Distribution cable partial discharge acoustic emission sensor

Abstract

The invention relates to a distribution cable partial discharge acoustic emission sensor, which belongs to the technical field of distribution cable state detection, and comprises an SMA joint, a built-in filtering and amplifying circuit, a metal shell, lead zirconate titanate piezoelectric ceramic, a ceramic bottom plate, a watch lug, a rubber watchband and a watchband buckle, according to the method, the resonant frequency of lead zirconate titanate piezoelectric ceramic is designed according to the frequency band where the distribution cable partial discharge acoustic emission signals are concentrated, the lead zirconate titanate piezoelectric ceramic is of a cylindrical structure with the diameter being 30 mm and the height being 52 mm, the resonant frequency is 40 kHz, and therefore the acoustic emission signals generated when the distribution cable is subjected to partial discharge can be detected as sensitively as possible; the bottom of the lead zirconate titanate piezoelectric ceramic is cut into an arc shape with the curvature radius of 50mm, so that the lead zirconate titanate piezoelectric ceramic is in close contact with the skin of the distribution cable; the method can be widely applied to distribution cable partial discharge on-line detection scenes, and a brand new technical means can be provided for intelligent operation and maintenance of urban distribution cables.

Description

Technical Field:

[0001] The present invention belongs to the technical field of partial discharge detection of distribution cables, and particularly relates to a partial discharge acoustic emission sensor for distribution cables. Background Art:

[0002] Cables are widely used in urban distribution networks, and their reliable operation is crucial for the power supply stability of the power system. However, distribution cables that have been in operation for a long time (especially those with defects such as air gaps and spikes introduced during construction and production) are inevitably subject to long-term effects of electric fields, thermal fields, and mechanical forces, resulting in insulation degradation, partial discharge, and then insulation faults, seriously threatening the safe and stable operation of the power grid. However, for a long time, the partial discharge detection of distribution cables has not received much attention. In recent years, with the continuous development of China's economy and society, the requirements for the reliability of urban power supply have been increasing day by day. Strengthening the partial discharge detection of distribution cables to timely detect insulation defects inside the cables, so as to achieve fault early warning, is of great significance.

[0003] Traditional methods for detecting partial discharge in distribution cables mainly include the pulse current method and the ultra / very high frequency method. The pulse current method detects partial discharge by sleeving a high-frequency current transformer on the cable grounding wire, and rich partial discharge information can be obtained. The ultra / very high frequency method detects the electromagnetic signals diffracted by partial discharge by installing sensor devices at cable joints to obtain discharge information. These electrical methods have high sensitivity, but the main difficulty they face is the severe electromagnetic noise interference on site. False alarms, signal drowning and other situations often occur. Therefore, it is very necessary to study a non-electrical partial discharge detection method applicable to distribution cables.

[0004] For power equipment such as transformers and GIS in the power system, the acoustic wave method is a very important means for detecting partial discharge, which has advantages such as strong anti-electromagnetic interference ability, high signal-to-noise ratio, and convenient discharge fault location. This method mainly uses lead zirconate titanate piezoelectric ceramics (Piezoelectric transducers, PZT) as sensing elements, and installs the PZT on the equipment shell to sense the acoustic emission information generated by partial discharge. In theory, the acoustic wave method can also be applied to the partial discharge detection of distribution cables. However, in practice, existing PZT sensors are all designed for high-voltage equipment such as transformers and GIS. Due to the differences in structure and materials, the acoustic signal characteristics generated by partial discharge in distribution cables are different from those of the above-mentioned equipment, and existing sensors cannot be directly transplanted to the partial discharge detection of distribution cables. Therefore, this project intends to carry out research on partial discharge acoustic emission sensors for distribution cables to provide a new technical means for the intelligent operation and maintenance of urban distribution cables. Summary of the Invention:

[0005] The present invention provides a partial discharge acoustic emission sensor for distribution cables. The sensor includes an SMA connector, an in-built filtering and amplifying circuit, a metal shell, a lead zirconate titanate piezoelectric ceramic, a ceramic base plate and a mounting structure. The basic working principle of the sensor is as follows: The sensor is fixed to the distribution cable through the mounting structure, and its ceramic base plate is in close contact with the outer skin of the distribution cable. When partial discharge occurs in the distribution cable, the acoustic wave signal diffracted is transmitted to the outer skin of the cable, and then acts on the lead zirconate titanate piezoelectric ceramic in the sensor through the ceramic base plate and generates an electrical signal through the piezoelectric effect. The electrical signal is collected and analyzed after passing through the in-built filtering and amplifying circuit.

