Aircraft Wire Harness Processing", etc.) and technical requirements, among which insulation testing is an essential step.

[0003] Insulation resistance testing primarily refers to the quantitative detection of the insulation performance between the corresponding wires / cables and the helicopter shell. Based on the test results, the reliability of the insulation is determined. The principle involves applying a 500V DC high voltage between the wires / cables and the helicopter shell, and measuring the resistance formed by leakage current due to imperfect insulation. Insulation resistance is a limiting factor in designing high impedance circuits. A decrease in insulation resistance means an increase in leakage current, forming a feedback loop that will disrupt the normal operation of the circuit. Excessive leakage current can generate heat or DC current, leading to insulation failure or deterioration of electrical performance. Therefore, insulation resistance is a crucial indicator for assessing insulation performance.

[0004] However, when measuring the insulation resistance of aircraft cables, the applied DC voltage is usually high. Existing measuring equipment lacks protection measures and alarm circuits. When the operation is not standardized or the tested line is not well insulated, the continuous high voltage output of the insulation megohmmeter may damage the electronic components in the line or cause personal injury. Summary of the Invention

[0005] This application provides a cable insulation testing circuit to address the lack of protective measures and alarm circuits in existing measuring equipment.

[0006] In a first aspect, this application provides a cable insulation testing circuit, including a main control module, a line status inspection module, an insulation testing module, a discharge module, a signal indication module, a touch screen module, and a line control module, wherein:

[0007] The input terminal of the main control module is connected to the touch screen module, and the output terminal of the main control module is connected to the line status check module, insulation test module, discharge module, signal indication module, touch screen module and line control module respectively.

[0008] The main control module is used to send control commands to the line status check module, insulation test module, discharge module, signal indication module, touch screen module, and line control module; receive test data and status information from the line status check module, insulation test module, discharge module, signal indication module, touch screen module, and line control module, and process the data.

[0009] The line status check module is used to check whether the line under test has power supply before testing, whether the test line is short-circuited, and whether the discharge is completed after the test.

[0010] The insulation test module is used to output high voltage for insulation testing. The output voltage is stepped and boosted from V1, V2, V3, V4 to V5. The leakage current is monitored in real time, and the insulation test module has a built-in current limiting unit.

[0011] The discharge module is used to discharge the circuit under test before and after the insulation test to prevent the capacitors in the circuit from becoming charged and causing electric shock accidents.

[0012] The signal indicator module is used to indicate the insulation test status, whether there is a high voltage output or a test abnormality.

[0013] The touchscreen module is used to display test information and receive and send control commands.

[0014] The line control module consists of multiple relays and is used to control the connection and disconnection of related lines.

[0015] Specifically, the main control module includes a minimum system based on the ATMEGA328 microcontroller and a digital-to-analog converter (DAC). Pins 1, 2, 9, 10, and 11 of the microcontroller are connected to the five relay control terminals of the line control module, pins 7 and 8 of the microcontroller are connected to a 7.3728MHz crystal oscillator, pins 12 and 13 of the microcontroller are connected to the indicator lights and buzzer drive circuits of the signal indication module, pins 14, 15, and 17 of the microcontroller are connected to the DAC8853 of the DAC, pins 23 and 24 of the microcontroller are connected to the signal acquisition unit ADS1112 of the line status check module, pin 29 of the microcontroller is connected to the reset circuit, and pins 30 and 31 of the microcontroller are connected to the touch screen module.

[0016] Specifically, the main control module's digital-to-analog conversion unit mainly includes DAC8830 and OPA277, which are used to convert the microcontroller's digital signal instructions into 0-5V analog voltage instructions for the high-voltage module, i.e., the output terminal is connected to the high-voltage output circuit of the insulation test module.

[0017] Specifically, the signal acquisition unit of the line status inspection module includes ADS1112 and TL081. The acquisition port AI N0 of ADS1112 is connected to the emitter follower formed by TL081 to acquire insulation test results. The acquisition port AI N1 of ADS1112 is connected to the resistance test line of the resistance detection unit to acquire line resistance. The acquisition port AI N2 of ADS1112 is connected to the internal voltage detection unit of the insulation test module to acquire high voltage output. The acquisition port AI N3 of ADS1112 is connected to the voltage test line of the voltage detection unit to acquire line voltage.

