Integrated electromagnetic ultrasonic composite sensor on the box wall of high-voltage switchgear and installation method

Abstract

The present invention relates to a high-voltage switchgear cabinet wall integrated electromagnetic ultrasonic composite sensor and an installation method. The sensor includes a complementary dipole double patch antenna formed with the switchgear cabinet wall, a transient earth voltage probe, and an ultrasonic probe. The complementary dipole double patch antenna includes an insulating cover, as well as an insulating plate and a metal patch assembly. The transient earth voltage probe includes two insulating sheets and two transient earth voltage metal patches. The ultrasonic probe includes a PZT sensor connected to the outer wall of the switchgear cabinet wall. Compared with the prior art, the design is simple and convenient for processing, realizing the simultaneous combined measurement of electromagnetic wave signals, ultrasonic signals, very high frequency, transient earth voltage, and ultrasonic waves generated by insulation defects and discharges of internal components of the high-voltage switchgear, achieving live detection / patrol inspection, and can also provide signals for on-line monitoring devices or intensive care systems.

Description

Technical Field

[0001] The present invention relates to the field of partial discharge detection of high-voltage switchgear, and in particular to an integrated electromagnetic ultrasonic composite sensor for the box wall of a high-voltage switchgear and an installation method thereof. Background Art

[0002] High-voltage switchgear is a direct device for the power distribution network supplying power to users. Its faults will cause power outages for users, thus bringing huge economic losses to the power grid and causing certain social impacts. In addition, under the current policy of creating a good business environment, ensuring high-quality and reliable power supply is the only way for power grid operation and maintenance. Due to the complex internal structure and small insulation distance of high-voltage switchgear, it is more likely to have insulation defects than other electrical equipment in the power grid, and partial discharge (PD) phenomena such as surface creepage of equipment insulation occur under the conditions of moisture condensation. The long-term existence of PD will ultimately lead to insulation aging or deterioration and even damage of the equipment, and finally develop into an insulation breakdown accident of the high-voltage switchgear. Therefore, it is very important to judge the insulation status of high-voltage switchgear through on-line monitoring and live detection of PD.

[0003] Currently, the methods applied to detect PD signals of high-voltage switchgear mainly include ultrasonic (AE) detection method, transient earth voltage (TEV) detection method, and ultra-high frequency (UHF) detection method, etc. After years of application, the ultrasonic detection method has formed 1 power industry standard, namely DL / T 1416 "General Technical Conditions for Partial Discharge Tester by Ultrasonic Method" in 2015. After years of application, the transient earth voltage detection method has formed 2 power industry standards, namely DL / T 846.10 "General Technical Conditions for High-Voltage Test Equipment - Part 10: Partial Discharge Detection by Transient Earth Voltage" in 2016 and DL / T 195 "Calibration Specification for Partial Discharge Detector Based on Transient Earth Voltage Method" in 2018. PD inside the switchgear will generate electromagnetic waves, forming a skin effect on the metal wall and propagating along the metal surface, and at the same time generating a transient earth voltage on the metal surface. The existing technology can realize signal detection or monitoring by using a special transient earth voltage sensor. Ultra-high frequency is a new technology developed in recent years. It judges whether PD occurs in the equipment by measuring the electromagnetic waves radiated by insulation hidden dangers of high-voltage equipment under operating voltage. This method can be non-contact measurement and is widely used in on-line detection of electrical equipment. For the own characteristics of high-voltage switchgear equipment, as Figure 7 shown in (a)-(d), currently there are UHF detection sensors such as metal radiation patches, reconfigurable antennas (square loop microstrip patches), microstrip slot antennas, and snowflake-shaped microstrip antennas.

