A cable online detection method and system based on voltage level dynamic regulation

Abstract

This invention relates to an online cable testing method and system based on dynamic voltage level control. The method includes: emitting a high-frequency detection signal through a wideband impedance tester, which is then transmitted to the cable under test via a capacitive coupling circuit and a second-order passive high-pass filter circuit; acquiring the cable's power frequency signal through a loop antenna, amplifying and shaping it, and then converting it into a square wave signal via a comparator for input to a microcontroller; the microcontroller calculates the corresponding duty cycle and period based on the received square wave signal; if the duty cycle of the square wave signal is outside a suitable range, the amplification factor adjuster and the comparator voltage adjuster are adjusted to bring the duty cycle of the square wave signal within a suitable range to match the voltage level of the cable under test. Compared with existing technologies, this invention can perform differentiated algorithm correction and parameter compensation based on the actual voltage level, effectively improving the adaptability and calculation accuracy of the detection algorithm.

Description

Technical Field

[0001] This invention relates to the field of online cable testing technology, and in particular to an online cable testing method and system based on dynamic voltage level control. Background Technology

[0002] Currently, the application scale of power cables in power supply scenarios such as urban power distribution networks, industrial parks, rail transit, and large public buildings is increasing significantly year by year. Compared with traditional overhead lines, power cables have significant advantages such as strong operational stability, less susceptibility to weather and environmental interference, low urban space occupancy, and outstanding power supply security. They have become a key infrastructure for power transmission and distribution and a core component for ensuring reliable power supply to regional power grids.

[0003] Currently, a large number of high-voltage, medium-voltage, and low-voltage power cables are laid in enclosed environments such as direct burial, cable trenches, and integrated tunnels, enduring complex and harsh conditions including dampness, acid and alkali corrosion, geological subsidence, and external pressure. Simultaneously, these cable lines are constantly subjected to electrical stresses such as load fluctuations, alternating temperature rises, and overvoltage impacts. As the years of operation increase, the insulation layer gradually ages and deteriorates, easily inducing hidden early-stage hazards such as water treeing, electrical tree defects, partial discharge, insulation damage, and shielding layer damage. These defects are characterized by long development cycles, high concealment, and difficulty in early detection. If they are not identified and intervened in a timely manner, they will continue to worsen and eventually lead to serious power accidents such as single-phase grounding, phase-to-phase short circuits, line tripping, and even fires. This not only causes large-scale, prolonged power outages, affecting the orderly operation of industrial production and residents' daily lives, but also results in high equipment maintenance costs and economic losses, seriously threatening the safe and stable operation of the power system.

[0004] For a long time, the operation and maintenance of power cables has generally relied on a traditional model combining periodic power outage preventive testing with manual on-site inspections. This maintenance method requires power outages, directly reducing power supply reliability. Furthermore, manual inspections are inefficient, labor-intensive, and easily limited by subjective factors such as environment and personnel experience. Offline testing can only obtain static operating data of the line at a certain moment, failing to continuously track the dynamic evolution of cable insulation conditions, making it difficult to detect slowly developing latent faults, and exhibiting blind spots and predictive lag. With the continuous increase in grid load density and the ever-increasing demands for user power supply reliability, the traditional offline maintenance model can no longer meet the current needs of refined, intelligent, and routine grid operation and maintenance management. Condition-based maintenance replacing periodic maintenance has become an inevitable trend in grid operation and maintenance development.

[0005] Driven by both industry development and practical needs, online cable inspection technology has garnered widespread attention. Online cable inspection allows for continuous, 24 / 7 collection of key cable status parameters under normal operating conditions without power outages. It enables real-time monitoring of line health, accurate identification of early minor defects and abnormal operating conditions, and early warning, location, and tracing of potential faults. This technology effectively overcomes the bottlenecks of traditional inspection methods, such as power outage limitations, discontinuous monitoring, and delayed hazard detection. It helps maintenance personnel shift from reactive emergency repairs to proactive prediction, enabling them to scientifically formulate maintenance plans, rationally arrange equipment operation and maintenance strategies, effectively reduce the incidence of sudden cable failures, extend the overall service life of cables, and reduce losses from unplanned power outages. Furthermore, combined with intelligent data analysis methods, it can further enhance the power grid equipment management capabilities, facilitate the digital and intelligent transformation of power grid operation and maintenance, and provide a solid technical guarantee for the safe, efficient, economical, and stable operation of new power systems. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a cable online detection method and system based on dynamic voltage level control, so as to carry out differentiated algorithm correction and parameter compensation according to the actual voltage level, thereby improving the adaptability and calculation accuracy of the detection algorithm.

