An integrated electromagnetic composite sensor for the cabinet wall of a high-voltage switchgear and its installation method

Abstract

The present invention relates to a high-voltage switchgear cabinet wall integrated electromagnetic composite sensor and an installation method. The sensor includes a complementary dipole double patch antenna and a transient earth voltage probe. The complementary dipole double patch antenna includes an insulating cover, an insulating plate and a metal patch assembly. The transient earth voltage probe includes an insulating sheet and a third metal patch disposed in a second cavity formed by a metal cover and the outer wall of the switchgear cabinet wall. Compared with the prior art, the design is simple and convenient for processing, realizing the synchronous combined measurement of transient earth voltage and ultra-high frequency of electromagnetic wave signals generated by insulation defects and discharges of internal components in the high-voltage switchgear, and realizing live detection / patrol inspection.

Description

Technical Field

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

[0002] High-voltage switchgears are direct devices facing the power distribution network for power supply to users. Their failures will cause power outages for users, thus bringing huge economic losses to the power grid and causing certain social impacts. In addition, 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 switchgears, they are 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, deterioration or even damage of the equipment, and finally develop into an insulation breakdown accident of the high-voltage switchgear. Therefore, it is extremely important to judge the insulation condition of high-voltage switchgears through on-line monitoring and live detection of PD.

[0003] Currently, the methods applied to detect PD signals of high-voltage switchgears 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 transient earth voltage detection method has formed two power industry standards, namely DL / T 846.10 "General Technical Conditions for High-Voltage Test Equipment - Part 10: Partial Discharge Detection of Transient Earth Voltage" in 2016 and DL / T 195 "Calibration Specification for Partial Discharge Detectors Based on Transient Earth Voltage Method" in 2018. The existing transient earth voltage detection method for high-voltage switchgears utilizes the PD inside the switchgear to generate electromagnetic waves, which form a skin effect on the metal wall and propagate along the metal surface, and at the same time generate a transient earth voltage on the metal surface. The signal detection or monitoring can be realized 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 measured non-contact and is widely used in on-line detection of electrical equipment. For the self-characteristics of high-voltage switchgear equipment, such as Figure 7 As shown in (a)-7(d), currently, there are UHF detection sensors such as metal radiation patches (CN 104868240 A), reconfigurable antennas (square loop microstrip patches, CN110927541 A), microstrip slot antennas (CN 104515940A), and snowflake-shaped microstrip antennas (High Voltage Engineering, Vol.42, No.10: 3207-3213, 2016).

[0004] Since the above transient earth voltage sensor is an external type, it is vulnerable to external electromagnetic interference, which often makes the detection personnel suspect the detection results obtained. It is impossible to determine whether the electromagnetic signal comes from inside the high-voltage switchgear cabinet or the interference source, thus missing the internal discharge signal and leading to a serious short-circuit fault caused by insulation breakdown. For the above existing UHF technology, the sensor processing is relatively complex, inconvenient to promote and use in equipment manufacturers, and certain special conditions are required for installation, which greatly limits the use of this UHF detection method in the on-line monitoring and live detection of insulation defects PD of high-voltage switchgear cabinet equipment. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above existing technologies and provide a wall-integrated electromagnetic composite sensor for high-voltage switchgear cabinets and an installation method to overcome the problems that the transient earth voltage sensor in the transient earth voltage detection method is vulnerable to electromagnetic interference and the UHF detection sensor in the UHF detection method is complex in processing and installation.

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

[0007] A wall-integrated electromagnetic composite sensor for high-voltage switchgear cabinets includes a complementary dipole double-patch antenna and a transient earth voltage probe. The complementary dipole double-patch antenna includes an insulating cover, an insulating board and a metal patch assembly. The metal patch assembly includes the same first metal patch and second metal patch. One side of the insulating board 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 board, the first metal patch and the second metal patch are placed in the first cavity formed by 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 board 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 the 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 the first coaxial cable connector through the gap, the first through hole and the second through hole in sequence. The transient earth voltage probe includes an insulating sheet and a third metal patch placed in the second cavity formed by the metal cover and the outer wall of the switchgear cabinet wall. The second through hole is within the coverage of the metal cover. One side of the insulating sheet is connected to the outer wall of the switchgear cabinet wall, and the other side is connected to the third metal patch. One end of the cable core wire of the second coaxial cable is respectively conductively connected to the working side of the capacitor and the third metal patch, and the other end is conductively connected to the second coaxial cable connector. The shielding layer of the second coaxial cable is connected to the grounding side of the capacitor and the working side of the inductor. The grounding side of the inductor is conductively connected to the metal cover. The first coaxial cable connector is conductively connected to the metal cover. The second coaxial cable connector is insulated from the metal cover.

