Single-core cable sheath comprehensive test device and test method

Abstract

The invention relates to a comprehensive testing device and a testing method for a single-core high-voltage power transmission cable. The comprehensive testing device comprises a single-chip microcomputer core circuit, a power supply circuit connected with the single-chip microcomputer core circuit, and a signal control circuit, a voltage doubling rectifying circuit, a signal measuring circuit, a signal receiving circuit and a screen display circuit which are simultaneously connected with the single-chip microcomputer core circuit and the power supply circuit, the power supply circuit is used for supplying power to other circuits in the comprehensive testing device; the single-chip microcomputer core circuit is used for receiving, sending and processing data. The voltage doubling rectifying circuit is used for generating a direct-current high-voltage signal; the signal control circuit is used for controlling the voltage doubling rectifying circuit; the signal measurement circuit is used for receiving a measurement signal, processing the measurement signal and sending the processed measurement signal to the single-chip microcomputer core circuit; the signal receiving circuit is used for receiving pulse signals during sheath nuclear phase detection; and the screen display circuit is used for sending the measured data to a screen of the display circuit through serial port connection after the single chip microcomputer chip calculates the measured data. According to the device, multiple functions are achieved, the device is small and portable, the types of tools are greatly simplified, and convenience is provided for field work.

Description

Technical Field

[0001] The present invention belongs to the field of electrical engineering technology, and more specifically, relates to a comprehensive testing device and a testing method for a sheath of a single-core high-voltage transmission cable. Background Art

[0002] In recent years, with the continuous development of social economy, the scale of power grid has been increasing. In the process of urbanization, the proportion of cable lines in power lines has increased year by year due to their advantages such as beautifying the urban environment, reliable power supply, and helping to improve the power factor of the line. The huge underground power network also puts forward higher requirements on the efficiency and detection accuracy of cable operation and inspection.

[0003] Prior art 1 discloses a one-time wiring high-voltage transmission line parameter test device (CN218099352U), in which all devices are wired at one time during the test preparation stage. When the substation grounding switch is disconnected, the auxiliary device and the line parameter system are operated separately through the integrated control console, and the opposite side device is wirelessly remotely controlled to complete the measurement of induced electricity, phase core, insulation resistance and line parameters. However, the shortcomings of the prior art are: the prior art is a design idea with a single function, which can only perform phase core, insulation resistance and capacitance separately. If you want to measure these data at the same time, you must bring three or more devices, which is inconvenient to carry; and prior art 1 uses a controller and a switch array to switch the measurement function, which is not the same circuit. There is a problem that the negative half-cycle voltage cannot be quickly reduced to near 0V when the high-voltage pulse is in use.

[0004] Prior art 2 discloses a high-voltage insulation resistance test device for anti-interference power transmission lines (CN104777366A), the structure of which includes an inductive voltage suppressor and a high-voltage insulation resistance test unit; wherein the inductive voltage suppressor is connected to the measurement circuit of the high-voltage insulation resistance test unit. The control unit in the high-voltage insulation resistance test unit is respectively connected to the power supply module, the display screen, the operating keyboard, the DC high-voltage inverter, and the measurement circuit. However, the disadvantage of the prior art 2 is that the insulation resistance is measured using capacitor voltage division, which is easily damaged during transportation or use, is not suitable for frequent movement or transportation, and has the risk of high cost of use.

[0005] Common contents in daily cable maintenance and repair include metal sheath phase detection, insulation resistance measurement, capacitance measurement, etc. However, few existing devices can perform multi-functional tests, and multiple instruments need to be carried in actual work, which is inconvenient. In addition, the existing devices are inefficient in metal sheath phase detection, the on-site operation is complicated, and the inspection personnel have high professional knowledge requirements. They are easily affected by environmental factors and prone to misjudgment, which causes many inconveniences in actual on-site work. Summary of the invention

[0006] In view of the fact that the existing devices cannot perform comprehensive measurements on daily detection tasks such as the phase core, insulation resistance, and capacitance of the cable metal sheath, and require multiple instruments, which are not convenient to carry, and cannot be simply, efficiently, and accurately detected during the phase core of the metal sheath, the present invention provides a single-core cable sheath comprehensive test device, the purpose of which is to simplify the types of tools and implements, use one device to achieve multiple functions, provide convenience for on-site work, and simplify the operating steps in the phase core detection of the metal sheath, and improve the detection efficiency and accuracy. The present invention integrates the phase core, insulation resistance measurement, and capacitance measurement functions into one circuit. Such a design can greatly reduce the cost, volume, and weight, and has the advantages of highly integrated functions, high reliability, easy to carry, small size, easy to use, and low cost.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a single-core cable sheath comprehensive testing device, which is applied to sheath core phase detection, insulation resistance measurement and capacitance measurement of a single-core high-voltage transmission cable, comprising:

[0009] A single-chip microcomputer core circuit, and a power supply circuit connected thereto, as well as a signal control circuit, a voltage doubling rectifier circuit, a signal measurement circuit, a signal receiving circuit and a screen display circuit connected to the single-chip microcomputer core circuit and the power supply circuit;

[0010] The power supply circuit is used to supply power to other circuits in the comprehensive test device; the single-chip microcomputer core circuit is used to receive, send and process data; the voltage doubler rectifier circuit is used to generate DC high-voltage signals; the signal control circuit is used to control the voltage doubler rectifier circuit; the signal measurement circuit is used to receive the measurement signal and send it to the single-chip microcomputer core circuit after processing; the signal receiving circuit is used to receive the pulse signal during the sheath core phase detection; the screen display circuit is used for the single-chip microcomputer chip to calculate the measured data and then send the data to the screen of the display circuit through the serial port connection.

[0011] Preferably, the single-chip microcomputer core circuit includes a single-chip microcomputer chip, and a crystal oscillator circuit, a reset circuit and a communication interface circuit connected to the single-chip microcomputer chip;

[0012] The single-chip microcomputer chip is used for data processing; the crystal oscillator circuit is used to provide a stable clock signal for the single-chip microcomputer chip to ensure the synchronous operation of the circuits of the single-chip microcomputer core circuit; the reset circuit is used to return the single-chip microcomputer core circuit to its initial state when the integrated test device has an abnormality or needs to be restarted; the communication interface circuit is used to exchange data between the single-chip microcomputer core circuit and other circuits to realize communication between systems.

