Power transmission line overhead ground wire impedance measurement circuit and method and ground wire state monitoring device

Abstract

The invention relates to a power transmission line overhead ground wire impedance measurement circuit and method and a ground wire state monitoring device. The power transmission line overhead ground wire impedance measurement circuit comprises a single-chip microcomputer, a full-bridge circuit, a measurement transformer, a voltage detection circuit and a current detection circuit. The single-chip microcomputer drives the full-bridge circuit to work and outputs a sinusoidal current signal, and after the sinusoidal current signal passes through the measuring transformer, a secondary coil of the measuring transformer outputs a sinusoidal voltage signal to the line segment to be measured; meanwhile, the primary side current of the measuring transformer is detected through the current detection circuit, and the induced voltage of the line segment to be measured is detected through the voltage detection circuit; and calculating the primary side current and the induced voltage through the single-chip microcomputer to obtain an impedance value of the line segment to be measured. Primary side current is collected through the current detection circuit, ground wire induced voltage is collected through the voltage detection circuit, the impedance value can be calculated according to the primary current and the induced voltage, and the ground wire impedance measurement precision is improved.

Description

Technical Field

[0001] This application relates to the field of transmission line monitoring technology, and in particular to the circuit, method and device for measuring the impedance of overhead ground wires of transmission lines and the ground wire condition monitoring device. Background Technology

[0002] In power transmission systems with voltage levels of 220 kV and above, in high-voltage overhead transmission lines, the ground wire (lightning protection wire) is not only used for lightning protection but also frequently used for communication, shielding, and reducing line impedance. Overhead ground wires form a closed loop with the earth and towers over long periods. During long-term operation, wear occurs at the ground wire clamps on the towers, increasing contact resistance. When a few hundred amperes of induced current pass through, severe heating occurs at the ground wire clamps, causing some steel strands to melt and the remaining strands to lose yield strength and break under ground wire stress, resulting in ground wire detachment. Changes in the shape of the ground wire directly lead to changes in its impedance, which not only affects short-circuit current shunting and overvoltage levels but also directly relates to the assessment of grounding grid security and communication interference.

[0003] However, traditional ground impedance measurement methods rely on manually applying a current source and voltmeter after a power outage to perform offline four-terminal measurements. This method has drawbacks such as long power outage time, high operational risks, and difficulty in eliminating parasitic parameters in the test circuit, resulting in low measurement accuracy. Therefore, accurately measuring the impedance and induced voltage of the ground wire is crucial to ensuring the safe and stable operation of the power system. Summary of the Invention

[0004] This application provides a circuit, method, and ground wire condition monitoring device for measuring the impedance of overhead ground wires in power transmission lines, in order to at least solve the problem of low accuracy in existing ground wire impedance measurement methods in related technologies.

[0005] In a first aspect, this application provides a power transmission line overhead ground wire impedance measurement circuit, including a microcontroller, a full-bridge circuit, a measurement transformer, a voltage detection circuit, and a current detection circuit; The full-bridge circuit has its input terminal connected to a power supply, its output terminal connected to the primary winding of the measuring transformer, and its control terminal connected to the microcontroller. The secondary winding of the measuring transformer is connected to the section of the overhead ground wire of the power transmission line to be tested. The voltage detection circuit is connected between the measuring transformer and the microcontroller. The current detection circuit is connected between the output terminal of the full-bridge circuit and the microcontroller. The microcontroller drives the full-bridge circuit to operate and outputs a sinusoidal current signal. After passing through the measuring transformer, the sinusoidal current signal is output as a sinusoidal voltage signal by the secondary coil of the measuring transformer to the line segment under test. At the same time, the primary current of the measuring transformer is collected by the current detection circuit, and the induced voltage of the line segment under test is collected by the voltage detection circuit. The microcontroller calculates the impedance value of the line segment under test by analyzing the primary current and the induced voltage.

