Cable joint partial discharge monitoring method, device and equipment and storage medium

Abstract

The invention provides a cable joint partial discharge monitoring method, device and equipment and a storage medium, and the method employs a narrow linewidth laser to emit a single-frequency laser, and the single-frequency laser is divided into a sensing optical fiber path and a reference optical fiber path through an optical isolator, a circulator and a coupler. An ultrasonic vibration signal is introduced into the sensing optical fiber by the optical fiber ultrasonic sensor and is combined with laser to generate a detection signal. The signal and a reference fiber laser are reflected by a Faraday mirror and then interfere with each other to generate an interference signal. After the signal is subjected to photoelectric conversion, the discharge state is judged according to the electric signal. The method realizes high-sensitivity online monitoring and ensures safe and stable operation of a power system.

Description

Technical Field

[0001] The present application belongs to the field of cable joint discharge detection, and in particular, relates to a cable joint partial discharge monitoring method, device, equipment and storage medium. Background Art

[0002] In recent years, with the development of power systems, the cableization rate of distribution lines has increased significantly. As an important component of power transmission, cables are composed of the main body, accessories and terminals. Among them, cable joints are one of the most prone to failure in the cable system. According to statistics, more than 70% of insulation failures occur in cable accessories, especially cable joints. Cable joints are easily affected by adverse conditions such as high voltage, high temperature, and humidity in the external environment. These conditions will accelerate the aging process of cable joints, increase the probability of defects such as electrical trees and water trees, and accelerate the development rate of defects.

[0003] When the cable joint has the above defects, partial discharge will occur. Partial discharge is an important indicator of cable insulation degradation. Therefore, timely and accurate monitoring of partial discharge of cable joints is of great significance for evaluating the insulation condition of cable joints, early detection of insulation defects, and ensuring the reliable operation of cable joints.

[0004] At present, there are two main methods for detecting partial discharge ultrasonic signals at cable joints: offline detection and live inspection. However, both methods have obvious disadvantages. The offline detection method requires power outage, which seriously affects the normal operation of the power system; while the live inspection method has the problems of high labor costs and difficulty in timely and accurate detection of internal occasional faults. At the same time, its detection prototype has a complex structure, poor reliability, and weak anti-electromagnetic interference ability. Summary of the invention

[0005] The purpose of the present application is to overcome the defects in the above-mentioned prior art and provide a cable joint partial discharge monitoring method, device, equipment and storage medium.

[0006] The present application provides a cable joint partial discharge monitoring method, comprising:

[0007] Single frequency laser light is emitted through narrow line width laser;

[0008] The single frequency laser is sequentially transmitted through the optical isolator and the circulator to the coupler;

[0009] The coupler divides the single frequency laser into two beams, which enter the sensing optical fiber and the reference optical fiber respectively;

[0010] According to the effect of the ultrasonic vibration signal of the partial discharge of the cable joint on the optical fiber ultrasonic mandrel optical fiber sensor, the optical fiber ultrasonic mandrel optical fiber sensor interferes with the single frequency laser entering the sensing optical fiber to generate a laser detection signal of the partial discharge of the cable joint;

[0011] The laser detection signal is reflected by a Faraday rotation mirror and returned to the coupler to interfere with the single-frequency laser in the reference optical fiber, thereby generating a laser interference signal;

[0012] Converting the laser interference signal into an electrical signal through a photoelectric converter;

[0013] The partial discharge state of the cable joint is determined according to the electrical signal.

[0014] Optionally, converting the laser interference signal into an electrical signal through a photoelectric converter comprises:

[0015] In the coupler, the laser interference signal is divided into three laser interference signals. The first laser interference signal and the second laser interference signal enter the first photoelectric converter and the second photoelectric converter respectively to be converted into the first electrical signal and the second electrical signal. The third laser interference signal is transmitted toward the narrow linewidth laser and is transferred to the third photoelectric converter at the circulator to be converted into the third electrical signal.

[0016] Optionally, the optical fiber ultrasonic mandrel-type optical fiber sensor comprises: a mandrel and a wound optical fiber;

[0017] The wound optical fiber is wound on the core shaft, and the core shaft is made of carbon fiber composite material.

[0018] Optionally, the winding angle of the wound optical fiber wound on the core shaft is 30 degrees obliquely downward.

[0019] Optionally, the number of winding layers of the wound optical fiber wound around the core shaft is 10 layers.

