Cable lead seal defect live detection system and detection method based on impedance spectroscopy

Abstract

The present invention provides a cable lead seal defect live detection system based on impedance spectrum and its detection method, including a portable computer detection system and an eddy current detection sensor, the portable computer detection system includes a device housing, a signal generation module, a signal receiving module, a signal processing module, a storage module, a power module and a computer system arranged inside the housing, and a display screen and a plurality of buttons embedded in the housing, the eddy current detection sensor is a cylindrical placement probe, including a probe housing and an internal coil, a magnetic core, the probe is connected to the portable computer detection system through a probe connector and a line, the portable computer detection system obtains an impedance spectrum by processing and displaying the impedance information of the probe coil collected by the eddy current detection sensor probe, and analyzes the cable defects. The detection system and method of the present invention can timely discover the hidden dangers of the cable line and ensure the safety of the power grid based on the detection of the cable in the lead-sealed state.

Description

Technical Field

[0001] The invention belongs to the field of cable detection, and in particular relates to a cable lead seal defect live detection system based on impedance spectrum and a detection method thereof. Background Art

[0002] With the continuous development and improvement of electromagnetic theory and its experiments, non-destructive testing and evaluation technologies such as eddy current testing have been continuously developed. Eddy current technology is widely used due to its many advantages. First of all, it is a non-contact detection and can penetrate the covering layer of non-conductors, which means that no special surface treatment is required during detection, thus shortening the detection cycle and reducing costs. At the same time, the sensitivity of eddy current detection is very high. Eddy current detection can be divided into single-frequency eddy current, multi-frequency eddy current, pulsed eddy current, far-field eddy current, etc. according to the different excitation methods and detection principles.

[0003] Traditional eddy current uses single-frequency excitation to detect surface and near-surface defects. Depending on the material being tested and the depth of the defect, the excitation frequency ranges from a few hertz to a few megahertz. In order to obtain a good detection signal, the excitation coil must induce the largest eddy current near the defect. The magnitude of the induced current is related to the excitation frequency, conductivity, magnetic permeability, the size and shape of the excitation coil, and the magnitude of the excitation current. Defects are detected by measuring changes in impedance or voltage. However, since it is also sensitive to other parameters, this affects the detection of defects.

[0004] In recent years, with the development of science and technology, eddy current detection technology has made breakthrough progress in development and use. From the perspective of hardware technology, the application of large-scale and ultra-large-scale integrated circuits has greatly reduced the size and power consumption of the instrument; from the perspective of software technology, the performance of computer microprocessors has been greatly improved, and "soft" has become a trend instead of "hard", and the intelligence level of the whole machine has been greatly improved, which has greatly reduced the requirements for the operating skills of the instrument users. At present, eddy current technology has been widely used in the detection of different materials and structures, mainly including: detection of aircraft structures, detection of pressure vessels, and detection of welding structures. In addition, it is also used to measure displacement, but eddy current detection technology has basically not been applied to high-voltage cable defect detection. For this reason, it is urgent to use modern technology and analytical methods to conduct technical research on the specific situation of cable accessory lead seals, so as to effectively judge the degree of lead seal cracking, discover problems in the early stage of failure, eliminate hidden dangers in time, and reduce the losses caused by power failures.

[0005] Since the application research of eddy current flaw detection technology in China is mostly carried out in the fields of aircraft structure, pressure vessel and welding structure detection, there are few studies on the defect status evaluation of cable accessory seals. The present invention intends to provide a cable seal defect live detection system and detection method based on impedance spectroscopy. Summary of the invention

[0006] In view of the problems existing in the prior art, the technical solutions adopted by the present invention to solve the problems existing in the prior art are as follows:

[0007] A cable lead seal defect live detection system based on impedance spectrum, characterized in that it includes a portable computer detection system and an eddy current detection sensor. The portable computer detection system includes a device shell, a signal generating module, a signal receiving module, a signal processing module, a storage module, a power supply module and a computer system arranged inside the shell, and a display screen and a plurality of buttons embedded in the shell. The eddy current detection sensor is a cylindrical placement probe, including a probe shell and an internal coil and a magnetic core. The probe is connected to the portable computer detection system through a probe connector and a line. The portable computer detection system obtains an impedance spectrum by processing and displaying the impedance information of the probe coil collected by the eddy current detection sensor probe, and analyzes the cable defects.

[0008] The probes are absolute or differential, in bridge or reflection configurations.

[0009] The probe is a point-type absolute probe, and the probe connector is a 16-pin LEMO or BNC connector.