[0006] Specifically, the measurement circuit also includes a resonant capacitor and a compensation inductor; The resonant capacitor, the primary coil of the measuring transformer, and the primary coil of the compensation inductor are connected in series between the first and second output terminals of the full-bridge circuit, and the secondary coil of the compensation inductor is connected to the voltage detection circuit. The resonant capacitor and the primary coil form a resonant circuit, which is used to convert the square wave signal output by the full-bridge circuit into the sinusoidal current signal.

[0007] Specifically, the voltage detection circuit includes a voltage conditioning circuit, and the measuring transformer further includes a sensing coil; The sensing coil is mutually inducted with the primary and secondary coils of the measuring transformer. The first end of the sensing coil is connected to the voltage conditioning circuit, and the second end is connected to the first end of the secondary coil of the compensation inductor. The second end of the secondary coil of the compensation inductor is connected to the voltage conditioning circuit. The sensing coil and the secondary coil of the compensation inductor are used to generate an induced voltage and send it to the voltage conditioning circuit; the voltage conditioning circuit is used to amplify, filter and convert the induced voltage, and output the processed signal to the microcontroller.

[0008] Specifically, the step of calculating the impedance value of the line segment under test by means of the microcontroller based on the primary current and induced voltage includes: Obtain the first mutual inductance value between the primary and secondary coils of the measuring transformer, and obtain the second mutual inductance value between the secondary coil of the measuring transformer and the sensing coil. The impedance value is calculated based on the first mutual inductance value, the second mutual inductance value, the primary measured current, and the induced voltage.

[0009] Specifically, the current detection circuit includes a current conditioning circuit; The current conditioning circuit is connected between the microcontroller and the primary coil of the measuring transformer. It is used to amplify, filter, and convert the received primary current measurement signal, and then output the processed signal to the microcontroller.

[0010] Specifically, the measurement circuit further includes a driving circuit; The driving circuit is connected between the output terminal of the microcontroller and the control terminal of the full-bridge circuit; the driving circuit is used to output a driving signal under the control of the microcontroller to drive the full-bridge circuit to switch on and off.

[0011] Secondly, this application provides a method for measuring the impedance of an overhead ground wire of a power transmission line, wherein the measurement method is implemented by the overhead ground wire impedance measuring circuit of any one of the above claims; the method includes: The full-bridge circuit is driven to output a sinusoidal current signal to the measuring transformer. After the sinusoidal current signal is transformed by the measuring transformer, a sinusoidal voltage signal is output to the line segment under test by the secondary coil of the measuring transformer. The primary current of the measuring transformer and the induced voltage of the line segment under test are detected. The first mutual inductance value of the primary and secondary windings of the measuring transformer and the second mutual inductance value of the secondary winding of the measuring transformer and the sensing coil are obtained. The impedance value is calculated based on the first mutual inductance value, the second mutual inductance value, the primary measured current and the induced voltage.

[0012] Specifically, the formula for calculating the impedance value is as follows:

[0013] Where Z is the impedance value of the line segment to be measured; M 12 It is the first mutual inductance value; M 2s I1 is the second mutual inductance value; V1 is the primary current measurement; ω is the angular frequency of the primary current measurement.

[0014] Thirdly, this application provides a ground wire status monitoring device, including the overhead ground wire impedance measurement circuit of the power transmission line as described in any of the above claims; the ground wire status monitoring device is fixed on the overhead ground wire of the power transmission line and is used to monitor the status of the high-voltage overhead ground wire in real time.

[0015] Specifically, the ground wire status monitoring device further includes: The wireless communication module is used for data exchange with the remote monitoring platform; A solar power module is used to collect solar energy and convert it into electrical energy. An energy storage battery is used to store the electrical energy and provide operating power to the ground wire status monitoring device; A temperature detection module is used to monitor the operating temperature of the high-voltage overhead ground wire in real time. The lightning strike detection module is used to monitor lightning current and lightning frequency in real time. The control unit is used to control the operation of the overhead ground wire impedance measurement circuit, wireless communication module, solar power supply module, energy storage battery, temperature detection module and lightning strike detection module.

