High-voltage cable built-in partial discharge on-line monitoring device and application method

Abstract

The invention discloses a high-voltage cable built-in partial discharge on-line monitoring device and an application method.The high-voltage cable built-in partial discharge on-line monitoring device comprises a device body, a partial discharge detection antenna and a circuit board, and the device body is used for being installed on a cable accessory protection shell of a high-voltage cable; the partial discharge detection antenna is arranged in the cable accessory protection shell and used for detecting electric field distribution formed after partial discharge signals transmitted by a cable core wire of a high-voltage cable pass through the inner semi-conductive layer, the cable main insulation layer and the outer semi-conductive layer, the circuit board is arranged in the device body, and a signal transmitting circuit is arranged on the circuit board. And the partial discharge detection antenna is connected with a signal transmitting circuit on the circuit board. The invention aims to realize accurate and effective monitoring of partial discharge signals and evaluate the operation insulation state of the high-voltage cable and accessories.

Description

Technical Field

[0001] The present invention relates to the field of built-in partial discharge signal detection for high-voltage cables, and in particular to an online monitoring device for built-in partial discharge for high-voltage cables and an application method thereof. Background Art

[0002] In recent years, with the continued acceleration of urbanization, the cableization rate of power grids has continued to rise. Cross-linked polyethylene power cables (XLPE cables) have been widely used in cable lines due to their superior electrical performance, heat resistance, and good mechanical properties. The production quality of the cable and accessories (such as the insulation resistance, breakdown strength, dielectric constant, dielectric loss, and thermal properties of the insulation material), the level of laying and installation technology, and the installation and operating environment (such as humidity, dust, and temperature fluctuations) all affect the insulation condition of the cable. Cable accessories, in particular, have become a weak link in the insulation of high-voltage cable lines and a typical source of operational failures. Partial discharge is one of the main causes of insulation degradation and is the primary characteristic parameter that characterizes insulation condition. When partial discharge occurs in the cable, the signal couples into the cable ground loop. Traditional high-frequency partial discharge detection uses a through-hole current sensor to collect the pulse current signal generated by partial discharge in the cable ground loop. However, the partial discharge monitoring device sensor is located some distance from the cable, and the cable grounding metal sheath partially shields the partial discharge signal, resulting in a weak coupled partial discharge signal. Electromagnetic interference is also present in the field. Extensive operational experience with partial discharge monitoring devices has shown that partial discharge detection is not ideal. Summary of the Invention

[0003] Technical problem to be solved by the present invention: In response to the above-mentioned problems of the prior art, a device and application method for online monitoring of built-in partial discharge of high-voltage cables are provided. The present invention aims to achieve accurate and effective monitoring of partial discharge signals and evaluate the operating insulation status of high-voltage cables and accessories.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A built-in partial discharge online monitoring device for high-voltage cables comprises a device body, a partial discharge detection antenna and a circuit board. The device body is used to be installed on a cable accessory protective shell of a high-voltage cable. The connection portion of the high-voltage cable located in the middle of the cable accessory protective shell removes the buffer layer, corrugated aluminum sheath and outer insulation of the high-voltage cable and retains the cable core wire, inner semi-conductive layer, cable main insulation and outer semi-conductive layer. The partial discharge detection antenna is arranged inside the cable accessory protective shell to detect the electric field distribution formed by the partial discharge signal transmitted by the cable core wire of the high-voltage cable after passing through the inner semi-conductive layer, cable main insulation and outer semi-conductive layer. The circuit board is arranged in the device body, and a signal transmission circuit is provided on the circuit board. The partial discharge detection antenna is connected to the signal transmission circuit on the circuit board.

[0005] Optionally, the signal transmission circuit on the circuit board is a wireless signal transmission circuit, a communication antenna is installed on the device body, and the communication antenna is connected to the wireless signal transmission circuit.

[0006] Optionally, the device body includes an upper shell and a connecting piece, the cable accessory protective shell is provided with a mounting flange, the upper shell is mounted on the mounting flange through the connecting piece, and the partial discharge detection antenna is installed inside the cable accessory protective shell after passing through the mounting flange.