[0013] Preferably, the power supply circuit includes a switch circuit and a power conversion circuit; the switch circuit is connected to the power conversion circuit;

[0014] The switch circuit is used to supply power to the comprehensive test device, and the power conversion circuit is used to convert the voltage provided by the switch circuit.

[0015] Preferably, the switch circuit includes a power supply battery, a transistor and a MOS tube, the power supply battery is connected to the source of the MOS tube, and the collector of the transistor is connected to the gate of the MOS tube; the transistor is used to control the on and off of the MOS tube, thereby controlling the subsequent power supply.

[0016] Preferably, the power conversion circuit includes a first power conversion circuit, a second power conversion circuit and a third power conversion circuit;

[0017] The first power conversion circuit is used to convert the voltage provided by the power supply battery in the switch circuit into a first power supply voltage, the second power conversion circuit is used to convert the first power supply voltage provided in the first power conversion circuit into a second power supply voltage, and the third power conversion circuit is used to convert the first power supply voltage provided in the first power conversion circuit into a third power supply voltage;

[0018] The input end of the first power conversion circuit is connected to the drain of the MOS tube in the switch circuit; the input ends of the second power conversion circuit and the third power conversion circuit are connected to the output end of the first power conversion circuit.

[0019] Preferably, the signal control circuit includes a differential amplifier chip, which adjusts the duty cycle of the pulse wave generated by the differential amplifier chip through the high-voltage feedback voltage fed back by the voltage doubler rectifier circuit and the given voltage output by the single-chip microcomputer chip to control the output voltage of the voltage doubler rectifier circuit.

[0020] Preferably, the voltage doubler rectifier circuit is a three-stage six-fold voltage amplification rectifier circuit structure.

[0021] Preferably, the signal measurement circuit includes an AD converter, a first signal measurement op amp, a second signal measurement op amp and a signal measurement voltage-dividing resistor. The cable under test is connected to the first signal measurement op amp via the signal measurement voltage-dividing resistor, and the second signal measurement op amp is connected to the first signal measurement op amp and the AD converter respectively.

[0022] Preferably, the signal receiving circuit comprises a core phase voltage divider resistor and a core phase operational amplifier, which are connected in series, and the measured voltage is input to the input terminal of the core phase operational amplifier through the core phase voltage divider resistor for processing.

[0023] Preferably, the screen display circuit includes a screen, and a screen display communication chip connected to the screen;

[0024] The screen is used to display the test process and results of the comprehensive test device; the screen display communication chip is used for data transmission with other circuits.

[0025] The second aspect of the present invention provides a testing method based on the above-mentioned single-core cable sheath comprehensive testing device, comprising:

[0026] Step 1, disconnect the cable sheath and grounding, connect the ABC three-phase of the comprehensive test device to the ABC three-phase of the cable to be tested respectively, and select the insulation resistance measurement function;

[0027] Step 2: Based on the insulation resistance measurement function selected in step 1, the comprehensive test device calculates the insulation resistance value and displays it on the screen, and the insulation resistance measurement is completed;

[0028] Step 3, based on the result of step 2, the capacitance test function is automatically performed, the integrated test device calculates the capacitance of the tested cable and displays it on the screen, and the capacitance test is completed;

[0029] Step 4: Based on the test result of step 2, determine whether the insulation resistance value is within the safe range. If so, proceed to step 5 to perform a core phase detection of the sheath; otherwise, terminate the test directly.

[0030] Step 5, select the sheath phase verification function of the comprehensive testing device, confirm the sheath phase verification result, and display the phase verification result on the screen.

[0031] Preferably, in step 2, the single-chip microcomputer chip sends a signal to the signal control circuit, the signal control circuit controls the voltage doubler rectifier circuit to generate a DC high voltage signal, the current is connected to the ground through the measured cable and the sampling resistor, the signal measurement circuit receives the voltage signal of the sampling resistor, transmits it to the single-chip microcomputer chip, and calculates the insulation resistance value of the measured cable;

[0032] The calculation formula for the insulation resistance of the tested cable is as follows:

[0033]

[0034] Among them, Rx is the insulation resistance of the cable under test, Vout is the DC high voltage output by the voltage doubler rectifier circuit, EARTH is the sampling resistor voltage, and R31 is the sampling resistor resistance.

[0035] Preferably, in step 3, the DC high voltage signal of the voltage doubler rectifier circuit is disconnected to start discharging, and the single-chip microcomputer chip calculates the time constant based on the discharge time, and calculates the capacitance of the measured cable based on the time constant and the resistance of the discharge circuit;

[0036] The capacitance of the cable under test is calculated based on the following formula:

[0037] Vt=V1·(e -t / RC )

[0038]

[0039] Where V1 is the voltage value when the capacitor is fully charged, Vt is the voltage value at any time, T is the time constant, R is the equivalent resistance in the discharge circuit, and C is the capacitance of the cable under test.

[0040] Preferably, in step 5, the single-chip microcomputer chip sends a pulse signal, which is transmitted to the signal receiving circuit through the cable under test. The signal receiving circuit samples the received pulse signal at the same time interval, and identifies the pulse signal information to confirm the source of the signal.

[0041] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects including but not limited to those of the prior art:

[0042] (1) In view of the problems that existing devices are unable to perform comprehensive measurements on daily inspection tasks such as the core phase, insulation resistance, and capacitance of the cable metal sheath, require multiple instruments, and are inconvenient to carry, the present invention proposes a single-core cable sheath comprehensive testing device that can simplify the types of tools and implements multiple functions with one device. The device is compact and portable, providing convenience for on-site work.

[0043] (2) In view of the problems that existing devices are inefficient in metal sheath nuclear phase detection, the on-site operation is complicated, the inspection personnel have high professional knowledge requirements, are easily affected by environmental factors, and are prone to misjudgment, the device proposed in the present invention utilizes a nuclear phase detection method based on pulse voltage, which can complete the phase detection in one operation, simplifies the operation steps, and improves the detection efficiency and accuracy.

[0044] (3) The present invention does not require switching of the control circuit, which solves the problem that the negative half-cycle voltage cannot be quickly reduced to near 0V when the high-voltage pulse is in use. The same circuit can be used to complete the detection of the three functions of sheath core phase, insulation resistance measurement and capacitance measurement, greatly saving cost and instrument weight.