[0016] The overhead ground wire impedance measurement circuit, method, and ground wire condition monitoring device provided in this application have at least the following technical advantages: This application employs a closed-loop architecture of "microcontroller-full-bridge-measuring transformer-dual-channel sampling." The full-bridge, driven by the microcontroller, directly outputs a sinusoidal current, which is then injected into the high-voltage overhead ground wire after passing through the measuring transformer. Simultaneously, the current detection circuit samples the primary side current, and the voltage detection circuit samples the induced voltage of the ground wire. Both signals are simultaneously latched by the microcontroller, eliminating wiring errors and phase drift caused by traditional "step-by-step measurement," thus improving the accuracy of ground impedance measurement. Furthermore, the measuring transformer avoids direct connection of the measuring probe to the ground wire loop and keeps the secondary side voltage within the measurable range of ordinary operational amplifiers, improving the signal-to-noise ratio. The entire circuit can be integrated into a ground wire status monitoring device, requiring only two test leads connected to the ground wire, eliminating the need for external measuring devices and reducing equipment size and weight.

[0017] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a structural block diagram of an overhead ground wire impedance measurement circuit for power transmission lines according to one embodiment of this application; Figure 2 This is a circuit diagram of an overhead ground wire impedance measurement circuit for power transmission lines according to one embodiment of this application; Figure 3 This is a structural block diagram of a high-voltage overhead ground wire status monitoring device according to one embodiment of this application; Figure 4 This is a physical diagram of a high-voltage overhead ground wire status monitoring device and its installation method in a ground wire, according to one embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0020] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0021] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0022] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0023] The overhead transmission line ground wire described in this application is widely used in high-voltage overhead transmission towers for grounding and lightning protection purposes. Due to the coupling effect between the conductor and the overhead ground wire, and under the impact of lightning strikes, the overhead transmission line ground wire is affected by induced current and tensile stress, which can easily cause overheating at the nodes, leading to potential strand breakage or fracture.

[0024] For the reasons mentioned above, this application provides a circuit, method, and ground wire condition monitoring device for measuring the impedance of overhead ground wires of power transmission lines.

[0025] Firstly, embodiments of this application provide a circuit for measuring the impedance of an overhead ground wire in a power transmission line, the specific structure of which is described in reference [reference needed]. Figure 1 This embodiment of the overhead ground wire impedance measurement circuit for power transmission lines includes a microcontroller, a full-bridge circuit, a measuring transformer, a voltage detection circuit, and a current detection circuit. The input terminal of the full-bridge circuit is connected to a power supply, the output terminal is connected to the primary winding of the measuring transformer, and the control terminal is connected to the microcontroller. The secondary winding of the measuring transformer is connected to the section of the high-voltage overhead ground wire of the power transmission line to be measured. The voltage detection circuit is connected between the measuring transformer and the microcontroller. The current detection circuit is connected between the output terminal of the full-bridge circuit and the microcontroller.

[0026] The microcontroller drives the full-bridge circuit to operate and outputs a sinusoidal current signal. After the sinusoidal current signal flows through the measuring transformer, the secondary coil of the measuring transformer outputs a sinusoidal voltage signal to the line segment under test. At the same time, the current detection circuit collects the primary current of the measuring transformer, and the voltage detection circuit collects the induced voltage of the line segment under test. The microcontroller calculates the impedance value of the line segment under test by analyzing the primary current and the induced voltage.

[0027] refer to Figure 2 The measurement circuit in this embodiment further includes a resonant capacitor and a compensation inductor. The resonant capacitor, the primary winding of the measurement transformer, and the primary winding of the compensation inductor are connected in series between the first and second output terminals of the full-bridge circuit. The secondary winding of the compensation inductor is connected to the voltage detection circuit. The resonant capacitor and the primary winding form a resonant circuit, which converts the square wave signal output by the full-bridge circuit into the sinusoidal current signal.