[0004] For the above ultrasonic and transient earth voltage detections, since they are external types, they are vulnerable to external electromagnetic interference, which often makes the inspectors doubt the results obtained from the detections and unable to determine whether the ultrasonic signals and electromagnetic signals come from inside the high-voltage switchgear or are generated by interference sources. As a result, the internal discharge signals are missed, leading to insulation breakdown and serious short-circuit faults. For the existing UHF technology mentioned above, the processing of the sensors is relatively complex, which is not convenient for popularization and use by equipment manufacturers, and certain special conditions are also required for installation, which greatly limits the application of this UHF detection method in the on-line monitoring and live detection of insulation defects PD in high-voltage switchgear equipment. Summary of the Invention

[0005] The purpose of the present invention is to provide a wall-integrated electromagnetic ultrasonic composite sensor for high-voltage switchgear and an installation method to overcome the defects of the above existing technologies.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A wall-integrated electromagnetic ultrasonic composite sensor for a high-voltage switchgear cabinet, comprising a complementary dipole double-patch antenna, a transient earth voltage probe, and an ultrasonic probe. The complementary dipole double-patch antenna includes an insulating cover, as well as an insulating plate and a metal patch assembly. The metal patch assembly includes the same first metal patch and second metal patch. One side of the insulating plate is connected to the inner wall of the switchgear cabinet wall, and the other side symmetrically connects the first metal patch and the second metal patch. The insulating plate, the first metal patch, and the second metal patch are placed in a first cavity formed between the insulating cover and the inner wall of the switchgear cabinet wall. A gap is formed between the first metal patch and the second metal patch. The insulating plate is provided with a first through hole, and the switchgear cabinet wall is provided with a second through hole. The gap, the first through hole, and the second through hole are coaxial. One end of a first coaxial cable is respectively conductively connected to the first metal patch and the second metal patch, and the other end is conductively connected to a first coaxial cable connector through the gap, the first through hole, and the second through hole in sequence. The transient earth voltage probe includes two insulating sheets and two transient earth voltage metal patches. The insulating sheets and the transient earth voltage metal patches are alternately stacked and connected to each other. One side of one of the insulating sheets is connected to the switchgear cabinet wall. One end of the cable core wire of a second coaxial cable is conductively connected to the outer transient earth voltage metal patch, and the other end is conductively connected to the second coaxial cable connector. The shielding layer of the second coaxial cable is conductively connected to the inner transient earth voltage metal patch and the working side of the inductor. The ultrasonic probe includes a PZT sensor connected to the outer wall of the switchgear cabinet wall. The PZT sensor is located in a third cavity formed by the conductive connection between the first metal cover and the outer wall of the switchgear cabinet wall. The PZT sensor is conductively connected to a third coaxial cable connector. The transient earth voltage probe and the ultrasonic probe are located in a second cavity formed between the first metal cover and the outer wall of the switchgear cabinet wall. The second through hole is within the coverage of the first metal cover. The first coaxial cable connector and the third coaxial cable connector are conductively connected to the first metal cover. The second coaxial cable connector is insulatingly connected to the first metal cover. The grounding side of the inductor is conductively connected to the first metal cover.

[0008] The second coaxial cable connector is connected to the first metal cover through an insulating washer.

[0009] The insulating cover and the switchgear cabinet wall are connected by insulating bolts. The first metal cover and the switchgear cabinet wall are connected by metal bolts. The second metal cover and the switchgear cabinet wall are connected by metal bolts.

[0010] The first coaxial cable connector and the first metal cover are connected by metal bolts. The second coaxial cable connector and the first metal cover are connected by insulating bolts. The third coaxial cable connector and the first metal cover are connected by metal bolts.

[0011] One end of the cable core wire of the first coaxial cable is connected to the second metal patch, and the shielding layer of the first coaxial cable is connected to the first metal patch.

[0012] The first metal patch, the second metal patch, and the two transient earth voltage metal patches are all copper patches.

[0013] The insulating board is adhesively bonded to the first metal patch and the second metal patch respectively, and the insulating sheet is adhesively bonded to the transient earth voltage metal patch.