[0018] Specifically, the line control module includes relays 1, 2, 3, 4, and 5, all of which are normally open relays with identical control circuits and control terminals connected to a microcontroller. One of the two contacts of relay 1 is connected to the voltage check unit of the line status check module, and the other is connected to the line under test. One of the two contacts of relay 2 is connected to the discharge module, and the other is connected to the line under test. The two contacts of relay 3 are connected to the power supply of the insulation test module. One of the two contacts of relay 4 is connected to the high-voltage output circuit of the insulation test module, and the other is connected to the insulation resistance measurement circuit. One of the two contacts of relay 4 is connected to the resistance check unit of the line status check module, and the other is connected to the line under test.

[0019] Specifically, the signal indication module includes an indicator light and a buzzer, and its driving circuit is similar to that of a relay control circuit. The control terminal of both is connected to a microcontroller.

[0020] Specifically, the insulation test module has a built-in current limiting unit that limits the maximum output current to 5mA; the ratio of the high voltage output of the insulation test module to the input control signal voltage is 100; and the response time of the relays in the line control module when they engage and disengage should be less than 3ms.

[0021] 8. The cable insulation test circuit according to claim 1, wherein the voltage range of V1 is 40-60V, the voltage range of V2 is 90-110V, the voltage range of V3 is 190-210V, the voltage range of V4 is 340-360V, and the voltage range of V5 is 490-510V.

[0022] Secondly, this application provides a cable insulation testing method, the method comprising:

[0023] Step 1: After connecting the circuit under test to the test circuit, send a command to the main control module through the touch screen. The touch screen will then jump to the circuit inspection interface and display the inspection information.

[0024] Step 2: The main control module sends a control signal to the line status check module and the line control module. The relay 1 of the line control module is activated, and the voltage check unit of the line status check module is connected to the line under test.

[0025] Step 3: If the voltage of the tested line is normal or can drop to zero after discharge, relays 1 and 2 will be disconnected and relay 5 will be connected. The resistance checking unit of the line status checking module will be connected to the tested line. If the tested line is short-circuited, the main control module will send a command to the line control module, relay 5 will be disconnected, and the main control module will send a command to the signal indication module. The signal indicator light will flash and the buzzer will sound. The operator needs to check and start the test again.

[0026] Step 4: If the resistance checking unit is normal, the main control module sends a command to the line control module, and relays 1 and 2 are activated to complete the circuit discharge.

[0027] Step 5: The main control module sends a command to the touch screen module, the touch screen jumps to the insulation test interface and displays the status information; the main control module sends a command to the line control module, relay 1 and relay 2 are disconnected, relay 3 is energized, and the insulation test module is powered on.

[0028] Step 6: The main control module sends a command to the insulation test module, which then starts outputting voltage V1. The internal voltage monitoring unit of the insulation test module monitors the real-time output voltage and, after confirming that it meets the accuracy requirements, sends a feedback signal to the main control module. The main control module then sends a command to the line control module, which activates relay 4. The high-voltage output circuit of the insulation test module is then connected to the circuit under test. The internal voltage monitoring unit and leakage current monitoring unit of the insulation test module monitor the circuit in real time. If the circuit is normal, the voltage increases in a stepwise manner according to V1, V2, V3, V4, and V5. If an abnormality occurs, a feedback signal is immediately sent to the main control module. The main control module then sends a command to the line control module, which deactivates relays 3 and 4. The main control module then sends a command to the signal indicator module, which causes the signal indicator light to flash and the buzzer to sound.

[0029] Step 7: After the insulation test is completed, the main control module sends a command to the line control module, relays 1 and 2 are activated, and relays 3 and 4 are deactivated. After the circuit discharge is completed, the main control module sends the test results to the touch screen for display.

[0030] Specifically, step 2 also includes:

[0031] If an abnormal voltage is detected in the tested line, a signal is sent to the main control module. Upon receiving the signal, the main control module sends a command to the line control module, causing relay 2 to engage and connecting the discharge module line to the tested line. If the voltage of the tested line does not drop, it indicates that an external power source may be connected to the tested line. The main control module then sends a command to the line control module, causing relays 1 and 2 to disengage. The main control module then sends a command to the signal indicator module, causing the signal indicator light to flash and the buzzer to sound. The operator must then check and restart the test.