[0010] The frequency range detected by the system is 10 Hz-12 MHz.

[0011] The system is provided with both high-pass and low-pass filters, the frequency of the low-pass filter is adjustable in the range of 10 Hz-2000 Hz, and the frequency of the high-pass filter is adjustable in the range of 5 Hz-1000 Hz.

[0012] The probe drive includes three drive voltages: low, medium and high, corresponding to 2V, 5V and 8V respectively.

[0013] The detection method of the cable lead seal defect live detection system based on impedance spectroscopy comprises the following steps:

[0014] Step 1: Connect the probe and portable computer detection system according to the equipment requirements;

[0015] Step 2, start the portable computer detection system, adjust the detection mode to eddy current impedance phase measurement, set the basic parameters such as test mode, absolute measurement path, output signal frequency, sampling rate, signal driving voltage, etc.;

[0016] Step 3. Enter the test operation interface by pressing the button, select the appropriate display parameters, adjust the display mode, and select the display position; the display mode is divided into three types: "Impedance", "Sweep Frequency", and "Sweep Frequency + Impedance". Generally, the "Impedance" mode is selected according to the report requirements. The other two modes are auxiliary analysis, and the display position is generally set to "Center";

[0017] Step 4: Calibrate the sensor. Take the flat lead sealing surface as the calibration base surface, calibrate the eddy current flaw detection system, and click the automatic lift-off / balance button to place the cursor in the center of the screen;

[0018] Step 5. Perform signal detection. For the cable joint, locate the lead bulge of the cable joint. Hold the probe against the cable joint. Keep the probe against the surface without pressing hard to avoid damaging the cable. Move the probe back and forth. For easy comparison and observation, click the phase angle button during the movement. Rotate the knob to adjust the afterglow to the horizontal level. Continue to click the gain button, which is divided into three types: "H / V gain", "horizontal gain" and "vertical gain". Adjust the appropriate gain until the afterglow covers the entire screen.

[0019] Step 6: Locate the defect by sliding the probe along the lead sealing surface of the cable joint at a uniform speed, and observe the changes in the eddy current spectrum on the display screen in real time. Adjust the gain, filter frequency and other parameters in real time according to the signal size. For the typical arc loop area, try to change the measurement trajectory to find the point with the maximum signal strength.

[0020] Step 7: Store the test results. The eddy current spectrum and its parameter table are stored in the system's internal storage unit, and the storage data and report file name information are recorded.

[0021] The display modes are divided into three types: "impedance", "sweep frequency", and "sweep frequency + impedance". Generally, the "impedance" mode is selected. The other two modes are auxiliary analysis. When the current signal of the probe coil is injected, the electromagnetic characteristic parameters of the conductor being measured and the detection distance remain unchanged, the impedance Z of the probe coil becomes a single-valued function of the discontinuity of the conductor being measured. The discontinuity of the conductor will affect the flow of eddy currents, causing the eddy current signal vector point in the impedance plane diagram to move. Therefore, the impedance Z of the probe coil can be used to detect the discontinuity of the measured object. The detection results of the defect and the non-defect are obviously different. The amplitude of the defect is larger, and the phase is offset, forming a typical arc loop; the more serious the cracking of the lead seal, the greater the detection signal intensity, and the easier it is to distinguish.

[0022] The present invention has the following advantages:

[0023] The detection system and method of the present invention can be used for lead seal status detection of various cable accessories, so that the lead seal status detection is no longer limited to the reference sheath grounding current and contact voltage values. No installation or power outage is required during the detection process, and the normal operation of the cable is not affected. The lead seal status can be grasped before the lead seal is completely cracked, reducing the possibility of line failure, greatly improving the efficiency and quality of lead seal detection of transformer cable accessories, saving manpower and material costs, and ensuring the safe and stable operation of the power system.

[0024] Based on the monitoring of the lead seal status of cable accessories, it is possible to take precautions, discover hidden dangers of cable lines in time, ensure the safety of the power grid, and reduce the economic losses caused by cable failures. It is of great significance and positive role. It can reduce large-scale power outages caused by accidents and improve the power supply reliability of the power system. It has great economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a system structure block diagram of the present invention;

[0026] Figure 2 This is an eddy current detection spectrum of a non-defective part of the lead seal on a 110kV high-voltage cable intermediate joint in an embodiment of the present invention;

[0027] Figure 3 This is an eddy current detection spectrum of a lead seal defect on a 110kV high-voltage cable intermediate joint in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described in detail below through embodiments and in conjunction with the accompanying drawings. Figure 1 As shown, a cable lead seal defect live detection system based on impedance spectroscopy includes a portable computer detection system and an eddy current detection sensor. The portable computer detection system includes a device housing, a signal generating module, a signal receiving module, a signal processing module, a storage module, a power supply module and a computer system arranged inside the housing, and a display screen and a plurality of buttons embedded in the housing. The eddy current detection sensor is a cylindrical probe, including a probe housing and an internal coil and a magnetic core. The probe is connected to the portable computer detection system through a probe connector and a line.