[0006] The lead zirconate titanate piezoelectric ceramic is a cylindrical structure with a diameter of 30 mm and a height of 52 mm, so as to ensure that the resonance frequency of the piezoelectric ceramic is 40 kHz, and to detect the acoustic emission signal during partial discharge of the distribution cable as sensitively as possible. The top of the cylindrical piezoelectric ceramic is plated with a metal electrode, which is used to introduce the electrical signal generated by the piezoelectric effect into the filtering and amplifying circuit.

[0007] The bottom of the lead zirconate titanate piezoelectric ceramic is cut into an arc shape with a radius of curvature of 50 mm, which helps the piezoelectric ceramic to be in close contact with the outer skin of the distribution cable.

[0008] The in-built filtering and amplifying circuit is self-equipped with a button battery power supply module, which is used to filter and amplify the response signal of the piezoelectric ceramic. The filtering circuit is a band-pass type with a bandwidth of 10 kHz to 200 kHz, and the gain of the amplifying circuit is 20 dB. The in-built filtering and amplifying circuit is electrically connected to the lead zirconate titanate piezoelectric ceramic through a lead.

[0009] The encapsulation structure is composed of a cylindrical metal shell, a ceramic base plate and a rubber watchband. The cylindrical metal shell is made of aluminum alloy, with a diameter of 40 mm and a height of 60 mm. An SMA connector is installed on the top for realizing electrical signal feed-through. The ceramic base plate is made of alumina ceramic and is in an arc shape with a radius of curvature of 50 mm. It is installed at the bottom end of the cylindrical metal shell. One side of it is in direct contact with the outer skin of the distribution cable, and the other side is tightly bonded to the lead zirconate titanate piezoelectric ceramic. The rubber watchband is connected to the metal shell, and a watchband buckle is provided at the end of the rubber watchband. The other end of the rubber watchband passes through the watchband buckle and can be locked by the watchband buckle. Using this watchband structure, the sensor can be tightly installed on the distribution cable.

[0010] The present invention can be widely applied to the on-line monitoring scenario of partial discharge of distribution cables. Especially considering the frequency characteristics of partial discharge acoustic emission of distribution cables, the resonance frequency of the piezoelectric ceramic is designed specifically, which can provide a new technical means for the intelligent operation and maintenance of urban distribution cables. Description of the Drawings:

[0011] Figure 1Schematic diagram of the structure of a partial discharge acoustic emission sensor for a distribution cable provided by the present invention.

[0012] Figure 2 Installation schematic diagram of a partial discharge acoustic emission sensor for a distribution cable provided by the present invention.

[0013] In the figure, 1 - SMA connector, 2 - built-in filtering and amplifying circuit, 3 - metal shell, 4 - lead zirconate titanate piezoelectric ceramic, 5 - ceramic base plate, 6 - watch lug, 7 - rubber watch band, 8 - watch band buckle, 9 - sensor, 10 - distribution cable. Specific implementation manner:

[0014] The partial discharge acoustic emission sensor for a distribution cable provided by the present invention will be further described in detail below with reference to the accompanying drawings:

[0015] In Figure 1 the shown partial discharge acoustic emission sensor for a distribution cable mainly includes an SMA connector 1, a built-in filtering and amplifying circuit 2, a metal shell 3, a lead zirconate titanate piezoelectric ceramic 4, a ceramic base plate 5, a watch lug 6, a rubber watch band 7, and a watch band buckle 8.