[0007] Optionally, the cable accessory protective shell includes a middle shell and end shells arranged on both sides of the middle shell, an accessory partition is provided between the middle shell and the end shell, and a lead seal is provided at the outer end of the end shell to keep the middle shell and the interior of the end shell sealed, and the device body is used to be installed on the end shell of the cable accessory protective shell.

[0008] Optionally, the partial discharge detection antenna is a double-sided helical antenna.

[0009] Optionally, the double-sided helical antenna includes a substrate and helical antennas of the same shape and overlapping with each other, which are respectively arranged on the front and back sides of the substrate, and the inner terminals of the helical antennas on both sides are connected through vias on the substrate, and the outer terminals are connected to the circuit board.

[0010] In addition, the present invention also provides an application method of the above-mentioned built-in partial discharge online monitoring device for high-voltage cables, comprising the following steps of designing a partial discharge detection antenna: S1, extract the electrical parameters of the high-voltage cable per unit length, including resistance R, inductance L and capacitance C; S2, based on the electrical parameters of the high-voltage cable per unit length, establishes a length of l The cable distribution model of the high-voltage cable is l The cable distribution model of the high-voltage cable is used to calculate the transfer function of the high-voltage cable; S3, the length is calculated based on the transfer function of the high voltage cable. l The 3dB bandwidth of the high-voltage cable is the value of the output signal amplitude attenuation to the input signal. The frequency width corresponding to the times; S4, with length l The 3dB bandwidth of the high-voltage cable is used as the upper limit of the center frequency of the partial discharge detection antenna. The structural parameters of the partial discharge detection antenna are simulated and adjusted in combination with the installation position and installation distance of the partial discharge detection antenna. In this way, the structural parameters of the partial discharge detection antenna that meets the center frequency requirements are obtained, including the material, radius and thickness of the substrate, the inner circle radius, outer circle radius, number of spirals, line width and line spacing of the spiral antenna.

[0011] Optionally, in step S2, a length ofl The cable distribution model of the high-voltage cable includes the resistance R m,1 ~Resistor R m,N and capacitor C m,1 ~Capacitor C m,N , resistor R m,1 ~Resistor R m,N Indicates the resistance and capacitance C of the 1st to Nth unit length cables m,1 ~Capacitor C m,N Indicates the capacitance and resistance R of the 1st to Nth unit length cables m,1 ~Resistor R m,N Connect in series, any capacitor C m,1 One end is connected to the resistor R m,1 one end and the other end is grounded.

[0012] Optionally, in step S2, the length is l The cable distribution model of the high-voltage cable calculates the functional expression of the transfer function of the high-voltage cable as follows: , In the above formula, is the transfer function, is the resistance per unit length of cable, is the capacitance per unit length of cable, The length is l The number of high voltage cables per unit length, is the unit length serial number, is the Laplace operator.

[0013] Optionally, in step S3, the length is calculated based on the transfer function of the high-voltage cable. l The functional expression of the 3dB bandwidth of the high-voltage cable is: , In the above formula, The length is l The 3dB bandwidth of the high voltage cable, is the resistance per unit length of cable, is the capacitance per unit length of cable, The length is l The number of high voltage cables per unit length, It is a unit length serial number.

[0014] Optionally, after step S4, the method further includes selecting a matching circuit that minimizes the input reflection coefficient of the partial discharge detection antenna from a plurality of preset matching circuits, so that the center frequency of the partial discharge detection antenna can be adjusted within the 3dB bandwidth of the high-voltage cable and the input reflection coefficient is minimized.

[0015] Compared with the prior art, the present invention mainly has the following advantages: 1. The partial discharge detection antenna of the present invention is arranged inside the cable accessory protective shell to detect the electric field distribution formed by the partial discharge signal transmitted by the cable core wire of the high-voltage cable after passing through the inner semi-conductive layer and the main insulation of the cable. The partial discharge signal is directly received by the built-in partial discharge detection antenna, and the detection sensitivity and accuracy are high. Methods such as the pulse current method and the high-frequency current method are affected by the partial discharge signal propagation channel and cannot achieve direct detection of the partial discharge signal.