[0007] The objective of this invention can be achieved through the following technical solutions: A cable online detection method based on dynamic voltage level control includes: For cables under test with different voltage levels, a high-frequency detection signal is emitted by a wideband impedance tester and transmitted to the cable under test through a capacitive coupling circuit and a second-order passive high-pass filter circuit. The power frequency signal of the cable under test is acquired by a loop antenna, amplified and shaped by an amplifier, and then converted into a square wave signal by a comparator for input to the microcontroller; the amplifier is equipped with an amplification factor adjuster, and the comparator is equipped with a comparison voltage adjuster. The microcontroller calculates the corresponding duty cycle and period based on the received square wave signal. If the duty cycle of the square wave signal is outside the preset suitable range, the amplification factor adjuster and the comparison voltage adjuster are adjusted to make the duty cycle of the square wave signal within the suitable range to match the cable under test with the corresponding voltage level. The microcontroller inputs the detection result of the square wave signal into the broadband impedance tester for online detection of the cable status.

[0008] Furthermore, the capacitive coupling circuit includes a first voltage divider capacitor and a second voltage divider capacitor connected in series. A sampling voltage point is provided between the first voltage divider capacitor and the second voltage divider capacitor, and this sampling voltage point is connected to a second-order passive high-pass filter circuit.

[0009] Furthermore, the second-order passive high-pass filter circuit includes a first filter capacitor, a second filter capacitor, a first filter resistor, and a second filter resistor. The first filter capacitor and the first filter resistor are connected in series and then in parallel across the two ends of the capacitive coupling circuit. The second filter capacitor and the second filter resistor are connected in series and then in parallel across the two ends of the first filter resistor. The two ends of the second filter resistor are connected to a broadband impedance tester.

[0010] Furthermore, the amplifier is a high-speed CMOS transimpedance amplifier based on an inverter.

[0011] Furthermore, both the amplification factor adjuster and the comparison voltage adjuster are sliding rheostats.

[0012] Furthermore, both the amplification factor adjuster and the comparison voltage adjuster are digital potentiometers.

[0013] Furthermore, both the amplification factor adjuster and the comparison voltage adjuster are provided with multiple taps to correspond to different amplification factors and comparison voltages; The adjustment process of the amplification factor adjuster and the comparison voltage adjuster includes calibration mode and detection mode; The calibration mode processing procedure includes: If the detected square wave signal duty cycle is lower than the appropriate range, the taps of the comparator voltage regulator are adjusted to make the comparator voltage the preset median voltage. Then, the taps of the amplification factor regulator are gradually increased to increase the amplification factor. The square wave signal duty cycle is re-detected. If it is still lower than the appropriate range and the taps of the amplification factor regulator are adjusted to the maximum, the taps of the comparator voltage regulator are gradually increased to decrease the comparator voltage value until the detected square wave signal duty cycle is within the appropriate range. The tap positions of the amplification factor regulator and the comparator voltage regulator corresponding to the current cable voltage level are recorded. If the detected square wave signal duty cycle is higher than the appropriate range, the taps of the comparator voltage regulator are adjusted to make the comparator voltage the preset median voltage. Then, the taps of the amplification factor regulator are gradually decreased to reduce the amplification factor. The square wave signal duty cycle is re-detected. If it is still higher than the appropriate range and the taps of the amplification factor regulator are adjusted to the minimum, the taps of the comparator voltage regulator are gradually decreased to increase the comparator voltage value until the detected square wave signal duty cycle is within the appropriate range. The tap positions of the amplification factor regulator and the comparator voltage regulator corresponding to the current cable voltage level are recorded.

[0014] Furthermore, the processing procedure for the detection mode includes: Obtain the voltage level of the cable under test, and adjust the taps of the amplification factor regulator and the comparison voltage regulator according to the tap positions of the amplification factor regulator and the comparison voltage regulator corresponding to the voltage level as determined by the calibration mode.

[0015] Furthermore, the appropriate range of the duty cycle of the square wave signal is 30% to 70%.

