Preparation Method of Flexible Piezoelectric Ultrasonic Sensor for Partial Discharge of Cable and the Sensor

Abstract

The present invention discloses a preparation method and a sensor of a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable. In the method, the sensitive element of the flexible piezoelectric ultrasonic sensor is a Pb(Zr 1‑x ,Ti x )O3 ferroelectric thin film. The ferroelectric thin film is prepared on mica by a sol-gel method. After the thin film is plated with interdigital electrodes, it is polarized, and finally, the ferroelectric thin film is electromagnetically shielded and packaged, so as to obtain a flexible piezoelectric ultrasonic sensor with high sensitivity and applicable to the detection of ultrasonic signals of partial discharge of a cable. The process of the present invention is simple, easy to operate, and has good repeatability; it is mainly applied to the fields of cable testing and sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable testing, and particularly relates to a preparation method of a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable and the sensor. Background Art

[0002] When a cable undergoes partial discharge, certain physical and chemical changes will occur, and these changes can be used to diagnose potential hazards of the cable. According to different detection signals, on-line partial discharge monitoring methods are divided into electrical measurement methods and non-electrical measurement methods. Electrical measurement methods mainly include differential method, electromagnetic coupling method, ultra-high frequency monitoring method, capacitive coupling method, high-frequency current method, and inductive coupling method. These methods have their own deficiencies in aspects such as anti-electromagnetic interference, sensitivity, economy, installation method, and installation location.

[0003] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention proposes a preparation method of a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable and the sensor, which can be directly attached to the surface of the cable and various parts of the cable components. This installation method solves the problem of interface impedance matching, the attenuation degree of ultrasonic signal energy is low, and the sensing sensitivity is greatly improved.

[0005] The object of the present invention is achieved through the following technical solutions. A preparation method of a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable includes:

[0006] Step S1: Weigh solute raw materials and solvent raw materials according to the content of each element in the chemical formula Pb(Zr 1-x ,Ti x )O3, where x takes values in the range of 40%-60%. The solute raw materials include lead acetate, zirconium n-propoxide, and titanium isopropoxide, and the solvent raw materials include acetic acid;

[0007] Step S2: Stir the solvent raw materials at room temperature for the first period of time to obtain a solvent. Add lead acetate in the solute raw materials to the solvent, heat and stir in a water bath for the second period of time, then stop heating and stir until room temperature. Add the titanium isopropoxide to the solution and stir at room temperature for the third period of time; continue to add zirconium n-propoxide and stir at room temperature for the fourth period of time; let it stand for the fifth period of time to obtain a sol;

[0008] Step S3: Wash fluorophlogopite and dry it, and reduce the thickness of the fluorophlogopite to a mica sheet that can be attached to the surface of the cable;

[0009] Step S4: The mica sheet is spin-coated with the sol to form a wet film on the mica sheet. The wet film is dried at 350 °C for a seventh period of time and then at 500 °C for a seventh period of time to form a PZT thin film.

[0010] Step S5: The dried PZT thin film is heated at 350 °C for a seventh period of time, at 500 °C for an eighth period of time, and at 650 °C for a ninth period of time, and then cooled to room temperature. Steps S4 to S5 are repeated until the thickness of the PZT thin film is within a predetermined thickness range.

[0011] Step S6: Interdigitated electrodes are deposited on the PZT thin film. After the leads of the interdigitated electrodes are connected to the bare wires, polarization is performed. The polarization voltage is 900 V and the polarization time is a tenth period of time. The PMMA solution is used to cover part of the interdigitated electrodes, leaving the leads of the interdigitated electrodes.

[0012] Step S7: Silicone grease is coated on the non-conductive side of the first conductive film. The substrate side of the PZT thin film is attached to the silicone grease. The leads are extended to the bottom of the PET film using conductive tape. Silver paste is used to connect the conductive tape to the leads. After the silver paste dries, a hole is drilled at the other end of the conductive tape, and a rivet is used for fixation. The insulating film separates the rivet from the conductive side of the conductive film. A second conductive film with the same width as the first conductive film and a shorter length is prepared. The first conductive film and the second conductive film are aligned on one side of the PZT thin film and fixed with the conductive sides facing outward.

[0013] Step S8: The conductive tape is connected to the first wire through a rivet. The other side of the first wire is soldered to the single-head jumper of the coaxial cable with a single core, and is soldered to the shielded copper mesh and the signal wire respectively. An additional second wire is soldered to the shielded copper mesh. The conductive tape wraps around and covers the rivet and is connected to the conductive side of the PZT thin film.