[0008] The first metal patch, the second metal patch and the third metal patch are all copper patches.

[0009] The insulating plates are adhesively bonded to the first metal patch and the second metal patch respectively, and the third metal patch is adhesively bonded to the insulating sheet.

[0010] The insulating sheet is adhesively bonded to the cabinet wall of the switchgear, and the insulating plates are adhesively bonded to the cabinet wall of the switchgear.

[0011] The insulating cover is connected to the cabinet wall of the switchgear by insulating bolts, and the metal cover is connected to the cabinet wall of the switchgear by metal bolts.

[0012] The first coaxial cable connector is connected to the metal cover by metal bolts, and the second coaxial cable connector is connected to the metal cover by insulating bolts.

[0013] An insulating washer is provided between the metal cover and the second coaxial cable connector.

[0014] One end of the cable core wire of the first coaxial cable is connected to the second metal patch, and one end of the shielding layer of the first coaxial cable is connected to the first metal patch.

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

[0016] An installation method for the integrated electromagnetic composite sensor on the cabinet wall of the high-voltage switchgear, the method comprising 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 plate, the other side of the insulating plate is connected to the inner wall of the cabinet wall of the switchgear, 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 cabinet wall of the switchgear;

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

[0021] Step S6: One side of the insulating sheet is connected to the third metal patch, and the other side is connected to the outer wall of the cabinet wall of the switchgear;

[0022] Step S7: One end of the cable core wire of the second coaxial cable is conductively connected to the working side of the capacitor and the third metal patch respectively, 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 grounding side of the capacitor and the working side of the inductor, and the grounding side of the inductor is conductively connected to the metal cover;

[0023] Step S8: The metal cover is connected to the outer wall of the cabinet wall of the high-voltage switchgear;

[0024] Step S9: The first coaxial cable connector is conductively connected to the metal cover, and the second coaxial cable connector is insulatedly connected to the metal cover.

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

[0026] (1) The complementary dipole double-patch antenna and the capacitive voltage divider are respectively used as the UHF probe and the transient earth voltage probe of the electromagnetic composite sensor. The design is simple and convenient for processing, realizing the synchronous joint measurement of the transient earth voltage and UHF of the electromagnetic wave signal generated by the insulation defect discharge of the internal components of the high-voltage switchgear.

[0027] (2) The electromagnetic composite sensor is easy to install and has few installation steps, greatly expanding its scope of use and providing a reliable implementation method for the integration, modularization and standardization of the sensing unit.

[0028] (3) The electromagnetic composite sensor uses an inductive element to block the mutual influence of the propagation of high-frequency electromagnetic wave signals. The two output signals can mutually corroborate whether the electromagnetic wave signal comes from the insulation defect discharge inside the high-voltage switchgear, and can avoid missing the internal discharge signal and causing a serious short-circuit fault due to insulation breakdown.

[0029] (4) The electromagnetic composite sensor uses the switchgear cabinet body as the grounding plane. The two electromagnetic wave signal output terminals can be operated under the live working condition to realize live detection / patrol inspection, and can also provide signals for the on-line monitoring device or the intensive care system. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] Figure 2 is a sectional view taken along line A-A of the present invention;

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

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

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

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

[0036] Figure 7 (a) is a 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 wall of the switch cabinet; 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 switch cabinet; 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 third metal patch; 18 is an inductor; 19 is a capacitor; 20 is a metal cover; 21 is a second coaxial cable connector; 22 is an insulating washer. Detailed implementation manners

[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 the detailed implementation manners 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 composite sensor for the wall of a high-voltage switch cabinet, which realizes the synchronous joint measurement of the transient earth voltage and UHF electromagnetic waves of the insulation defects of the internal components of the high-voltage switch cabinet, as Figure 1As shown in the figure, the electromagnetic composite sensor includes a complementary dipole double-patch antenna and a transient earth voltage 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 an insulating sheet 16 and a third metal patch 17 placed in the second cavity formed by the metal cover 20 and the outer wall of the switchgear cabinet wall 5. The second through hole 14 is within the coverage of the metal cover 20. One side of the insulating sheet 16 is connected to the outer wall of the switchgear cabinet wall 5, and the other side is connected to the third metal patch 17. One end of the cable core of the second coaxial cable 12 is conductively connected to the working side of the capacitor 19 and the third metal patch 17 respectively, and the other end is conductively connected to the second coaxial cable connector 21. The shielding layer of the second coaxial cable 12 is connected to the grounding side of the capacitor 19 and the working side of the inductor 18. The grounding side of the inductor 18 is conductively connected to the metal cover 20. The first coaxial cable connector 6 is conductively connected to the metal cover 20, and the second coaxial cable connector 21 is insulated from the metal cover 20.