[0014] An insulating sheet is adhesively bonded to the inner wall of the switchgear cabinet, and the insulating board is adhesively bonded to the inner wall of the switchgear cabinet.

[0015] The insulating board is a polyethylene insulating board, and the insulating sheet is a phenolic plastic insulating sheet.

[0016] An installation method for the integrated electromagnetic ultrasonic composite sensor on the wall of the high-voltage switchgear cabinet includes the following steps:

[0017] Step S1: One end of the first coaxial cable is conductively connected to the feeding points of the first metal patch and the second metal patch respectively;

[0018] Step S2: The first metal patch and the second metal patch are symmetrically connected to one side of the insulating board, the other side of the insulating board is connected to the inner wall of the switchgear cabinet, and the second through hole, the gap, and the first through hole are coaxial;

[0019] Step S3: The insulating cover is connected to the inner wall of the switchgear cabinet;

[0020] Step S5: The other end of the first coaxial cable is conductively connected to the first coaxial cable connector;

[0021] Step S6: The two insulating sheets and the two transient earth voltage metal patches are alternately stacked and connected, and one side of one insulating sheet is connected to the outer wall of the switchgear cabinet;

[0022] Step S7: One end of the cable core wire of the second coaxial cable is conductively connected to the outer transient earth voltage metal patch, the other end is conductively connected to the second coaxial cable connector, and the shielding layer of the second coaxial cable is conductively connected to the inner transient earth voltage metal patch and the working side of the inductor;

[0023] Step S8: The PZT sensor is connected to the outer wall of the switchgear cabinet, and the second metal cover is conductively connected to the outer wall of the switchgear cabinet;

[0024] Step S9: The grounding side of the inductor is conductively connected to the first metal cover, the first coaxial cable connector and the third coaxial cable connector are conductively connected to the first metal cover, the second coaxial cable connector is insulated from the first metal cover, and the first metal cover is connected to the outer wall of the switchgear cabinet.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) By using a complementary dipole double-patch antenna, constructing a capacitive voltage divider, and selecting a PZT sensor as the UHF probe, transient earth voltage probe, and ultrasonic probe of the integrated electromagnetic-ultrasonic composite sensor on the cabinet wall of the high-voltage switchgear respectively, the design is simple and convenient for processing, realizing the synchronous combined measurement of UHF, transient earth voltage, and ultrasonic waves of the electromagnetic wave signal and ultrasonic signal generated by the insulation defect discharge of the internal components of the high-voltage switchgear.

[0027] (2) The installation (replacement or removal can be referred to) of the integrated electromagnetic-ultrasonic composite sensor on the cabinet wall of the high-voltage switchgear is easy and has few steps, greatly expanding its scope of use, and providing a reliable implementation method for the integration, modularization, and standardization of the equipment sensing unit.

[0028] (3) The electromagnetic-ultrasonic composite sensor uses inductance to block the mutual influence of the propagation of high-frequency electromagnetic wave signals. The two output electromagnetic wave signals can corroborate each other, and the ultrasonic wave signal with a time difference Δt can confirm whether the current detected signal comes from the defect discharge of the internal insulation of the high-voltage switchgear, avoiding the occurrence of a serious short-circuit fault caused by insulation breakdown due to missing the internal discharge signal.

[0029] (4) The formed integrated electromagnetic-ultrasonic composite sensor on the cabinet wall of the high-voltage switchgear uses the switchgear cabinet body as the grounding plane, and the three signal output terminals can be operated under the live operating condition to realize live detection / patrol inspection, and can also provide signals for the on-line monitoring device or intensive care system. Brief Description of the Drawings

[0030] Figure 1 is the structural schematic diagram of the present invention;

[0031] Figure 2 is the A-A sectional view of the present invention;

[0032] Figure 3 is the installation structural schematic diagram of the present invention;

[0033] Figure 4 is the working principle diagram of the transient earth voltage probe of the present invention;

[0034] Figure 5 (a)-(h) are the schematic diagrams of the installation steps of the electromagnetic-ultrasonic composite sensor of the present invention;