[0045] (4) The present invention uses resistance voltage division to measure insulation resistance, has high temperature stability, can maintain good performance under different temperature conditions, and has a wide range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the core circuit of the single-chip microcomputer according to an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of three functional measurement principles of an embodiment of the present invention;

[0048] Figure 3 is a schematic diagram of a signal control circuit according to an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of a voltage doubler rectifier circuit according to an embodiment of the present invention;

[0050] Figure 5 It is a schematic diagram of a screen display circuit according to an embodiment of the present invention;

[0051] Figure 6 is a circuit schematic diagram of the signal measurement part of an embodiment of the present invention;

[0052] Figure 7 is a circuit schematic diagram of the signal measurement part of an embodiment of the present invention;

[0053] Figure 8 is a circuit schematic diagram of the signal measurement part of an embodiment of the present invention;

[0054] Fig. 9 is a schematic diagram of a power supply circuit according to an embodiment of the present invention;

[0055] Fig.10 This is a field wiring diagram of a single-core cable sheath comprehensive testing device according to an embodiment of the present invention;

[0056] Fig.11 is a schematic diagram of a signal receiving circuit according to an embodiment of the present invention;

[0057] Fig.12 This is a wiring diagram for measuring insulation resistance according to an embodiment of the present invention;

[0058] Fig.13 This is a schematic diagram of a cross-connection test circuit according to an embodiment of the present invention;

[0059] Fig.14 It is a schematic diagram of a high voltage pulse waveform according to an embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0061] In view of the problems that the existing devices are unable to perform comprehensive measurements on daily inspection tasks such as the core phase of the cable metal sheath, insulation resistance, and capacitance, and require multiple instruments and are not easy to carry, the present invention proposes a single-core cable sheath comprehensive test device, which can simplify the types of tools and implements, realize multiple functions with one device, is compact and portable, and provides convenience for on-site work. In view of the problems that the existing devices are inefficient in metal sheath core phase detection, the on-site operation is complicated, the inspection personnel have high professional knowledge requirements, are easily affected by environmental factors, and are prone to misjudgment, such as Figure 1-13As shown, the device proposed by the present invention utilizes a nuclear phase detection method based on high-voltage pulse voltage, a high-voltage insulation resistance measurement method, and a high-voltage capacitance measurement method to form a detection device in one.

[0062] like Figure 1 As shown, the embodiment of the present invention provides a single-core cable sheath comprehensive testing device, which can simultaneously perform three functions of sheath core phase detection, insulation resistance measurement and capacitance measurement, and is applied to sheath core phase detection, insulation resistance measurement and capacitance measurement of single-core high-voltage transmission cables, including: a single-chip microcomputer core circuit, and a power supply circuit connected thereto, and a signal control circuit, a voltage doubling rectifier circuit, a signal measurement circuit, a signal receiving circuit and a screen display circuit connected to the single-chip microcomputer core circuit and the power supply circuit at the same time;

[0063] The power supply circuit is used to supply power to other circuits in the comprehensive test device; the single-chip core circuit is used to receive, send and process data, and is the core of the comprehensive test device; the voltage doubler rectifier circuit is used to generate a DC high voltage signal; the signal control circuit is used to control the voltage doubler rectifier circuit; the signal measurement circuit is used to receive the measurement signal, and send it to the single-chip core circuit after processing; the signal receiving circuit is used to receive the pulse signal during the sheath core phase detection; the screen display circuit is used for the processor to calculate the measured data and send the data to the screen of the display circuit through the serial port connection. The present invention has the advantages of highly integrated functions, high reliability, convenient carrying, small size, easy use and low cost.

[0064] The three functions of insulation resistance measurement, capacitance measurement and sheath core phase in the comprehensive test device provided by the embodiment of the present invention share a power supply circuit, a single-chip core circuit, a voltage doubling rectifier circuit, a signal control circuit and a screen display circuit. The discharge resistor required for capacitance measurement can be used for discharge after the insulation resistance measurement is completed, and can also be used for discharge in the negative half cycle of the pulse voltage during the sheath core phase.

[0065] The insulation resistance measurement and capacitance measurement shared signal measurement circuit in the comprehensive test device provided by the embodiment of the present invention has the effect of being more lightweight and interdependent in structure compared to when they are separated. After the insulation resistance measurement is completed, there is high voltage in the circuit at this time, and the circuit needs to be discharged with a discharge resistor. When measuring capacitance, the discharge constant needs to be calculated, and a discharge resistor is also needed. When the phase is nuclear, the negative half-cycle voltage of the pulse voltage should be close to 0V, and a discharge resistor is needed to pull the voltage down. The connection method of the discharge resistor is that one end is connected to the high-voltage output end of the voltage doubler rectifier circuit, the other end is grounded, and the middle is sucked and connected through a relay.

[0066] The core circuit of the microcontroller is as follows Figure 1As shown, the core circuit of the single-chip microcomputer includes a single-chip microcomputer chip, and peripheral circuits such as a crystal oscillator circuit, a reset circuit, and a communication interface circuit connected to the single-chip microcomputer chip. Among them, the crystal oscillator circuit is used to provide a stable clock signal for the single-chip microcomputer chip to ensure the synchronous operation of each circuit of the single-chip microcomputer core circuit; the reset circuit is used to return the single-chip microcomputer core circuit to an initial state when the integrated test device is abnormal or needs to be restarted; the communication interface circuit is used for data exchange between the single-chip microcomputer core circuit and other circuits to achieve communication between systems.

[0067] In a preferred but non-restrictive embodiment of the present invention, the model of the single-chip microcomputer chip is MSP430F149; Pin 52 and Pin 53 of the single-chip microcomputer chip MSP430149 are connected to the crystal oscillator circuit, and the crystal oscillator frequency is 8KHz. Pin 64 and Pin 1 of the single-chip microcomputer chip MSP430149 are respectively used for the power supply of the analog power supply and the digital power supply inside the single-chip microcomputer chip. An inductor is added for isolation in design, and filter capacitors are connected in parallel; the single-chip microcomputer chip MSP430F149 also supports a variety of low-power modes, such as active mode (AM), low power consumption 0 (LPM0), etc. These modes allow the single-chip microcomputer to adjust the power consumption according to actual needs to adapt to different application scenarios. For example, in low-power mode, the core central processing unit CPU of the single-chip microcomputer can stop working, while the peripheral mode continues to work to reduce overall power consumption. These characteristics make the MSP430F149 single-chip microcomputer particularly suitable for occasions that need to run for a long time and have strict requirements on power consumption.