[0045] Specifically:

[0046] The high-voltage switchgear cabinet wall 5 is grounded through the switchgear grounding wire resistance 9. A power supply 10 is installed in the high-voltage switchgear, and the electromagnetic composite sensor is connected to the signal acquisition device 15.

[0047] The first metal patch 2, the second metal patch 3, and the third metal patch 17 are all copper patches; the insulating plate 1 is bonded to the first metal patch 2 and the second metal patch 3 respectively, the third metal patch 17 is bonded to the insulating sheet 16, the insulating sheet 16 is bonded to the switchgear cabinet wall 5, and the insulating plate 1 is bonded to the switchgear cabinet wall 5. The insulating plate 1 is a polyethylene insulating plate, and the insulating sheet 16 is a phenolic plastic insulating sheet. One end of the first coaxial cable 11 is connected to the first coaxial cable connector 6 through a 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 a connector 8 with a coaxial cable. The connector 8 with a coaxial cable is threadedly connected to the second coaxial cable connector 21.

[0048] The insulating cover 4 is connected to the switch cabinet wall 5 by insulating bolts, and the metal cover 20 is connected to the switch cabinet wall 5 by metal bolts; the first coaxial cable connector 6 is connected to the metal cover 20 by metal bolts, and the second coaxial cable connector 21 is connected to the metal cover 20 by insulating bolts.

[0049] An insulating washer 22 is provided between the metal cover 20 and the second coaxial cable connector 21.

[0050] One end of the cable core wire of the first coaxial cable 11 is connected to the second metal patch 3, and one end of the shielding layer of the first coaxial cable 11 is connected to the first metal patch 2.

[0051] 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.

[0052] 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 plane, where the bottom lining ground plane is in metallic conduction contact with the switch cabinet wall 5; or the conductive copper thin sheet can be pasted on the insulating board 1 such as polyethylene for arrangement.

[0053] For the above transient earth voltage probe, its working principle is as Figure 4 shown. The insulating sheet 16 arranged between the third metal patch 17 and the switch cabinet wall forms a capacitor Cc, and together with the series capacitor 19, 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 switch cabinet wall to block high-frequency electromagnetic waves from entering the acquisition device from the grounding side.

[0054] Figure 5 (a)-(h) show the installation method of the integrated electromagnetic composite sensor on the switch cabinet wall of the high-voltage switchgear, which mainly includes 8 steps as follows (the replacement or removal can also refer to this):

[0055] 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.

[0056] Step 2, the first metal patch 2 and the second metal patch 3 are firmly pasted on the insulating board 1 with the first through hole 13 in a planar manner.

[0057] Step 3: The component formed in Step 2 is firmly and flatly pasted on the inner side of the high-voltage switchgear cabinet wall 5 in accordance with the designed position of the high-voltage switchgear, with the second through-hole 14, the gap, and the first through-hole 13 coaxially arranged.

[0058] Step 4: The component formed in Step 3 is sealed and reliably connected with 4 insulating bolts by using an insulating cover 4 of appropriate size to achieve the installation of the complementary dipole double-patch antenna on the high-voltage switchgear cabinet wall 5.

[0059] Step 5: The insulating sheet 16 and the third metal patch 17 are firmly and flatly pasted on the outer side of the high-voltage switchgear cabinet wall 5.

[0060] Step 6: The cable core wire and the shielding layer (grounded) of the second coaxial cable 12 are conductively welded to the capacitor 19 and the inductor 18 respectively. Among them, the cable core wire is connected to the outer side of the third metal patch 17 and the working side of the capacitor 19, and the shielding layer is conductively welded to the grounded side of the capacitor 19 and the working side of the inductor 18.

[0061] Step 7: After the grounded side of the inductor 18 is conductively welded to the metal cover 20, the metal cover 20 is conductively and reliably installed on the outer side of the high-voltage switchgear cabinet wall 5 by using 4 metal bolts.

