Ultrasonic signal detection method and device for partial discharge of cables

Abstract

The invention discloses a method and a device for detecting partial discharge ultrasonic signals of cables. In the method, a flexible piezoelectric ultrasonic sensor is tightly attached to the surface of a cable to be tested to generate an ultrasonic signal, which is connected to a preamplifier input port through a coaxial cable to amplify the ultrasonic signal, wherein a conductive tape is connected to a first wire through a rivet, the other side of the first wire is welded to a single-core coaxial cable single-head jumper, which is respectively welded to a shielding copper mesh and a signal line, a second wire is additionally welded to the shielding copper mesh, the conductive tape is wrapped around the rivet and connected to the conductive side of a PZT film; the signal at the output port of the preamplifier is transmitted to a data acquisition card through a transmission line to collect and transmit the partial discharge data to a host computer, and the host computer processes and analyzes the partial discharge data.

Description

Technical Field

[0001] The invention belongs to the technical field of cable testing, and in particular to a method and a device for detecting partial discharge ultrasonic signals of a cable. Background Art

[0002] As an important power equipment in the power transmission link of my country's power industry, power cables are of vital importance in the process of social and economic development. Affected by factors such as working environment, construction and overload operation, the life of cables is shortened and the probability of failure increases. In order to ensure the normal operation of cables, various insulation defect detection technologies have emerged, which are mainly divided into electrical quantity detection and non-electrical quantity detection. Compared with electrical quantity detection, non-electrical quantity detection methods are not affected by electromagnetic interference, among which ultrasonic detection technology is mature and has good economic efficiency. However, traditional ultrasonic sensors are limited by their own structure, and their installation method seriously reduces the sensitivity of the detection method. Therefore, it is urgent to find a new ultrasonic detection method.

[0003] Traditional ultrasonic sensors are composed of piezoelectric crystals, sound-absorbing backing, sound matching layers, leads and housings, and are characterized by a flat sound receiving surface. Figure 1 As shown in the figure, there is a line contact between the sensor and the cable. When partial discharge occurs in the cable, the ultrasonic signal generated at the partial discharge spreads in the form of a spherical wave. The ultrasonic signal will undergo a series of attenuation processes when propagating in the medium, especially when passing through the interface between the cable outer sheath and the air and entering the sensor from the air. The mismatch of the acoustic impedance characteristics at the interface will cause a significant attenuation of the ultrasonic signal energy, resulting in a very weak ultrasonic signal received by the sensor and a very low sensitivity of the detection system.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a cable partial discharge ultrasonic signal detection method and detection device, which avoids the reflection attenuation of ultrasonic signals at the multi-layer gas-solid interface of cable outer sheath-air-sensor when traditional ultrasonic sensors detect cable partial discharge, and can more accurately extract partial discharge signals, thereby greatly improving the sensitivity of cable partial discharge ultrasonic detection technology.

[0006] The object of the present invention is achieved through the following technical solutions: a method for detecting partial discharge ultrasonic signals of a cable comprises:

[0007] The flexible piezoelectric ultrasonic sensor is closely attached to the surface of the cable to be tested to generate an ultrasonic signal, wherein, in the flexible piezoelectric ultrasonic sensor, a PZT film is coated on the mica sheet and a forked electrode is plated on the PZT film, silicone grease is coated on the non-conductive side of the first conductive film, the substrate side of the PZT film is attached to the silicone grease, a conductive tape is used to extend the pins of the forked electrode to the bottom of the PET film, the conductive tape is connected to the pins using silver paste, and a second conductive film having the same width as the first conductive film and a shorter length is aligned with the first conductive film and fixed on one side of the PZT film with the conductive side facing outward;

[0008] The ultrasonic signal is amplified by connecting to the preamplifier input port through a coaxial cable, wherein the conductive tape is connected to the first wire through a rivet, the other side of the first wire is welded to the single-core coaxial cable single-end jumper, and is respectively welded to the shielding copper mesh and the signal line, a second wire is additionally welded to the shielding copper mesh, and the conductive tape is wrapped around the rivet and connected to the conductive side of the PZT film;

[0009] The signal from the output port of the preamplifier is transmitted to the data acquisition card through a transmission line to collect and transmit the partial discharge data to the host computer, which processes and analyzes the partial discharge data.