[0035] Figure 6 (a)-(c) are the three-way single discharge detection time-domain signals of the electromagnetic-ultrasonic composite sensor of the present invention under different pressurization conditions;

[0036] Figure 7 (a) is the metal radiation patch UHF sensor in the prior art;

[0037] Figure 7(b) is a UHF sensor of a square annular microstrip patch in the prior art;

[0038] Figure 7 (c) is a UHF sensor of a microstrip slot antenna in the prior art;

[0039] Figure 7 (d) is a UHF sensor of a snowflake-shaped microstrip antenna in the prior art;

[0040] Reference numerals:

[0041] 1 is an insulating board; 2 is a first metal patch; 3 is a second metal patch; 4 is an insulating cover; 5 is the cabinet wall of a switchgear; 6 is a first coaxial cable connector; 7 is a feeding point; 8 is a connector with a coaxial cable; 9 is the grounding resistance of the switchgear; 10 is a power source; 11 is a first coaxial cable; 12 is a second coaxial cable; 13 is a first through hole; 14 is a second through hole; 15 is a signal acquisition device; 16 is an insulating sheet; 17 is a transient earth voltage metal patch; 18 is an inductor; 19 is a third coaxial cable; 20 is a first metal cover; 21 is a second coaxial cable connector; 22 is an insulating washer; 23 is a third coaxial cable connector; 24 is a second metal cover; 25 is a PZT sensor. Detailed implementation mode

[0042] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0043] Embodiment

[0044] This embodiment provides an integrated electromagnetic ultrasonic composite sensor for the cabinet wall of a high-voltage switchgear, as Figure 1 shown, including a complementary dipole double-patch antenna for coupling UHF electromagnetic wave signals, which is composed of an insulating cover 4, a first metal patch 2, a second metal patch 3, an insulating board 1, a first coaxial cable connector 6 and the cabinet wall 5 of a high-voltage switchgear; a capacitive voltage-dividing type transient earth voltage probe for coupling electromagnetic wave signals, which is composed of two transient earth voltage metal patches 17, two insulating sheets 16, an inductor 18, a second coaxial cable connector 21, a first metal cover 20 and the cabinet wall 5 of a high-voltage switchgear; a ultrasonic probe for coupling ultrasonic signals, which is composed of a PZT sensor 25, a second metal cover 24 and a third coaxial cable connector 23 and the cabinet wall 5 of a high-voltage switchgear; thus forming an integrated cabinet wall electromagnetic ultrasonic composite sensor for realizing synchronous joint measurement of UHF, transient earth voltage and ultrasonic waves of electromagnetic waves and ultrasonic signals generated by insulation defects and discharges of internal components of a high-voltage switchgear.

[0045] Specifically:

[0046] One side of the insulating board 1 is connected to the inner wall of the switchgear cabinet wall 5, and the other side symmetrically connects the first metal patch 2 and the second metal patch 3. The insulating board 1, the first metal patch 2, and the second metal patch 3 are placed in the first cavity formed by the insulating cover 4 and the inner wall of the switchgear cabinet wall 5. A gap is formed between the first metal patch 2 and the second metal patch 3. The insulating board 1 is provided with a first through hole 13, and the switchgear cabinet wall 5 is provided with a second through hole 14. The gap, the first through hole 13, and the second through hole 14 are coaxial. One end of the first coaxial cable 11 is respectively conductively connected to the first metal patch 2 and the second metal patch 3, and the other end is conductively connected to the first coaxial cable connector 6 through the gap, the first through hole 13, and the second through hole 14 in sequence.

[0047] The insulating sheets 16 and the transient earth voltage metal patches 17 are stacked alternately and connected to each other. One side of one insulating sheet 16 is connected to the switchgear cabinet wall 5. One end of the cable core wire of the second coaxial cable 12 is conductively connected to the transient earth voltage metal patch 17 on the outside, and the other end is conductively connected to the second coaxial cable connector 21. The shielding layer of the second coaxial cable 12 is conductively connected to the transient earth voltage metal patch 17 on the inside and the working side of the inductor 18.