[0016] 2. Since accessories are the parts of the cable most prone to insulation defects, the present invention reserves flange interfaces at the lead-sealed areas of the cable terminals and intermediate joints (cable accessory protective shells) to install partial discharge detection antennas, thereby facilitating the sensitive acquisition of cable partial discharge signals while avoiding damage to the cable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the device in an embodiment of the present invention.

[0018] Figure 2 It is a schematic diagram of a partial cross-sectional structure of the installation of the device in an embodiment of the present invention.

[0019] Figure 3 Schematic diagram of the structure of a partial discharge detection antenna in an embodiment of the present invention.

[0020] Figure 4 Flowchart of an application method of a partial discharge detection antenna in an embodiment of the present invention.

[0021] Figure 5 Schematic diagram of the electric field distribution of the cable cross section in an embodiment of the present invention.

[0022] Figure 6 This is the electric field distribution diagram of the main insulation layer and outer semi-conductive layer of the cable in an embodiment of the present invention.

[0023] Figure 7 Schematic diagram of a cable distribution model in an embodiment of the present invention.

[0024] Legend: 1. Device body; 10. Communication antenna; 11. Upper shell; 12. Connector; 2. Partial discharge detection antenna; 21. Base plate; 22. Helical antenna; 3. Circuit board; 4. High-voltage cable; 41. Cable core; 42. Inner semi-conductive layer; 43. Cable main insulation; 44. Outer semi-conductive layer; 45. Buffer layer; 46. Corrugated aluminum sheath; 47. Outer insulation; 5. Cable accessory protective shell; 51. Mounting flange. DETAILED DESCRIPTION

[0025] The following describes embodiments of the present invention in detail. Examples of such embodiments are illustrated in the accompanying drawings, where identical or similar reference numerals throughout denote identical or similar elements or elements having identical or similar functions. The embodiments described below with reference to the accompanying drawings are illustrative and intended solely to explain the present invention and are not to be construed as limiting the present invention. In the description of the present invention, references to "first," "second," and so on are intended solely for the purpose of distinguishing technical features and are not to be construed as indicating or implying relative importance, the number of such referenced technical features, or the order of such referenced technical features. Where references to orientation, such as "upper," "lower," and so on, are made based on the orientations or positional relationships shown in the accompanying drawings, such orientations are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. Such orientations are not intended to indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Unless otherwise expressly defined, terms such as "dispose," "install," and "connect" in the description of the present invention should be interpreted broadly. Persons skilled in the art can reasonably determine the specific meanings of such terms within the present invention based on the specific content of the technical solution.

[0026] like Figure 1 and Figure 2 As shown, the high-voltage cable built-in partial discharge online monitoring device of this embodiment includes a device body 1, a partial discharge detection antenna 2 and a circuit board 3. The device body 1 is used to be installed on the cable accessory protective shell 5 of the high-voltage cable 4. The connection part of the high-voltage cable 4 located in the middle of the cable accessory protective shell 5 removes the buffer layer 45, the corrugated aluminum sheath 46 and the outer insulation 47 of the high-voltage cable 4 and retains the cable core 41, the inner semi-conductive layer 42, the cable main insulation 43 and the outer semi-conductive layer 44. The partial discharge detection antenna 2 is arranged inside the cable accessory protective shell 5 to detect the electric field distribution formed by the partial discharge signal transmitted by the cable core 41 of the high-voltage cable 4 after passing through the inner semi-conductive layer 42, the cable main insulation 43 and the outer semi-conductive layer 44. The circuit board 3 is arranged in the device body 1. The circuit board 3 is provided with a signal transmission circuit. The partial discharge detection antenna 2 is connected to the signal transmission circuit on the circuit board 3. Outside the main cable insulation 43 and the outer semi-conductive layer 44 of the high-voltage cable 4, there is electromagnetic radiation of a partial discharge signal. This signal radiation can be used to effectively detect the partial discharge signal inside the cable.