[0010] In the cable partial discharge ultrasonic signal detection method, the flexible piezoelectric ultrasonic sensor is closely attached to the cable surface to avoid the generation of air gaps.

[0011] In the cable partial discharge ultrasonic signal detection method, the spacing between the interdigitated electrode fingers is 300 μm.

[0012] In the cable partial discharge ultrasonic signal detection method, the thickness of the mica sheet is 20 μm.

[0013] In the cable partial discharge ultrasonic signal detection method, a heat shrink tube is used to fix the first wire and the second wire, and the conductive film is connected to the ground wire.

[0014] In the cable partial discharge ultrasonic signal detection method, the mica sheet is adsorbed on a coating machine and spin-coated with PZT sol. The coating machine rotates at 1000 rpm from 0 to 10 seconds and at 3000 rpm from 10 to 40 seconds. In the first 10 seconds, the PZT sol is evenly dripped along the central circular hole of the coating machine cover to coat the mica sheet to form a PZT film.

[0015] A detection device for executing the cable partial discharge ultrasonic signal detection method comprises:

[0016] A flexible piezoelectric ultrasonic sensor comprising:

[0017] Mica flakes, with a thickness not exceeding 20 μm;

[0018] A PZT thin film, which is stacked on the mica sheet;

[0019] An interdigitated electrode stacked on the PZT film;

[0020] A conductive tape connected to the pins of the interdigital electrodes via a silver paste layer;

[0021] The first conductive film and the second conductive film have the same width, and the second conductive film and the first conductive film are aligned and fixed on one side of the PZT film with the conductive side facing outwards;

[0022] a preamplifier connected to the flexible piezoelectric ultrasonic sensor via a coaxial cable;

[0023] A data acquisition card connected to the preamplifier to acquire partial discharge data;

[0024] A host computer is connected to the data acquisition card to generate partial discharge information based on the local data.

[0025] Compared with the prior art, the present invention has the following advantages: the cable partial discharge ultrasonic signal detection method and detection device described in the present invention use a flexible piezoelectric ultrasonic sensor to detect the ultrasonic signal of cable partial discharge. The flexible piezoelectric ultrasonic sensor can be completely attached to the cable surface, so the ultrasonic signal can smoothly enter the sensor from the cable outer sheath during transmission without being reflected by the cable outer sheath-air interface and the air-sensor interface. Compared with traditional ultrasonic sensors, flexible piezoelectric ultrasonic sensors can better receive cable partial discharge ultrasonic signals, so the detection sensitivity of the sensing system is greatly improved, thereby realizing the accurate extraction of partial discharge signals. The sensitivity of the cable partial discharge ultrasonic detection technology can be greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 illustrating the preferred embodiments and are not considered to be limitations 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 also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used throughout the drawings to represent the same components.

[0027] In the attached picture:

[0028] Figure 1 It is a schematic diagram of the installation method of the ultrasonic sensor in the prior art;

[0029] Figure 2is a schematic diagram of an ultrasonic sensor installation method for a cable partial discharge ultrasonic signal detection method according to an embodiment of the present invention;

[0030] Figure 3 is a schematic structural diagram of a flexible piezoelectric ultrasonic sensor according to an embodiment of the present invention;

[0031] Figure 4 1. It is a schematic diagram comparing the partial discharge test results of a conventional ultrasonic sensor and the flexible piezoelectric ultrasonic sensor cable of the present invention;

[0032] Figure 5 It is a schematic diagram of the structure of a detection device for executing a method for detecting partial discharge ultrasonic signals of cables according to an embodiment of the present invention.

[0033] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0034] The following will refer to the attached Figures 1 to 5 Specific embodiments of the present invention are described in more detail. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0035] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles 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 attached claims.

