Broadband circularly polarized slot antenna for partial discharge detection in high-voltage electrical equipment

Abstract

This invention provides a broadband circularly polarized slot antenna for partial discharge detection in high-voltage electrical equipment, comprising a first dielectric substrate, a second dielectric substrate, a coupled feed structure, an annular slotted metal patch, a metal ground, a shorting pin, a metal post, and a coaxial line. The first dielectric substrate is disposed parallel to the upper center of the second dielectric substrate. The coupled feed structure is printed on the upper surface of the first dielectric substrate, the annular slotted metal patch is printed on the lower surface of the first dielectric substrate, and the metal ground is printed on the upper surface of the second dielectric substrate. An annular slot is formed in the center of the annular slotted metal patch, and the coupled feed structure is coupled to the annular slot. This invention can better match the complex electromagnetic environment formed by multiple reflections inside high-voltage equipment, thereby improving the acquisition efficiency and detection reliability of partial discharge signals, thus completely solving the detection blind zone problem caused by the random polarization of discharge signals in traditional linearly polarized antennas.

Description

Technical Field

[0001] This invention relates to the field of partial discharge detection in high-voltage electrical equipment, and specifically to a broadband circularly polarized slot antenna for partial discharge detection in high-voltage electrical equipment. Background Technology

[0002] Partial discharge faults are a major cause of high-voltage equipment failures. Therefore, timely and accurate detection of partial discharge faults is of great significance for ensuring the normal operation of power equipment. Currently, there are many methods for detecting partial discharge faults, such as ultra-high frequency (UHF) method, pulsed current method (HFCT), ultrasonic method, and transient ground voltage method, among which the ultra-high frequency method is the most widely used.

[0003] The ultra-high frequency (UHF) detection principle utilizes antenna sensors to capture the high-frequency electromagnetic wave signals generated during partial discharge in high-voltage equipment. Based on installation type, existing antennas are mainly divided into two categories: external antennas and internal antennas. External antennas offer the significant advantage of ease of installation and operation, but their anti-interference capability is poor, making them susceptible to environmental factors. Typical external antennas include horn antennas and dual-wire Archimedean spiral antennas. Internal antennas, installed inside the switchgear, can avoid interference from external electromagnetic signals. Examples include biconical antennas and slotted antennas, thus offering superior sensitivity and anti-interference capabilities compared to external antennas.

[0004] Due to the complex spatial configuration of the internal structure of high-voltage equipment, the electromagnetic signals generated by partial discharge undergo multiple reflections and refractions within the equipment cavity. This results in the signals received by the built-in antenna containing electromagnetic waves with various polarizations. This random polarization characteristic of the discharge signals within high-voltage equipment makes existing antenna sensors prone to detection blind spots, failing to accurately capture the discharge signals. This poses a safety hazard to the normal operation of high-voltage electrical equipment and urgently requires improvement and refinement. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment, thereby solving the detection blind zone problem caused by the random polarization of the discharge signal when traditional antennas are used for partial discharge detection of high-voltage electrical equipment.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment includes a first dielectric substrate, a second dielectric substrate, a coupled feed line structure, an annular slotted metal patch, a metal ground, a short-circuit pin, a metal post, and a coaxial line.

[0008] The first dielectric substrate is disposed parallel to the middle of the second dielectric substrate; a coupling feed structure is printed on the upper surface of the first dielectric substrate, an annular slotted metal patch is printed on the lower surface of the first dielectric substrate, and a metal ground is printed on the upper surface of the second dielectric substrate; an annular slot is formed in the middle of the annular slotted metal patch, and the coupling feed structure is coupled to the annular slot.

[0009] The outer conductor of the coaxial line is connected to the annular slotted metal patch and the metal ground, respectively, and the inner conductor of the coaxial line is connected to the coupling feeder structure.

[0010] The short-circuit pin is disposed between the first dielectric substrate and the second dielectric substrate, and the upper and lower ends of the short-circuit pin are respectively connected to the annular slotted metal patch and the metal ground.

[0011] A plurality of metal pillars are provided on the metal ground, and the plurality of metal pillars are not in contact with the annular slotted metal patch. The lower end of each metal pillar is connected to the metal ground.

