Photoelectric detection device and method for transient overvoltage of three-phase alternating-current high-voltage line

Abstract

The invention discloses a photoelectric detection device and method for transient overvoltage of a three-phase alternating-current high-voltage line. The photoelectric detection device comprises a lithium niobate substrate, a buffer layer, a single-mode optical fiber, a polarization maintaining optical fiber, an input end Y branch, an output end Y branch, an optical waveguide arm A, an optical waveguide arm B, an antenna and an electrode. The buffer layer covers the outer part of the lithium niobate substrate, and the material of the buffer layer is silicon dioxide; the input end Y branch, the output end Y branch, the optical waveguide arm A, the optical waveguide arm B, the antenna and the electrode are located in the lithium niobate substrate; one end of the polarization maintaining optical fiber is connected with an input optical signal, and the other end is connected with the input end Y branch; an optical signal is divided into two paths through the input end Y branch, and the first path of optical signal is transmitted to the output end Y branch after passing through the optical waveguide arm B; the second path of optical signal is transmitted to the output end Y branch after passing through the optical waveguide arm A; and the output end Y branch is connected with the photoelectric converter. And the transient response of the power transmission line and the capability of accurately capturing transient overvoltage are improved.

Description

Technical Field

[0001] The present invention relates to the field of transient overvoltage signal measurement in power systems, and in particular to a photoelectric detection device and method for transient overvoltage in three-phase AC high-voltage lines. Background Art

[0002] High-voltage transmission lines stretch for tens or even hundreds of kilometers and are significantly affected by the geographical environment and climate. Traditional transmission line inspections rely primarily on periodic inspections, but this approach has limitations. It lacks detection of specific environmental and climatic conditions and cannot timely monitor changes in external forces within the line corridor. Therefore, online monitoring systems for transient overvoltages in high-voltage power grids have emerged. These systems can monitor and respond to transient overvoltage conditions in real time, improving system safety and stability. New power systems are placing increasing demands on signal measurement, making ensuring the accuracy and reliability of metering devices a top priority. With the accelerated construction of new power systems, the influx of distributed renewable energy, charging facilities, and energy storage devices has led to more complex and variable dynamic characteristics of power system electrical parameter signals. The accelerated digital transformation of the power grid has also increased the demand for high-frequency, high-precision sensing capabilities, making improving the accuracy and reliability of metering devices a key research priority.

[0003] In power systems, transient overvoltages can endanger the insulation of equipment, causing damage and shortening its lifespan. Transient overvoltages are extremely harmful to power systems, not only impacting their safe and stable operation but also potentially causing economic losses and personnel safety issues. Therefore, effective transient overvoltage protection measures are crucial to ensuring the safe and stable operation of power systems. Real-time acquisition of grid transient overvoltage waveforms and their characteristic parameters provides valuable guidance for analyzing the causes of grid accidents and improving grid insulation coordination, helping to ensure the safe and stable operation of the grid.

[0004] Due to the low sampling rate and poor dynamic response capability of the voltage transformer on the secondary side of the high-voltage line, it is unable to capture transient overvoltage signals in a timely and accurate manner, which may seriously cause serious failures in the power system. Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line, comprising: a lithium niobate substrate, a buffer layer, a single-mode optical fiber, a polarization-maintaining optical fiber, an input Y-branch, an output Y-branch, an optical waveguide arm A, an optical waveguide arm B, an antenna, and electrodes;

[0006] A buffer layer covering the outside of the lithium niobate substrate, wherein the buffer layer material is silicon dioxide;

[0007] The input end Y branch, the output end Y branch, the optical waveguide arm A, the optical waveguide arm B, the antenna and the electrodes are located inside the lithium niobate substrate;

[0008] A polarization-maintaining optical fiber, one end of which is connected to the input optical signal and the other end is connected to the input Y branch. The optical signal is split into two paths after passing through the input Y branch. The first optical signal passes through the optical waveguide arm B with an antenna and electrodes and is then transmitted to the output Y branch. The second optical signal passes through the connected optical waveguide arm A and is then transmitted to the output Y branch.

[0009] The output end Y branch is connected to the photoelectric converter.

[0010] Furthermore, the optical waveguide arm A and the optical waveguide arm B are asymmetric structures.