[0068] Power circuit such as Fig.11 As shown, the power supply circuit includes a switching circuit and a power conversion circuit. The switching circuit is connected to the power conversion circuit. The switching circuit is used to supply power to the comprehensive test device. The power conversion circuit is used to convert the voltage provided by the switching circuit. The switching circuit includes a power supply battery, a triode and a MOS tube. The power supply battery is connected to the source of the MOS tube, and the collector of the triode is connected to the gate of the MOS tube. By utilizing the switching characteristics of the triode, after the triode is turned on, the gate of the MOS tube is at a low level, and the source voltage of the MOS tube is higher than the gate voltage, that is, VS>VG, wherein VS is the source voltage of the MOS tube, and VG is the gate voltage of the MOS tube. At this time, the MOS tube is turned on, and the triode is used to control the on and off of the MOS tube, thereby controlling the subsequent power supply.

[0069] The power conversion circuit includes a first power conversion circuit, a second power conversion circuit and a third power conversion circuit; the first power conversion circuit is used to convert the voltage provided by the power supply battery in the switch circuit into a first power supply voltage, the second power conversion circuit is used to convert the first power supply voltage provided in the first power conversion circuit into a second power supply voltage, and the third power conversion circuit is used to convert the first power supply voltage provided in the first power conversion circuit into a third power supply voltage; the input end of the first power conversion circuit is connected to the drain of the MOS tube in the switch circuit; the input ends of the second power conversion circuit and the third power conversion circuit are connected to the output end of the first power conversion circuit; the first power conversion circuit includes a first power conversion chip, the second power conversion circuit includes a second power conversion chip, and the third power conversion circuit includes a third power conversion chip; the input end of the first power conversion chip is connected to the drain of the MOS tube, and the output end is respectively connected to the input ends of the second power conversion chip and the third power conversion chip.

[0070] In a preferred but non-limiting embodiment of the present invention, the model of the transistor is 9013 transistor, the model of the MOS tube is CMD85P03A, ​​and the power supply battery adopts a 24V lithium battery, which has the advantages of stable voltage, large capacity and small size. The model of the first power conversion chip is XL1509, the model of the second power conversion chip is ICL7660, and the model of the third power conversion chip is AMS1117. The 24V lithium battery voltage is converted into a first power supply voltage of +12V by the first power conversion chip XL1509, and then the +12V first power supply voltage is converted into a second power supply voltage of -12V by the second power conversion chip ICL7660. At this time, a ±12V power supply voltage can be obtained for powering the operational amplifier circuit, and then the +12V first power supply voltage is converted into a third power supply voltage of +3.3V by the third power conversion chip AMS1117; XL1509 is a high-efficiency step-down DC-DC converter with a fixed 150KHz switch frequency, can provide a maximum output current capability of 2A, with low ripple, excellent linear regulation and load regulation characteristics; XL1509 has a built-in fixed frequency oscillator and frequency compensation circuit, which simplifies the circuit design; the XL1509 chip includes a voltage detection loop, which can adjust the duty cycle linearly from 0 to 100%; built-in enable function and output over-current protection function; the typical value of the quiescent current of ICL7660 is 170uA, Intersil's ICL7660A input voltage range is 1.5-12, the operating frequency is 10kHz, only an external 10kHz small volume capacitor is required, only an external 10uF small volume capacitor is required, the efficiency is as high as 98%, and the output power can reach 700mW (taking DIP package as an example), which meets the output 100mA requirement; AMS1117-3.3 is a positive low-dropout regulator with an output voltage of +3.3V, suitable for high-efficiency linear regulators, with large quiescent current and small ripple.

[0071] Signal control circuit such as Figure 3 As shown, in the signal control circuit, VOL_FEED is the high-voltage feedback voltage fed back by the voltage doubler rectifier circuit, and ADJin is the given voltage output by the single-chip microcomputer chip. It is input after differential amplification processing by VOL_FEED and ADJin, and thereby feedback is used to correct the duty cycle of the pulse wave generated by the differential amplifier chip. The pulse wave controls the on-off of the transistor through the output, generates an adjustable voltage to the transformer, and after being stepped up by the transformer, enters the voltage doubler rectifier circuit, so that the voltage doubler rectifier circuit can output DC high voltage electricity.

[0072] In a preferred but non-limiting embodiment of the present invention, the differential amplifier circuit is an internal structure of the SG3525 chip.

[0073] Voltage doubler rectifier circuit Figure 4 As shown, it is used to output a DC high-voltage signal, and the high-voltage feedback voltage of the signal control circuit is fed back to the voltage doubler rectifier circuit. In a preferred embodiment of the present invention, the voltage doubler rectifier circuit is a three-stage six-fold voltage amplification rectifier circuit structure, including a first diode D3, a second diode D4, a third diode D5, a fourth diode D6, a fifth diode D7, a sixth diode D8, a first capacitor C2, a second capacitor C3, a third capacitor C4, a fourth capacitor C5, a fifth capacitor C6 and a sixth capacitor C7.

[0074] like Figure 4 As shown, in a preferred but non-restrictive embodiment of the present invention, according to the selected high-voltage gear, the resistance value of the resistor in the voltage sampling loop is controlled by the first relay KA1 and the second relay KA2, so as to measure a more accurate high-voltage voltage value HVMeas, and HVMeas is filtered by the filter circuit and input into the single-chip microcomputer chip for measurement. On the other side, the insulation measurement current is measured through R15~R18, and after measuring MEAS_CURR, it is filtered by the filter circuit and then enters the single-chip microcomputer chip for measurement. The voltage is sampled from HVMeas and MEAScurr and coupled, and used as the high-voltage feedback voltage (VOL_FEED) to modulate the duty cycle of the pulse wave output by the chip.

[0075] The working principle of the voltage doubling rectifier circuit is as follows: When the double voltage rectifier circuit e2 is in the positive half cycle (positive on top and negative on bottom), the first diode D3 is turned on and the second diode D4 is turned off. The current passes through the first diode D3 to charge the first capacitor C2, and the voltage on the first capacitor C2 is charged to a value close to the peak value √2E2 of the double voltage rectifier circuit e2, and remains basically unchanged. When the double voltage rectifier circuit e2 is in the negative half cycle (negative on top and positive on bottom), the second diode D4 is turned on and the first diode D3 is turned off. At this time, the voltage Uc2=√2E2 on the first capacitor C2 is added in series with the power supply voltage e2, and the current charges the second capacitor C3 through the second diode D4, and the charging voltage Uc3=e2 peak value+1.4E2≈2√2E2. After repeated charging, the voltage on the second capacitor C3 is basically 2√2E2, and the same applies to the following part. According to the selected reference voltage, HVMeas is filtered through the filter circuit and input into the single-chip microcomputer for measurement. On the other side, the insulation measurement current is measured through R15~R18, and after the MEAS_CURR is measured, it is filtered through the filter circuit and enters the microcontroller for measurement. The voltage is sampled from HVMeas and MEAScurr and coupled, and used as VOL_FEED to modulate the duty cycle of the pulse wave output by the chip.