[0012] Furthermore, the overall outer contour of the annular slotted metal patch is square, and an annular slot is provided in the middle of the annular slotted metal patch to divide the annular slotted metal patch into an inner circular patch and an outer hollow patch with a circular cutout in the middle.

[0013] The annular slot is provided with connecting branches and arc-shaped coupling lines; the connecting branches extend radially along the annular slot, and the two ends of the connecting branches are respectively connected to a circular patch and a hollow patch; the connecting branches are used to change the current distribution on the annular slot to excite circular polarization modes at high and low frequencies.

[0014] The arc-shaped coupling line extends circumferentially along the annular slot and does not contact the circular patch or the hollow patch; the arc-shaped coupling line is used to enhance electromagnetic coupling within its coverage area to optimize the mid-frequency axial ratio performance.

[0015] Furthermore, the shorting pin includes a first shorting pin and a second shorting pin;

[0016] A first shorting pin interface is provided at the edge of the circular patch, and a second shorting pin interface is provided at the inner edge of the hollow patch. The first shorting pin interface is connected to the metal ground through the first shorting pin, and the second shorting pin interface is connected to the metal ground through the second shorting pin, which is used to excite the circular polarization mode at the intermediate frequency and expand the axial ratio bandwidth.

[0017] Furthermore, the coupling feed structure includes a microstrip line, a first coupling patch, and a second coupling patch; one end of the microstrip line is disposed in the middle of the first dielectric substrate, and the other end of the microstrip line extends in a straight line to one side of the first dielectric substrate; the microstrip line intersects with the annular slot below to achieve coupling feed through the annular slot; the first coupling patch and the second coupling patch are symmetrically disposed on both sides of the microstrip line to provide inductive and capacitive reactance to the microstrip line to optimize impedance matching characteristics.

[0018] Furthermore, the first dielectric substrate and the second dielectric substrate are respectively provided with vias for the coaxial line to pass through; after the coaxial line passes through the via in the center of the second dielectric substrate from bottom to top, its outer conductor is connected to the metal ground; at the via in the center of the first dielectric substrate, the outer conductor of the coaxial line is connected to the circular patch in the annular slotted metal patch; after the inner conductor of the coaxial line passes through the via in the center of the first dielectric substrate from bottom to top, it is connected to one end of the microstrip line.

[0019] Furthermore, the dielectric constant of the first dielectric substrate and the second dielectric substrate is 4.6, and the thickness of both is 1 mm.

[0020] Furthermore, three to four metal pillars are provided on the metal ground, and the three to four metal pillars are discretely distributed near each edge of the metal ground, and are generally asymmetrically distributed.

[0021] Compared to traditional partial discharge detection antennas, this invention employs a circular polarization design, which not only effectively receives circularly polarized waves but is also compatible with linearly polarized waves of any direction. This wide adaptability better matches the complex electromagnetic environment inside high-voltage equipment caused by multiple reflections, thereby improving the acquisition efficiency and detection reliability of partial discharge signals. This completely solves the detection blind zone problem caused by the random polarization of discharge signals in traditional linearly polarized antennas. Furthermore, the combination of a metal ground and metal pillars in this invention effectively suppresses multipath reflections and acts as an electrostatic shielding layer to block power frequency coupling from high-voltage conductors, thus reducing the antenna profile and expanding the bandwidth. Attached Figure Description

[0022] Figure 1 This is an exploded view of a broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment, provided in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of the annular slotted metal patch in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the coupled feeder structure in an embodiment of the present invention.

[0025] Figure 4This is a schematic diagram of the structure of the metal ground in an embodiment of the present invention.

[0026] Figure 5 This is a comparison chart of S-parameter curves before and after loading the metal column in an embodiment of the present invention.

[0027] Figure 6 This is a comparison chart of the axial ratio curves before and after loading the metal column in an embodiment of the present invention.

[0028] Figure 7 This is a gain curve diagram of an embodiment of the present invention.

[0029] Figure 8 This is a radiation pattern of an embodiment of the present invention with a center frequency of 1.2 GHz and Phi of 0° and 90° respectively.