[0027] like Figure 1 As shown, in this embodiment, the signal transmission circuit on the circuit board 3 is a wireless signal transmission circuit, and a communication antenna 10 is installed on the device body 1, and the communication antenna 10 is connected to the wireless signal transmission circuit.

[0028] like Figure 1As shown, in this embodiment, the device body 1 includes an upper shell 11 and a connector 12. The cable accessory protective shell 5 is provided with a mounting flange 51. The upper shell 11 is installed on the mounting flange 51 through the connector 12. The partial discharge detection antenna 2 is installed inside the cable accessory protective shell 5 after passing through the mounting flange 51. The partial discharge detection antenna 2 can be conveniently installed by reserving the mounting flange 51 in the cable accessory protective shell 5. In this embodiment, the mounting flange 51 for mounting the partial discharge detection antenna 2 is made of a copper rod processed into an integral flange shape and welded. After processing and forming, the wall thickness is 20 mm and can withstand external forces during normal use. The connector 12 between the upper shell 11 and the cable accessory protective shell 5 is made of POM steel with excellent insulation performance. The interface is filled and coated with high-performance insulating material to ensure that the insulation performance is not affected. A double-layer sealing ring structure is designed on the flange to prevent impurities from entering.

[0029] like Figure 3 As shown, in this embodiment, the partial discharge detection antenna 2 is a double-sided helical antenna, which includes a substrate 21 and helical antennas 22 of the same shape and overlapping with each other, which are respectively arranged on the front and back sides of the substrate 21, and the terminals on the inner sides of the helical antennas 22 on both sides are connected through the via holes on the substrate 21, and the terminals on the outer sides are connected to the circuit board 3.

[0030] In addition, if Figure 4 As shown, this embodiment also provides an application method of a high-voltage cable built-in partial discharge online monitoring device, including the following steps of designing a partial discharge detection antenna 2: S1, extracting electrical parameters of the high-voltage cable 4 per unit length, including resistance R, inductance L and capacitance C; S2, based on the electrical parameters of the high-voltage cable 4 per unit length, establish a length of l The cable distribution model of the high-voltage cable 4 is l The cable distribution model of the high-voltage cable 4 is used to calculate the transfer function of the high-voltage cable 4; S3, according to the transfer function of high voltage cable 4, the length is calculated as l The 3dB bandwidth of the high-voltage cable 4 is the value of the output signal amplitude attenuation to the input signal. The frequency width corresponding to the times; S4, with length l The 3dB bandwidth of the high-voltage cable 4 is used as the upper limit of the center frequency of the partial discharge detection antenna 2. The structural parameters of the partial discharge detection antenna 2 are simulated and adjusted in combination with the installation position and installation distance of the partial discharge detection antenna 2, so as to obtain the structural parameters of the partial discharge detection antenna 2 with a center frequency that meets the requirements, including the material, radius and thickness of the substrate, the inner circle radius, outer circle radius, number of spirals, line width and line spacing of the helical antenna.

[0031] In this embodiment, the electrical parameters of the high-voltage cable 4 per unit length are extracted in step S1 by simulation. Alternatively, the electrical parameters of the high-voltage cable 4 per unit length can be obtained by measurement or by consulting factory data as needed. In this embodiment, the electrical parameters of the high-voltage cable 4 per unit length are extracted based on the structural characteristic parameters of the XLPE high-voltage cable (sizes of the copper conductor, the main insulation inner shielding layer, the main insulation, the main insulation outer semi-conductive layer, the water-blocking tape, etc., the dielectric constant ɛ r , thermal conductivity λ, thermal expansion coefficient α, elastic modulus E, Poisson's ratio), modeling and simulation are used to obtain the cable partial discharge signal transmission characteristics, extract the unit length of XLPE high-voltage cable resistance R, inductance L, capacitance C, and obtain the cable cross-section electric field distribution as shown below: Figure 5 As shown, the electric field distribution of the semi-conductive layer outside the main insulation of the cable is as follows Figure 6 As shown, see Figure 5 and Figure 6 It can be seen that the electric field strength gradually weakens from the cable core 41 to the outer semi-conductive layer 44. After passing through the cable main insulation 43, the electric field still exists. This means that it is feasible to design the partial discharge detection antenna 2 to receive the partial discharge signal transmitted through the cable from outside the cable main insulation 43. The partial discharge signal can be effectively detected outside the cable main insulation 43 of the high-voltage cable.