[0014] In the method for preparing the flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, in step S1, an additional 10% of lead acetate is measured.

[0015] In the method for preparing the flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, in step S3, the fluorophlogopite is ultrasonically cleaned a predetermined number of times in the order of pure water, alcohol, acetone, alcohol, and pure water, and each cleaning is for a sixth period of time. After the fluorophlogopite is cleaned, it is dried, and the thickness of the fluorophlogopite is thinned into a mica sheet that can be attached to the surface of the cable.

[0016] In the method for preparing the flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, the predetermined number of times is 5 times.

[0017] In the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, the first time period is 1 hour, the second time period is 15 minutes, the third time period is 30 minutes, the fourth time period is 5 - 10 minutes, the fifth time period is 24 hours, the sixth time period is 5 minutes, the seventh time period is 2 minutes, the eighth time period is 5 minutes, the ninth time period is 10 minutes, and the tenth time period is 1 hour.

[0018] In the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, the finger pitch of the interdigital electrode is 300 μm.

[0019] In the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, the thickness of the mica sheet is 20 μm.

[0020] In the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, in step S8, a heat shrinkable tube is used to fix the first wire and the second wire, and the conductive film is electrically connected to the ground wire.

[0021] In the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, in step S4, the mica sheet is adsorbed on a spin coater to spin coat the sol. The spin coater rotates at 1000 rpm from 0 to 10 seconds and at 3000 rpm from 10 to 40 seconds. The sol is evenly dropped along the central circular hole of the spin coater cover within the first 10 seconds.

[0022] A flexible piezoelectric ultrasonic sensor is made according to the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable.

[0023] Compared with the prior art, the present invention has the following advantages: The method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable according to the present invention prepares a PZT ferroelectric film on mica by the sol - gel method, polarizes the ferroelectric film after plating the interdigital electrode, and can obtain a flexible piezoelectric ultrasonic sensor for detecting ultrasonic signals of cable partial discharge after electromagnetic shielding packaging. It has good bending flexibility, can be attached to the cable surface, realizes excellent interfacial acoustic impedance matching, and thus can more effectively detect the ultrasonic signals generated by partial discharge in the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0025] In the accompanying drawings:

[0026] Figure 1 is a structural diagram of a flexible piezoelectric ultrasonic sensor prepared by a method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable according to an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of the sensitivity curve of a flexible piezoelectric ultrasonic sensor according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of a time-domain voltage signal obtained by measuring a partial discharge ultrasonic signal by a method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable according to an embodiment of the present invention;

[0029] Figure 4 is according to Figure 3 a schematic diagram of a frequency-domain voltage signal obtained after FFT processing by a method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable according to an embodiment of the present invention;

[0030] Figure 5 is a schematic diagram of an interdigital electrode of a flexible piezoelectric ultrasonic sensor according to an embodiment of the present invention.

[0031] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Embodiments

[0032] Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be completely conveyed to those skilled in the art.

[0033] It should be noted that in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims do not use the difference in terms as a way to distinguish components, but use the difference in the functions of components as the criterion for distinction. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended terms and should be interpreted as "including but not limited to". The subsequent description of the specification is for the purpose of describing the preferred embodiments of implementing the present invention, but the description is for the general purpose of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined by the appended claims.

[0034] For the convenience of understanding the embodiments of the present invention, the following will further explain and illustrate with specific embodiments in conjunction with the accompanying drawings, and the accompanying drawings do not limit the embodiments of the present invention.

[0035] For better understanding, as Figures 1 to 5 shown, a method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable includes:

[0036] Step S1: Weigh the solute raw materials and solvent raw materials according to the contents of the elements in the chemical formula Pb(Zr 1-x ,Ti x )O3. Among them, x takes values in the range of 40%-60%. The solute raw materials include lead acetate, zirconium n-propoxide, and titanium isopropoxide, and the solvent raw materials include acetic acid;

[0037] Step S2: Stir the solvent raw materials at room temperature for the first period of time to obtain a solvent. Add lead acetate in the solute raw materials to the solvent, heat and stir in a water bath for the second period of time, then stop heating and stir until room temperature. Add the titanium isopropoxide to the solution and stir at room temperature for the third period of time; continue to add zirconium n-propoxide and stir at room temperature for the fourth period of time; let it stand for the fifth period of time to obtain a sol;

[0038] Step S3: After cleaning and drying the fluorophlogopite, thin the thickness of the fluorophlogopite into a mica sheet that can be attached to the surface of the cable;