[0030] Figure 9 This is a radiation pattern of an embodiment of the present invention with a center frequency of 1.6 GHz and Phi of 0° and 90° respectively. Detailed Implementation

[0031] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] like Figures 1 to 4 As shown in the figure, an embodiment of the present invention provides a broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment, comprising a first dielectric substrate 11, a second dielectric substrate 12, a coupling feed structure 3, an annular slotted metal patch 4, a metal ground 5, a shorting pin, a metal post 6, and a coaxial line 7.

[0033] The first dielectric substrate 11 is disposed parallel to the center of the second dielectric substrate 12. The dielectric constant of both the first dielectric substrate 11 and the second dielectric substrate 12 is 4.6, and the thickness of both is 1 mm.

[0034] The coupling feed structure 3 is printed on the upper surface of the first dielectric substrate 11, the annular slotted metal patch 4 is printed on the lower surface of the first dielectric substrate 11, and the metal ground 5 is printed on the upper surface of the second dielectric substrate 12; the annular slotted metal patch 4 has a circular annular slot 401 in the middle, and the coupling feed structure 3 is coupled to the circular annular slot 401.

[0035] The outer conductor of the coaxial line 7 is connected to the annular slotted metal patch 4 and the metal ground 5 respectively, and the inner conductor of the coaxial line 7 is connected to the coupling feeder structure 3.

[0036] The short-circuit pin is disposed between the first dielectric substrate 11 and the second dielectric substrate 12, and the upper and lower ends of the short-circuit pin are respectively connected to the annular slotted metal patch 4 and the metal ground 5.

[0037] A plurality of metal pillars 6 are provided on the metal ground 5. The plurality of metal pillars 6 are not in contact with the annular slotted metal patch 4. The lower end of each metal pillar 6 is connected to the metal ground 5.

[0038] Specifically, in combination Figure 2 As shown, the overall outer contour of the annular slotted metal patch 4 is square, and the annular slot 401 is provided in the middle of the annular slotted metal patch 4 to divide the annular slotted metal patch 4 into a circular patch 41 located on the inner side and a hollow patch 42 with a circular cutout in the middle located on the outer side.

[0039] The annular slot 401 is provided with a connecting branch 402 and an arc-shaped coupling line 403; the connecting branch 402 extends radially along the annular slot 401, and its two ends are respectively connected to a circular patch 41 and a hollow patch 42; the connecting branch 402 is used to change the current distribution on the annular slot to excite circular polarization modes at high and low frequencies.

[0040] The arc-shaped coupling line 403 extends circumferentially along the annular slot 401 and does not contact the circular patch 41 or the hollow patch 42; the arc-shaped coupling line 403 is used to enhance electromagnetic coupling within its coverage area to optimize the mid-frequency axial ratio performance. Figure 2 Taking the direction shown in the figure as an example, the arc-shaped coupling line 403 in this embodiment is set at the lower right of the annular slot 401, which can enhance the electric field strength at the lower right of the annular slot 401, so that the total electric field vector in the annular slot 401 rotates with the phase at a stable amplitude in the low and medium frequencies, thereby suppressing the rise of the antenna intermediate frequency axial ratio.

[0041] Furthermore, this embodiment has two shorting pins, namely a first shorting pin 81 and a second shorting pin 82. In the annular slotted metal patch 4, a first shorting pin interface 404 is provided at the edge of the circular patch 41, and a second shorting pin interface 405 is provided at the inner edge of the hollow patch 42. The first shorting pin interface 404 is connected to the metal ground 5 through the first shorting pin 81, and the second shorting pin interface 405 is connected to the metal ground 5 through the second shorting pin 82, which is used to excite the circular polarization mode at the intermediate frequency and expand the axial ratio bandwidth.

[0042] Combination Figure 3As shown, the coupling feed structure 3 includes a microstrip line 31, a first coupling patch 32, and a second coupling patch 33. One end of the microstrip line 31 is disposed in the middle of the first dielectric substrate 11, and the other end of the microstrip line 31 extends in a straight line to one side of the first dielectric substrate 11. The microstrip line 31 intersects with the annular slot 401 below to achieve coupling feed through the annular slot 401. The first coupling patch 32 and the second coupling patch 33 are symmetrically disposed on both sides of the microstrip line 31 to provide inductive and capacitive reactance to the microstrip line 31 to optimize impedance matching characteristics.