[0032] In step S2 of this embodiment, a cable distribution model of a high-voltage cable 4 with a length of l is established based on the electrical parameters of the high-voltage cable 4 per unit length. Figure 7 As shown, in step S2 of this embodiment, the length is established l The cable distribution model of the high-voltage cable 4 includes the resistance R m,1 ~Resistor R m,N and capacitor C m,1 ~Capacitor C m,N , resistor R m,1 ~Resistor R m,N Indicates the resistance and capacitance C of the 1st to Nth unit length cables m,1 ~Capacitor C m,N Indicates the capacitance and resistance R of the 1st to Nth unit length cables m,1 ~Resistor R m,N Connect in series, any capacitor C m,1 One end is connected to the resistor R m,1 one end and the other end is grounded. Figure 7 The transfer function of the cable distribution model is shown It can be expressed as: , In the above formula, ~ is the coefficient of the denominator polynomial in the transfer function, The length is l The number of unit lengths of high voltage cables 4, is the Laplace operator. For a given capacitance C m,i and resistor R m,i ,have: , That is, the transfer function Except for the Laplace operator The first term In addition, the Laplace operator The higher-order terms of are much smaller than 1e when N (cable length) is greater than 100. -6 , can be ignored, and there is: .

[0033] Therefore, in step S2 of this embodiment, the length is l The function expression of the transfer function of the high-voltage cable 4 calculated by the cable distribution model of the high-voltage cable 4 can be approximately expressed as: , In the above formula, is the transfer function, is the resistance per unit length of cable, is the capacitance per unit length of cable, The length is l The number of unit lengths of high voltage cables 4, is the unit length serial number, is the Laplace operator.

[0034] In step S3 of this embodiment, the length is calculated based on the transfer function of the high-voltage cable 4. l The functional expression of the 3dB bandwidth of the high-voltage cable 4 is: , In the above formula, The length is l 3dB bandwidth of the high voltage cable 4, is the resistance per unit length of cable, is the capacitance per unit length of cable, The length is l The number of unit lengths of high voltage cables 4, It is a unit length serial number.

[0035] In this embodiment, step S4 obtains the structural parameters of a ZC-YJLW03-Z 64 / 110 1*800 cable partial discharge detection antenna 2 (cable length > 100 meters) with a center frequency that meets the requirements. These parameters include the material, radius, and thickness of the substrate 21, the inner and outer radius of the helical antenna 22, the number of spirals, the line width, and the spacing between the spirals. Specifically, the final optimized inner radius is 9 mm, the outer radius is 24 mm, and the substrate radius is 26 mm. The substrate is made of FR4. Each side of the substrate 21 has 19 spirals (19 total), with a line width of 0.3947 mm, a spacing of 0.35 mm, and a substrate thickness of 1.6 mm. When viewed from above, the shapes of the spiral antennas 22 on both sides completely overlap. A via is used at the starting point of the inner spiral to connect the inner ends of the spirals on both sides. At the end of the outer spiral, the traces on the back are slightly longer and are connected to the terminals on both the front and back sides with approximately 2 mm wire leads. The substrate 21 of the partial discharge detection antenna 2 is made of a PCB material with good conductivity and easy processing, so as to ensure that the antenna can efficiently receive partial discharge signals and is easy to install.

[0036] like Figure 4 As shown, as an optional implementation, after step S4, it also includes selecting a matching circuit that minimizes the input reflection coefficient of the partial discharge detection antenna 2 from a plurality of preset matching circuits, so that the center frequency of the partial discharge detection antenna 2 can be adjusted within the 3dB bandwidth range of the high-voltage cable 4 and the input reflection coefficient is minimized. The matching circuit here refers to the detection circuit of the partial discharge detection antenna 2.