[0020] Optionally, the optical fiber ultrasonic mandrel optical fiber sensor comprises: a mandrel optical fiber sensor fixture:

[0021] The mandrel-type optical fiber sensor fixture comprises: a cover plate and a rolling strip;

[0022] Both ends of the cable tie are connected to the cover plate;

[0023] The optical fiber ultrasonic mandrel optical fiber sensor is arranged on the cover plate, and the optical fiber ultrasonic mandrel optical fiber sensor is close to the cable connector, and the cable connector is away from one side of the optical fiber ultrasonic mandrel optical fiber sensor and is fixed by the fixed rolling belt clamp.

[0024] Optionally, the clamp cover is made of nickel alloy.

[0025] The present application also provides a cable joint partial discharge monitoring device, comprising:

[0026] A laser unit emits a single frequency laser through a narrow linewidth laser;

[0027] The single frequency laser is transmitted to the unit, and the single frequency laser is transmitted to the coupler through the optical isolator and the circulator; the coupler divides the single frequency laser into two beams, which enter the sensing optical fiber and the reference optical fiber respectively;

[0028] An acquisition unit, according to the effect of the ultrasonic vibration signal of the partial discharge of the cable joint on the optical fiber ultrasonic mandrel optical fiber sensor, the optical fiber ultrasonic mandrel optical fiber sensor interferes with the single frequency laser entering the sensing optical fiber, and generates a laser detection signal of the partial discharge of the cable joint;

[0029] An interference unit, which reflects the laser detection signal and the single-frequency laser in the reference optical fiber back to the coupler through a Faraday rotation mirror to interfere with each other, thereby generating a laser interference signal;

[0030] A conversion unit, converting the laser interference signal into an electrical signal through a photoelectric converter;

[0031] A determination unit determines a partial discharge state of the cable connector according to the electrical signal.

[0032] The present application also provides a cable joint partial discharge monitoring device, comprising:

[0033] Memory;

[0034] A processor, for retrieving from the memory a computer executable program of a cable joint partial discharge monitoring method as described in any one of claims 1 to 7, and executing: emitting a single-frequency laser through a narrow-linewidth laser; the single-frequency laser is transmitted to a coupler through an optical isolator and a circulator; the coupler divides the single-frequency laser into two beams, which enter a sensing optical fiber and a reference optical fiber respectively; according to the effect of an ultrasonic vibration signal during partial discharge of the cable joint on an optical fiber ultrasonic mandrel-type optical fiber sensor, the optical fiber ultrasonic mandrel-type optical fiber sensor interferes with the single-frequency laser entering the sensing optical fiber to generate a laser detection signal for partial discharge of the cable joint; the laser detection signal is reflected back to the coupler through a Faraday rotating reflector to interfere with the single-frequency laser in the reference optical fiber to generate a laser interference signal; the laser interference signal is converted into an electrical signal through a photoelectric converter; and the partial discharge state of the cable joint is determined according to the electrical signal.

[0035] The present application also provides a storage medium, comprising a computer executable program stored therein, wherein the computer executable program is used to be called by a processor to execute the steps of a cable joint partial discharge monitoring method as described in any one of claims 1 to 7.

[0036] The beneficial effects of this application are:

[0037] The present application provides a method for monitoring partial discharge of a cable joint, comprising: emitting a single frequency laser through a narrow linewidth laser; the single frequency laser passes through an optical isolator and a circulator in sequence and is transmitted to a coupler; the coupler divides the single frequency laser into two beams, which enter a sensing optical fiber and a reference optical fiber respectively; according to the effect of an ultrasonic vibration signal during partial discharge of the cable joint on an optical fiber ultrasonic mandrel optical fiber sensor, the optical fiber ultrasonic mandrel optical fiber sensor interferes with the single frequency laser entering the sensing optical fiber to generate a laser detection signal for partial discharge of the cable joint; the laser detection signal and the single frequency laser in the reference optical fiber are reflected back to the coupler through a Faraday rotating reflector to interfere and generate a laser interference signal; the laser interference signal is converted into an electrical signal through a photoelectric converter; and the partial discharge state of the cable joint is determined according to the electrical signal. The present application provides a method for online monitoring of an external partial discharge ultrasonic signal of a cable joint based on an optical fiber, thereby realizing reliable and highly sensitive online monitoring of partial discharge phenomena of the cable joint, and providing strong support for the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the partial discharge monitoring process of cable joints in this application;