[0032] In summary, this application provides a cable insulation test circuit. The circuit inspection and automatic discharge before and after insulation testing can effectively reduce circuit damage caused by operator error. The stepped boost high voltage output of the insulation test and the real-time monitoring of leakage current and output voltage can effectively reduce circuit damage caused by poor insulation or wiring errors in the tested circuit. Attached Figure Description

[0033] Figure 1 A schematic diagram of a cable insulation test circuit provided in this application;

[0034] Figure 2 A minimum system schematic diagram of a main control module provided in this application;

[0035] Figure 3 A schematic diagram of a digital-to-analog converter unit for a main control module provided in this application;

[0036] Figure 4 A schematic diagram of the signal acquisition unit of a line status inspection module provided in this application;

[0037] Figure 5 A relay control schematic diagram of a circuit control module provided in this application;

[0038] Figure 6 A buzzer control schematic diagram of a signal indication module provided in this application;

[0039] Figure 7 This application provides a schematic diagram of the indicator light control principle for a signal indication module. Detailed Implementation

[0040] Purpose of the invention: This invention provides a circuit and method for testing the insulation of aircraft cables, which can identify testing risks and avoid damage to electronic components in the circuit caused by continuous high-voltage output during insulation testing.

[0041] Example 1

[0042] like Figure 1As shown, this application provides a cable insulation testing circuit, including a main control module, a line status inspection module, an insulation testing module, a discharge module, a signal indication module, a touch screen module, and a line control module, wherein:

[0043] The input terminal of the main control module is connected to the touch screen module, and the output terminal of the main control module is connected to the line status check module, insulation test module, discharge module, signal indication module, touch screen module and line control module respectively.

[0044] The main control module is used to send control commands to the line status check module, insulation test module, discharge module, signal indication module, touch screen module, and line control module; receive test data and status information from the line status check module, insulation test module, discharge module, signal indication module, touch screen module, and line control module, and process the data.

[0045] The line status check module is used to check whether the line under test has power supply before testing, whether the test line is short-circuited, and whether the discharge is completed after the test.

[0046] The insulation test module is used to output high voltage for insulation testing. The output voltage is stepped and boosted from V1, V2, V3, V4 to V5. The leakage current is monitored in real time, and the insulation test module has a built-in current limiting unit.

[0047] The discharge module is used to discharge the circuit under test before and after the insulation test to prevent the capacitors in the circuit from becoming charged and causing electric shock accidents.

[0048] The signal indicator module is used to indicate the insulation test status, whether there is a high voltage output or a test abnormality.

[0049] The touchscreen module is used to display test information and receive and send control commands.

[0050] The line control module consists of multiple relays and is used to control the connection and disconnection of related lines.

[0051] Specifically, such as Figure 2As shown, the main control module includes a minimum system based on the ATMEGA328 microcontroller and a digital-to-analog converter unit. Pins 1, 2, 9, 10, and 11 of the microcontroller are connected to the five relay control terminals of the line control module, pins 7 and 8 of the microcontroller are connected to a 7.3728MHz crystal oscillator, pins 12 and 13 of the microcontroller are connected to the indicator lights and buzzer drive circuits of the signal indication module, pins 14, 15, and 17 of the microcontroller are connected to the DAC8853 of the digital-to-analog converter unit, pins 23 and 24 of the microcontroller are connected to the signal acquisition unit ADS1112 of the line status check module, pin 29 of the microcontroller is connected to the reset circuit, and pins 30 and 31 of the microcontroller are connected to the touch screen module.

[0052] Specifically, such as Figure 3 As shown, the main control module's digital-to-analog conversion unit mainly includes DAC8830 and OPA277, which are used to convert the microcontroller's digital signal instructions into 0-5V analog voltage instructions for the high-voltage module, i.e., the output terminal is connected to the high-voltage output circuit of the insulation test module.

[0053] Specifically, such as Figure 4 As shown, the signal acquisition unit of the line status inspection module includes ADS1112 and TL081. The acquisition port AI N0 of ADS1112 is connected to the emitter follower formed by TL081 to acquire insulation test results. The acquisition port AI N1 of ADS1112 is connected to the resistance test line of the resistance detection unit to acquire line resistance. The acquisition port AI N2 of ADS1112 is connected to the internal voltage detection unit of the insulation test module to acquire high voltage output. The acquisition port AI N3 of ADS1112 is connected to the voltage test line of the voltage detection unit to acquire line voltage.