[0011] Furthermore, the first optical signal passes through the optical waveguide arm B with an antenna and an electrode and is then transmitted to the output end Y branch, including:

[0012] When the antenna receives an external electric field, an induced electric field is formed on the electrode;

[0013] The induced electric field performs phase modulation on the first optical signal propagating along the optical waveguide arm B, and transmits the corresponding modulated optical signal to the output end Y branch.

[0014] Furthermore, the first optical signal and the second optical signal are phase-mismatched optical signals.

[0015] Furthermore, after the second optical signal passes through the connected optical waveguide arm A and is transmitted to the output end Y branch, it also includes:

[0016] When the first and second phase-mismatched optical signals are transmitted to the output end Y branch, the intensities of the phase-mismatched optical signals change due to the interference of the optical signals.

[0017] Furthermore, it also includes:

[0018] The intensity of the phase-mismatched optical signal changes, and its optical intensity transfer function is expressed as:

[0019]

[0020] I out is the output optical power of the electric field sensor, I in is the input optical power of the electric field sensor, α is the attenuation coefficient of the sensor, β is the extinction coefficient, is the phase shift caused by the external electric field modulation, is the static operating point of the sensor.

[0021] Furthermore, the output end Y branches and is connected to a photoelectric converter for converting the optical signal into an electrical signal.

[0022] Furthermore, the electrical signal is an electrical signal of an induced electric field received by the antenna.

[0023] Furthermore, the photoelectric detection device is encapsulated in a non-metallic shell, and the non-metallic shell material is Teflon.

[0024] The present invention also provides a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line based on any one of the above claims, and a method for online monitoring of transient overvoltage, comprising:

[0025] Installing a photoelectric detection device on the primary side of the power transmission line to be detected;

[0026] Battery powered;

[0027] The device is connected to the console computer via a wireless module to transmit the measurement data to the computer and perform decoupling calculations. The photoelectric detection device performs signal sampling via a low sampling rate module and obtains the voltage waveform amplitude and frequency of the three-phase electric field of the transmission line to be detected through synthetic electric field decoupling calculations.

[0028] Furthermore, it also includes:

[0029] The output voltage of the voltage transformer is used to calibrate the proportional coefficient of the photoelectric electric field measuring instrument in real time;

[0030] A transient voltage trigger threshold is set at 1.2 times the output voltage amplitude corresponding to the power frequency voltage. When the amplitude or frequency of any voltage waveform of the three-phase electric field of the transmission line to be detected exceeds the preset threshold, the high sampling mode of the photoelectric detection device is triggered, and the amplitude and waveform of the abnormal voltage signal in the high sampling mode are obtained. The fault type of the transmission line to be detected is determined based on the amplitude and waveform of the abnormal voltage signal.

[0031] Report the fault type and waveform parameters of the transient voltage, including peak value, rise time, and duration.

[0032] The present invention provides a photoelectric detection device and method for transient overvoltage in three-phase AC high-voltage power lines. First, the electric field meter is fabricated from lithium niobate, with waveguide arms employing an asymmetric structure. The conical antenna and electrodes are patterned using photolithography and deposited using electroplating. The final packaged sensor measures 6.0 mm × 1.0 mm × 0.5 mm. Second, during operation, the optical waveguide electric field meter is installed near the secondary transformer and powered by a power supply. A wireless transmission module is included within the meter, enabling remote transmission of collected data to a control computer for decoupling calculations. Under normal operation, the optical waveguide electric field meter operates in a low-sampling-rate mode to collect the power-frequency electric field of the three-phase transmission line. When a transient overvoltage occurs in the line, the power-frequency electric field waveform becomes distorted, with both amplitude and frequency experiencing sudden changes. When this exceeds a set threshold, the meter's high-sampling-rate mode is instantly triggered, allowing the precise waveform and amplitude of the transient overvoltage to be captured. Finally, operators determine the type of transient overvoltage and the type of system fault, and resolve the problem. At the existing technical level, it is possible to collect electric field data through optical waveguide electric field measuring instruments, improve the transient response of transmission lines and accurately capture transient overvoltages, ensuring the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a structural diagram of a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line provided by an embodiment of the present invention;

[0034] Figure 2 1 is a top view of a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line provided by an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the installation of a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line provided by an embodiment of the present invention;

[0036] Figure 4 1 is a flow chart of a method for online monitoring of transient overvoltage provided by an embodiment of the present invention;

[0037] Figure 5 This is an application flow chart for online monitoring of transient overvoltage provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following description sets forth numerous specific details to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific implementations disclosed below.