[0036] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0037] For a better understanding, Figures 2 to 5 As shown, a method for detecting partial discharge ultrasonic signals of a cable includes:

[0038] The flexible piezoelectric ultrasonic sensor is closely attached to the surface of the cable to be tested to generate ultrasonic signals, such as Figure 3As shown, in the flexible piezoelectric ultrasonic sensor, a PZT film 6 is coated on the mica sheet and a forked electrode 4 is plated on the PZT film 6, silicone grease is coated on the non-conductive side of the first conductive film 5, the substrate side of the PZT film 6 is attached to the silicone grease, a conductive tape is used to extend the pins of the forked electrode 4 to the bottom of the PET film, a silver paste 3 is used to connect the conductive tape and the pins, and a second conductive film having the same width and shorter length as the first conductive film 5 is aligned with the first conductive film 5 on one side of the PZT film 6 and fixed with the conductive side facing outward;

[0039] The ultrasonic signal is amplified by connecting to the preamplifier input port through a coaxial cable, wherein the conductive tape is connected to the first wire through a rivet, the other side of the first wire is welded to the single-head jumper of the single-core coaxial cable 1, and is respectively welded to the shielding copper mesh and the signal line, and an additional second wire is welded to the shielding copper mesh, and the conductive tape 2 is wrapped around the rivet and connected to the conductive side of the PZT film 6;

[0040] The signal at the output port of the preamplifier is transmitted to the data acquisition card through a transmission line to collect and transmit the partial discharge data to the host computer, which processes and analyzes the partial discharge data. This method uses a flexible piezoelectric ultrasonic sensor as an ultrasonic signal detection sensor. The sensor has good flexibility and can be attached to the surface of the cable, thereby improving the acoustic impedance matching between the sensor and the cable interface and reducing the energy loss during the transmission of the ultrasonic signal to the sensor, thereby achieving accurate extraction of partial discharge information. Figure 4 As shown, compared with the traditional ultrasonic detection method, this method can achieve higher sensitivity of cable partial discharge ultrasonic signal detection. The invention is easy to operate and has high sensitivity.

[0041] In a preferred embodiment of the cable partial discharge ultrasonic signal detection method, the flexible piezoelectric ultrasonic sensor is closely attached to the cable surface to avoid the generation of air gaps.

[0042] In a preferred embodiment of the cable partial discharge ultrasonic signal detection method, the distance between the four fingers of the interdigitated electrodes is 300 μm.

[0043] In a preferred implementation of the cable partial discharge ultrasonic signal detection method, the thickness of the mica sheet is 20 μm.

[0044] In a preferred embodiment of the cable partial discharge ultrasonic signal detection method, a heat shrink tube is used to fix the first wire and the second wire, and the conductive film 5 is connected to the ground wire.

[0045] In a preferred embodiment of the cable partial discharge ultrasonic signal detection method, the mica sheet is adsorbed on a coating machine and spin-coated with PZT sol. The coating machine rotates at a speed of 1000 rpm from 0 to 10 seconds and at a speed of 3000 rpm from 10 to 40 seconds. In the first 10 seconds, PZT sol is evenly dripped along the central circular hole of the coating machine cover to coat the mica sheet to form a PZT film 6.

[0046] In one embodiment, the method includes,

[0047] The flexible piezoelectric ultrasonic sensor is tightly attached to the cable surface to avoid air gaps, and is connected to the preamplifier input port via a coaxial cable to amplify the signal obtained by the test;

[0048] The signal of the output port of the preamplifier is transmitted to the data acquisition card through the transmission line for collection and then transmitted to the host computer;

[0049] The host computer processes and analyzes the partial discharge data.

