A non-invasive device and method for preventing heating at an overlap of an overhead line

Abstract

A kind of non-invasive device and method for preventing the heating of overhead line lap joint, comprising four-line detection clamp, Kelvin double-arm bridge, bridge balance detection circuit, digital potentiometer, microcontroller, power supply and power management module, peripheral expansion module;Four-line detection clamp is used to load power supply voltage to the overhead line lap joint to be measured;Kelvin double-arm bridge is used to detect the resistance value of the overhead line lap joint to be measured;Bridge balance detection circuit is connected in Kelvin double-arm bridge for detecting whether Kelvin double-arm bridge reaches balance;Digital potentiometer is used to adjust its resistance size to make Kelvin double-arm bridge reach bridge balance;The present application is based on Kelvin double-arm bridge, and the characteristics of measuring accuracy and device light are considered, suitable for overhead work of transmission line, and the clamp fitting of lap joint does not need to be removed in the detection process, so as to avoid unnecessary damage to equipment, while ensuring the efficiency and safety of detection process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of overhead line, more particularly, relates to a non-invasive device and method for preventing heating at the overlap of overhead lines. BACKGROUND

[0002] The heating problem at the overlap of overhead transmission lines not only aggravates the invalid loss of electric energy and limits the carrying capacity of the line, but also may cause serious deformation of the overlap clamp and even melting in extreme cases, which poses a significant threat to the safe and stable operation of the transmission line.

[0003] Currently, the research on the heating problem at the overlap of overhead transmission lines mainly focuses on the following three aspects: 1. Research on the causes of heating of the drainage plate of the strain clamp and the change of heating temperature. This type of research has more theoretical results, but it is difficult to guide the maintenance work on site because it is difficult to stop the heating of the drainage plate of the strain clamp. 2. Research on new strain clamps, i.e. upgrading the existing strain clamps so that they are not prone to heating after installation. However, the existing strain clamps of the transmission line are large in volume and difficult to replace in bulk with new strain clamps, and even if they are replaced with new strain clamps, there is still a certain probability of heating. 3. Research on optimizing the method of live treatment after heating. This type of research cannot prevent heating and can only passively wait for heating to be treated. Therefore, it is urgent to study how to prevent the heating of the drainage plate of the strain clamp after it is put into operation.

[0004] In addition to theoretical research, there are some practical methods to "observe" the state of the drainage plate of the strain clamp on the construction site. The commonly used method is to disassemble the connecting clamp fittings for manual "visual" inspection of the installation quality of the contact surface. However, this method not only highly depends on subjective judgment and lacks objective and unified quantitative standards, but also often causes unnecessary secondary damage to the clamp fittings in actual operation.

[0005] The existing technology for detecting heating at the overlap of overhead transmission lines includes:

[0006] The patent CN109186776A proposes a detection method, device and equipment for heating of a power transmission line clamp. It includes: applying a rated current to the power transmission line, which is the current required when the power transmission line is fully loaded; determining the rated temperature reached by the power transmission line under the condition of inputting the rated current; detecting the actual temperature reached by the power transmission line under the condition of inputting the rated current; and determining the heating point of the clamp by comparing the rated temperature and the actual temperature. However, this method cannot be implemented in the field. The rated current of a high-voltage line is usually several hundred amperes, and there is no equipment in the field that can provide such a large current. Even if there is equipment with such a large power, its volume and weight are very large, and the clamps of overhead lines are in the air. It is difficult to transport such a large power to the air, which is not conducive to field detection, and is only a laboratory method.

[0007] The patent CN113295961A proposes an edge computing method for early warning and dynamic capacity increase of heating of an overhead power transmission line clamp. It includes 1, heating information collection of the power transmission line clamp based on ultra-high frequency sensing; 2, edge computing of clamp heating based on hierarchical Bayesian processing; 3, multi-dimensional sensor information collection and heating calculation of overhead power transmission lines; and 4, dynamic capacity increase edge computing based on an echo state network model. However, this method is too complex, uses too many sensors, and is not conducive to field detection. Its accuracy needs to be verified.