[0028] The voltage detection circuit includes a voltage conditioning circuit, and the measuring transformer further includes a sensing coil. The sensing coil is mutually inducted with the primary and secondary coils of the measuring transformer. A first end of the sensing coil is connected to the voltage conditioning circuit, and a second end is connected to the first end of the secondary coil of the compensating inductor. The second end of the secondary coil of the compensating inductor is connected to the voltage conditioning circuit. The sensing coil and the secondary coil of the compensating inductor generate an induced voltage and send it to the voltage conditioning circuit. The voltage conditioning circuit amplifies, filters, and converts the induced voltage, and then outputs the processed signal to the microcontroller.

[0029] like Figure 2 As shown, the input terminal of the full-bridge circuit is connected to the power supply to obtain the operating voltage V. in The microcontroller output is connected to the driver circuit, which outputs four drive signals S1, S2, S3 and S4. These four drive signals are then output to the control terminals of the four switching transistors of the full-bridge circuit. The drive signals drive the switching transistors to turn on and off, so that the full-bridge circuit outputs a square wave signal that meets the requirements.

[0030] In this embodiment, the measuring transformer includes a primary winding L1, a secondary winding L2, and a sensing coil L... s The compensating inductor T2 includes the primary coil L. s and secondary coil L r The mutual inductance between L1 and L2 is M. 12 L s The mutual inductance with L1 and L2 are M respectively. 1s M 2s L c and Lr The mutual inductance is M r In this embodiment, the first output terminal of the full-bridge circuit is connected to the first terminal of the primary winding L1 of the measuring transformer T1 via a resonant capacitor C1, and the second terminal of the primary winding L1 of the measuring transformer T1 is connected to the primary winding L of the compensating inductor T2. c The first terminal is the primary coil L of the compensating inductor T2. c The second end is connected to the second output terminal of the full-bridge circuit. The two ends of the secondary coil L2 of the measuring transformer are used as nodes A and B of the external load. Nodes A and B are respectively connected to the test segment of the high-voltage overhead ground wire. The sensing coil L of the measuring transformer T1 is used for... s and the secondary coil L of the compensating inductor T2 r After being connected in series, they are connected to the voltage conditioning circuit, and the input of the current conditioning circuit is connected to the output of the full-bridge circuit.

[0031] In this embodiment, the full-bridge circuit outputs a 1kHz square wave, which, after passing through the L1 and C1 resonant circuit, outputs a sinusoidal current. The measured currents on the primary and secondary sides of the transformer are I1 (primary current) and I2 (secondary current), respectively. The sensing coil L... s The voltage across the terminals is V 1s The secondary coil L of the compensating inductor T2 r The voltage across the terminals is V 1c The induced voltage received by the voltage conditioning circuit is V1 = V 1s +V 1c .

[0032] In this embodiment, when calculating the impedance value of the line segment to be tested, it is also necessary to obtain the first mutual inductance value between the primary and secondary coils of the measuring transformer, and the second mutual inductance value between the secondary coil of the measuring transformer and the sensing coil; then, the impedance value is calculated based on the first mutual inductance value, the second mutual inductance value, the primary current, and the induced voltage.

[0033] Specifically, the primary winding L1 of the transformer and the sensing coil L are measured. s The mutual inductance is M 1s The mutual inductance between the primary and secondary sides of the compensating inductor T2 is M. r ,satisfy:

[0034] Given that the mutual inductance between the primary coil L1 and the secondary coil L2 is M 12 Secondary coil L2 and sensing coil L s The mutual inductance is M 2s Sensing coil L s With compensation inductor L r The output voltage after series connection is V1, which is used to measure the circuit resistance.

[0035] In this embodiment, when measuring voltage, the entire bridge circuit is turned off, and the voltage between contacts A and B is obtained by measuring the voltage V1.

[0036] The formula for calculating the impedance value is:

[0037] Where Z is the impedance value of the line segment to be measured; M 12 It is the first mutual inductance value; M 2s I1 is the second mutual inductance value; V1 is the primary current measurement; ω is the angular frequency of the primary current measurement.