[0039] The present invention provides a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line, which uses a small-volume optical waveguide electric field measuring instrument (i.e., the photoelectric detection device provided by the present invention) to measure the voltage waveform in the transmission line in real time. The front view and top view of the photoelectric detection device are shown in FIG. Figure 1 、 2 As shown, the installation principle diagram of the measuring device is as follows Figure 3 As shown, the detection process is as follows Figure 4 As shown in the application flow chart Figure 5 shown.

[0040] A photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line, comprising: a lithium niobate substrate, a buffer layer, a single-mode optical fiber, a polarization-maintaining optical fiber, an input-end Y-branch, an output-end Y-branch, an optical waveguide arm A, an optical waveguide arm B, an antenna, and electrodes;

[0041] A buffer layer covering the outside of the lithium niobate substrate, wherein the buffer layer material is silicon dioxide;

[0042] The input end Y branch, the output end Y branch, the optical waveguide arm A, the optical waveguide arm B, the antenna and the electrodes are located inside the lithium niobate substrate;

[0043] A polarization-maintaining optical fiber, one end of which is connected to the input optical signal and the other end is connected to the input Y branch. The optical signal is split into two paths after passing through the input Y branch. The first optical signal passes through the optical waveguide arm B with an antenna and electrodes and is then transmitted to the output Y branch. The second optical signal passes through the connected optical waveguide arm A and is then transmitted to the output Y branch.

[0044] The output end Y branch is connected to the photoelectric converter.

[0045] The optical waveguide arm A and the optical waveguide arm B are asymmetric structures.

[0046] When the antenna receives an external electric field, an induced electric field is formed on the electrode;

[0047] The induced electric field performs phase modulation on the first optical signal propagating along the optical waveguide arm B, and transmits the corresponding modulated optical signal to the output end Y branch.

[0048] One optical signal and the second optical signal are phase-mismatched optical signals.

[0049] After the second optical signal passes through the connected optical waveguide arm A and is transmitted to the output end Y branch, when the first and second phase-mismatched optical signals are transmitted to the output end Y branch, the intensity of the phase-mismatched optical signal changes due to the interference of the optical signals.

[0050] The intensity of the phase-mismatched optical signal changes, and its optical intensity transfer function is expressed as:

[0051]

[0052] I out is the output optical power of the electric field sensor, I in is the input optical power of the electric field sensor, α is the attenuation coefficient of the sensor, β is the extinction coefficient, is the phase shift caused by the external electric field modulation, is the static operating point of the sensor.

[0053] The output end Y branch is connected to the photoelectric converter to convert the optical signal into an electrical signal.

[0054] The photoelectric detection device is encapsulated in a non-metallic shell, and the material of the non-metallic shell is Teflon.

[0055] Based on the photoelectric detection device for transient overvoltage of a three-phase AC high-voltage line provided by the present invention, a method for online monitoring of transient overvoltage is provided. Figure 4 As shown, the following steps are included:

[0056] Step S101, installing a photoelectric detection device on the primary side of the power transmission line to be detected;

[0057] Step S102, using battery power supply;

[0058] Step S103, connecting to the console computer through a wireless module, transmitting the measurement data to the computer and performing decoupling calculation; under normal conditions, the photoelectric detection device performs signal sampling through a low sampling rate module, and obtains the voltage waveform amplitude and frequency of the three-phase electric field of the transmission line to be detected through synthetic electric field decoupling calculation.

[0059] Furthermore, it also includes:

[0060] The output voltage of the voltage transformer is used to calibrate the proportional coefficient of the photoelectric electric field measuring instrument in real time;

[0061] A transient voltage trigger threshold is set at 1.2 times the output voltage amplitude corresponding to the power frequency voltage. When the amplitude or frequency of any voltage waveform of the three-phase electric field of the transmission line to be detected exceeds the preset threshold, the high sampling mode of the photoelectric detection device is triggered, and the amplitude and waveform of the abnormal voltage signal in the high sampling mode are obtained. The fault type of the transmission line to be detected is determined based on the amplitude and waveform of the abnormal voltage signal.