[0008] The patent CN112290451A proposes a heating detection and cooling system and method for a power transmission line clamp. By mounting a drone, an infrared thermal imager can quickly obtain an infrared thermal image of the power transmission line clamp. The control module can determine whether the temperature of the power transmission line clamp exceeds the preset temperature threshold based on the infrared thermal image, thereby quickly detecting the heating condition of the power transmission line clamp. At the same time, when the ground remote control platform receives the heating warning information, it controls the spray gun to spray a hollow sphere. When the hollow sphere hits the power transmission line clamp and breaks, the conductive viscous liquid inside the hollow sphere adheres to the power transmission line clamp, thereby quickly enhancing the conductivity of the power transmission line clamp, reducing the resistivity, and further reducing the heating temperature of the power transmission line clamp. However, this is a post-treatment after heating, i.e., the line is in operation and heating occurs, and then the method is used for cooling treatment. This patent detects the resistance and other parameters of the power transmission line clamp before the line is energized, thereby preventing the clamp from heating after the line is energized. SUMMARY

[0009] To address the shortcomings of existing technologies, this invention provides a non-destructive device and method for preventing overheating at overhead line joints. Based on the Kelvin double-arm bridge method, it conducts in-depth research on issues such as the selection of bridge arm resistance parameters. This invention also innovatively designs a high-precision, low-resistance digital potentiometer, representing an innovation in the core technology of the balanced bridge. To address the resistance temperature drift problem, the Kelvin double-arm bridge method has been improved, ultimately resulting in a measuring instrument with advantages such as high measurement accuracy, stable operation, compact portability, and suitability for high-altitude operations on power lines.

[0010] The present invention adopts the following technical solution.

[0011] The first aspect of this invention provides a non-destructive device for preventing overheating at overhead line joints, comprising a four-wire detection clamp, a Kelvin double-arm bridge, a bridge balance detection circuit, a digital potentiometer, a microcontroller, a power supply, a power management module, and a temperature measurement module; characterized in that:

[0012] The four-wire detection clamp includes a first clamp, a second clamp, a first detection wire and a second detection wire connected to the first clamp, and a third detection wire and a fourth detection wire connected to the second clamp.

[0013] The first clamp and the second clamp are respectively clamped at the joint R of the overhead line to be tested. x At both ends, the first detection line of the four-wire detection clamp is connected in series with the first bridge arm resistor R1, the second bridge arm resistor R2, and the digital potentiometer R. p One end is connected; the third detection line of the four-wire detection clamp is connected to the digital potentiometer R through the series-connected third bridge arm resistor R3, fourth bridge arm resistor R4, and digital potentiometer R. p The other end is connected; the second detection wire of the four-wire detection clamp is connected to the positive terminal of the power supply of the Kelvin double-arm bridge; the fourth output terminal of the four-wire detection clamp is connected to the digital potentiometer R. p The other end is connected to the digital potentiometer R. p One end is connected to the negative terminal of the power supply of the Kelvin double-arm bridge through the fifth resistor R0; wherein, R1 and R2 are one series arm of the Kelvin double-arm bridge, and R3 and R4 are the other series arm of the Kelvin double-arm bridge.

[0014] The bridge balance detection circuit includes a signal amplification module and an AD conversion module. The signal input terminal of the signal amplification module is connected to the contacts of R1 and R2 and the contacts of R3 and R4 respectively to obtain the bridge arm output. The output signal of the signal amplification circuit is output to the microcontroller through the AD conversion module.

[0015] The temperature measurement module transmits the temperature value at the junction of the overhead line tower to the microcontroller through a temperature measurement probe installed at the junction of the overhead line.

[0016] The microcontroller adjusts the resistance of the digital potentiometer according to the AD conversion module output to make the Kelvin double-arm bridge balanced, calculates the resistance of the overhead line joint to be detected according to the resistance value of the digital potentiometer at this time, and corrects the detected resistance value by the measured temperature value. x

[0017] According to the corrected resistance value of the overhead line joint and the resistance value of the overhead line joint detected in the last time unit, the heating state of the overhead line joint is comprehensively judged in combination with the set heating threshold.

[0018] Preferably, the first detection line, the second detection line, the third detection line and the fourth detection line are copper wires, and the copper wires are wrapped with anticorrosive insulation skin.