[0038] In addition, the current detection circuit of this application includes a current conditioning circuit, wherein the current conditioning circuit is connected between the microcontroller and the primary winding of the measuring transformer, and is used to amplify, filter, and convert the received primary current measurement signal, and output the processed signal to the microcontroller. The measuring circuit also includes a driving circuit, wherein the driving circuit is connected between the output terminal of the microcontroller and the control terminal of the full-bridge circuit; the driving circuit is used to output a driving signal under the control of the microcontroller to drive the switching of the full-bridge circuit.

[0039] In summary, the overhead ground wire impedance measurement circuit for power transmission lines provided in this application achieves the following technical effects in the measurement of high-voltage overhead ground wire impedance: 1. A single excitation completes synchronous current-voltage acquisition. The full-bridge circuit directly outputs a 1 kHz sinusoidal current under the PWM drive of the microcontroller. After being boosted by the measurement transformer, the current is injected into the ground wire. At the same time, the current detection circuit samples the primary side current I1, and the voltage detection circuit samples the induced voltage V2 of the ground wire. The two signals are latched by the microcontroller's clock simultaneously, eliminating the wiring errors and phase drift caused by the traditional "step-by-step measurement". The system error is reduced from ±2% to within ±0.5%.

[0040] 2. The transformer achieves high-voltage isolation and range matching. The measuring transformer converts the low-voltage, high-current on the primary side into a high-voltage, low-current on the secondary side. This avoids directly connecting the high-voltage probe to the ground circuit and keeps the secondary voltage within the measurable range of ordinary operational amplifiers, thus improving the signal-to-noise ratio. The turns ratio accuracy is 0.1%, ensuring traceability of measurement values ​​without the need for additional calibration.

[0041] 3. The microcontroller's closed-loop calculation improves the level of intelligence. The microcontroller calculates the impedance Z=V2 / I in real time based on the synchronously sampled I1 and V2, and automatically performs phase correction, temperature compensation and digital filtering. The results are uploaded to the backend via UART / CAN, realizing on-site calculation without manual calculation, and shortening the test time from minutes to seconds.

[0042] 4. Enhanced on-site adaptability: The entire circuit can be integrated into the pole terminal box, with only two test leads connected to the ground wire; no external high-voltage source or independent voltage transformer is required, reducing the equipment size by 60% and weight by 50%, meeting the needs of live-line work and unattended monitoring.

[0043] In summary, this application, through an integrated design of "sinusoidal excitation - transformer isolation - synchronous sampling - microcontroller calculation", improves the accuracy of overhead ground wire impedance measurement by an order of magnitude while ensuring safe isolation. At the same time, it significantly simplifies the wiring process and on-site operation, making it suitable for the refined operation and maintenance of UHV and long-distance lines.

[0044] Secondly, one embodiment of this application provides a method for measuring the impedance of an overhead ground wire of a power transmission line, the method being implemented by the overhead ground wire impedance measuring circuit of a power transmission line as described in any of the preceding embodiments; the method includes: Step S1: Drive the full-bridge circuit to output a sinusoidal current signal to the measuring transformer. Step S2: After the sinusoidal current signal is transformed by the measuring transformer, a sinusoidal voltage signal is output to the line segment under test by the secondary coil of the measuring transformer. Step S3: Detect the primary current of the measuring transformer and the induced voltage of the line segment to be tested; Step S4: Obtain the first mutual inductance value of the primary and secondary windings of the measuring transformer, and the second mutual inductance value between the secondary winding of the measuring transformer and the sensing coil. Calculate the impedance value based on the first mutual inductance value, the second mutual inductance value, the primary measured current, and the induced voltage.

[0045] In a preferred embodiment, the formula for calculating the impedance value is:

[0046] Where Z is the impedance value of the line segment to be measured; M 12 It is the first mutual inductance value; M 2s I1 is the second mutual inductance value; V1 is the primary current measurement; ω is the angular frequency of the primary current measurement.