[0043] Combination Figure 1 As shown, the first dielectric substrate 11 and the second dielectric substrate 12 are respectively provided with vias for the coaxial line 7 to pass through; after the coaxial line 7 passes through the via in the center of the second dielectric substrate 12 from bottom to top, its outer conductor is connected to the metal ground 5; at the via in the center of the first dielectric substrate 11, the outer conductor of the coaxial line 7 is connected to the circular patch 41 in the annular slotted metal patch 4; after the inner conductor of the coaxial line 7 passes through the via in the center of the first dielectric substrate 11 from bottom to top, it is connected to one end of the microstrip line 31 to feed power to the microstrip line 31.

[0044] In this invention, the metal pillars 6 disposed on the metal ground 5 can reduce the antenna profile and expand the bandwidth. The number of metal pillars 6 needs to be moderate; too many or too few pillars may cause the antenna main lobe to shift or increase cross-polarization. Importantly, the metal pillars 6 must not contact the coupling feed structure 3 (which acts as the radiator) and the annular slotted metal patch 4, and should be discretely disposed at the edges of the metal ground 5 to avoid excessive concentration that could affect the overall axial ratio. Furthermore, based on the asymmetric feed structure of the radiator, all the metal pillars 6 should also be distributed asymmetrically.

[0045] Preferably, 3 to 4 metal pillars 6 are provided on the metal ground 5, and the 3 to 4 metal pillars 6 are discretely distributed near each edge of the metal ground 5 and are generally asymmetrically distributed.

[0046] Combination Figure 4 As shown, in this embodiment of the invention, there are three metal pillars 6: a first metal pillar 601, a second metal pillar 602, and a third metal pillar 603. Figure 4 Taking the direction shown as an example, the first metal pillar 601 is located at the upper left edge of the metal ground 5, the second metal pillar 602 is located at the upper right edge of the metal ground 5, and the third metal pillar 603 is located at the middle right position of the lower edge of the metal ground 5. The three metal pillars 6 are discrete from each other and are asymmetrically distributed as a whole.

[0047] The metal pillar 6 can be solid or hollow. In this embodiment, the metal pillar 6 is solid. In other feasible embodiments, the metal pillar 6 can be made hollow. A hollow metal pillar 6 can shift the matching and axial ratio bandwidth to higher frequencies.

[0048] In this embodiment of the invention, the first dielectric substrate 11 and the coupled feed line structure 3 and the annular slotted metal patch 4 printed thereon form a radiator, and the second dielectric substrate 12 and the metal ground 5 printed thereon form a reflector. The three metal pillars 6 can form a new reflection path between the radiator and the reflector, so that the reflected wave and the direct wave are superimposed in phase in the antenna radiation direction, reducing the phase difference between the reflected wave and the direct wave in the radiation direction, and finally achieving the effect of reducing the antenna profile.

[0049] Please refer to Figure 5 The figure shows a comparison of S-parameter curves before and after loading the metal pillar 6 in this embodiment of the invention. The results demonstrate that the metal pillar 6 in this embodiment plays a decisive role in achieving ultra-wideband impedance matching (|S11| < -10 dB, relative bandwidth 40%) in the 1.14 GHz–1.71 GHz frequency band. Based on the improvements brought by the metal pillar 6, this embodiment of the invention, when designing the operating frequency band, can not only accurately cover the core region of 500MHz–1.5GHz (compliant with IEEE Std C37.122 standard) where the electromagnetic wave energy of partial discharge in high-voltage equipment is most concentrated, but also extend to the high-frequency band of 1.5–1.71GHz to capture nanosecond-level rapid discharge characteristics such as surface discharge oscillation waves of GIS insulators and corona pulse harmonics in transformer oil. This frequency band design avoids common power frequency harmonic interference (less than 500MHz) and communication frequency band interference (greater than 1.8 GHz in the 2G / 3G / 4G bands), significantly improving detection reliability and ensuring stable detection in the complex electromagnetic environment inside high-voltage equipment. Based on the above broadband matching performance, the embodiments of the present invention can efficiently couple discharge signals in transformers, GIS and cable terminals, significantly improving the detection sensitivity and pattern recognition accuracy of various types of defects such as surface discharge and floating discharge.