[0019] Preferably, the four bridge arm resistance parameters R1, R2, R3 and R4 of the Kelvin double-arm bridge are selected according to the calculation formula:

[0020]

[0021] Wherein, R p is the resistance value of the digital potentiometer, R x is the resistance value of the overhead line joint to be detected calculated when the bridge is balanced, U out is the actual output voltage of the voltage source, U A is the voltage at the connection of the first resistance R1 and the second resistance R2, U B is the resistance at the connection of the third resistance R3 and the fourth resistance R4, I1 is the current on R1, and I2 is the current on R2.

[0022] Preferably, the signal amplification module is specifically an operational amplifier, the non-inverting input end of the operational amplifier is connected between the first resistance R1 and the second resistance R2 of the Kelvin double-arm bridge, the inverting input end of the operational amplifier is connected between the third resistance R3 and the fourth resistance R4 of the Kelvin double-arm bridge, and the output end of the operational amplifier is connected with the input end of the AD conversion module.

[0023] Preferably, the microcontroller uses the bisection method to dynamically adjust the resistance value of the digital potentiometer, so that the bridge reaches balance, and when the voltage difference between the non-inverting input end and the inverting input end of the operational amplifier is less than the voltage difference threshold ψ after being converted by the AD conversion module, it is indicated that the bridge reaches balance.

[0024] Preferably, the digital potentiometer is composed of a plurality of resistors and a plurality of MOS tubes, and the number of resistors connected is controlled by controlling the conduction of different MOS tubes. When the nth MOS tube is controlled to be turned on and the remaining MOS tubes are turned off, n resistors are connected. All MOS tubes are controlled by independent MOS gate drive chips, and all gate drive chips are connected to the microcontroller for unified control. ​

[0025] Preferably, the MOS tube in the digital potentiometer is selected as a low on-resistance MOS tube, the on-resistance of which is less than or equal to 1 mΩ, and the accuracy of the resistance is less than or equal to 1%.

[0026] Preferably, the power supply and power management are composed of a DC / DC boost module and a low-dropout regulator (LDO) module, the bridge balance detection circuit is powered by a voltage that is boosted by the DC / DC boost module and then converted by the low-dropout regulator (LDO) module, and the positive electrode of the power supply of the Kelvin double-arm bridge is the output of the DC / DC boost module.

[0027] Preferably, the heat generation state of the overhead line joint is comprehensively judged according to the corrected overhead line joint resistance value and the overhead line joint resistance value detected in the last time unit and the set heat generation threshold, specifically:

[0028] The comprehensive resistance value of the fused corrected overhead line joint resistance value and the overhead line joint resistance value detected in the last time unit is calculated:

[0029]

[0030] Wherein, R x,t is the corrected overhead line joint resistance value at this time, R x,t-1 is the corrected overhead line joint resistance value in the last time unit, and a is a set coefficient.

[0031] When the comprehensive resistance value is greater than the set heat generation threshold, the heat generation state is considered abnormal

[0032] The set heat generation threshold is: if the four-wire detection clamp is a compression type strain clamp, the heat generation threshold is the standard resistance value of the set overhead line joint conductor; if the four-wire detection clamp is a non-compression type strain clamp, the heat generation threshold is 1.1 times the standard resistance value of the set overhead line joint conductor.

[0033] The second aspect of the application proposes a non-destructive method for preventing heat generation at the overhead line joint using the device of the first aspect of the application, characterized in that it comprises:

[0034] The resistance parameters of the Kelvin double-arm bridge are calculated and adjusted.

[0035] The resistance value of the digital potentiometer is adjusted to balance the Kelvin double-arm bridge.

[0036] The resistance value of the overhead line joint is measured using the Kelvin double-arm bridge that has reached bridge balance, and the detected resistance value is corrected in real time by measuring the temperature value of the overhead line tower joint.

[0037] The overhead line joint heat generation state is comprehensively judged according to the corrected overhead line joint resistance value, the overhead line joint resistance value detected in the last time unit and the set heat generation threshold.