[0039] Step S4: Spin-coat the sol on the mica sheet to form a wet film on the mica sheet. The wet film is dried at 350°C for the seventh period of time and then dried at 500°C for the seventh period of time to form a PZT film 6;

[0040] Step S5: The dried PZT film 6 is heated at 350°C for the seventh period of time, heated at 500°C for the eighth period of time, and heated at 650°C for the ninth period of time, and then cooled to room temperature. Repeat Step S4 to Step S5 until the thickness of the PZT film 6 is within a predetermined thickness range;

[0041] Step S6: Deposit interdigital electrodes 4 on the PZT film 6. After connecting the leads of the interdigital electrodes 4 to the bare wires, polarize them. The polarization voltage is 900V and the polarization time is the tenth period of time. Cover the part of the interdigital electrodes 4 with PMMA solution, and keep the leads of the interdigital electrodes 4;

[0042] Step S7: Apply silicone grease on the non-conductive side of the first conductive film 5. Attach the substrate side of the PZT film 6 to the silicone grease. Extend the pins to the bottom of the PET film using the conductive tape 2. Connect the conductive tape 2 and the pins using silver paste 3. After the silver paste 3 dries, drill a hole at the other end of the conductive tape 2 and fix it with a rivet. Use an insulating film to separate the rivet from the conductive side of the first conductive film. Prepare a second conductive film with the same width as the first conductive film 5 but shorter in length. Align the first conductive film 5 and the second conductive film on one side of the PZT film 6 and fix them with the conductive sides facing outward.

[0043] Step S8: Connect the conductive tape 2 to the first wire through a rivet. Weld the other side of the first wire to the single-head jumper of the single-core coaxial cable 1, and weld them to the shielded copper mesh and the signal wire respectively. Weld an additional second wire to the shielded copper mesh. Wrap the conductive tape 2 around and cover the rivet and connect it to the conductive side of the PZT film 6.

[0044] In the preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, in step S1, an additional 10% of lead acetate is measured.

[0045] In the preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, in step S3, the fluorophlogopite is ultrasonically cleaned a predetermined number of times in the order of pure water, alcohol, acetone, alcohol, and pure water, with each cleaning lasting for the sixth time period. After the fluorophlogopite is cleaned, it is dried, and the thickness of the fluorophlogopite is thinned into a mica sheet that can be attached to the surface of the cable.

[0046] In the preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, the predetermined number of times is 5 times.

[0047] In the preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, the first time period is 1 hour, the second time period is 15 minutes, the third time period is 30 minutes, the fourth time period is 5 - 10 minutes, the fifth time period is 24 hours, the sixth time period is 5 minutes, the seventh time period is 2 minutes, the eighth time period is 5 minutes, the ninth time period is 10 minutes, and the tenth time period is 1 hour.

[0048] In the preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, the finger spacing of the interdigital electrode 4 is 300 μm.

[0049] In the preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, the thickness of the mica sheet is 20 μm.

[0050] In a preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, in step S8, a heat shrinkable tube is used to fix the first wire and the second wire, and the conductive film 5 is electrically connected to the ground wire.

[0051] In a preferred embodiment of the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge in a cable, in step S4, the mica sheet is adsorbed on a spin coater to spin coat the sol. The spin coater rotates at 1000 rpm for 0 - 10 seconds and at 3000 rpm for 10 - 40 seconds, and the sol is evenly dropped along the central circular hole of the spin coater cover within the first 10 seconds.

[0052] In one embodiment, the preparation method steps are as follows:

[0053] (1) Weigh the solutes according to the content of each element in the chemical formula Pb(Zr 1-x ,Ti x )O3. The value of x ranges from 40% to 60%. The solute raw materials are lead acetate, zirconium propoxide, and titanium isopropoxide, and an additional 10% of lead acetate is taken. Measure the solvent according to the demand. The solvent raw material is acetic acid.

[0054] (2) Mix the measured solvent raw materials in step (1) and stir at room temperature for one hour to obtain the solvent.

[0055] (3) Add lead acetate to the solvent in step (2), heat with water bath and stir for 15 minutes, then stop heating and stir until room temperature; add titanium isopropoxide to the solution and stir at room temperature for 30 minutes; add zirconium propoxide to the solution and stir at room temperature for 5 - 10 minutes; let it stand for 24 hours to obtain the sol.