[0050] Please refer to Figure 6The figure shows a comparison of the axial ratio curves before and after loading the metal pillar 6 in an embodiment of the present invention. The results demonstrate that the metal pillar 6 in this embodiment significantly affects the amplitude and phase difference of the electric field vector on the annular slot, which is crucial for improving the axial ratio bandwidth and is a core feature of the present invention. After loading the metal pillar 6, the axial ratio of this embodiment is less than 3 dB in the 1.11 GHz–1.71 GHz frequency band, with a relative axial ratio bandwidth of 40%, exhibiting a wide axial ratio bandwidth. Simultaneously, this improved characteristic enables the embodiment of the present invention to possess omnidirectional polarization acquisition capability, thereby completely solving the detection blind zone problem caused by the randomness of discharge signal polarization in traditional linearly polarized antennas. Especially in complex scenarios such as elliptical polarized waves formed by multiple reflections within high-voltage equipment cavities and tilted polarization components of transformer bushing discharges, the signal reception stability of this embodiment is significantly improved. The wide axial ratio bandwidth of 1.14–1.71 GHz synchronously covers the core frequency band of partial discharge energy (500 MHz–1.5 GHz) and the high-frequency diagnostic band (greater than 1.5 GHz). Combined with the characteristic that circular polarization is insensitive to the incident direction of electromagnetic waves, it can ignore mechanical rotation restrictions in the limited installation space of substations, ensuring full polarization and full-spectrum high-fidelity capture of transient pulses such as floating discharge and surface flashover, providing underlying signal guarantee for discharge mode recognition based on joint time and frequency domain analysis.

[0051] Please refer to Figure 7 The figure shows the gain curve of an embodiment of the present invention. As can be seen from the figure, the gain of the embodiment of the present invention is 5.5–7.4 dBic, and the gain is stable with a ±1 dB bandwidth of 40%, exhibiting high gain characteristics.

[0052] Please refer to Figure 8 and Figure 9 ,in, Figure 8 The diagram shows the radiation pattern of this invention at a center frequency of 1.2 GHz and Phi values ​​of 0° and 90°, respectively. Figure 9 The diagram shows the radiation pattern of an embodiment of the present invention at a center frequency of 1.6 GHz and Phi values ​​of 0° and 90°, respectively. The results demonstrate that the embodiment of the present invention exhibits good radiation characteristics, with a stable radiation pattern and a cross-polarization ratio greater than 15 dB.

[0053] In summary, the broadband circularly polarized slot antenna for partial discharge detection in high-voltage electrical equipment provided by this invention achieves an operating frequency band of 1.14 GHz–1.71 GHz, with a matching and axial ratio cross-bandwidth of 40%, capable of covering the core region of 500 MHz–1.5 GHz where the electromagnetic wave energy of partial discharge in high-voltage equipment is most concentrated (compliant with IEEE Std C37.122 standard). This design endows the antenna with omnidirectional polarization acquisition capability, which can completely solve the detection blind zone problem caused by the randomness of discharge signal polarization in traditional linearly polarized antennas. Furthermore, this invention has a gain of 5.5–7.4 dBic in the navigation band, exhibiting advantages such as high gain, stable radiation pattern, and stable gain.

[0054] This invention innovatively adopts a design method that combines metal pillars with slot antennas. By setting multiple metal pillars on a metal ground, it successfully solves the problem of excessively high profile of slot antennas with reflectors, reducing the antenna profile height to 0.11λ (where λ is the wavelength corresponding to the lowest frequency of the antenna's operating band).