[0038] The present application has the advantages that, compared with the prior art, the present application provides an innovative method, by accurately measuring the contact resistance and other key parameters of the power transmission line joint, and comprehensively calculating the detection result of the last time to compare with the standard value, so as to predict whether the heat risk exists after power transmission. The method changes the post-control of heat into pre-control when there is no heat, which greatly reduces the defect rate after operation, avoids the operation risk of live working for heat treatment, and provides quantitative data for the acceptance stage of the power transmission line, so that the acceptance work is free from the dependence on the subjective judgment of the construction personnel, and the operation and maintenance efficiency of the overhead power transmission line is improved. Moreover, the non-damage type overhead line joint heat prevention device does not need to remove the line clamp fittings of the joint during the detection process, but only needs to clamp the clamp of the device at both ends of the drainage plate, so that unnecessary damage to the equipment is avoided, and the efficiency and safety of the detection process are ensured. In addition, the digital potentiometer in the device is specially designed and processed, so that the device is small and light, the measurement accuracy is high, and the device is suitable for high-altitude operation of the power line. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is the circuit principle diagram of the non-damage type overhead line joint heat prevention device in the present application;

[0040] Figure 2 is the hardware structure of the detection device.

[0041] Figure 3 is the schematic diagram of the line joint measurement on the construction site;

[0042] Figure 4 is the schematic diagram of the tension clamp drainage plate measurement;

[0043] Figure 5 is the schematic diagram of the digital potentiometer structure. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. The embodiments described in the present application are only a part of the embodiments of the present application, but not all the embodiments. Based on the spirit of the present application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0045] Embodiment 1 of the present invention proposes a non-destructive device for preventing overheating at overhead line joints, comprising a four-wire detection clamp, a Kelvin double-arm bridge, a bridge balance detection circuit, a digital potentiometer, a microcontroller, a power supply, a power management module, and a temperature measurement module; characterized in that:

[0046] like Figure 4 As shown, the four-wire detection clamp includes a first clamp, a second clamp, a first detection wire and a second detection wire connected to the first clamp, and a third detection wire and a fourth detection wire connected to the second clamp.

[0047] like Figure 3 As shown, the first clamp and the second clamp are respectively clamped at the joint R of the overhead line to be tested. x At both ends, the first detection line of the four-wire detection clamp is connected in series with the first bridge arm resistor R1, the second bridge arm resistor R2, and the digital potentiometer R. p One end is connected; the third detection line of the four-wire detection clamp is connected to the digital potentiometer R through the series-connected third bridge arm resistor R3, fourth bridge arm resistor R4, and digital potentiometer R. p The other end is connected; the second detection wire of the four-wire detection clamp is connected to the positive terminal of the power supply of the Kelvin double-arm bridge; the fourth output terminal of the four-wire detection clamp is connected to the digital potentiometer R. p The other end is connected to the digital potentiometer R. p One end is connected to the negative terminal of the power supply of the Kelvin double-arm bridge through the fifth resistor R0; where, as Figure 1 As shown, R1 and R2 are one series arm of the Kelvin double-arm bridge, and R3 and R4 are the other series arm of the Kelvin double-arm bridge.

[0048] The bridge balance detection circuit includes a signal amplification module and an AD conversion module. The signal input terminal of the signal amplification module is connected to the contacts of R1 and R2 and the contacts of R3 and R4 respectively to obtain the bridge arm output. The output signal of the signal amplification circuit is output to the microcontroller through the AD conversion module.

[0049] The temperature measurement module transmits the temperature value at the junction of the overhead line tower to the microcontroller through a temperature measurement probe installed at the junction of the overhead line.

[0050] The microcontroller adjusts the resistance of the digital potentiometer based on the output of the AD conversion module to balance the Kelvin double-arm bridge, and calculates the resistance R at the overhead line connection to be tested based on the resistance value of the digital potentiometer at this time. x Resistance value:

[0051]

[0052] R p R is the resistance value of the digital potentiometer. xThe resistance value at the joint of the overhead line under test is calculated when the bridge is balanced.

[0053] The measured resistance value is corrected by measuring the actual temperature value;

[0054] The heating status of the overhead line connection is determined by comparing the corrected resistance value at the connection with the set heating threshold.

[0055] It should be noted that, as Figure 2 As shown, the microprocessor uses an STM32F407 microcontroller with a main frequency of up to 170MHz to ensure the smooth operation of the system; the AD conversion module uses a 32-bit ADC with an internal precision voltage source to ensure sampling accuracy.

[0056] Preferably, the first detection line, the second detection line, the third detection line and the fourth detection line are copper wires, and the copper wires are wrapped with anti-corrosion insulation.