[0056] (4) Fluorophlogopite is ultrasonically cleaned 5 times in the order of pure water, alcohol, acetone, alcohol, and pure water, 5 minutes each time. Wipe off the impurities on the mica that have not been removed by ultrasonic cleaning, blow away the surface alcohol and impurities with a nitrogen gun and then dry it, and reduce the mica thickness to be attachable to the cable surface.

[0057] (5) Adsorb the mica sheet in step (4) on a spin coater to spin coat the sol. The spin coater rotates at 1000 rpm for 0 - 10 seconds and at 3000 rpm for 10 - 40 seconds, and an appropriate amount of sol is evenly dropped along the central circular hole of the spin coater cover within the first 10 seconds.

[0058] (6) Dry the wet film obtained in step (5) on a hot stage at 350°C for 2 minutes and at 500°C for 2 minutes in sequence.

[0059] (7) Heat the dried film in step (6) at 350°C for 2 minutes, at 500°C for 5 minutes, and at 650°C for 10 minutes in sequence, and then cool to room temperature. Repeat steps (5) - (7) until the PZT film 6 reaches the required thickness.

[0060] (8) Deposit the interdigital electrode 4 on the PZT thin film 6 obtained in step (7).

[0061] (9) Connect the pins of the interdigital electrode 4 to the bare wire and then polarize it. The polarization voltage is 900 V and the polarization time is 1 hour.

[0062] (10) Cover the part of the interdigital electrode 4 of the PZT thin film 6 obtained in step (9) with PMMA solution, leaving the pins of the interdigital electrode 4.

[0063] (11) Cut a conductive thin film 5 of appropriate size, apply a small amount of silicone grease on the non-conductive side, and attach the substrate side of the PZT thin film 6 to the silicone grease.

[0064] (12) Use the conductive tape 2 to extend the pins to the bottom of the PET thin film. Keep the pin part of the interdigital electrode 4. Connect the conductive tape 2 to the pins of the interdigital electrode 4 with silver paste 3. After the silver paste 3 dries, drill a hole at the other end of the conductive tape 2 and fix it with a rivet. Insulate the rivet from the conductive side of the conductive thin film 5 with an insulating film at the signal wire hole.

[0065] (13) Prepare a conductive thin film 5 with the same width and slightly shorter length as in step (11). Align one side of the PZT thin film 6 with the conductive side facing outwards, and fix the two conductive thin films 5.

[0066] (14) Connect the conductive tape 2 in step (13) to the fine wire through a rivet, and weld the other side of the wire to the single-head jumper of the single-core coaxial cable 1, respectively welding to the shielded copper mesh and the signal wire. Weld an additional wire to the shielded copper mesh and fix all the wires with heat shrink tubing.

[0067] (15) The conductive tape 2 wraps around and covers the rivet part and connects to the conductive side part of the thin film.

[0068] (16) After step (15), wrap the conductive tape 2 from the welding point to the connection point of the conductive thin film 5 and the wire. Finally, connect the two parts of the conductive tape 2 of the conductive thin film 5 and the wire to form a whole. Use the buzzer file of a multimeter to test the conduction effect, and the conductive thin film 5 should conduct to the ground wire.

[0069] (17) Test the ultrasonic signal detection ability of the flexible piezoelectric ultrasonic sensor obtained in step (16).

[0070] The specific implementation cases are as follows:

[0071] Take x as 48%, and the composition of the PZT thin film 6 is Pb(Zr 0.52 ,Ti 0.48 )O3, denoted as Example 1.

[0072] In step (8), the finger pitch of the interdigital electrode 4 is 300 μm. In step (4), the mica substrate is thinned to 20 μm. The sensitivity curve of the sensor is tested and the partial discharge ultrasonic signal is tested by using the sensor. The test results show that the piezoelectric ultrasonic sensor has high sensitivity and stable response, and has good detection performance for cable partial discharge.

[0073] A flexible piezoelectric ultrasonic sensor is made according to the preparation method of the flexible piezoelectric ultrasonic sensor for detecting cable partial discharge. The raw material of the sensitive element of the flexible piezoelectric ultrasonic sensor is Pb(Zr 1-x ,Ti x )O3 film. The content of Ti is adjusted in the range of 40%-60%. The PZT film 6 is grown on the fluorophlogopite by the sol-gel method. After polarization by the metal interdigital electrode 4, a flexible piezoelectric ultrasonic sensor for detecting the partial discharge ultrasonic signal of the cable is obtained after encapsulation.

[0074] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and these all belong to the scope of protection of the present invention.