[0055] Compared to traditional partial discharge detection antennas, this invention employs a circular polarization design, which not only effectively receives circularly polarized waves but is also compatible with linearly polarized waves of any direction. This wide adaptability better matches the complex electromagnetic environment inside high-voltage equipment caused by multiple reflections, thereby improving the acquisition efficiency and detection reliability of partial discharge signals. This completely solves the detection blind zone problem caused by the randomness of discharge signal polarization in traditional linearly polarized antennas. Furthermore, the combination of a metal ground and metal pillars in this invention effectively suppresses multipath reflections and acts as an electrostatic shielding layer to block power frequency coupling of high-voltage conductors.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A broadband circularly polarized slot antenna for partial discharge detection in high-voltage electrical equipment, characterized in that, It includes a first dielectric substrate, a second dielectric substrate, a coupling feed structure, an annular slotted metal patch, a metal ground, a shorting pin, a metal pillar, and a coaxial cable; The first dielectric substrate is disposed parallel to the middle of the second dielectric substrate above it; The coupling feed structure is printed on the upper surface of the first dielectric substrate, the annular slotted metal patch is printed on the lower surface of the first dielectric substrate, and the metal ground is printed on the upper surface of the second dielectric substrate. The annular slotted metal patch has an annular slot in the middle, and the coupling feeder structure is coupled to the annular slot. The outer conductor of the coaxial line is connected to the annular slotted metal patch and the metal ground, respectively, and the inner conductor of the coaxial line is connected to the coupling feeder structure. The short-circuit pin is disposed between the first dielectric substrate and the second dielectric substrate, and the upper and lower ends of the short-circuit pin are respectively connected to the annular slotted metal patch and the metal ground. A plurality of metal pillars are provided on the metal ground, and the plurality of metal pillars are not in contact with the annular slotted metal patch. The lower end of each metal pillar is connected to the metal ground.

2. The broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment according to claim 1, characterized in that, The overall outer contour of the annular slotted metal patch is square, and an annular slot is provided in the middle of the annular slotted metal patch to divide the annular slotted metal patch into an inner circular patch and an outer hollow patch with a circular cutout in the middle. The annular slot is provided with connecting branches and arc-shaped coupling lines; the connecting branches extend radially along the annular slot, and the two ends of the connecting branches are respectively connected to a circular patch and a hollow patch; the connecting branches are used to change the current distribution on the annular slot to excite circular polarization modes at high and low frequencies. The arc-shaped coupling line extends circumferentially along the annular slot and does not contact the circular patch or the hollow patch. The arc-shaped coupling line is used to enhance electromagnetic coupling within its coverage area to optimize the mid-frequency axial ratio performance.

3. The broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment according to claim 2, characterized in that, The shorting pin includes a first shorting pin and a second shorting pin; A first shorting pin interface is provided at the edge of the circular patch, and a second shorting pin interface is provided at the inner edge of the hollow patch. The first shorting pin interface is connected to the metal ground through the first shorting pin, and the second shorting pin interface is connected to the metal ground through the second shorting pin, which is used to excite the circular polarization mode at the intermediate frequency and expand the axial ratio bandwidth.

4. The broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment according to claim 3, characterized in that, The coupling feed structure includes a microstrip line, a first coupling patch, and a second coupling patch; one end of the microstrip line is disposed in the middle of the first dielectric substrate, and the other end of the microstrip line extends in a straight line to one side of the first dielectric substrate; the microstrip line intersects with the annular slot below to achieve coupling feed through the annular slot. The first and second coupling patches are symmetrically disposed on both sides of the microstrip line to provide inductive and capacitive reactance to the microstrip line to optimize impedance matching characteristics.

5. The broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment according to claim 4, characterized in that, The first dielectric substrate and the second dielectric substrate are respectively provided with vias for the coaxial line to pass through; after the coaxial line passes through the via in the center of the second dielectric substrate from bottom to top, its outer conductor is connected to the metal ground; at the via in the center of the first dielectric substrate, the outer conductor of the coaxial line is connected to the circular patch in the annular slotted metal patch; after the inner conductor of the coaxial line passes through the via in the center of the first dielectric substrate from bottom to top, it is connected to one end of the microstrip line.

6. The broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment according to claim 1, characterized in that, The dielectric constant of the first dielectric substrate and the second dielectric substrate is 4.6, and the thickness of each substrate is 1 mm.

7. The broadband circularly polarized slot antenna for partial discharge detection of high-voltage electrical equipment according to claim 1, characterized in that, Three to four metal pillars are set on the metal ground, and the three to four metal pillars are discretely distributed near each edge of the metal ground, and are generally asymmetrically distributed.

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