[0050] A detection device for executing the cable partial discharge ultrasonic signal detection method comprises:

[0051] A flexible piezoelectric ultrasonic sensor comprising:

[0052] Mica flakes, with a thickness not exceeding 20 μm;

[0053] A PZT thin film 6, which is stacked on the mica sheet;

[0054] An interdigital electrode 4, which is stacked on the PZT film 6;

[0055] A conductive tape 2 connected to the pins of the interdigital electrodes 4 via a layer of silver paste 3;

[0056] The first conductive film 5 and the second conductive film have the same width, and the second conductive film and the first conductive film 5 are aligned and fixed on one side of the PZT film 6 with the conductive side facing outwards;

[0057] a preamplifier connected to the flexible piezoelectric ultrasonic sensor via a coaxial cable;

[0058] A data acquisition card connected to the preamplifier to acquire partial discharge data;

[0059] A host computer is connected to the data acquisition card to generate partial discharge information based on the local data.

[0060] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A method for detecting partial discharge of a cable using ultrasonic signals, characterized in that: It includes the following steps, The flexible piezoelectric ultrasonic sensor is closely attached to the surface of the cable to be tested to generate an ultrasonic signal, wherein, in the flexible piezoelectric ultrasonic sensor, a PZT film is coated on the mica sheet and a forked electrode is plated on the PZT film, silicone grease is coated on the non-conductive side of the first conductive film, the substrate side of the PZT film is attached to the silicone grease, a conductive tape is used to extend the pins of the forked electrode to the bottom of the PET film, the conductive tape is connected to the pins using silver paste, and a second conductive film having the same width as the first conductive film and a shorter length is aligned with the first conductive film and fixed on one side of the PZT film with the conductive side facing outward; The ultrasonic signal is amplified by connecting to the preamplifier input port through a coaxial cable, wherein the conductive tape is connected to the first wire through a rivet, the other side of the first wire is welded to the single-core coaxial cable single-end jumper, and is respectively welded to the shielding copper mesh and the signal line, a second wire is additionally welded to the shielding copper mesh, and the conductive tape is wrapped around the rivet and connected to the conductive side of the PZT film; The signal from the output port of the preamplifier is transmitted to the data acquisition card through a transmission line to collect and transmit the partial discharge data to the host computer, which processes and analyzes the partial discharge data.

2. The method for detecting partial discharge of a cable by ultrasonic signals according to claim 1, wherein: Preferably, the flexible piezoelectric ultrasonic sensor is closely attached to the surface of the cable to avoid the generation of air gaps.

3. The method for detecting partial discharge of a cable by ultrasonic signals according to claim 1, wherein: The interdigital electrode finger pitch is 300 μm.

4. The method for detecting partial discharge of a cable by ultrasonic signals according to claim 1, wherein: The thickness of the mica sheet is 20 μm.

5. The method for detecting partial discharge of a cable by ultrasonic signals according to claim 1, wherein: The first wire and the second wire are fixed by a heat shrink tube, and the conductive film is connected to the ground wire.

6. The method for detecting partial discharge of a cable by ultrasonic signals according to claim 1, wherein: The mica sheet is adsorbed on the coating machine and spin-coated with PZT sol. The rotation speed of the coating machine is 1000 rpm from 0 to 10 seconds and 3000 rpm from 10 to 40 seconds. In the first 10 seconds, PZT sol is evenly dripped along the central circular hole of the coating machine cover to coat the mica sheet to form a PZT film.

7. A detection device for executing the cable partial discharge ultrasonic signal detection method according to any one of claims 1 to 6, characterized in that: These include, A flexible piezoelectric ultrasonic sensor comprising: Mica flakes, with a thickness not exceeding 20 μm; A PZT thin film, which is stacked on the mica sheet; An interdigitated electrode stacked on the PZT film; A conductive tape connected to the pins of the interdigital electrodes via a silver paste layer; The first conductive film and the second conductive film have the same width, and the second conductive film and the first conductive film are aligned and fixed on one side of the PZT film with the conductive side facing outwards; a preamplifier connected to the flexible piezoelectric ultrasonic sensor via a coaxial cable; A data acquisition card connected to the preamplifier to acquire partial discharge data; A host computer is connected to the data acquisition card to generate partial discharge information based on the local data.

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