[0076] like Figure 1 As shown in the figure, the +3.3V voltage output by the power supply circuit is connected to the 1st and 64th pins of the microcontroller chip respectively. Figure 5 and Figure 8 As shown, the +3.3V voltage output by the power supply circuit is connected to the 5th pin of the AD converter AD7705 and the 16th pin of the screen display communication chip SP3232, and the +12V and -12V output by the power supply circuit are connected to the 4th and 8th pins of the operational amplifier respectively.

[0077] The single-chip microcomputer chip transmits an enable signal to the 10th pin of the differential amplifier chip SG3525 through the 31st pin. The connection between the signal control circuit and the voltage doubler rectifier circuit is connected to the transformer of the voltage doubler rectifier circuit through the 14th pin of the differential amplifier chip SG352511. In the voltage doubler rectifier circuit, the 7th pin of the rectifier op amp LM358 is connected to the 1st pin of the differential amplifier chip SG3525 to input the feedback signal, and at the same time, the voltage and current signals of the op amp are connected to the single-chip microcomputer chip through the rectifier op amp LM358. In the screen display circuit, the 1st and 4th pins of the screen display communication chip SP3232 are connected to the 34th and 35th pins of the single-chip microcomputer. In the signal receiving circuit, the 3rd pin of the three signal receiving op amps inputs the signal, and the 1st pin outputs the pulse signal, and they are respectively connected to the 13th, 14th and 15th pins of the single-chip microcomputer.

[0078] The embodiment of the present invention adopts the +12V first power supply voltage generated by the power supply circuit to supply power to the DC high voltage module power supply, which is more convenient for on-site use.

[0079] Signal measurement circuit such as Figure 6-8 As shown, Figure 6 , Figure 7 and Figure 8 They are part of the signal measurement circuit, Figure 6 EARTH is connected to the cable under test, through Figure 7 After the first signal measurement op amp TL1055 and the second signal measurement op amp OP07, it forms Figure 8 The input signal IputVol of the AD converter AD7705.

[0080] The signal measurement circuit includes an AD converter, a first signal measurement op amp, a second signal measurement op amp and a signal measurement voltage-dividing resistor. The measured cable is connected to the first signal measurement op amp through the signal measurement voltage-dividing resistor, and the second signal measurement op amp is connected to the first signal measurement op amp and the AD converter respectively.

[0081] In one embodiment of the present invention, the signal measurement voltage-dividing resistor is R31, which is connected in parallel to the input end of the first signal measurement operational amplifier TL1055. Unlike the prior art, an adjustable feedback circuit is added to achieve coarse and fine adjustment of the output voltage. Because insulation resistance measurement and capacitance measurement are required, the voltage accuracy must be within 0.001V. When the voltage enters the first signal measurement operational amplifier TL1055 through the signal measurement voltage-dividing resistor, negative amplification is performed first, and then connected to the second signal measurement operational amplifier OP07 for negative amplification. The waveform of the output signal is clean and accurate, and the output signal is connected to the input end of the AD converter AD7705 for data processing.

[0082] The signal measurement circuit is a voltage divider circuit that first sends the voltage to the first signal measurement op amp TL1055 for one-to-one reverse operation. The reverse accuracy can be roughly adjusted by adjusting the feedback resistor of the op amp. The voltage is then reversely amplified by the second signal measurement op amp OP07. This time, it can be fine-tuned through the feedback resistor to ensure that the output voltage is consistent with the input voltage, and then sent to pin 7 of the AD converter AD7705.

[0083] like Figure 2 As shown, when measuring insulation resistance, the electrical signal on the sampling resistor is converted into a digital signal by a 12-bit high-speed AD converter, and the digital signal is transmitted to the single-chip microcomputer chip, which converts the digital signal into the insulation resistance value through calculation; the insulation resistance value calculation formula is as follows:

[0084]

[0085] Among them, Rx is the insulation resistance of the cable under test, Vout is the DC high voltage output by the voltage doubler rectifier circuit, EARTH is the sampling resistor voltage, and R31 is the sampling resistor resistance.

[0086] When measuring capacitance, four discharge resistors are required, namely the first discharge resistor R11, the second discharge resistor R24, the third discharge resistor R25 and the fourth discharge resistor R26. During discharge, discharge is performed through the first relay KA1 and the second relay KA2 to calculate the discharge time constant and capacitance.

[0087] Signal receiving circuit such as Fig.11 As shown, the signal receiving circuit includes a core phase voltage divider resistor and a core phase operational amplifier, which are connected in series, and the measured voltage is input to the input end of the core phase operational amplifier through the core phase voltage divider resistor for processing.

[0088] The signal receiving circuit divides the voltage by connecting the core phase voltage divider resistors in series, and processes the small voltage signal after voltage division through the core phase operational amplifier to obtain a suitable voltage signal and send it to the microcontroller chip. The microcontroller chip determines the number of pulses or frequency by detecting the rising edge of the signal.

[0089] In a preferred but non-restrictive embodiment of the present invention, the core phase amplifier in the signal receiving circuit adopts LM358, which is a dual operational amplifier, and includes two independent, high-gain, internal frequency compensated operational amplifiers. It is suitable for single power supply with a wide power supply voltage range, and is also suitable for dual power supply working mode. Under the recommended working conditions, the power supply current is independent of the power supply voltage. Its scope of use includes sensor amplifiers, DC gain modules and all other occasions where operational amplifiers can be used with a single power supply. When the current signal is transmitted to the core phase operational amplifier circuit through the measuring resistor, due to the infinite input resistance of the core phase operational amplifier, the converted voltage signal has almost no attenuation. A fixed voltage is connected to the negative input terminal of the core phase operational amplifier. This voltage is the reference voltage. When the voltage at the positive input terminal is higher than the reference voltage, a high level is output, otherwise a low level is output, and then the pulses are counted through the single-chip microcomputer chip.

[0090] Screen display circuit Figure 5 As shown, the screen display circuit includes a screen display communication chip and a screen, and the screen display communication chip and the screen are electrically connected; the screen is used to display the test process and results of the comprehensive test device; the screen display communication chip is used for data transmission with other circuits.