[0016] The lead zirconate titanate piezoelectric ceramic 4 is a cylindrical structure with a diameter of 30 mm and a height of 52 mm, and its resonant frequency is 40 kHz. The bottom of it is cut into an arc shape with a radius of curvature of 50 mm, which helps the lead zirconate titanate piezoelectric ceramic 4 to be in close contact with the surface of the distribution cable 10. The top of the lead zirconate titanate piezoelectric ceramic 4 is plated with a metal electrode, which is used to introduce the electrical signal generated by the piezoelectric effect into the built-in filtering and amplifying circuit 2;

[0017] The built-in filtering and amplifying circuit 2 is self-equipped with a button battery power supply module, which is used to filter and amplify the response signal of the lead zirconate titanate piezoelectric ceramic 4. The filtering circuit is a band-pass type with a bandwidth of 10 kHz to 200 kHz, and the gain of the amplifying circuit is 20 dB. The built-in filtering and amplifying circuit 2 is electrically connected to the lead zirconate titanate piezoelectric ceramic 4 through leads;

[0018] The metal shell 3 encapsulates the lead zirconate titanate piezoelectric ceramic 4 and the built-in filtering and amplifying circuit 2 therein;

[0019] The ceramic base plate 5 is an arc-shaped alumina ceramic with a radius of curvature of 50 mm and is installed at the bottom end of the metal shell 3;

[0020] The SMA connector 1 is installed at the top end of the metal shell 2 and is used to lead out the output signal of the built-in filtering and amplifying circuit 2 from the metal shell 3;

[0021] The rubber watch band 7 is connected to the metal shell 3 through the watch lug 6 structure, and a watch band buckle 8 is provided at the end of the rubber watch band 7. The other end of the rubber watch band 7 passes through the watch band buckle 8 and can be locked by the watch band buckle 8;

[0022] As Figure 2 shown, when performing partial discharge detection on a distribution cable, the sensor 9 is fixed to the distribution cable 10 through a watchband, and vaseline is applied to the ceramic base plate 5 to make the ceramic base plate 5 in close contact with the outer skin of the distribution cable 10, ensuring no air gap. After the cable discharges, the generated acoustic emission signal can be detected by the sensor 9, and partial discharge detection is achieved through the output signal of the sensor 9.

Claims

1. A partial discharge acoustic emission sensor for a distribution cable, characterized in that: It includes an SMA connector, an internal filter and amplifier circuit, a metal shell, a lead zirconate titanate piezoelectric ceramic, a ceramic base plate and a mounting structure.

2. The partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The lead zirconate titanate piezoelectric ceramic is a cylindrical structure with a diameter of 30 mm and a height of 52 mm, and its resonant frequency is 40 kHz. A metal electrode is plated on the top of the lead zirconate titanate piezoelectric ceramic to introduce the electrical signal generated by the piezoelectric effect into the internal filter and amplifier circuit.

3. The partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The bottom of the lead zirconate titanate piezoelectric ceramic is cut into an arc shape with a curvature radius of 50 mm.

4. The partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The internal filter and amplifier circuit is self-equipped with a button battery power supply module, which is used to filter and amplify the response signal of the lead zirconate titanate piezoelectric ceramic. The filter circuit is a band-pass type with a bandwidth of 10 kHz to 200 kHz, and the gain of the amplifier circuit is 20 dB. The internal filter and amplifier circuit is electrically connected to the lead zirconate titanate piezoelectric ceramic through leads.

5. The partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The bandwidth of the internal filter and amplifier circuit is 10 kHz to 200 kHz, and the gain of the amplifier circuit is 20 dB.

6. The partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The mounting structure includes a lug, a rubber watch band, and a watch band buckle.

7. A partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The metal shell encapsulates the lead zirconate titanate piezoelectric ceramic and the internal filter and amplifier circuit therein.

8. A partial discharge acoustic emission sensor for a distribution cable according to claim 7, characterized in that: The rubber watch band is connected to the metal shell through a lug structure, and a watch band buckle is provided at the end of the rubber watch band. The other end of the rubber watch band passes through the watch band buckle and can be locked by the watch band buckle.

9. A partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The ceramic base plate is an arc-shaped alumina ceramic with a curvature radius of 50 mm and is installed at the bottom end of the metal shell.

10. The partial discharge acoustic emission sensor for a distribution cable according to claim 1, characterized in that: The SMA connector is installed at the top of the metal shell and is used to lead out the output signal of the internal filter and amplifier circuit from the metal shell.

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