[0016] This invention also provides an online cable inspection system based on dynamic voltage level control, comprising: A wideband impedance tester is used to emit high-frequency detection signals; A capacitive coupling circuit is connected to the cable under test and is used to transmit high-frequency detection signals to the cable under test, as well as to divide the power frequency signal transmitted to the cable under test. The second-order passive high-pass filter circuit is connected to the capacitive coupling circuit and the output terminal of the wideband impedance tester, respectively. It is used to transmit high-frequency detection signals to the capacitive coupling circuit and to filter the voltage-divided power frequency signal. A loop antenna is used to acquire the power frequency signal of the cable under test; An amplifier is used to amplify and shape the cable power frequency signal acquired by the loop antenna, and is equipped with an amplification factor adjuster; The comparator is used to convert the amplified and shaped cable power frequency signal into a square wave signal, and is equipped with a comparison voltage regulator; The microcontroller is used to calculate the corresponding duty cycle and period based on the received square wave signal. If the duty cycle of the square wave signal is outside the preset appropriate range, the amplification factor adjuster and the comparison voltage adjuster are adjusted to make the duty cycle of the square wave signal within the appropriate range to match the cable under test with the corresponding voltage level. The microcontroller inputs the detection result of the square wave signal into the broadband impedance tester for online detection of the cable status.

[0017] Compared with the prior art, the present invention has the following advantages: (1) This invention uses capacitive coupling to reduce voltage and a second-order passive high-pass filter circuit to weaken high-voltage power frequency interference and transmit megahertz-level high-frequency detection signals with low loss. At the same time, a loop antenna is used to pick up the power frequency signal of the cable. After amplification and shaping, the signal characteristics are analyzed by a microcontroller. Combined with the amplitude difference of different voltage levels, the amplification factor and comparison threshold are dynamically adjusted by a digital potentiometer to adapt to the detection of all voltage levels. Differentiated algorithm correction and parameter compensation are carried out according to the actual voltage level to provide a reliable basis for impedance spectrum data correction and effectively improve the adaptability and calculation accuracy of the detection algorithm.

[0018] (2) The present invention first divides the power frequency signal of the cable through two capacitors connected in series by a capacitor coupling circuit to obtain a stable weak current signal after voltage reduction and adaptation. Then, the power frequency signal after voltage division is filtered by a second-order passive high-pass filter circuit and attenuated significantly, with the amplitude almost returning to zero. It can effectively weaken the impact of high voltage power frequency components on the downstream detection circuit and improve the electrical isolation safety between the high voltage side and the low voltage detection side. The high-frequency detection signal emitted by the broadband impedance tester can be successfully transmitted to the cable under test through the second-order passive high-pass filter circuit and capacitive coupling circuit. The high-frequency energy attenuation is weak, and the coupling insertion loss and phase distortion are controlled at extremely low levels. This ensures that the excitation signal is fully injected into the device under test to the maximum extent, providing a clean and stable pre-signal foundation for the accurate acquisition and reliable analysis of broadband impedance characteristic parameters.

[0019] (3) This invention takes into account that only when the amplifier amplification factor is appropriate and the comparator comparison voltage is appropriate can the duty cycle of the square wave be appropriate; if the duty cycle of the square wave is 100% or 0%, the period of the square wave signal cannot be detected, so the energized state of the cable cannot be detected. Only when the duty cycle of the detected square wave signal is appropriate and the period is 20ms, it indicates that the cable is energized; To address this, a calibration mode and a testing mode are set up for adjusting the amplification factor and comparison voltage. In calibration mode, the tap positions of the amplification factor regulator and comparison voltage regulator corresponding to different voltage levels are determined. In testing mode, the corresponding tap positions of the amplification factor regulator and comparison voltage regulator can be directly obtained according to the voltage level of the cable under test, realizing automatic adjustment of the taps of the amplification factor regulator and comparison voltage regulator to adapt to the testing requirements of the current voltage level. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of an online cable detection method based on dynamic voltage level control provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the detection framework of an online cable detection method based on dynamic voltage level control provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a capacitive coupling circuit provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a second-order passive high-pass filter circuit provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the processing procedure for a calibration mode provided in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0026] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a cable online detection method based on dynamic voltage level control, including: S1: For cables under test with different voltage levels, a high-frequency detection signal is emitted by a wideband impedance tester and transmitted to the cable under test through a capacitive coupling circuit and a second-order passive high-pass filter circuit. S2: The power frequency signal of the cable under test is collected by a loop antenna, amplified and shaped by an amplifier, and then converted into a square wave signal by a comparator for input to the microcontroller; the amplifier is equipped with an amplification factor adjuster, and the comparator is equipped with a comparison voltage adjuster; S3: The microcontroller calculates the corresponding duty cycle and period based on the received square wave signal. If the duty cycle of the square wave signal is outside the preset appropriate range, the amplification factor adjuster and the comparison voltage adjuster are adjusted to bring the duty cycle of the square wave signal within the appropriate range to match the cable under test with the corresponding voltage level. The microcontroller inputs the detection result of the square wave signal into the broadband impedance tester for online detection of the cable status.