[0062] Step 8: After the first coaxial cable connector 6 is threadedly connected to the connector 8 with a coaxial cable, the first coaxial cable connector 6 is conductively and reliably installed on the metal cover 20 by using 4 metal bolts to complete the fixed installation of the UHV electromagnetic wave signal output interface of the complementary dipole double-patch antenna; after the second coaxial cable connector 21 is threadedly connected to the connector 8 with a coaxial cable, the second coaxial cable connector 21 is insulatively and reliably installed on the metal cover 20 by using 4 insulating bolts and insulating washers 22 to complete the fixed installation of the electromagnetic wave signal output interface of the transient earth voltage probe.

[0063] Figure 6 (a)-(c) are the output time-domain waveform diagrams of the integrated electromagnetic composite sensor on the high-voltage switchgear cabinet wall. The measured dimensional 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 dimensional parameters of the capacitive electromagnetic wave coupling transient earth voltage probe after processing are as follows: the length of the third metal patch 17 is 5 cm, the width is 5 cm, the thickness is 2 mm, the insulating sheet 16 is made of insulating wood (phenolic plastic), the length of the insulating sheet 16 is 6 cm, the width is 6 cm, and the thickness is 2 mm; the capacitance value Cs of the capacitor 19 is 3 μF, and the value of the inductor 18 is L = 1100 nh.

Claims

1. A wall - integrated electromagnetic composite sensor for high - voltage switchgear cabinets, characterized in that, it includes a complementary dipole double - patch antenna and a transient earth voltage 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 between 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 an insulating sheet (16) and a third metal patch (17) placed in the second cavity formed between the metal cover (20) and the outer wall of the switchgear cabinet wall (5). The second through - hole (14) is within the coverage of the metal cover (20). One side of the insulating sheet (16) is connected to the outer wall of the switchgear cabinet wall (5), and the other side is connected to the third metal patch (17). One end of the cable core of the second coaxial cable (12) is conductively connected to the working side of the capacitor (19) and the third metal patch (17) respectively, and the other end is conductively connected to the second coaxial cable connector (21). The shielding layer of the second coaxial cable (12) is connected to the grounding side of the capacitor (19) and the working side of the inductor (18). The grounding side of the inductor (18) is conductively connected to the metal cover (20). The first coaxial cable connector (6) is conductively connected to the metal cover (20). The second coaxial cable connector (21) is insulated from the metal cover (20); The first metal patch (2), the second metal patch (3) and the third metal patch (17) are all copper patches; The insulating plate (1) is bonded to the first metal patch (2) and the second metal patch (3) respectively, and the third metal patch (17) is bonded to the insulating sheet (16).

2. The wall - integrated electromagnetic composite sensor for high - voltage switchgear cabinets according to claim 1, characterized in that, the insulating sheet (16) is bonded to the switchgear cabinet wall (5), and the insulating plate (1) is bonded to the switchgear cabinet wall (5).

3. The wall - integrated electromagnetic composite sensor for high - voltage switchgear cabinets according to claim 1, characterized in that, the insulating cover (4) is connected to the switchgear cabinet wall (5) through insulating bolts, and the metal cover (20) is connected to the switchgear cabinet wall (5) through metal bolts.

4. An integrated electromagnetic composite sensor for the cabinet wall of a high-voltage switchgear according to claim 1, characterized in that the first coaxial cable connector (6) is connected to the metal cover (20) by metal bolts, and the second coaxial cable connector (21) is connected to the metal cover (20) by insulating bolts.

5. An integrated electromagnetic composite sensor for the cabinet wall of a high-voltage switchgear according to claim 1, characterized in that an insulating washer (22) is provided between the metal cover (20) and the second coaxial cable connector (21).

6. An integrated electromagnetic 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 one end of the shielding layer of the first coaxial cable (11) is connected to the first metal patch (2).

7. An integrated electromagnetic composite sensor for the cabinet wall of a high-voltage switchgear according to claim 1, characterized in that the insulating board (1) is a polyethylene insulating board, and the insulating sheet (16) is a phenolic plastic insulating sheet.

8. An installation method for the integrated electromagnetic composite sensor for the cabinet wall of a high-voltage switchgear according to any one of claims 1-7, characterized in that the method comprises 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 board (1), the other side of the insulating board (1) is connected 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; 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: One side of the insulating sheet (16) is connected to the third metal patch (17), and the other side 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 working side of the capacitor (19) and the third metal patch (17) respectively, 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 grounding side of the capacitor (19) and the working side of the inductor (18), and the grounding side of the inductor (18) is conductively connected to the metal cover (20); Step S8: The metal cover (20) is connected to the outer wall of the high-voltage switchgear cabinet wall (5); Step S9: The first coaxial cable connector (6) is conductively connected to the metal cover (20), and the second coaxial cable connector (21) is insulatingly connected to the metal cover (20).

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