[0048] The PZT sensor 25 is connected to the outer wall of the switchgear cabinet wall 5. The PZT sensor 25 is located in the third cavity formed by the conductive connection between the first metal cover 20 and the outer wall of the switchgear cabinet wall 5. The PZT sensor 25 is conductively connected to the third coaxial cable connector 23. The transient earth voltage probe and the ultrasonic probe are located in the second cavity formed by the first metal cover 20 and the outer wall of the switchgear cabinet wall 5. The second through hole 14 is within the coverage of the first metal cover 20. The first coaxial cable connector 6 and the third coaxial cable connector 23 are conductively connected to the first metal cover 20. The second coaxial cable connector 21 is insulated from the first metal cover 20. The grounding side of the inductor 18 is conductively connected to the first metal cover 20.

[0049] The high-voltage switchgear cabinet wall 5 is grounded through the switchgear grounding wire resistance 9. A power supply 10 is provided inside the high-voltage switchgear. The electromagnetic ultrasonic composite sensor is connected to the signal acquisition device 15. One end of the first coaxial cable 11 is connected to the first coaxial cable connector 6 through the connector 8 with a coaxial cable. The connector 8 with a coaxial cable is threadedly connected to the first coaxial cable connector 6. One end of the second coaxial cable 12 is connected to the second coaxial cable connector 21 through the connector 8 with a coaxial cable. The connector 8 with a coaxial cable is threadedly connected to the second coaxial cable connector 21. One end of the third coaxial cable 19 is connected to the third coaxial cable connector 23 through the connector 8 with a coaxial cable. The connector 8 with a coaxial cable is threadedly connected to the third coaxial cable connector 23.

[0050] The second coaxial cable connector 21 is connected to the first metal cover 20 through an insulating washer 22.

[0051] The insulating cover 4 is connected to the switchgear cabinet wall 5 by insulating bolts, the first metal cover 20 is connected to the switchgear cabinet wall 5 by metal bolts, and the second metal cover 24 is connected to the switchgear cabinet wall 5 by metal bolts; the first coaxial cable connector 6 is connected to the first metal cover 20 by metal bolts, and the second coaxial cable connector 21 is connected to the first metal cover 20 by insulating bolts.

[0052] One end of the cable core wire of the first coaxial cable 11 is connected to the second metal patch 3, and the shielding layer of the first coaxial cable 11 is connected to the first metal patch 2.

[0053] The first metal patch 2, the second metal patch 3, and the two transient earth voltage metal patches 17 are all copper patches; the insulating board 1 is bonded to the first metal patch 2 and the second metal patch 3 respectively, and the insulating sheet 16 is bonded to the transient earth voltage metal patch 17; one insulating sheet 16 is bonded to the switchgear cabinet wall 5, and the insulating board 1 is bonded to the switchgear cabinet wall 5; the insulating board 1 is a polyethylene insulating board, and the insulating sheet 16 is a phenolic plastic insulating sheet.

[0054] For the above complementary dipole double-patch antenna, its operating characteristics are determined by the length l, width w, thickness h, gap spacing b of the first metal patch 2 and the second metal patch 3, and the thickness k of the insulating board 1. Since a gap is left between the first metal patch 2 and the second metal patch 3 for symmetric arrangement, according to the dipole theory, the gap impedance (i.e., the UHF sensor impedance) is proportional to the dipole admittance. Then, knowing the performance of the dipole, the performance of its complementary gap can be predicted, making the structure of the dipole and the gap complementary.

[0055] The copper patches and the insulating board 1 of the complementary dipole double-patch antenna can be formed by placing a conductive copper thin sheet on the surface of the dielectric substrate of the bottom lining ground plate, where the bottom lining ground plate is in metallic conduction contact with the switchgear cabinet wall 5; or the conductive copper thin sheet can be pasted on the insulating board 1 such as polyethylene for arrangement.