[0028] The above scheme first employs capacitive coupling for voltage reduction combined with a second-order passive high-pass filter circuit to weaken high-voltage power frequency interference and transmit megahertz-level high-frequency detection signals with low loss. Simultaneously, a loop antenna is used to pick up the cable power frequency signal, which is then amplified and shaped before being analyzed by a microcontroller to determine its characteristics. Considering the amplitude differences across different voltage levels, the amplification factor and comparison threshold are dynamically adjusted via a digital potentiometer to adapt to detection across all voltage levels. Differential algorithm correction and parameter compensation are performed based on the actual voltage level, providing a reliable basis for impedance spectrum data correction and effectively improving the adaptability and calculation accuracy of the detection algorithm.

[0029] The processing in step S1 is as follows: Capacitive coupling isolation step-down is used to isolate, adapt, and reduce the amplitude of the high-voltage power frequency signal, effectively weakening the impact of the high-voltage power frequency component on the downstream detection circuit and improving the electrical isolation safety between the high-voltage side and the low-voltage detection side. The stabilized low-voltage signal after step-down adaptation is then connected to a second-order passive high-pass filter circuit for spectrum filtering, efficiently filtering out invalid interference components such as the power frequency fundamental wave, low-frequency harmonics, and low-frequency stray noise from the environment.

[0030] The broadband impedance tester actively excites and outputs a high-frequency, low-voltage detection signal, with operating frequencies reaching the megahertz (MHz) level. This high-frequency excitation signal is synchronously transmitted via a capacitive coupling channel and a second-order passive high-pass filter link. High-frequency energy attenuation is minimal, and coupling insertion loss and phase distortion are controlled to extremely low levels. This ensures that the excitation signal is fully injected into the device under test, providing a clean and stable pre-amplifier signal foundation for the accurate acquisition and reliable analysis of subsequent broadband impedance characteristic parameters. Specifically, such as Figure 3As shown, the capacitive coupling circuit adopts the principle of voltage division by two capacitors in series, including a first voltage divider capacitor C1 and a second voltage divider capacitor C2 connected in series. A sampling voltage point is provided between the first voltage divider capacitor and the second voltage divider capacitor, and this sampling voltage point is connected to a second-order passive high-pass filter circuit.

[0031] The calculation is based on a maximum power frequency voltage of 35kV. When C1 = 10nF and C2 = 330uF, the voltage at point A is: This shows that the sampling voltage at point A has been attenuated by a large margin.

[0032] like Figure 4 As shown, the second-order passive high-pass filter circuit includes a first filter capacitor C1, a second filter capacitor C2, a first filter resistor R1, and a second filter resistor R2. The first filter capacitor C1 and the first filter resistor R1 are connected in series and then in parallel across the two ends of the capacitive coupling circuit. The second filter capacitor C2 and the second filter resistor R2 are connected in series and then in parallel across the two ends of the first filter resistor R2. The two ends of the second filter resistor R2 are connected to a broadband impedance tester.

[0033] When C1=C2=1nF and R1=R2=1.6kΩ, the cutoff frequency of the second-order passive high-pass filter is: Therefore, the 50Hz 1V power frequency signal after step-down will be significantly attenuated after filtering, with the amplitude almost reaching zero; while the required high-frequency detection signal can pass through the filter smoothly with almost no loss and no impact.

[0034] In step S2, the loop antenna receives the power frequency signal generated after the cable is energized. The high-speed CMOS transimpedance amplifier (hereinafter referred to as "amplifier") based on the inverter amplifies the power frequency signal. The comparator converts the sine wave signal into a square wave signal. The microcontroller calculates the duty cycle and period of the square wave signal.