[0062] Report the fault type and waveform parameters of the transient voltage, including peak value, rise time, and duration.

[0063] The present invention provides a photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line, wherein an input optical signal enters the electric field sensor through a polarization-maintaining optical fiber and is divided into two paths at the first Y branch. One of the optical signals will pass through an optical waveguide arm B with an antenna and an electrode. When the antenna receives an external electric field in the Z direction, an induced electric field will be formed on the electrode, and the induced electric field will phase-modulate the optical signal propagating along the waveguide arm. When the two optical signals containing phase mismatch are transmitted to the second Y branch, the intensity of the optical signal will change due to the interference of the optical signal. The output end of the sensor converts the optical signal into an electrical signal by connecting a photoelectric converter, and obtains the spatial electric field signal received by the antenna. The light intensity transfer function of the optical waveguide electric field sensor can be expressed as:

[0064]

[0065] I out is the output optical power of the electric field sensor, I in is the input optical power of the electric field sensor, α is the attenuation coefficient of the sensor, β is the extinction coefficient, is the phase shift caused by the external electric field modulation, is the static operating point of the sensor, can be written as:

[0066]

[0067] if It can be ideally controlled to be π / 2, and the half-wave electric field E π is large enough so that πE(t) / E π When <1, formula (2) can be simplified as:

[0068]

[0069] COMSOL simulation was used to determine the relationship between waveguide dimensions and the mode field distribution and equivalent refractive index of the guided modes within the waveguide. When the widths of the two waveguide arms were 9μm and 5μm, and the thicknesses were 4μm and 3μm, respectively, the output spectrum of the sensor from the asymmetric Mach-Zehnder interferometer was a complete sinusoidal interference spectrum. The electric field meter was fabricated from lithium niobate, and the waveguide arms employed an asymmetric structure. The conical antenna and electrodes were patterned using photolithography and deposited via electroplating. To minimize distortion of the surrounding electromagnetic field due to the surrounding sensor package, the sensor chip was encapsulated in a non-metallic Teflon housing. The resulting packaged sensor measured 6.0mm × 1.0mm × 0.5mm.

[0070] During measurement, the output voltage signal of the photoelectric electric field meter is linearly related to the measured electric field, and the measured electric field is related to the primary voltage and the layout position of the electric field meter. Real-time calibration is required when measuring voltage.

[0071] During the measurement process, three optical waveguide electric field meters were installed near the three-phase primary-side high-voltage transformers to measure the power-frequency electric field. The output voltage signals were transmitted to a control console computer via a wireless module. Because the electric field meters were located close to the three-phase transmission line, the electric field data obtained was a three-phase coupled electric field. This required decoupling calculations in the computer to obtain a single-phase power-frequency electric field waveform.

[0072] A voltage transformer is used to calibrate the proportional coefficient of the photoelectric electric field measuring instrument in real time, and a threshold value of 1.2 times the output voltage amplitude corresponding to the power frequency voltage is set.

[0073] The optical waveguide electric field measuring instrument has two measurement modes: low sampling rate and high sampling rate. In order to save storage space, only the low sampling rate mode is operated under normal circumstances. Only when the amplitude and frequency of the collected waveform exceed the set threshold, it is confirmed that there is a transient overvoltage in the line, triggering the high sampling rate mode of the measuring instrument, and simultaneously collecting the transient overvoltage waveform. Professionals can then determine whether the system has a fault and perform corresponding maintenance.

[0074] A photoelectric detection device for transient overvoltage of a three-phase AC high-voltage line, the method of use of which is as follows Figure 3 As shown:

[0075] 1) The optical waveguide electric field meter is installed near the primary side high-voltage transformer and below the high-voltage conductor, and is powered by a power supply or battery.

[0076] 2) The optical waveguide electric field measuring instrument is connected to the console computer through a wireless module, and the measurement data is directly transmitted to the computer for decoupling calculation.

[0077] 3) Under normal circumstances, the electric field sensor uses a low sampling rate mode to collect the power frequency electric field and displays the power frequency electric field waveforms of the three phases A, B, and C on the console computer.