[0056] For the above transient earth voltage probe, its working principle is as Figure 4 shown. The insulating sheet 16 arranged between the inner transient earth voltage metal patch 17 and the switchgear cabinet wall forms a capacitor Cc1, and the insulating sheet 16 arranged between the two transient earth voltage metal patches 17 forms a capacitor Cc2. Together with the series capacitors, it forms a capacitive voltage-dividing electromagnetic wave coupling transient earth voltage probe. An inductor 18 is connected in series between the shielding layer (grounded) of the second coaxial cable 12 and the switchgear cabinet wall to block high-frequency electromagnetic waves from entering the acquisition device from the grounding side.

[0057] Figure 5 (a)-(h) show the installation method of the integrated electromagnetic ultrasonic composite sensor on the switchgear cabinet wall, which mainly consists of 8 steps, as follows (the replacement or removal can also refer to):

[0058] Step 1: The cable core wire and the shielding layer (grounded) of the first coaxial cable 11 are respectively welded to the feeding points 7 of the second metal patch 3 and the first metal patch 2 with good electrical conductivity.

[0059] Step 2: The first metal patch 2 and the second metal patch 3 are symmetrically and firmly pasted on one side of the insulating board 1.

[0060] Step 3: The other side of the insulating board 1 is firmly pasted to the inner wall of the switchgear cabinet wall 5, and the second through hole 14, the gap and the first through hole 13 are coaxial.

[0061] Step 4: An insulating cover 4 with appropriate size seals and reliably connects the components formed in Step 3 with 4 insulating bolts, realizing the installation of the complementary dipole double-patch antenna on the high-voltage switchgear cabinet wall 5.

[0062] Step 5: Two insulating sheets 16 and two transient earth voltage metal patches 17 are alternately stacked and bonded, and one side of one insulating sheet 16 is firmly pasted to the outer wall of the high-voltage switchgear cabinet wall 5.

[0063] Step 6: The cable core wire and the shielding layer (grounded) of the second coaxial cable 12 are respectively welded to the two transient earth voltage metal patches 17 with good electrical conductivity. The cable core wire is welded to the outer transient earth voltage metal patch 17, and the shielding layer is welded to the inner transient earth voltage metal patch 17 and the working side of the inductor 18.

[0064] Step 7: The PZT sensor 25 is closely attached to the switchgear cabinet wall, and vaseline is applied at the attachment to enhance ultrasonic signal coupling. Four metal bolts are used to connect the second metal cover 24 to the high-voltage switchgear cabinet wall 5 to realize the reliable installation of the PZT sensor 25.

[0065] Step 8: After the grounded side of the inductor 18 is welded to the first metal cover 20 with good electrical conductivity; then, after the second coaxial cable connector 21 is threadedly connected to the connector 8 of the second coaxial cable, the coaxial cable connector 1 is insulated and reliably installed on the metal cover with 4 insulating bolts and insulating washers 22, completing the fixed installation of the electromagnetic wave signal output interface of the transient earth voltage probe; after the first coaxial cable connector 6 is threadedly connected to the connector 8 of the first coaxial cable, the first coaxial cable connector 6 is conductively and reliably installed on the first metal cover 20 with 4 metal bolts, completing the fixed installation of the ultra-high frequency electromagnetic wave signal output interface of the complementary dipole double-patch antenna; after the third coaxial cable connector 23 is threadedly connected to the connector 8 of the third coaxial cable, the third coaxial cable connector 23 is conductively and reliably installed on the first metal cover 20 with 4 metal bolts, completing the fixed installation of the ultrasonic signal output interface of the ultrasonic probe based on the PZT sensor 25; then, the first metal cover 20 is reliably installed on the outer wall of the high-voltage switchgear cabinet wall 5 with 4 metal bolts.