[0054] Specifically, such as Figure 5 As shown, the line control module includes relays 1, 2, 3, 4, and 5, all of which are normally open relays with identical control circuits. All relays' control terminals are connected to a microcontroller. One contact of relay 1 is connected to the voltage check unit of the line status check module, and the other is connected to the line under test. One contact of relay 2 is connected to the discharge module, and the other is connected to the line under test. Two contacts of relay 3 are connected to the power supply of the insulation test module. One contact of relay 4 is connected to the high-voltage output circuit of the insulation test module, and the other is connected to the insulation resistance measurement circuit. One contact of relay 4 is connected to the resistance check unit of the line status check module, and the other is connected to the line under test.

[0055] Specifically, such as Figure 6-7As shown, the signal indication module includes an indicator light and a buzzer. Its driving circuit is similar to that of a relay control circuit, and the control terminal is connected to a microcontroller.

[0056] Specifically, the insulation test module has a built-in current limiting unit that can limit the maximum output current to 5mA.

[0057] Specifically, the ratio of the high voltage output of the insulation test module to the input control signal voltage is 100.

[0058] Specifically, the response time for the relays in the line control module to engage and disengage should be less than 3ms.

[0059] Specifically, the voltage range of V1 is 40-60V, the voltage range of V2 is 90-110V, the voltage range of V3 is 190-210V, the voltage range of V4 is 340-360V, and the voltage range of V5 is 490-510V.

[0060] Specifically, the touch screen module can display the current operating status of the circuit, the inspection results of the line status inspection module, the insulation test results, the operating status of the high voltage output circuit in the insulation test mode, the on / off status of the five relays in the line control module, and whether the test is abnormal.

[0061] In summary, this application provides a cable insulation test circuit. The circuit inspection and automatic discharge before and after insulation testing can effectively reduce circuit damage caused by operator error. The stepped boost high voltage output of the insulation test and the real-time monitoring of leakage current and output voltage can effectively reduce circuit damage caused by poor insulation or wiring errors in the tested circuit.

[0062] Example 2

[0063] This application provides a cable insulation testing method, implemented using the cable insulation testing circuit provided in the above embodiments, the method comprising:

[0064] Step 1: After connecting the circuit under test to the test circuit, send a command to the main control module through the touch screen. The touch screen will then jump to the circuit inspection interface and display the inspection information.

[0065] Step 2: The main control module sends a control signal to the line status check module and the line control module. The relay 1 of the line control module is activated, and the voltage check unit of the line status check module is connected to the line under test.

[0066] If an abnormal voltage is detected in the tested line, a signal is sent to the main control module. Upon receiving the signal, the main control module sends a command to the line control module, causing relay 2 to engage and connecting the discharge module line to the tested line. If the voltage of the tested line does not drop, it indicates that an external power source may be connected to the tested line. The main control module then sends a command to the line control module, causing relays 1 and 2 to disengage. The main control module then sends a command to the signal indicator module, causing the signal indicator light to flash and the buzzer to sound. The operator must then check and restart the test.

[0067] Step 3: If the voltage of the tested line is normal or can drop to zero after discharge, relays 1 and 2 will disconnect, and relay 5 will connect. The resistance check unit of the line status check module will be connected to the tested line. If the tested line is short-circuited, the main control module will send a command to the line control module, relay 5 will disconnect, and the main control module will send a command to the signal indicator module. The signal indicator light will flash and the buzzer will sound. The operator needs to check and start the test again.

[0068] Step 4: If the resistance checking unit is normal, the main control module sends a command to the line control module, and relays 1 and 2 are activated to complete the circuit discharge.

[0069] Step 5: The main control module sends a command to the touchscreen module, which then redirects to the insulation test interface and displays status information. The main control module also sends a command to the line control module, causing relays 1 and 2 to deactivate, relay 3 to activate, and power to the insulation test module to be connected.