[0035] The amplitude of the power frequency signal received by the loop antenna varies depending on the voltage level (35KV, 10KV, 400V). Changing the amplification factor of the amplifier and the comparison voltage of the comparator changes the duty cycle of the output square wave.

[0036] The setup requirements for the loop antenna, amplifier, and comparator are as follows: 1) The installation distance between the loop antenna and the cable, as well as the number of coil turns, line width, turn spacing, and diameter of the loop antenna, will affect the power frequency signal. Therefore, it is necessary to optimize the loop antenna structure design to ensure the stability of power frequency signal acquisition.

[0037] 2) Due to the significant voltage differences between voltage levels, different voltage levels require different amplification factors and comparison voltages. Furthermore, the presence of high voltage hazard when the cable is energized makes direct measurement of the detected signal impossible. While both the amplification factor adjuster and the comparison voltage adjuster could be set as sliding rheostats, these cannot be directly modified. Therefore, a digital potentiometer is used to replace the sliding rheostat, and an algorithm dynamically adjusts the digital potentiometer to ensure the duty cycle of the square wave acquired by the microcontroller remains within a reasonable range.

[0038] Specifically, the structure of each part is as follows: 1. Loop antenna For loop antennas, in the process of detecting whether a cable is energized, the loop antenna, as the core signal receiving component, directly affects the stability of the detection and the accuracy of the result judgment due to the consistency of the received signal. To ensure that the amplitude and frequency response of the antenna received signals remain highly consistent under different detection scenarios and operating conditions, and to avoid signal distortion or deviation caused by differences in antenna structure, this loop antenna is specifically designed and manufactured using a PCB (printed circuit board) in an integrated manner. PCB technology has extremely high dimensional accuracy, which can strictly control the number of coil turns, line width, spacing, and loop diameter of the loop antenna according to the design parameters, avoiding structural deviations caused by traditional methods such as manual winding, and ensuring the uniformity of the antenna's electromagnetic parameters.

[0039] The cable online detection system based on broadband impedance spectrum directly connects the cable plug to the cable conductor by modifying the cable plug, while the power line passes through the center of the PCB loop antenna, ensuring the consistency of the positions of the power line and the PCB loop antenna.

[0040] 2. Amplifier The amplifier is a high-speed CMOS transimpedance amplifier based on an inverter. The advantage of a high-speed CMOS transimpedance amplifier based on an inverter is essentially the synergy of the characteristics of CMOS process technology and the advantages of inverter structure. It inherits the low power consumption, high integration, and low cost characteristics of CMOS process technology, and solves the pain point of traditional transimpedance amplifiers that are difficult to balance high speed and low power consumption, and where performance and cost are mutually constrained, through the high gain bias and simple cascading capability of inverters. It is suitable for scenarios where cable live detection interfaces have low power consumption and miniaturization requirements.

[0041] 3. Dynamically adjust the digital potentiometer If the amplifier's amplification factor is insufficient or the comparator's comparison voltage is too high, the square wave signal will be detected as having a 0% duty cycle.

[0042] If the amplifier gain is too high and the comparator comparison voltage is too low, the square wave signal duty cycle will be detected as 100%.

[0043] Only when the amplifier gain is appropriate and the comparator voltage is moderate can the duty cycle of the square wave be moderate.

[0044] If the microcontroller detects a square wave with a duty cycle of 100% or 0%, it cannot detect the period of the square wave signal, and therefore cannot detect the energized state of the cable. Only when the detected square wave signal has a suitable duty cycle and a period of 20ms can it be determined that the cable is energized.

[0045] To prevent clipping distortion at the top of the amplified sine wave, the voltage range of the comparison voltage is controlled between 1.5V and 2.5V.

[0046] Even at the same voltage level, differences in installation and different environments can affect the detection of loop antennas. To prevent the square wave duty cycle from reaching 100% or 0%, the square wave duty cycle should be kept between 30% and 70% in calibration mode.

[0047] Preliminary experimental tests showed that different voltage levels (110KV, 66KV, 35KV, 10KV, 400V) can all generate square wave signals with a 30% to 70% accuracy through amplifiers and comparators.

[0048] In this embodiment, the amplifier's first digital potentiometer has a total resistance of 100k ohms and 32 taps. This corresponds to an amplifier gain between 2 and 63 times.