[0057] Preferably, the parameters of the four arm resistors of the Kelvin double-arm bridge are selected as follows:

[0058]

[0059] Among them, U out U is the actual output voltage of the voltage source. A U is the voltage at the connection point of the first bridge arm resistor R1 and the second bridge arm resistor R2. B The resistance at the connection point of the third bridge arm resistor R3 and the fourth bridge arm resistor R4. For r 21 and r 31 The sum of the partial pressures, For R p The voltage at both ends, Figure 1 r in 11 r 12 r 21 r 22 These are the internal resistances of the first, second, third, and fourth detection lines, respectively; r 31 r 32 r 41 and r 42 All are the internal resistances of the wires in a Kelvin double-arm bridge, r 21 and r 31 The resistance is much smaller than R p Therefore, the voltage it receives much smaller It can be ignored, therefore we can obtain:

[0060]

[0061] When the bridge is balanced, U A =UB ,have:

[0062] set up

[0063] When the bridge is unbalanced, i.e. R x When the resistance value changes, R' x =R x +ΔR, then U A U B The voltage difference between them is:

[0064]

[0065] Where ΔR is the difference in resistance between the unbalanced and balanced states of the bridge, and R' is the resistance value between the unbalanced and balanced states of the bridge. x R is the resistance at the junction of the overhead line being tested when the bridge is unbalanced. x This is the resistance value at the junction of the overhead line being tested when the bridge is balanced;

[0066] Taking the derivative with respect to ΔU, we get:

[0067]

[0068] when When k is positive, we can find the answer. Since ΔR is much smaller than R1, When R2 = R1, the voltage difference reaches its maximum value. When R2 is approximately 0 and k is approximately 1, the voltage difference reaches its maximum value.

[0069] In summary, when selecting the bridge arm resistance parameters R1, R2, R3, and R4, the calculation formula is as follows:

[0070]

[0071] Among them, R p R is the resistance value of the digital potentiometer. x U is the resistance value at the joint of the overhead line under test, calculated during bridge balancing. out U is the actual output voltage of the voltage source. A U is the voltage at the connection point of the first bridge arm resistor R1 and the second bridge arm resistor R2. B I1 is the resistance at the connection point of the third bridge arm resistor R3 and the fourth bridge arm resistor R4, I2 is the current through R1, and I3 is the current through R2.

[0072] Specifically, in this embodiment, the final bridge arm resistance parameters are R1 = R3 = 100Ω and R2 = R4 = 1MΩ;

[0073] Preferably, the signal amplification module is an operational amplifier. The non-inverting input of the operational amplifier is connected between the first resistor R1 and the second resistor R2 of the Kelvin double-arm bridge, the inverting input of the operational amplifier is connected between the third resistor R3 and the fourth resistor R4 of the Kelvin double-arm bridge, and the output of the operational amplifier is connected to the input of the AD conversion module.

[0074] Preferably, the microcontroller uses a binary search method to dynamically adjust the resistance value of the digital potentiometer to balance the bridge. When the voltage difference between the non-inverting and inverting input terminals of the operational amplifier is less than the voltage difference threshold ψ after passing through the AD conversion module, it indicates that the bridge is balanced.

[0075] Preferably, such as Figure 5 As shown, the digital potentiometer consists of several resistors and several MOSFETs. The number of resistors connected is controlled by controlling the conduction of different MOSFETs. When the nth MOSFET is turned on, the other MOSFETs are turned off, and n resistors are connected. All MOSFETs are controlled by independent MOSFET gate driver chips, and all gate driver chips are connected to a microcontroller for unified control.

[0076] Preferably, the MOSFET in the digital potentiometer is a low on-resistance MOSFET, the on-resistance of which is less than or equal to 1mΩ and the accuracy of the resistor is less than or equal to 1%.

[0077] Preferably, the power supply and power management consist of a DC / DC boost module and a low-dropout regulator (LDO) module. The bridge balance detection circuit is powered by the voltage boosted by the DC / DC boost module and then transformed by the LDO module. The positive terminal of the power supply of the Kelvin double-arm bridge is the output of the DC / DC boost module.