[0078] 5) Use a voltage transformer to calibrate the proportional coefficient of the photoelectric electric field measuring instrument in real time, and set 1.2 times the output voltage amplitude corresponding to the power frequency voltage as the threshold.

[0079] 4) Optionally, when the amplitude or frequency of the collected electric field waveform exceeds a set threshold, it is confirmed that a transient overvoltage has occurred in the line, and the high sampling rate mode is triggered at this time, and the waveform of the transient overvoltage is captured at the same time.

[0080] 5) Optionally, after obtaining the accurate waveform of the transient overvoltage, the dispatcher can assist in determining the type of fault and resolve the fault in a timely manner.

[0081] Figure 1 In the example, the input optical signal enters the electric field sensor through a polarization-maintaining fiber and is split into two paths at the first Y-branch. One optical signal passes through an optical waveguide arm B, which is equipped with an antenna and electrodes. When the antenna receives an external electric field in the Z direction, an induced electric field is formed on the electrode, which phase-modulates the optical signal propagating along the waveguide arm. When the two phase-mismatched optical signals reach the second Y-branch, the optical signal intensity changes due to interference. The output of the sensor is connected to a photoelectric converter to convert the optical signal into an electrical signal, obtaining the spatial electric field signal received by the antenna. Figure 1 Middle: ① lithium niobate substrate; ② buffer layer; ③ single-mode optical fiber; ④ polarization-maintaining optical fiber; ⑤ input Y-branch; ⑥ output Y-branch; ⑦ optical waveguide arm A; ⑧ optical waveguide arm B; ⑨ antenna; ⑩ electrode.

[0082] Figure 2 In this work, the optical waveguide is fabricated on an x-cut, y-propagating LN substrate using a proton exchange annealing process. After applying a buffer layer, the conical antenna and electrodes on one arm of the asymmetric MZI are patterned using photolithography and deposited using electroplating. To minimize electromagnetic field distortion from the surrounding instrumentation package, the instrumentation chip is enclosed in a non-metallic Teflon housing. The two waveguide arms are 30 mm long, 4 μm deep, and 5 μm and 8 μm wide, respectively. Figure 2 Middle: ① lithium niobate substrate; ② buffer layer; ③ waveguide arm A; ④ waveguide arm B.

[0083] Figure 3 In this example, the power supply provides voltage to optical waveguide electric field measuring instruments a, b, and c. These instruments measure the power frequency voltages of three-phase transmission lines A, B, and C, respectively. However, due to the close proximity of the three-phase lines to the electric field measuring instruments, the measured electric field is the composite field strength of phases A, B, and C. Each measuring instrument transmits its measurement data to the control room computer via a wireless module. Decoupling calculations are then performed to determine the single-phase power frequency electric field of each of A, B, and C.

[0084] Figure 5First, the electric field meter is installed in a suitable location and thresholds for the power-frequency electric field waveform amplitude and frequency are set. The meter samples the signal in low-sampling-rate mode and wirelessly transmits the data to the control room computer for synthetic electric field decoupling calculations. When the output voltage waveform amplitude or frequency of the single-phase electric field meter exceeds the set threshold, the meter's high-sampling-rate mode is triggered, rapidly capturing the abnormal voltage signal amplitude and waveform. This helps determine the line fault type and resolves it, ultimately restoring normal operation of the power system.

[0085] The present invention provides a photoelectric detection device and method for transient overvoltage in three-phase AC high-voltage power lines. First, the electric field meter is fabricated from lithium niobate, with waveguide arms employing an asymmetric structure. The conical antenna and electrodes are patterned using photolithography and deposited using electroplating. The final packaged sensor measures 6.0 mm × 1.0 mm × 0.5 mm. Second, during operation, the optical waveguide electric field meter is installed near the secondary transformer and powered by a power supply. A wireless transmission module is included within the meter, enabling remote transmission of collected data to a control computer for decoupling calculations. Under normal operation, the optical waveguide electric field meter operates in a low-sampling-rate mode to collect the power-frequency electric field of the three-phase transmission line. When a transient overvoltage occurs in the line, the power-frequency electric field waveform becomes distorted, with both amplitude and frequency experiencing sudden changes. When this exceeds a set threshold, the meter's high-sampling-rate mode is instantly triggered, allowing the precise waveform and amplitude of the transient overvoltage to be captured. Finally, operators determine the type of transient overvoltage and the type of system fault, and resolve the problem. At the existing technical level, it is possible to collect electric field data through optical waveguide electric field measuring instruments, improve the transient response of transmission lines and accurately capture transient overvoltages, ensuring the safe and stable operation of the power system.