[0037] The built-in partial discharge online monitoring device for high-voltage cables of this embodiment can accurately monitor the partial discharge signal inside the cable body. As an optional implementation method, the application method of the built-in partial discharge online monitoring device for high-voltage cables of this embodiment also includes: obtaining the waveform characteristics of the partial discharge signal, inputting the waveform characteristics of the partial discharge signal into a pre-trained machine learning model to obtain the type of the partial discharge signal, the machine learning model is pre-trained to establish a mapping relationship between the waveform characteristics of the partial discharge signal and the type of the partial discharge signal, and the waveform characteristics of the partial discharge signal include some or all of the following characteristics: Pulse peak: the maximum amplitude of the pulse signal, which can be measured by an oscilloscope; Peak time: the time when the pulse occurs The phase at the time of the pulse can be measured by an oscilloscope; pulse rise time: the time required for the pulse to rise from 10% to 90% of the maximum amplitude; fall time: the time required for the pulse to fall from 90% to 10% of the maximum amplitude; pulse width: the duration of the pulse, usually starting from 10% of the maximum amplitude on the rising edge and ending at 10% of the maximum amplitude on the falling edge; 50% maximum pulse duration: a measure of the pulse width, starting from 50% of the maximum amplitude on the rising edge and ending at 50% of the maximum amplitude on the falling edge; phase-resolved partial discharge maps can reflect the relationship between the number of discharges, discharge amount, and phase over multiple cycles; pulse amplitude distribution: the amplitude distribution characteristics of the pulse signal can be used to identify the type of multi-discharge source. Among them, the machine learning model can use a support vector machine or a deep learning neural network model.

[0038] As an optional implementation, in this embodiment, the high-voltage cable built-in partial discharge online monitoring device of this embodiment is installed at the line terminal and the intermediate joint of the high-voltage cable 4. The application method of the high-voltage cable built-in partial discharge online monitoring device of this embodiment also includes locating the cable insulation defect position by using the partial discharge waveform time and amplitude collected by the high-voltage cable built-in partial discharge online monitoring device at the two line terminals of the high-voltage cable 4.

[0039] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A built-in partial discharge online monitoring device for high-voltage cables, characterized in that: The invention comprises a device body (1), a partial discharge detection antenna (2) and a circuit board (3); the device body (1) is used to be installed on a cable accessory protective shell (5) of a high-voltage cable (4); the buffer layer (45), the corrugated aluminum sheath (46) and the outer insulation (47) of the high-voltage cable (4) are removed from the connection portion of the high-voltage cable (4) located in the middle of the cable accessory protective shell (5), and the cable core wire (41), the inner semi-conductive layer (42), the cable main insulation (43) and the outer semi-conductive layer (44) are retained; the partial discharge detection antenna (2) is arranged inside the cable accessory protective shell (5) to detect the electric field distribution formed after the partial discharge signal transmitted by the cable core wire (41) of the high-voltage cable (4) passes through the inner semi-conductive layer (42), the cable main insulation (43) and the outer semi-conductive layer (44); the circuit board (3) is arranged in the device body (1); a signal transmission circuit is arranged on the circuit board (3); the partial discharge detection antenna (2) is connected to the signal transmission circuit on the circuit board (3).

2. The high-voltage cable built-in partial discharge online monitoring device according to claim 1 is characterized in that: The signal transmission circuit on the circuit board (3) is a wireless signal transmission circuit, and a communication antenna (10) is installed on the device body (1), and the communication antenna (10) is connected to the wireless signal transmission circuit.

3. The high-voltage cable built-in partial discharge online monitoring device according to claim 1 is characterized in that: The device body (1) comprises an upper shell (11) and a connecting piece (12); a mounting flange (51) is provided on the cable accessory protective shell (5); the upper shell (11) is mounted on the mounting flange (51) via the connecting piece (12); and the partial discharge detection antenna (2) is mounted inside the cable accessory protective shell (5) after passing through the mounting flange (51).