Claims

1. A preparation method of a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable, characterized in that, It includes the following steps: Step S1: According to the contents of each element in the chemical formula Pb(Zr 1-x ,Ti x )O3, weigh the solute raw materials and the solvent raw materials. Among them, x takes values in the range of 40% - 60%. The solute raw materials include lead acetate, zirconium propoxide, and titanium isopropoxide, and the solvent raw materials include acetic acid; Step S2: Stir the solvent raw material at room temperature for the first period of time to obtain a solvent. Add lead acetate in the solute raw materials to the solvent, stop heating after stirring in a water bath for the second period of time, and stir until the room temperature. Add the titanium isopropoxide to the solution and stir at room temperature for the third period of time. Continuously add zirconium propoxide and stir at room temperature for the fourth period of time. Let it stand for the fifth period of time to obtain a sol; Step S3: After cleaning and drying the fluorophlogopite, thin the thickness of the fluorophlogopite into mica flakes that can be attached to the surface of the cable; Step S4: Spin-coat the mica flakes with the sol to form a wet film on the mica flakes. The wet film is dried at 350 °C for the seventh period of time and then dried at 500 °C for the seventh period of time to form a PZT thin film; Step S5: The dried PZT thin film is heated at 350 °C for the seventh period of time, heated at 500 °C for the eighth period of time, heated at 650 °C for the ninth period of time, and cooled to room temperature. Repeat Step S4 to Step S5 until the thickness of the PZT thin film is within the predetermined thickness range; Step S6: Deposit interdigital electrodes on the PZT thin film. After connecting the pins of the interdigital electrodes to the bare wires, perform polarization. The polarization voltage is 900 V and the polarization time is the tenth period of time. Cover the part of the interdigital electrodes with PMMA solution, and keep the pins of the interdigital electrodes; Step S7: Coat silicone grease on the non-conductive side of the first conductive film. Attach the substrate side of the PZT thin film to the silicone grease. Use conductive tape to extend the pins to the bottom of the PET film. Use silver paste to connect the conductive tape to the pins. After the silver paste dries, punch holes at the other end of the conductive tape and fix them with rivets. Insulating film separates the rivets from the conductive side of the first conductive film. Prepare a second conductive film with the same width as the first conductive film and a shorter length. Align the first conductive film and the second conductive film on one side of the PZT thin film and fix them with the conductive sides facing outwards; Step S8: Connect the conductive tape to the first wire through a rivet. Weld the other side of the first wire to the single-core coaxial cable single-head jumper, and weld them to the shielded copper mesh and the signal wire respectively. Weld an additional second wire to the shielded copper mesh. The conductive tape wraps around and covers the rivet and connects to the conductive side of the PZT thin film.

2. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 1, wherein, Preferably, in Step S1, an additional 10% of lead acetate is measured.

3. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 1, wherein, In the said Step S3, the fluorophlogopite is ultrasonically cleaned a predetermined number of times in the order of pure water, alcohol, acetone, alcohol, and pure water, with each cleaning for the sixth period of time. After the fluorophlogopite is cleaned, it is dried, and the thickness of the fluorophlogopite is thinned into mica flakes that can be attached to the surface of the cable.

4. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 3, wherein, The predetermined number of times is 5 times.

5. The method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable according to claim 3, wherein, The first period of time is 1 hour, the second period of time is 15 minutes, the third period of time is 30 minutes, the fourth period of time is 5 - 10 minutes, the fifth period of time is 24 hours, the sixth period of time is 5 minutes, the seventh period of time is 2 minutes, the eighth period of time is 5 minutes, the ninth period of time is 10 minutes, and the tenth period of time is 1 hour.

6. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 1, wherein, The finger pitch of the interdigital electrodes is 300 μm.

7. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 1, wherein, The thickness of the mica flakes is 20 μm.

8. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 3, wherein, In the said Step S8, use heat shrink tubing to fix the first wire and the second wire, and the conductive film is electrically connected to the ground wire.

9. The preparation method of the flexible piezoelectric ultrasonic sensor for detecting partial discharge of cables according to claim 1, wherein, In the step S4, the mica sheet adsorbs on the spin coater to spin coat the sol. The spin coater rotates at 1000 rpm for 0 to 10 seconds and at 3000 rpm for 10 to 40 seconds. The sol is evenly dropped along the central round hole of the spin coater cover within the first 10 seconds.

10. A flexible piezoelectric ultrasonic sensor, characterized in that, It is made by the method for preparing a flexible piezoelectric ultrasonic sensor for detecting partial discharge of a cable according to any one of claims 1-9.

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