[0049] The comparator's second digital potentiometer has a total resistance of 200k ohms and 16 taps. The corresponding comparison voltages of the comparator are between 1.5V and 2.5V, as shown in Table 1.

[0050] Table 1 The adjustment process for the amplifier's first digital potentiometer and the comparator's second digital potentiometer includes calibration mode and detection mode; like Figure 5 As shown, the calibration mode processing procedure includes: If the detected square wave signal duty cycle is below the appropriate range, adjust the taps of the comparator voltage regulator to make the comparator voltage the preset median voltage; then gradually increase the taps of the amplification factor regulator to increase the amplification factor; re-detect the square wave signal duty cycle. If it is still below the appropriate range and the taps of the amplification factor regulator are adjusted to the maximum, gradually increase the taps of the comparator voltage regulator to decrease the comparator voltage value until the detected square wave signal duty cycle is within the appropriate range. Record the tap positions of the amplification factor regulator and the comparator voltage regulator corresponding to the current cable voltage level. If the detected square wave signal duty cycle is higher than the appropriate range, adjust the taps of the comparator voltage regulator to make the comparator voltage the preset median voltage; then gradually decrease the taps of the amplification factor regulator to reduce the amplification factor; re-detect the square wave signal duty cycle. If it is still higher than the appropriate range and the taps of the amplification factor regulator are adjusted to the minimum, gradually decrease the taps of the comparator voltage regulator to increase the comparator voltage value until the detected square wave signal duty cycle is within the appropriate range. Record the tap positions of the amplification factor regulator and the comparator voltage regulator corresponding to the current cable voltage level.

[0051] During operation, input the voltage value to be connected to the current cable and configure the current mode to calibration mode. After powering on and the voltage stabilizing, begin calibration.

[0052] The processing steps for the detection mode include: Obtain the voltage level of the cable under test. Based on the tap positions of the amplification factor regulator and the comparator voltage regulator corresponding to the voltage level determined by the calibration mode, adjust the taps of the first digital potentiometer of the amplifier and the second digital potentiometer of the comparator to adapt to the testing requirements of the current voltage level.

[0053] Example 2 This embodiment provides an online cable testing system based on dynamic voltage level control, comprising: A wideband impedance tester is used to emit high-frequency detection signals; A capacitive coupling circuit is connected to the cable under test and is used to transmit high-frequency detection signals to the cable under test, as well as to divide the power frequency signal transmitted to the cable under test. The second-order passive high-pass filter circuit is connected to the output of the capacitive coupling circuit and the wideband impedance tester, respectively. It is used to transmit high-frequency detection signals to the capacitive coupling circuit and to filter the voltage-divided power frequency signal. A loop antenna is used to acquire the power frequency signal of the cable under test. An amplifier is used to amplify and shape the cable power frequency signal acquired by the loop antenna, and is equipped with an amplification factor adjuster; The comparator is used to convert the amplified and shaped cable power frequency signal into a square wave signal, and is equipped with a comparison voltage regulator; The microcontroller is used to calculate the corresponding duty cycle and period based on the received square wave signal. If the duty cycle of the square wave signal is outside the preset appropriate range, the amplification factor regulator and the comparison voltage regulator are adjusted to bring the duty cycle of the square wave signal within the appropriate range to match the cable under test with the corresponding voltage level. The microcontroller inputs the detection result of the square wave signal into the broadband impedance tester for online detection of the cable status.

[0054] It should be noted that the specific content and beneficial effects of the system in this application can be found in the above method embodiments, and will not be repeated here.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for online cable testing based on dynamic voltage level control, characterized in that, include: For cables under test with different voltage levels, a high-frequency detection signal is emitted by a wideband impedance tester and transmitted to the cable under test through a capacitive coupling circuit and a second-order passive high-pass filter circuit. The power frequency signal of the cable under test is acquired by a loop antenna, amplified and shaped by an amplifier, and then converted into a square wave signal by a comparator for input to the microcontroller; the amplifier is equipped with an amplification factor adjuster, and the comparator is equipped with a comparison voltage adjuster. The microcontroller calculates the corresponding duty cycle and period based on the received square wave signal. If the duty cycle of the square wave signal is outside the preset suitable range, the amplification factor adjuster and the comparison voltage adjuster are adjusted to make the duty cycle of the square wave signal within the suitable range to match the cable under test with the corresponding voltage level. The microcontroller inputs the detection result of the square wave signal into the broadband impedance tester for online detection of the cable status.

2. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, The capacitive coupling circuit includes a first voltage divider capacitor and a second voltage divider capacitor connected in series. A sampling voltage point is provided between the first voltage divider capacitor and the second voltage divider capacitor, and this sampling voltage point is connected to a second-order passive high-pass filter circuit.

3. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, The second-order passive high-pass filter circuit includes a first filter capacitor, a second filter capacitor, a first filter resistor, and a second filter resistor. The first filter capacitor and the first filter resistor are connected in series and then in parallel across the two ends of the capacitive coupling circuit. The second filter capacitor and the second filter resistor are connected in series and then in parallel across the two ends of the first filter resistor. The two ends of the second filter resistor are connected to a broadband impedance tester.

4. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, The amplifier is a high-speed CMOS transimpedance amplifier based on an inverter.

5. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, Both the amplification factor adjuster and the comparison voltage adjuster are sliding rheostats.

6. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, Both the amplification factor adjuster and the comparison voltage adjuster are digital potentiometers.

7. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, Both the amplification factor adjuster and the comparison voltage adjuster are equipped with multiple taps to correspond to different amplification factors and comparison voltages; The adjustment process of the amplification factor adjuster and the comparison voltage adjuster includes calibration mode and detection mode; The calibration mode processing procedure includes: If the duty cycle of the detected square wave signal is lower than the appropriate range, the comparison voltage is adjusted to the preset median voltage by adjusting the tap of the comparison voltage regulator. Then, gradually increase the taps of the amplification factor regulator to increase the amplification factor; re-detect the duty cycle of the square wave signal. If it is still below the appropriate range and the taps of the amplification factor regulator are adjusted to the maximum, gradually increase the taps of the comparison voltage regulator to decrease the comparison voltage value until the detected duty cycle of the square wave signal is within the appropriate range. Record the tap positions of the amplification factor regulator and the comparison voltage regulator corresponding to the current cable voltage level. If the detected square wave signal duty cycle is higher than the appropriate range, the taps of the comparator voltage regulator are adjusted to make the comparator voltage the preset median voltage. Then, the taps of the amplification factor regulator are gradually decreased to reduce the amplification factor. The square wave signal duty cycle is re-detected. If it is still higher than the appropriate range and the taps of the amplification factor regulator are adjusted to the minimum, the taps of the comparator voltage regulator are gradually decreased to increase the comparator voltage value until the detected square wave signal duty cycle is within the appropriate range. The tap positions of the amplification factor regulator and the comparator voltage regulator corresponding to the current cable voltage level are recorded.

8. The online cable detection method based on dynamic voltage level control according to claim 7, characterized in that, The processing steps for the detection mode include: Obtain the voltage level of the cable under test, and adjust the taps of the amplification factor regulator and the comparison voltage regulator according to the tap positions of the amplification factor regulator and the comparison voltage regulator corresponding to the voltage level as determined by the calibration mode.

9. The online cable detection method based on dynamic voltage level control according to claim 1, characterized in that, The appropriate range of the duty cycle of the square wave signal is 30% to 70%.

10. A cable online detection system based on dynamic voltage level control, characterized in that, include: A wideband impedance tester is used to emit high-frequency detection signals; A capacitive coupling circuit is connected to the cable under test and is used to transmit high-frequency detection signals to the cable under test, as well as to divide the power frequency signal transmitted to the cable under test. The second-order passive high-pass filter circuit is connected to the capacitive coupling circuit and the output terminal of the wideband impedance tester, respectively. It is used to transmit high-frequency detection signals to the capacitive coupling circuit and to filter the voltage-divided power frequency signal. A loop antenna is used to acquire the power frequency signal of the cable under test; An amplifier is used to amplify and shape the cable power frequency signal acquired by the loop antenna, and is equipped with an amplification factor adjuster; The comparator is used to convert the amplified and shaped cable power frequency signal into a square wave signal, and is equipped with a comparison voltage regulator; The microcontroller is used to calculate the corresponding duty cycle and period based on the received square wave signal. If the duty cycle of the square wave signal is outside the preset appropriate range, the amplification factor adjuster and the comparison voltage adjuster are adjusted to make the duty cycle of the square wave signal within the appropriate range to match the cable under test with the corresponding voltage level. The microcontroller inputs the detection result of the square wave signal into the broadband impedance tester for online detection of the cable status.

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