[0066] Figure 6 (a)-(c) are the output time-domain waveform diagrams of the integrated electromagnetic ultrasonic composite sensor on the box wall of the high-voltage switch cabinet. The measured size parameters of the complementary dipole double-patch antenna after processing are as follows: the lengths of the first metal patch 2 and the second metal patch 3 are 5 cm, the widths are 10 cm, the thicknesses are 5 mm, the gap spacing is 1 cm, and the thickness of the insulating board 1 (polyethylene) is 1 cm; the measured size parameters of the capacitive electromagnetic wave coupling transient earth voltage probe after processing are as follows: the lengths of the two transient earth voltage metal patches 17 are 5 cm, the widths are 5 cm, the thicknesses are 2 mm, the two insulating sheets 16 are made of insulating wood (phenolic plastic), and the lengths are 5 cm, the widths are 5 cm, and the thicknesses are 2 mm; the inductance 18 L = 1100 nh; the main parameters of the selected PZT sensor 25 are: the resonance frequency is 150 kHz, and the peak sensitivity in the frequency band of 30 kHz to 200 kHz is 75 dB.

Claims

1. An integrated electromagnetic-ultrasonic composite sensor for the cabinet wall of a high-voltage switchgear, characterized in that, It includes a complementary dipole double-patch antenna, a transient earth voltage probe, and an ultrasonic probe. The complementary dipole double-patch antenna includes an insulating cover (4), an insulating plate (1), and a metal patch assembly. The metal patch assembly includes the same first metal patch (2) and second metal patch (3). One side of the insulating plate (1) is connected to the inner wall of the switchgear cabinet wall (5), and the other side symmetrically connects the first metal patch (2) and the second metal patch (3). The insulating plate (1), the first metal patch (2), and the second metal patch (3) are placed in the first cavity formed by the insulating cover (4) and the inner wall of the switchgear cabinet wall (5). A gap is formed between the first metal patch (2) and the second metal patch (3). The insulating plate (1) is provided with a first through hole (13), and the switchgear cabinet wall (5) is provided with a second through hole (14). The gap, the first through hole (13), and the second through hole (14) are coaxial. One end of the first coaxial cable (11) is conductively connected to the first metal patch (2) and the second metal patch (3) respectively, and the other end is conductively connected to the first coaxial cable connector (6) through the gap, the first through hole (13), and the second through hole (14) in sequence. The transient earth voltage probe includes two insulating sheets (16) and two transient earth voltage metal patches (17). The insulating sheets (16) and the transient earth voltage metal patches (17) are alternately stacked and connected to each other. One side of one insulating sheet (16) is connected to the switchgear cabinet wall (5). One end of the cable core wire of the second coaxial cable (12) is conductively connected to the outer transient earth voltage metal patch (17), and the other end is conductively connected to the second coaxial cable connector (21). The shielding layer of the second coaxial cable (12) is conductively connected to the inner transient earth voltage metal patch (17) and the working side of the inductor (18). The ultrasonic probe includes a second metal cover (24) and a PZT sensor (25) connected to the outer wall of the switchgear cabinet wall (5). The PZT sensor (25) is located in the third cavity formed by the conductive connection of the first metal cover (20), the second metal cover (24), and the outer wall of the switchgear cabinet wall (5). The PZT sensor (25) is conductively connected to the third coaxial cable connector (23). The transient earth voltage probe and the ultrasonic probe are located in the second cavity formed by the first metal cover (20) and the outer wall of the switchgear cabinet wall (5). The second through hole (14) is within the coverage of the first metal cover (20). The first coaxial cable connector (6) and the third coaxial cable connector (23) are conductively connected to the first metal cover (20). The second coaxial cable connector (21) is insulatedly connected to the first metal cover (20). The grounding side of the inductor (18) is conductively connected to the first metal cover (20); The second coaxial cable connector (21) is connected to the first metal cover (20) through an insulating washer (22); The insulating cover (4) is connected to the switchgear cabinet wall (5) by insulating bolts. The first metal cover (20) is connected to the switchgear cabinet wall (5) by metal bolts. The second metal cover (24) is connected to the switchgear cabinet wall (5) by metal bolts.