[0091] In a preferred but non-limiting embodiment of the present invention, the screen display communication chip model is SP3232, which is an RS-232 interface transceiver chip, and its main function is the conversion of serial to parallel and parallel to serial data. The screen uses a large color serial port screen, which supports the RS-232 communication protocol. The signal generated by the processor is TTL level, so it is necessary to use the SP3232 chip for level conversion. The data is sent to the SP3232 chip through the processor, and then sent to the screen after processing. Conversely, the data sent by the screen also needs to be processed by the SP3232 chip and sent to the processor.

[0092] The three measurement functions in the single-core cable sheath comprehensive test device provided by the embodiment of the present invention share the power supply circuit, the single-chip core circuit, the voltage doubler rectifier circuit, the signal control circuit and the screen display circuit. When in the insulation resistance measurement and capacitance measurement functions, the measurement is completed by the power supply circuit, the single-chip core circuit, the voltage doubler rectifier circuit, the signal control circuit, the signal measurement circuit and the screen display circuit. When in the sheath core phase detection function, the measurement is completed by the power supply circuit, the single-chip core circuit, the voltage doubler rectifier circuit, the signal control circuit, the signal receiving circuit and the screen display circuit.

[0093] The embodiment of the present invention uses the core circuit of the single-chip microcomputer to control the overall circuit and realize the signal generation and detection functions. The prototype of the comprehensive test device also supports the output of video signals, and can display a concise operation interface on the display screen for touch operation. The device parameters are as follows.

[0094] Table 1 Parameters of single-core cable sheath comprehensive test device

[0095]

[0096]

[0097] The voltage setting of the comprehensive test device provided by the embodiment of the present invention has three gears of conventional voltage 1000V, 2500V and 5000V for selection, and has a variable output voltage setting function, which can achieve 50V increments within the range of 1000V to 5000V. While testing the insulation resistance, the capacitance can be measured to provide important parameters of the capacitance during series resonance.

[0098] The comprehensive test device provided in the embodiment of the present invention is divided into three voltage levels of 1000V, 2500V, and 5000V, which can cope with the insulation resistance measurement of most cables, and the DC high voltage output error is less than 0.5%. In terms of safety, it has a self-protection function.

[0099] like Figure 4As shown, the power supply circuit, voltage doubling rectifier circuit and signal control circuit in the DC high voltage module are used to increase the DC voltage to the required 1000V, 2500V or 5000V DC high voltage, which is directly applied to both ends of the cable to be tested. The electrical signal on the sampling resistor is converted into a digital signal through a 12-bit high-speed AD converter, and the single-chip microcomputer converts the digital signal into an insulation resistance value through calculation.

[0100] like Fig.11 As shown in the figure, the pulse voltage detection method is innovatively proposed in the metal sheath phase detection function. By directly detecting at both ends of the complete cross-connection section, there is no need to dismantle the grounding boxes at various locations for verification. The phase can be completed in one operation. The insulation resistance measurement and capacitance measurement functions only require one operation. The sheath phase detection requires a separate operation, which simplifies the operation steps and improves the detection efficiency. Taking the pulse voltage signal as the detection object, the accuracy is greatly improved, and there is no need for multiple judgments.

[0101] like Fig.12 As shown in the figure, the single-core cable sheath comprehensive test device is uniquely designed, compact and portable, simple and practical, and can quickly and accurately complete the nuclear phase and insulation resistance and capacitance tests on the cable sheath. At the beginning of the test, the high-voltage symbol flashes on the LCD screen of the comprehensive test device, and the light on the screen panel flashes to prompt. The test starts automatically and displays the test time (minutes: seconds). At 15 seconds, there will be a buzzer prompt, and there will be a prompt every minute thereafter. After 10 minutes, the high-voltage output will be automatically shut down and the capacitance value will be displayed. During the test, there will be a flashing light signal on the right side of the device and a flashing high-voltage symbol on the screen to remind the operator to pay attention to safety. After the test is completed, the system will automatically discharge.

[0102] Insulation resistance measurement principle: Figure 6-8 As shown, the cable sheath and grounding are disconnected, and the ABC three-phases of the comprehensive test device are respectively connected to the ABC three-phases of the cable sheath, and the G terminal is grounded. After pressing the start button, the single-chip microcomputer chip sends a signal to the signal control circuit, so that the voltage doubler rectifier circuit sends a DC high voltage, and the current passes through the cable sheath and is connected to the ground. Finally, the voltage signal is received by the signal measurement circuit, and the electrical signal on the sampling resistor is converted into a digital signal through a 12-bit high-speed AD converter. The voltage on the voltage-dividing resistor is measured by the signal measurement circuit. According to the formula V1 / R1=V2 / (R+R1), R1 is the voltage-dividing resistor, R is the insulation resistance to be measured, V1 is the voltage on the voltage-dividing resistor, and V2 is the voltage output by the voltage-doubling rectifier circuit. The insulation resistance is calculated, and the single-chip microcomputer core circuit converts the digital signal into the insulation resistance value through calculation, and transmits the data to the screen through the screen display circuit.

[0103] Capacitance measurement principle: disconnect the cable sheath and ground, connect the ABC three-phase of the comprehensive test device to the ABC three-phase of the cable sheath respectively, firstly, the voltage doubler rectifier circuit generates a DC high voltage signal, and after the DC high voltage signal fills the capacitor, disconnect the DC high voltage output and start discharging. The capacitance calculation formula is as follows:

[0104] Vt=V1·(e -t / RC )

[0105]

[0106] Where V1 is the voltage value when the capacitor is fully charged, Vt is the voltage value at any time, T is the time constant, R is the equivalent resistance in the discharge circuit, and C is the capacitance of the cable under test.

[0107] The hardware part of the capacitance measurement consists of the discharge RC circuit of the resistance measurement part. After each insulation resistance measurement, the capacitance measurement is automatically performed.

[0108] Sheath core phase detection principle: disconnect the cable sheath and ground, connect the ABC three phases of the comprehensive test device to the ABC three phases of the cable sheath respectively, and the signal sent by the single chip microcomputer of the comprehensive test device is based on the following Fig.11 The line shown reaches the signal receiving circuit, and the signal receiving circuit samples the received pulse signal at the same time interval and identifies the pulse signal information to confirm the source of the signal.