[0029] Probes are available in absolute or differential configurations, in bridge or reflection configurations.

[0030] The probe is a point-type absolute probe, and the probe connector is a 16-pin LEMO or BNC connector.

[0031] The system detects frequencies in the range of 10Hz-12MHz.

[0032] The system has both high-pass and low-pass filters. The low-pass filter frequency is adjustable in the range of 10Hz-2000Hz, and the high-pass filter frequency is adjustable in the range of 5Hz-1000Hz.

[0033] The probe drive includes three drive voltages: low, medium and high, corresponding to 2V, 5V and 8V respectively.

[0034] The detection method of the cable seal defect live detection system based on impedance spectroscopy includes the following steps:

[0035] Step 1: Connect the probe and portable computer detection system according to the equipment requirements;

[0036] Step 2, start the portable computer detection system, adjust the detection mode to eddy current impedance phase measurement, set the basic parameters such as test mode, absolute measurement path, output signal frequency, sampling rate, signal driving voltage, etc.;

[0037] Step 3. Enter the test operation interface by pressing the button, select the appropriate display parameters, adjust the display mode, and select the display position; the display mode is divided into three types: "Impedance", "Sweep Frequency", and "Sweep Frequency + Impedance". Generally, the "Impedance" mode is selected according to the report requirements. The other two modes are auxiliary analysis, and the display position is generally set to "Center";

[0038] Step 4: Calibrate the sensor. Take the flat lead sealing surface as the calibration base surface, calibrate the eddy current flaw detection system, and click the automatic lift-off / balance button to place the cursor in the center of the screen;

[0039] Step 5. Perform signal detection. For the cable joint, locate the lead bulge of the cable joint. Hold the probe against the cable joint. Keep the probe against the surface without pressing hard to avoid damaging the cable. Move the probe back and forth. For easy comparison and observation, click the phase angle button during the movement. Rotate the knob to adjust the afterglow to the horizontal level. Continue to click the gain button, which is divided into three types: "H / V gain", "horizontal gain" and "vertical gain". Adjust the appropriate gain until the afterglow covers the entire screen.

[0040] Step 6: Locate the defect by sliding the probe along the lead sealing surface of the cable joint at a uniform speed, and observe the changes in the eddy current spectrum on the display screen in real time. Adjust the gain, filter frequency and other parameters in real time according to the signal size. For the typical arc loop area, try to change the measurement trajectory to find the point with the maximum signal strength.

[0041] Step 7: Store the test results. The eddy current spectrum and its parameter table are stored in the system's internal storage unit, and the storage data and report file name information are recorded.

[0042] like Figure 2 and Figure 3 The figure shows the eddy current detection spectrum of the lead seal defect and non-defect on the middle joint of a 110kV high-voltage cable. Under the high-voltage cable operating environment, the detection signals at the non-defect are basically the same, and the detection signal intensity difference at the defect is small. The lead seal cracking defect can be distinguished under different operating voltages and load currents.