[0070] Step 6: The main control module sends a command to the insulation test module, which then starts outputting voltage V1. The internal voltage monitoring unit of the insulation test module monitors the real-time output voltage and, after confirming that it meets the accuracy requirements, sends a feedback signal to the main control module. The main control module then sends a command to the line control module, causing relay 4 to engage. The high-voltage output circuit of the insulation test module is then connected to the circuit under test. The internal voltage monitoring unit and leakage current monitoring unit of the insulation test module monitor the circuit in real time. If the circuit is normal, the voltage increases in a stepwise manner according to V1, V2, V3, V4, and V5. If any abnormality occurs, a feedback signal is immediately sent to the main control module. The main control module then sends a command to the line control module, causing relays 3 and 4 to disengage. The main control module then sends a command to the signal indicator module, causing the signal indicator light to flash and the buzzer to sound.

[0071] Step 7: After the insulation test is completed, the main control module sends a command to the line control module, relays 1 and 2 are activated, and relays 3 and 4 are deactivated. After the circuit discharge is completed, the main control module sends the test results to the touch screen for display.

[0072] In summary, this application provides a cable insulation test circuit. The circuit inspection and automatic discharge before and after insulation testing can effectively reduce circuit damage caused by operator error. The stepped boost high voltage output of the insulation test and the real-time monitoring of leakage current and output voltage can effectively reduce circuit damage caused by poor insulation or wiring errors in the tested circuit.

Claims

1. A cable insulation test circuit, characterized by, The device comprises a main control module, a line state checking module, an insulation testing module, a discharge module, a signal indicating module, a touch screen module and a line control module. The input end of the main control module is connected with the touch screen module, and the output end of the main control module is connected with the line state checking module, the insulation testing module, the discharge module, the signal indicating module, the touch screen module and the line control module. The main control module is used for sending control instructions to the line state checking module, the insulation testing module, the discharge module, the signal indicating module, the touch screen module and the line control module, and receiving test data and state information of the line state checking module, the insulation testing module, the discharge module, the signal indicating module, the touch screen module and the line control module and data processing. The line state checking module is used for checking whether the measured line has power supply before testing, whether the test line is short-circuited, and whether the discharge after testing is completed. The insulation testing module is used for outputting high voltage for insulation testing, outputting electric step voltage from V1, V2, V3, V4 to V5, and monitoring the size of leakage current in real time, and the insulation testing module is provided with a built-in current limiting unit. The discharge module is used for discharging the measured line before and after insulation testing, preventing the line from being electrified by the capacitor and causing electric shock accidents. The signal indicating module is used for indicating the insulation testing state, such as high voltage output or test abnormality. The touch screen module is used for displaying test information and receiving and sending control instructions. The line control module is composed of multiple relays and is used for controlling the connection and disconnection of related lines. The line control module comprises relay 1, relay 2, relay 3, relay 4 and relay 5, all of which are normally open relays with the same control circuit and control end connected with the microcontroller; two contacts of the relay 1 are connected with the voltage checking unit of the line state checking module and the measured line respectively; two contacts of the relay 2 are connected with the discharge module and the measured line respectively; two contacts of the relay 3 are connected with the power supply of the insulation testing module; two contacts of the relay 4 are connected with the high voltage output circuit of the insulation testing module and the insulation resistance measuring circuit respectively; two contacts of the relay 5 are connected with the resistance checking unit of the line state checking module and the measured line respectively.

2. The cable insulation test circuit of claim 1, wherein, The main control module comprises a minimum system with the microcontroller ATMEGA328 as the core and a digital-analog conversion unit, the 1, 2, 9, 10 and 11 pins of the microcontroller are connected with the control ends of the five relays of the line control module, the 7 and 8 pins of the microcontroller are connected with the 7.3728 MHZ crystal oscillator, the 12 and 13 pins of the microcontroller are connected with the indicator light and buzzer driving circuit of the signal indicating module, the 14, 15 and 17 pins of the microcontroller are connected with the DAC8853 of the digital-analog conversion unit, the 23 and 24 pins of the microcontroller are connected with the signal acquisition unit ADS1112 of the line state checking module, the 29 pin of the microcontroller is connected with the reset circuit, and the 30 and 31 pins of the microcontroller are connected with the touch screen module.

3. The cable insulation test circuit of claim 1, wherein, The digital-analog conversion unit of the main control module mainly comprises DAC8830 and OPA277, which is used for converting the digital signal instruction of the microcontroller into 0-5V analog voltage instruction to the high-voltage module, i.e. the output end is connected with the high-voltage output circuit of the insulation test module.