[0047] Thirdly, one embodiment of this application provides a high-voltage overhead ground wire status monitoring device, including the overhead ground wire impedance measurement circuit as described in any of the above claims; the ground wire status monitoring device is fixed on the high-voltage overhead ground wire and is used to monitor the status of the high-voltage overhead ground wire in real time.

[0048] Preferred, Reference Figure 3 The ground wire status monitoring device further includes: The wireless communication module is used for data exchange with the remote monitoring platform; A solar power module is used to collect solar energy and convert it into electrical energy. An energy storage battery is used to store the electrical energy and provide operating power to the ground wire status monitoring device; A temperature detection module is used to monitor the operating temperature of the high-voltage overhead ground wire in real time. The lightning strike detection module is used to monitor lightning current and lightning frequency in real time. The control unit is used to control the operation of the overhead ground wire impedance measurement circuit, wireless communication module, solar power supply module, energy storage battery, temperature detection module and lightning strike detection module.

[0049] The high-voltage overhead ground wire status monitoring device in this embodiment adopts current monitoring and temperature monitoring technology to comprehensively evaluate the ground wire status. It can measure key parameters such as ground wire induced current, impulse current, lightning current and ground wire temperature in real time. The device is powered by lithium battery and solar panel, which can ensure reliable operation of the device for no less than 30 days under no-sunlight conditions, and effectively evaluate the operational defects of the overhead transmission line ground wire.

[0050] It can also sense multiple state variables, such as real-time monitoring of overhead ground wire operating temperature, induced current, inrush current, and lightning strike current. The control unit supports the analysis of current carrying capacity, induced current, and operating temperature data to determine the ground wire connectivity status. It can also perform lightning strike analysis, including lightning strike frequency and regional statistical analysis, to guide overhead line operation and maintenance.

[0051] A physical diagram of the high-voltage overhead ground wire status monitoring device in this embodiment is provided for reference. Figure 4 During use, the high-voltage overhead ground wire status monitoring device is fixedly installed on the ground wire. The device can be powered by a solar panel and interact with the ground remote monitoring platform through a wireless communication module, so there is no need to set up an additional power supply or for staff to measure the ground wire impedance on site.

[0052] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A circuit for measuring the impedance of an overhead ground wire in a power transmission line, characterized in that, Includes a microcontroller, a full-bridge circuit, a measuring transformer, a voltage detection circuit, and a current detection circuit; The full-bridge circuit has its input terminal connected to a power supply, its output terminal connected to the primary winding of the measuring transformer, and its control terminal connected to the microcontroller. The secondary winding of the measuring transformer is connected to the section of the overhead ground wire of the power transmission line to be tested. The voltage detection circuit is connected between the measuring transformer and the microcontroller. The current detection circuit is connected between the output terminal of the full-bridge circuit and the microcontroller. The microcontroller drives the full-bridge circuit to operate and outputs a sinusoidal current signal. After passing through the measuring transformer, the sinusoidal current signal is output as a sinusoidal voltage signal by the secondary coil of the measuring transformer to the line segment under test. At the same time, the primary current of the measuring transformer is collected by the current detection circuit, and the induced voltage of the line segment under test is collected by the voltage detection circuit. The microcontroller calculates the impedance value of the line segment under test by analyzing the primary current and the induced voltage.

2. The overhead ground wire impedance measurement circuit for power transmission lines according to claim 1, characterized in that, The measurement circuit also includes a resonant capacitor and a compensation inductor; The resonant capacitor, the primary coil of the measuring transformer, and the primary coil of the compensation inductor are connected in series between the first and second output terminals of the full-bridge circuit, and the secondary coil of the compensation inductor is connected to the voltage detection circuit. The resonant capacitor and the primary coil form a resonant circuit, which is used to convert the square wave signal output by the full-bridge circuit into the sinusoidal current signal.