4. The high-voltage cable built-in partial discharge online monitoring device according to claim 1 is characterized in that: The partial discharge detection antenna (2) is a double-sided helical antenna.

5. The high-voltage cable built-in partial discharge online monitoring device according to claim 4 is characterized in that: The double-sided helical antenna comprises a substrate (21) and helical antennas (22) of identical shape and overlapping each other, which are respectively arranged on the front and back sides of the substrate (21); the inner terminals of the helical antennas (22) on both sides are connected through via holes on the substrate (21), and the outer terminals are connected to the circuit board (3).

6. An application method of the high-voltage cable built-in partial discharge online monitoring device according to claim 5, characterized in that: The method comprises the following steps of designing a partial discharge detection antenna (2): S1, extracting electrical parameters of the high voltage cable (4) per unit length, including resistance R, inductance L and capacitance C; S2, based on the electrical parameters of the high-voltage cable (4) per unit length, is established as l The cable distribution model of the high-voltage cable (4) is based on the length of l The cable distribution model of the high-voltage cable (4) calculates the transfer function of the high-voltage cable (4); S3, the length is calculated based on the transfer function of the high voltage cable (4) l The 3dB bandwidth of the high-voltage cable (4) is the value of the attenuation of the output signal amplitude to the input signal. The frequency width corresponding to the time of multiple; S4, with length l The 3dB bandwidth of the high-voltage cable (4) is used as the upper limit of the center frequency of the partial discharge detection antenna (2), and the structural parameters of the partial discharge detection antenna (2) are simulated and adjusted in combination with the installation position and installation distance of the partial discharge detection antenna (2), so as to obtain the structural parameters of the partial discharge detection antenna (2) whose center frequency meets the requirements, including the material, radius and thickness of the substrate (21), the inner circle radius, outer circle radius, number of spirals, line width and line spacing of the spiral antenna (22).

7. The application method of the high-voltage cable built-in partial discharge online monitoring device according to claim 6 is characterized in that: In step S2, a length of l The cable distribution model of the high voltage cable (4) includes the resistance R m,1 ~Resistance R m,N And the capacitor C m,1 ~Capacitor C m,N , resistor R m,1 ~Resistance R m,N Indicates the resistance and capacitance C of the 1st to Nth unit length cables m,1 ~Capacitor C m,N Indicates the capacitance and resistance R of the 1st to Nth unit length cables m,1 ~Resistance R m,N Connected in series, any capacitor C m,1 One end is connected to the resistor R m,1 one end and the other end is grounded.

8. The application method of the high-voltage cable built-in partial discharge online monitoring device according to claim 7 is characterized in that: In step S2, the length is l The cable distribution model of the high-voltage cable (4) calculates the functional expression of the transfer function of the high-voltage cable (4) as follows: ， In the above formula, is the transfer function, is the resistance per unit length of cable, is the capacitance per unit length of cable, The length is l The number of unit lengths of high voltage cables (4), is the unit length serial number, is the Laplace operator.

9. The application method of the high-voltage cable built-in partial discharge online monitoring device according to claim 7 is characterized in that: In step S3, the length is calculated based on the transfer function of the high voltage cable (4): l The functional expression of the 3dB bandwidth of the high voltage cable (4) is: ， In the above formula, The length is l The 3dB bandwidth of the high voltage cable (4), is the resistance per unit length of cable, is the capacitance per unit length of cable, The length is l The number of unit lengths of high voltage cables (4), It is a unit length sequence number.

10. The application method of the high-voltage cable built-in partial discharge online monitoring device according to claim 6, characterized in that: After step S4, the method further includes selecting a matching circuit that minimizes the input reflection coefficient of the partial discharge detection antenna (2) from among a plurality of preset matching circuits, so that the center frequency of the partial discharge detection antenna (2) can be adjusted within the 3dB bandwidth of the high-voltage cable (4) and the input reflection coefficient is minimized.

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