[0078] It should be noted that, preferably, in addition to the temperature measurement module, this embodiment also includes a threshold alarm and an instant printing module to form an external expansion module. The threshold alarm module is used to automatically trigger an alarm when abnormal heating of the contact resistance is detected; the instant printing module is used to print the measurement results instantly through the built-in printer.

[0079] Preferably, the step of comprehensively judging the heating state of the overhead line joint based on the corrected resistance value of the overhead line joint, the resistance value of the overhead line joint detected in the previous time unit, and the set heating threshold specifically involves:

[0080] Calculate the combined resistance value of the overhead line joint after fusion correction and the resistance value of the overhead line joint detected in the previous time unit:

[0081]

[0082] Among them, Rx,t The corrected overhead line joint resistance value R x,t-1 The corrected overhead line joint resistance value of the previous time unit; α is a set coefficient; in this embodiment, α is set to 0.2.

[0083] When the comprehensive resistance value is greater than the set heating threshold, the heating state is considered abnormal

[0084] The set heating threshold is: if the four-wire detection clamp is a compression type strain clamp, the heating threshold is the set standard resistance value of the overhead line joint conductor; if the four-wire detection clamp is a non-compression type strain clamp, the heating threshold is 1.1 times the set standard resistance value of the overhead line joint conductor.

[0085] Embodiment 2 of the present application proposes a non-destructive method for preventing heating at the overhead line joint, using the device of embodiment 1 of the present application, characterized in that it comprises:

[0086] Calculate and adjust the resistance parameter of the Kelvin double-arm bridge;

[0087] Adjust the resistance value of the digital potentiometer to balance the Kelvin double-arm bridge;

[0088] Use the Kelvin double-arm bridge that reaches the bridge balance to measure the resistance value of the overhead line joint; and real-time measure the temperature value of the overhead line tower joint to correct the detected resistance value;

[0089] According to the corrected overhead line joint resistance value, the set standard resistance value, and the change amount of the last detection result, comprehensively judge the heating state of the overhead line joint.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application. Any modification or equivalent replacement that does not deviate from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.

Claims

1. A non-destructive device for preventing overheating at overhead line joints, comprising a four-wire detection clamp, a Kelvin double-arm bridge, a bridge balance detection circuit, a digital potentiometer, a microcontroller, a power supply, a power management module, and a temperature measurement module; characterized in that: The four-wire detection clamp includes a first clamp, a second clamp, a first detection wire and a second detection wire connected to the first clamp, and a third detection wire and a fourth detection wire connected to the second clamp. The first clamp and the second clamp are respectively clamped onto the joint of the overhead line to be tested. At both ends, the first detection line of the four-wire detection clamp is connected in series with the first bridge arm resistor R1, the second bridge arm resistor R2, and the digital potentiometer R. p One end is connected; the third detection line of the four-wire detection clamp is connected to the digital potentiometer R through the series-connected third bridge arm resistor R3, fourth bridge arm resistor R4, and digital potentiometer R. p The other end is connected; the second detection wire of the four-wire detection clamp is connected to the positive terminal of the power supply of the Kelvin double-arm bridge; the fourth output terminal of the four-wire detection clamp is connected to the digital potentiometer R. p The other end is connected to the digital potentiometer R. p One end is connected to the fifth resistor It is connected to the negative terminal of the power supply of the Kelvin double-arm bridge; wherein, R1 and R2 are one series arm of the Kelvin double-arm bridge, and R3 and R4 are the other series arm of the Kelvin double-arm bridge. The bridge balance detection circuit includes a signal amplification module and an AD conversion module. The signal input terminal of the signal amplification module is connected to the contacts of R1 and R2 and the contacts of R3 and R4 respectively to obtain the bridge arm output. The output signal of the signal amplification circuit is output to the microcontroller through the AD conversion module. The temperature measurement module transmits the temperature value at the junction of the overhead line tower to the microcontroller through a temperature measurement probe installed at the junction of the overhead line. The microcontroller adjusts the resistance of the digital potentiometer based on the output of the AD conversion module to balance the Kelvin double-arm bridge, and calculates the connection point of the overhead line to be tested based on the resistance value of the digital potentiometer at this time. The resistance value is determined and corrected using the measured temperature value. The heating status of the overhead line joint is determined by combining the corrected resistance value of the overhead line joint, the resistance value of the overhead line joint detected in the previous time unit, and the set heating threshold. The determination of the heating status of the overhead line joint based on the corrected resistance value of the overhead line joint, the resistance value of the overhead line joint detected in the previous time unit, and the set heating threshold is as follows: Calculate the combined resistance value of the overhead line joint after fusion correction and the resistance value of the overhead line joint detected in the previous time unit: in, This is the corrected resistance value at the overhead line connection point. The corrected resistance value at the overhead line connection for the previous time unit; The set coefficient; When the overall resistance value is greater than the set heating threshold, the heating state is considered abnormal. The set heating threshold is as follows: if the four-wire detection clamp is a compression-type tension clamp, the heating threshold is the standard resistance value of the conductor at the overhead line splice; if the four-wire detection clamp is a non-compression-type tension clamp, the heating threshold is 1.1 times the standard resistance value of the conductor at the overhead line splice.