3. The overhead ground wire impedance measurement circuit for transmission lines according to claim 2, characterized in that, The voltage detection circuit includes a voltage conditioning circuit, and the measuring transformer also includes a sensing coil. The sensing coil is mutually inducted with the primary and secondary coils of the measuring transformer. The first end of the sensing coil is connected to the voltage conditioning circuit, and the second end is connected to the first end of the secondary coil of the compensation inductor. The second end of the secondary coil of the compensation inductor is connected to the voltage conditioning circuit. The sensing coil and the secondary coil of the compensation inductor are used to generate an induced voltage and send it to the voltage conditioning circuit; the voltage conditioning circuit is used to amplify, filter and convert the induced voltage, and output the processed signal to the microcontroller.

4. The overhead ground wire impedance measurement circuit for power transmission lines according to claim 3, characterized in that, The step of calculating the impedance value of the line segment under test by means of the microcontroller based on the primary current and induced voltage includes: Obtain the first mutual inductance value between the primary and secondary coils of the measuring transformer, and obtain the second mutual inductance value between the secondary coil of the measuring transformer and the sensing coil. The impedance value is calculated based on the first mutual inductance value, the second mutual inductance value, the primary measured current, and the induced voltage.

5. The overhead ground wire impedance measurement circuit for power transmission lines according to claim 1, characterized in that, The current detection circuit includes a current conditioning circuit; The current conditioning circuit is connected between the microcontroller and the primary coil of the measuring transformer. It is used to amplify, filter, and convert the received primary current measurement signal, and then output the processed signal to the microcontroller.

6. The overhead ground wire impedance measurement circuit for transmission lines according to claim 1, characterized in that, The measurement circuit also includes a drive circuit; The driving circuit is connected between the output terminal of the microcontroller and the control terminal of the full-bridge circuit; the driving circuit is used to output a driving signal under the control of the microcontroller to drive the full-bridge circuit to switch on and off.

7. A method for measuring the impedance of an overhead ground wire in a power transmission line, characterized in that, The measurement method is implemented by the overhead ground wire impedance measurement circuit of the power transmission line as described in any one of claims 1-6; the method includes: The full-bridge circuit is driven to output a sinusoidal current signal to the measuring transformer. After the sinusoidal current signal is transformed by the measuring transformer, a sinusoidal voltage signal is output to the line segment under test by the secondary coil of the measuring transformer. The primary current of the measuring transformer and the induced voltage of the line segment under test are detected. The first mutual inductance value of the primary and secondary windings of the measuring transformer and the second mutual inductance value of the secondary winding of the measuring transformer and the sensing coil are obtained. The impedance value is calculated based on the first mutual inductance value, the second mutual inductance value, the primary measured current and the induced voltage.

8. The method for measuring the impedance of overhead ground wires of transmission lines according to claim 7, characterized in that, The formula for calculating the impedance value is: Where Z is the impedance value of the line segment to be measured; M 12 It is the first mutual inductance value; M 2s I1 is the second mutual inductance value; V1 is the primary current measurement; ω is the angular frequency of the primary current measurement.

9. A high-voltage overhead ground wire condition monitoring device, characterized in that, Includes the overhead ground wire impedance measurement circuit for power transmission lines as described in any one of claims 1-6; the ground wire status monitoring device is fixed on the overhead ground wire of the power transmission line and is used to monitor the status of the high-voltage overhead ground wire in real time.

10. The high-voltage overhead ground wire status monitoring device according to claim 9, characterized in that, The ground wire status monitoring device also includes: The wireless communication module is used for data exchange with the remote monitoring platform; A solar power module is used to collect solar energy and convert it into electrical energy. An energy storage battery is used to store the electrical energy and provide operating power to the ground wire status monitoring device; A temperature detection module is used to monitor the operating temperature of the high-voltage overhead ground wire in real time. The lightning strike detection module is used to monitor lightning current and lightning frequency in real time. The control unit is used to control the operation of the overhead ground wire impedance measurement circuit, wireless communication module, solar power supply module, energy storage battery, temperature detection module and lightning strike detection module.

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