4. The cable insulation test circuit of claim 1, wherein, The signal acquisition unit of the line state inspection module comprises ADS1112 and TL081, the acquisition port AIN0 of ADS1112 is connected with the emitter formed by TL081, which is used for acquiring the insulation test result, the acquisition port AIN1 of ADS1112 is connected with the resistance test circuit of the resistance detection unit, which is used for acquiring the line resistance, the acquisition port AIN2 of ADS1112 is connected with the internal voltage detection unit of the insulation test module, which is used for acquiring the high-voltage output, and the acquisition port AIN3 of ADS1112 is connected with the voltage test circuit of the voltage detection unit, which is used for acquiring the line voltage.

5. The cable insulation test circuit of claim 1, wherein, The signal indication module comprises indicator light and buzzer, and the driving circuit thereof is similar to the relay control circuit, and the control end is connected with the microcontroller.

6. The cable insulation test circuit of claim 1, wherein, The built-in current limiting unit of the insulation test module limits the maximum output current to 5mA; the ratio of the output high voltage of the insulation test module to the input control signal voltage is 100; and the action response time of the relay of the line control module when being attracted and disconnected should be less than 3ms.

7. The cable insulation test circuit of claim 1, wherein, The voltage range of V1 is 40-60V, the voltage range of V2 is 90-110V, the voltage range of V3 is 190-210V, the voltage range of V4 is 340-360V, and the voltage range of V5 is 490-510V.

8. A method of testing cable insulation, characterized by, The method comprises: Step 1: after the measured line is connected with the test circuit, the main control module is sent with an instruction through the touch screen, the touch screen jumps to the line inspection interface and displays the inspection information; Step 2: the main control module sends a control signal to the line state inspection module and the line control module, the relay 1 of the line control module is attracted, and the voltage inspection unit of the line state inspection module is connected with the measured line; Step 3: if the voltage of the measured line is normal or the voltage of the measured line can be lowered to zero after being discharged, the relays 1 and 2 are disconnected, the relay 5 is connected, the resistance inspection unit of the line state inspection module is connected with the measured line, if the measured line is short-circuited, the main control module sends an instruction to the line control module, the relay 5 is disconnected, the main control module sends an instruction to the signal indication module, the signal indication light flashes and the buzzer rings, and the operator needs to check and start the test again; Step 4: if the resistance inspection unit is normal, the main control module sends an instruction to the line control module, the relays 1 and 2 are attracted, and the circuit is discharged; Step 5: the main control module sends an instruction to the touch screen module, the touch screen jumps to the insulation test interface and displays the state information; the main control module sends an instruction to the line control module, the relays 1 and 2 are disconnected, the relay 3 is attracted, and the power supply of the insulation test module is connected. Step 6: The main control module sends instructions to the insulation test module, the insulation test module starts to output V1 voltage, the insulation test module internal voltage monitoring unit monitors the real-time output voltage, confirms the accuracy, sends feedback signal to the main control module, the main control module sends instructions to the line control module, relay 4 is attracted, the insulation test module high voltage output circuit is connected with the measured line, the insulation test module internal voltage monitoring unit and leakage current monitoring unit real-time monitoring, the line is normal, then the voltage is increased in steps V1, V2, V3, V4, V5, once the abnormal occurs, immediately sends feedback signal to the main control module, the main control module sends instructions to the line control module, relay 3, relay 4 is disconnected, the main control module sends instructions to the signal indicating module, the signal indicating lamp flashes and the buzzer rings; Step 7: After the insulation test is completed, the main control module sends instructions to the line control module, relay 1, relay 2 is attracted, relay 3, relay 4 is disconnected, after the circuit is discharged, the main control module sends test results to the touch screen display.

9. The method of claim 8, wherein, Step 2 also includes: If the test finds that the measured line voltage is abnormal, send signal to the main control module, the main control module receives the signal, sends instructions to the line control module, relay 2 is attracted, the discharge module line is connected with the measured line, the measured line voltage does not decrease, which shows that whether there is an external power supply in the measured line is not disconnected, the main control module sends instructions to the line control module, relay 1, relay 2 is disconnected, the main control module sends instructions to the signal indicating module, the signal indicating lamp flashes and the buzzer rings, the operator needs to check and start the test again.

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