2. The non-destructive device for preventing overheating at overhead line joints according to claim 1, characterized in that: The first, second, third, and fourth detection lines are made of copper wire, and the copper wire is wrapped with a corrosion-resistant insulating sheath.

3. The non-destructive device for preventing overheating at overhead line joints according to claim 1, characterized in that: Resistance parameters of the four arms of a Kelvin double-arm bridge The selected calculation formula is: Among them, R p R is the resistance value of the digital potentiometer. x U is the resistance value at the joint of the overhead line under test, calculated during bridge balancing. out U is the actual output voltage of the voltage source. A U is the voltage at the connection point of the first resistor R1 and the second resistor R2. B I1 is the resistance at the connection point of the third resistor R3 and the fourth resistor R4, I2 is the current through R1, and I3 is the current through R2.

4. The non-destructive device for preventing overheating at overhead line joints according to claim 1, characterized in that: The signal amplification module is specifically an operational amplifier. The non-inverting input of the operational amplifier is connected between the first resistor R1 and the second resistor R2 of the Kelvin double-arm bridge. The inverting input of the operational amplifier is connected between the third resistor R3 and the fourth resistor R4 of the Kelvin double-arm bridge. The output of the operational amplifier is connected to the input of the AD conversion module.

5. The non-destructive device for preventing overheating at overhead line joints according to claim 4, characterized in that: The microcontroller uses a binary search method to dynamically adjust the resistance value of the digital potentiometer to balance the bridge. When the voltage difference between the non-inverting and inverting input terminals of the operational amplifier is less than the voltage difference threshold ψ after passing through the AD conversion module, it indicates that the bridge is balanced.

6. The non-destructive device for preventing overheating at overhead line joints according to claim 5, characterized in that: The digital potentiometer consists of several resistors and several MOSFETs. The number of resistors connected is controlled by controlling the conduction of different MOSFETs. When the nth MOSFET is turned on, the other MOSFETs are turned off, and n resistors are connected. All MOSFETs are controlled by independent MOSFET gate driver chips, and all gate driver chips are connected to a microcontroller for unified control.

7. The non-destructive device for preventing overheating at overhead line joints according to claim 6, characterized in that: The MOSFET in the digital potentiometer is a low on-resistance MOSFET, with an on-resistance of less than or equal to 1mΩ and a resistor accuracy of less than or equal to 1%.

8. The non-destructive device for preventing overheating at overhead line joints according to claim 1, characterized in that: The power supply and power management consist of a DC / DC boost module and a low-dropout regulator (LDO) module. The bridge balance detection circuit is powered by the voltage boosted by the DC / DC boost module and then transformed by the LDO module. The positive terminal of the power supply of the Kelvin double-arm bridge is the output of the DC / DC boost module.

9. A non-destructive method for preventing overheating at overhead line joints using the device described in any one of claims 1-8, characterized in that, include: Calculate and adjust the resistance parameters of the Kelvin double-arm bridge; Adjust the resistance of the digital potentiometer to balance the Kelvin double-arm bridge; The resistance at the junction of an overhead line is measured using a Kelvin double-arm bridge that has achieved bridge balance. The temperature at the connection point of the overhead line tower is measured in real time to correct the detected resistance value. The heating status of the overhead line connection is determined by combining the corrected resistance value of the overhead line connection, the resistance value of the overhead line connection detected in the previous time unit, and the set heating threshold.

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