[0043] Based on the principle of electromagnetic induction, this system has an independent eddy current detection channel and an external dedicated lead seal eddy current detection probe. On the basis of keeping the probe parameters and lift-off height unchanged, the impedance of the probe coil is detected to achieve the detection of discontinuity on the surface of the tested lead seal, that is, cracks, holes, scratches and other defects. The system can read the impedance value of the eddy current sensor in real time, display the detection single impedance diagram and swept impedance diagram separately or simultaneously, realize the synchronous comparative analysis of the single impedance diagram and the swept impedance diagram, and has the functions of synchronous saving, browsing and exporting of data images and setting parameters. It is powerful in acquisition settings, signal reception, signal processing and power management. The system supports adjustable phase angle of impedance diagram, which can realize 360-degree rotation of impedance diagram; supports adjustable center position, which can realize moving impedance diagram to any position on the screen; supports separate adjustment of horizontal and vertical gain to cope with complex test environment on site; has afterglow retention function, which can set and adjust retention time; has high-pass and low-pass filters, the low-pass filter frequency range is 10-2000Hz adjustable, and the high-pass filter is 5-1000Hz adjustable and can be set to off; has two completely independent frequencies, can work simultaneously under the same trigger, and compare the impedance diagrams at two different frequencies to detect defects; has two completely independent frequencies, can work simultaneously under the same trigger, and compare the impedance diagrams at two different frequencies to detect defects; can display up to three impedance images with configured parameters at the same time, including single impedance diagrams and swept impedance diagrams at different frequencies, and customize their display positions; can display two real-time parameters at the same time, including the peak-to-peak value of each impedance diagram , maximum vertical peak, maximum horizontal peak and peak-to-peak angle; it can freeze and save the current impedance image on the screen with one click, and has the function of signal calibration when the image is frozen to adjust the signal gain and phase angle; it has one-click data saving and one-click automatic lift-off balancing functions, which can realize rapid balancing and automatic lift-off of the equipment; the setting parameters can be displayed and edited on one page at the same time, and the instrument can be quickly configured for testing; and the operation panel has a shuttle knob for fast switching and operation; it has a PC-side data analysis software platform, which can view and analyze the test data exported by the host; it has strong signal receiving capability and does not require a preamplifier; it can set an instant reference signal for real-time comparative analysis; it has an intelligent power management system that can display the current power and working status in real time. The host has three power supply modes, namely direct power supply from the charging adapter, built-in lithium-ion battery power supply and built-in AA alkaline battery box power supply. At the same time, it can automatically identify the type of built-in battery to prevent the adapter from charging the alkaline battery by mistake.

[0044] The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope and spirit of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and modifications.

Claims

1. A detection method for a cable seal defect live detection system based on impedance spectroscopy, characterized in that: The cable lead seal defect live detection system based on impedance spectrum includes a portable computer detection system and an eddy current detection sensor. The portable computer detection system includes a device housing, a signal generation module, a signal receiving module, a signal processing module, a storage module, a power module and a computer system arranged inside the housing, and a display screen and a plurality of buttons embedded in the housing. The eddy current detection sensor is a cylindrical placement probe, including a probe housing and an internal coil and a magnetic core. The probe is connected to the portable computer detection system through a probe connector and a line. The portable computer detection system obtains an impedance spectrum by processing and displaying the impedance information of the probe coil collected by the eddy current detection sensor probe, and analyzes the cable defects. The system also has high-pass and low-pass filters. The low-pass filter frequency is adjustable in the range of 10Hz-2000 Hz, and the high-pass filter frequency is adjustable in the range of 5Hz-1000 Hz. The detection method comprises the following steps: Step 1: Connect the eddy current detection sensor and the portable computer detection system according to the equipment requirements; Step 2, start the portable computer detection system, adjust the detection mode to eddy current impedance phase measurement, set the basic parameters such as test mode, absolute measurement path, output signal frequency, sampling rate, signal driving voltage, etc.; Step 3: Enter the test operation interface by pressing the button, select the appropriate display parameters, adjust the display mode, and select the display position; Step 4: Calibrate the sensor, take the flat lead sealing surface as the calibration base surface, and calibrate the detection system; Step 5. Perform signal detection. For the cable joint, locate the lead bulge of the cable joint. Hold the probe against the cable joint, keep the probe against the surface, move the probe back and forth, click the phase angle button during the movement, rotate the knob to adjust the afterglow to the horizontal, continue to click the gain button, and adjust the appropriate gain until the afterglow covers the entire screen. Step 6: Locate the defect by sliding the probe along the lead sealing surface of the cable connector at a constant speed and observing the impedance spectrum changes on the display screen in real time. Adjust the gain and filter frequency parameters in real time according to the signal size. For the typical arc loop area, try to change the measurement track to find the point with the maximum signal strength. Step 7: Store the test results. The eddy current spectrum and its parameter table are stored in the system's internal storage unit, and the storage data and report file name information are recorded.

2. The detection method of the cable seal defect live detection system based on impedance spectroscopy according to claim 1, characterized in that: The probes are absolute or differential, in bridge or reflection configurations.

3. The detection method of the cable seal defect live detection system based on impedance spectroscopy as claimed in claim 2, characterized in that: The probe is a point-type absolute probe, and the probe connector is a 16-pin LEMO or BNC connector.

4. The detection method of the cable seal defect live detection system based on impedance spectroscopy according to claim 1, characterized in that: The frequency range detected by the system is 10 Hz-12 MHz.

5. The detection method of the cable seal defect live detection system based on impedance spectroscopy according to claim 1, characterized in that: The probe drive includes three drive voltages: low, medium and high, corresponding to 2V, 5V and 8V respectively.

Images