[0086] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0087] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0088] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0089] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modifications or equivalents that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line, characterized in that: include: Lithium niobate substrate, buffer layer, single-mode optical fiber, polarization-maintaining optical fiber, input end Y branch, output end Y branch, optical waveguide arm A, optical waveguide arm B, antenna and electrodes; A buffer layer covering the outside of the lithium niobate substrate, wherein the buffer layer material is silicon dioxide; The input end Y branch, the output end Y branch, the optical waveguide arm A, the optical waveguide arm B, the antenna and the electrodes are located inside the lithium niobate substrate; A polarization-maintaining optical fiber is connected to the input optical signal at one end and to the input Y-branch at the other end. The optical signal is split into two paths after passing through the input Y-branch. The first path of the optical signal passes through the optical waveguide arm B with an antenna and electrodes and is then transmitted to the output Y-branch. The second optical signal passes through the connected optical waveguide arm A and is transmitted to the output end Y branch; The output end Y branch is connected to the photoelectric converter.

2. The device according to claim 1, characterized in that The optical waveguide arm A and the optical waveguide arm B are asymmetric structures.

3. The device according to claim 1, characterized in that The first optical signal passes through the optical waveguide arm B with an antenna and electrodes and is then transmitted to the output branch Y, including: When the antenna receives an external electric field, an induced electric field is formed on the electrode; The induced electric field performs phase modulation on the first optical signal propagating along the optical waveguide arm B, and transmits the corresponding modulated optical signal to the output end Y branch.

4. The device according to claim 1, characterized in that The first optical signal and the second optical signal are phase-mismatched optical signals.

5. The device according to claim 1 or 4, characterized in that After the second optical signal passes through the connected optical waveguide arm A and is transmitted to the output end Y branch, the method further includes: When the first and second phase-mismatched optical signals are transmitted to the output end Y branch, the intensities of the phase-mismatched optical signals change due to the interference of the optical signals.

6. The device according to claim 5, characterized in that Also includes: The intensity of the phase-mismatched optical signal changes, and its optical intensity transfer function is expressed as: I out is the output optical power of the electric field sensor, I in is the input optical power of the electric field sensor, α is the attenuation coefficient of the sensor, β is the extinction coefficient, is the phase shift caused by the external electric field modulation, is the static operating point of the sensor.

7. The device according to claim 1, characterized in that The output end Y branch is connected to the photoelectric converter to convert the optical signal into an electrical signal.

8. The device according to claim 7, characterized in that The electrical signal is an electrical signal of the induced electric field received by the antenna.

9. The method according to claim 1, characterized in that The photoelectric detection device is encapsulated in a non-metallic shell, and the material of the non-metallic shell is Teflon.

10. A method for online monitoring of transient overvoltage based on the photoelectric detection device for transient overvoltage in a three-phase AC high-voltage line according to any one of claims 1 to 9, characterized in that: include: Installing a photoelectric detection device on the primary side of the power transmission line to be detected; Battery powered; The device is connected to the console computer through a wireless module to transmit the measured data to the computer and perform decoupling calculations. Under normal conditions, the photoelectric detection device samples signals through a low sampling rate module, and obtains the voltage waveform amplitude and frequency of the three-phase electric field of the transmission line to be detected through synthetic electric field decoupling calculations.

11. The method according to claim 10, characterized in that Also includes: The output voltage of the voltage transformer is used to calibrate the proportional coefficient of the photoelectric electric field measuring instrument in real time; A transient voltage trigger threshold is set at 1.2 times the output voltage amplitude corresponding to the power frequency voltage. When the amplitude or frequency of any voltage waveform of the three-phase electric field of the transmission line to be detected exceeds the preset threshold, the high sampling mode of the photoelectric detection device is triggered, and the amplitude and waveform of the abnormal voltage signal in the high sampling mode are obtained. The fault type of the transmission line to be detected is determined based on the amplitude and waveform of the abnormal voltage signal. Report the fault type and waveform parameters of the transient voltage, including peak value, rise time, and duration.

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