[0109] The working principle of the comprehensive test device according to the embodiment of the present invention is as follows:

[0110] The single-chip microcomputer chip control signal controls the working state of the SG3525 chip in the control circuit. Specifically, the single-chip microcomputer core circuit controls whether the SG3525 chip is working by controlling the level of pin 10 of the SG3525 chip. At the same time, the digital-to-analog conversion module DA in the single-chip microcomputer core circuit outputs a reference voltage to pin 2 of the SG3525 chip. When the SG3525 chip is working, the PWM wave output through pins 11 and 14 controls the operation of the half-bridge drive transformer composed of two MOS tubes. The voltage doubler rectifier circuit generates a DC high-voltage signal, which is fed back to pin 1 of the SG3525 chip to maintain a stable DC high-voltage output. At the same time, the feedback voltage is sent to the single-chip microcomputer chip for data processing and uploaded to the screen through the screen display circuit.

[0111] The signal measurement circuit is used for insulation resistance measurement and capacitance measurement. After the DC high-voltage signal generated by the voltage-doubling rectifier circuit enters the cable to be tested, it is sampled through the series-connected signal measurement voltage-dividing resistor. The sampling resistor voltage is transmitted to the signal measurement op amp circuit for voltage stabilization and filtering, and then sent to pin 7 of the AD converter AD7705. The AD converter AD7705 processes the data and sends it to the single-chip microcomputer chip. The single-chip microcomputer chip processes the data and calculates the insulation resistance and capacitance of the cable to be tested.

[0112] Example

[0113] like Fig.10 As shown in the figure, the cross-connection test line system consists of two cross-connection grounding boxes (J1, J2), two direct grounding boxes (outdoor terminal direct grounding, GIS direct grounding) and the cable lines therebetween. The system includes three cross-connection sections of about 800m, and the lines and grounding boxes are all in a state of waiting to be put into operation.

[0114] like Fig.12 As shown in the figure, a single-core cable sheath comprehensive test device is used for field testing. When the phase connection is correct, the signal sent by the device reaches the signal receiving circuit according to the line. The signal receiving circuit samples the received pulse signal at the same interval and repeatedly identifies the number of pulse signals. Fig.13 As shown, the three-phase test results are A-AC; B-BA; C-CB, proving that the device has a good detection effect.

[0115] The embodiment of the present invention also provides a single-core cable sheath comprehensive testing method, comprising:

[0116] Step 1: Disconnect the cable sheath and grounding, connect the ABC phases of the comprehensive test device to the ABC phases of the cable to be tested, and select the insulation resistance measurement function.

[0117] Step 2: Based on the insulation resistance measurement function selected in step 1, the comprehensive test device calculates the insulation resistance value and displays it on the screen, and the insulation resistance measurement is completed.

[0118] Specifically, the single-chip microcomputer chip sends a signal to the signal control circuit, the signal control circuit controls the voltage doubler rectifier circuit to generate a DC high-voltage signal, the current is connected to the ground through the cable under test and the sampling resistor, the signal measurement circuit receives the voltage signal of the sampling resistor, transmits it to the single-chip microcomputer chip, and calculates the insulation resistance value of the cable under test.

[0119] The calculation formula for the insulation resistance of the tested cable is as follows:

[0120]

[0121] Among them, Rx is the insulation resistance of the cable under test, Vout is the DC high voltage output by the voltage doubler rectifier circuit, EARTH is the sampling resistor voltage, and R31 is the sampling resistor resistance.

[0122] Step 3, based on the result of step 2, the capacitance test function is automatically performed, the integrated test device calculates the capacitance of the tested cable and displays it on the screen, and the capacitance test is completed.

[0123] Specifically, the DC high voltage signal of the voltage doubler rectifier circuit is disconnected to start discharging, and the single-chip microcomputer chip calculates the time constant based on the discharge time, and calculates the capacitance of the measured cable based on the time constant and the resistance of the discharge circuit.

[0124] The capacitance of the cable under test is calculated based on the following formula:

[0125] Vt=V1·(e -t / RC )

[0126]

[0127] Where V1 is the voltage value when the capacitor is fully charged, Vt is the voltage value at any time, T is the time constant, R is the equivalent resistance in the discharge circuit, and C is the capacitance of the cable under test.

[0128] Step 4, based on the test result of step 2, determine whether the insulation resistance value is within the safe range. If so, proceed to step 5 to perform the sheath core phase detection; otherwise, terminate the test directly.

[0129] In a preferred but non-limiting embodiment of the present invention, the safety range of the insulation resistance is at least 1 MΩ.

[0130] Step 5, select the sheath phase verification function of the comprehensive testing device, confirm the sheath phase verification result, and display the phase verification result on the screen.

[0131] Specifically, the single-chip microcomputer chip sends out a pulse signal, which is transmitted to the signal receiving circuit through the cable under test. The signal receiving circuit samples the received pulse signal at the same time interval, identifies the pulse signal information, and confirms the source of the signal.

[0132] In a preferred but non-limiting embodiment of the present invention, the pulse signal information is identified by repeatedly identifying the number of pulse signals, such as Fig.13As shown, within a certain period of time, the signal pulse waveform received by phase B is the same as the pulse signal sent by phase A. It can be determined that the propagation direction of the pulse signal is A-AB. The wiring judgment of phase A and phase C, and phase B and phase C is similar, and will not be repeated here. If the correct direction of the signal is specified as A-AC; B-BA; C-CB or A-AB; B-BC; C-CA, the phase verification result is the correct connection.

[0133] In a preferred but non-limiting embodiment of the present invention, the pulse signal is identified by identifying the frequency of the pulse signal, and the voltage doubler rectifier circuit is controlled by the single chip core circuit to emit a high voltage pulse waveform, such as Fig.14 As shown, the frequency of the A-phase pulse signal is 1 Hz, the frequency of the B-phase pulse signal is 0.5 Hz, and the frequency of the C-phase pulse signal is 0.2 Hz; the phase verification result is determined by comparing the frequencies of the pulse transmission signal and the pulse receiving signal in each direction.

[0134] The signal receiving circuit divides the voltage through a high-voltage non-inductive resistor in series, and processes the divided small voltage signal through the core phase operational amplifier circuit to obtain a suitable voltage signal and send it to the IO port of the microcontroller. The microcontroller uses a counter to count and finally displays the phase sequence result on the display screen through the screen display circuit.