2. The integrated electromagnetic-ultrasonic composite sensor for the box wall of a high-voltage switchgear according to claim 1, characterized in that, The first coaxial cable connector (6) is connected to the first metal cover (20) by metal bolts. The second coaxial cable connector (21) is connected to the first metal cover (20) by insulating bolts. The third coaxial cable connector (23) is connected to the first metal cover (20) by metal bolts.

3. The integrated electromagnetic-ultrasonic composite sensor for the cabinet wall of a high-voltage switchgear according to claim 1, characterized in that, One end of the cable core wire of the first coaxial cable (11) is connected to the second metal patch (3), and the shielding layer of the first coaxial cable (11) is connected to the first metal patch (2).

4. The integrated electromagnetic-ultrasonic composite sensor for the cabinet wall of a high-voltage switchgear according to claim 1, wherein The first metal patch (2), the second metal patch (3), and the two transient earth voltage metal patches (17) are all copper patches.

5. The integrated electromagnetic-ultrasonic composite sensor for the cabinet wall of a high-voltage switchgear according to claim 1, characterized in that, The insulating plate (1) is bonded to the first metal patch (2) and the second metal patch (3) respectively. The insulating sheet (16) is bonded to the transient earth voltage metal patch (17).

6. The integrated electromagnetic-ultrasonic composite sensor for the box wall of a high-voltage switch cabinet according to claim 1, wherein One insulating sheet (16) is bonded to the switchgear cabinet wall (5), and the insulating plate (1) is bonded to the switchgear cabinet wall (5).

7. The integrated electromagnetic-ultrasonic composite sensor for the box wall of a high-voltage switchgear according to claim 1, wherein The insulating plate (1) is a polyethylene insulating plate, and the insulating sheet (16) is a phenolic plastic insulating sheet.

8. An installation method for the integrated electromagnetic-ultrasonic composite sensor on the cabinet wall of the high-voltage switchgear according to any one of claims 1-7, characterized in that, The method includes the following steps: Step S1: One end of the first coaxial cable (11) is conductively connected to the feeding points (7) of the first metal patch (2) and the second metal patch (3) respectively. Step S2: The first metal patch (2) and the second metal patch (3) are symmetrically connected to one side of the insulating plate (1). The other side of the insulating plate (1) is connected to the inner wall of the switchgear cabinet wall (5). The second through hole (14), the gap, and the first through hole (13) are coaxial. Step S3: The insulating cover (4) is connected to the inner wall of the switchgear cabinet wall (5). Step S5: The other end of the first coaxial cable (11) is conductively connected to the first coaxial cable connector (6). Step S6: The two insulating sheets (16) and the two transient earth voltage metal patches (17) are alternately stacked and connected. One side of one insulating sheet (16) is connected to the outer wall of the switchgear cabinet wall (5). Step S7: One end of the cable core wire of the second coaxial cable (12) is conductively connected to the outer transient earth voltage metal patch (17), and the other end is conductively connected to the second coaxial cable connector (21). The shielding layer of the second coaxial cable (12) is conductively connected to the inner transient earth voltage metal patch (17) and the working side of the inductor (18). Step S8: The PZT sensor (25) is connected to the outer wall of the switchgear cabinet wall (5), and the second metal cover (24) is conductively connected to the outer wall of the switchgear cabinet wall (5). Step S9: The grounding side of the inductor (18) is conductively connected to the first metal cover (20). The first coaxial cable connector (6) and the third coaxial cable connector (23) are conductively connected to the first metal cover (20). The second coaxial cable connector (21) is insulatedly connected to the first metal cover (20). The first metal cover (20) is connected to the outer wall of the switchgear cabinet wall (5).

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