[0135] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A single-core cable sheath comprehensive testing device, characterized in that: Applied to sheath core phase detection, insulation resistance measurement and capacitance measurement of single-core high-voltage transmission cables, including: A single-chip microcomputer core circuit, and a power supply circuit connected thereto, as well as a signal control circuit, a voltage doubling rectifier circuit, a signal measurement circuit, a signal receiving circuit and a screen display circuit connected to the single-chip microcomputer core circuit and the power supply circuit; The power supply circuit is used to supply power to other circuits in the comprehensive test device; the single-chip microcomputer core circuit is used to receive, send and process data; the voltage doubler rectifier circuit is used to generate DC high-voltage signals; the signal control circuit is used to control the voltage doubler rectifier circuit; the signal measurement circuit is used to receive the measurement signal and send it to the single-chip microcomputer core circuit after processing; the signal receiving circuit is used to receive the pulse signal during the sheath core phase detection; the screen display circuit is used for the single-chip microcomputer chip to calculate the measured data and send the data to the screen of the display circuit through the serial port connection.

2. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The core circuit of the single-chip microcomputer includes a single-chip microcomputer chip, and a crystal oscillator circuit, a reset circuit and a communication interface circuit connected to the single-chip microcomputer chip; The single-chip microcomputer chip is used for data processing; the crystal oscillator circuit is used to provide a stable clock signal for the single-chip microcomputer chip to ensure the synchronous operation of each circuit of the single-chip microcomputer core circuit; the reset circuit is used to return the single-chip microcomputer core circuit to the initial state when the integrated test device is abnormal or needs to be restarted; The communication interface circuit is used for data exchange between the microcontroller core circuit and other circuits to achieve communication between systems.

3. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The power supply circuit includes a switch circuit and a power supply conversion circuit; the switch circuit is connected to the power supply conversion circuit; The switch circuit is used to supply power to the comprehensive test device, and the power conversion circuit is used to convert the voltage provided by the switch circuit.

4. The single-core cable sheath comprehensive testing device according to claim 3 is characterized in that: The switch circuit includes a power supply battery, a transistor and a MOS tube. The power supply battery is connected to the source of the MOS tube, and the collector of the transistor is connected to the gate of the MOS tube. The transistor is used to control the on and off of the MOS tube, thereby controlling the subsequent power supply.

5. The single-core cable sheath comprehensive testing device according to claim 3 is characterized in that: The power conversion circuit includes a first power conversion circuit, a second power conversion circuit and a third power conversion circuit; The first power conversion circuit is used to convert the voltage provided by the power supply battery in the switch circuit into a first power supply voltage, the second power conversion circuit is used to convert the first power supply voltage provided in the first power conversion circuit into a second power supply voltage, and the third power conversion circuit is used to convert the first power supply voltage provided in the first power conversion circuit into a third power supply voltage; The input end of the first power conversion circuit is connected to the drain of the MOS tube in the switch circuit; the input ends of the second power conversion circuit and the third power conversion circuit are connected to the output end of the first power conversion circuit.

6. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The signal control circuit includes a differential amplifier chip, which adjusts the duty cycle of the pulse wave generated by the differential amplifier chip and controls the output voltage of the voltage doubler rectifier circuit through the high-voltage feedback voltage fed back by the voltage doubler rectifier circuit and the given voltage output by the single-chip microcomputer chip.

7. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The voltage doubler rectifier circuit is a three-stage six-fold voltage amplification rectifier circuit structure.

8. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The signal measurement circuit includes an AD converter, a first signal measurement op amp, a second signal measurement op amp and a signal measurement voltage-dividing resistor. The measured cable is connected to the first signal measurement op amp through the signal measurement voltage-dividing resistor, and the second signal measurement op amp is connected to the first signal measurement op amp and the AD converter respectively.

9. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The signal receiving circuit includes a core phase voltage divider resistor and a core phase operational amplifier, which are connected in series, and the measured voltage is input to the input end of the core phase operational amplifier through the core phase voltage divider resistor for processing.

10. The single-core cable sheath comprehensive testing device according to claim 1 is characterized in that: The screen display circuit includes a screen and a screen display communication chip connected to the screen; The screen is used to display the test process and results of the comprehensive test device; the screen display communication chip is used for data transmission with other circuits.

11. A testing method based on the single-core cable sheath comprehensive testing device according to any one of claims 1 to 10, characterized in that: include: Step 1, disconnect the cable sheath and grounding, connect the ABC three-phase of the comprehensive test device to the ABC three-phase of the cable to be tested respectively, and select the insulation resistance measurement function; Step 2: Based on the insulation resistance measurement function selected in step 1, the comprehensive test device calculates the insulation resistance value and displays it on the screen, and the insulation resistance measurement is completed; Step 3, based on the result of step 2, the capacitance test function is automatically performed, the integrated test device calculates the capacitance of the tested cable and displays it on the screen, and the capacitance test is completed; Step 4: Based on the test result of step 2, determine whether the insulation resistance value is within the safe range. If so, proceed to step 5 to perform a core phase detection of the sheath; otherwise, terminate the test directly. Step 5, select the sheath phase verification function of the comprehensive testing device, confirm the sheath phase verification result, and display the phase verification result on the screen.

12. The testing method according to claim 11, characterized in that: In step 2, the single-chip microcomputer chip sends a signal to the signal control circuit, the signal control circuit controls the voltage doubler rectifier circuit to generate a DC high-voltage signal, the current is connected to the ground through the measured cable and the sampling resistor, the signal measurement circuit receives the voltage signal of the sampling resistor, transmits it to the single-chip microcomputer chip, and calculates the insulation resistance value of the measured cable; The calculation formula for the insulation resistance of the tested cable is as follows: Among them, Rx is the insulation resistance of the cable under test, Vout is the DC high voltage output by the voltage doubler rectifier circuit, EARTH is the sampling resistor voltage, and R31 is the sampling resistor resistance.

13. The testing method according to claim 11, characterized in that: In step 3, the DC high voltage signal of the voltage doubler rectifier circuit is disconnected to start discharging, and the single-chip microcomputer chip calculates the time constant based on the discharge time, and calculates the capacitance of the measured cable based on the time constant and the resistance of the discharge circuit; The capacitance of the cable under test is calculated based on the following formula: Vt=V1·(e -t / RC ) Where V1 is the voltage value when the capacitor is fully charged, Vt is the voltage value at any time, T is the time constant, R is the equivalent resistance in the discharge circuit, and C is the capacitance of the cable under test.

14. The testing method according to claim 11, characterized in that: In step 5, the single-chip microcomputer chip sends out a pulse signal, which is transmitted to the signal receiving circuit through the cable under test. The signal receiving circuit samples the received pulse signal at the same time interval, and identifies the pulse signal information to confirm the source of the signal.

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