[0039] Figure 2 It is a schematic diagram of an optical fiber core shaft type optical fiber sensor in this application;

[0040] Figure 3 This is a schematic diagram of the fixing method of the mandrel-type optical fiber sensor fixture in this application. DETAILED DESCRIPTION

[0041] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that various forms of implementing the present disclosure should not be limited by the embodiments set forth herein. On the contrary, the embodiments are provided to more thoroughly understand the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0042] Please refer to Figure 1 As shown, a method for monitoring partial discharge of a cable joint comprises the following steps:

[0043] S101. Emits single frequency laser through a narrow linewidth laser.

[0044] A narrow linewidth laser is activated, which emits a laser beam having a single frequency.

[0045] The narrow linewidth laser is part of a fiber interferometer based on 3x3 phase demodulation.

[0046] The fiber optic interferometer based on 3×3 phase demodulation is one of the core components for realizing online monitoring of partial discharge ultrasonic signals of cable joints.

[0047] The fiber interferometer based on 3×3 phase demodulation is mainly composed of the following key components:

[0048] Narrow linewidth lasers are used to emit single frequency laser light and serve as the light source of the system.

[0049] The optical isolator is connected after the narrow linewidth laser to prevent the optical signal from reflecting back to the laser and protect the laser from the influence of reflected light.

[0050] The circulator allows the optical signal to be transmitted in only one direction. It is used to guide the optical signal into the coupler and direct the returning interference light to the photoelectric converter.

[0051] The 3×3 coupler splits the input optical signal into three beams with phase differences of 120°.

[0052] Photoelectric converters (PD1, PD2, PD3) are used to convert received optical signals into electrical signals (voltage signals) for subsequent processing and analysis.

[0053] The Faraday rotator is installed at the end of the sensing fiber and the reference fiber respectively, and is used to reflect the optical signal in the fiber back to the coupler to form an interference effect. The Faraday rotator can eliminate the influence of the polarization state on the interference signal and improve the stability and anti-interference ability of the system.

[0054] S102, the single frequency laser passes through the optical isolator and the circulator in sequence and is transmitted to the coupler.

[0055] After the laser beam is emitted from the narrow linewidth laser, it first passes through an optical isolator to prevent the reflected light in the optical path from interfering with the laser. Then, the laser beam enters the circulator and is guided by the circulator to the 3×3 coupler.

[0056] S103, the coupler divides the single frequency laser into two beams, which enter the sensing optical fiber and the reference optical fiber respectively;

[0057] The single frequency laser emitted by the narrow linewidth laser enters the circulator after passing through the optical isolator. The circulator guides the optical signal to the 3×3 coupler, and the coupler divides the optical signal into two beams, one of which enters the sensing optical fiber and the other enters the reference optical fiber.

[0058] S104. According to the effect of the ultrasonic vibration signal of the cable joint partial discharge on the optical fiber ultrasonic mandrel optical fiber sensor, the optical fiber ultrasonic mandrel optical fiber sensor interferes with the single frequency laser entering the sensing optical fiber to generate a laser detection signal of the cable joint partial discharge.

[0059] like Figure 2 As shown, the present application collects ultrasonic vibration signals through a mandrel-type optical fiber sensor, and the mandrel-type optical fiber sensor includes a mandrel 201 and a wound optical fiber 202 .

[0060] The mandrel is made of carbon fiber composite material, which has a large elastic modulus and can produce large strain under the action of ultrasonic signals, thereby improving the sensitivity of the mandrel-type optical fiber sensor. The mandrel is in the shape of a cylinder with a bottom radius of 2 cm and a height of 3 cm. This design allows the optical fiber to be evenly and tightly wound around the mandrel while maintaining the stability and reliability of the structure.

[0061] In order to prevent the bending of the wound optical fiber 202 from affecting the detection performance of the mandrel-type optical fiber sensor, the present application uses the G657A2 anti-bending sensitive optical fiber. The optical fiber is tightly wound on the mandrel at an angle of 30° downward, with a total of ten layers. This winding method helps to enhance the strain effect of the optical fiber under the action of the ultrasonic signal, thereby improving the detection sensitivity of the mandrel-type optical fiber sensor.

[0062] The design of the mandrel fiber optic sensor enables it to fit tightly on the cable connector and be fixed by the mandrel fiber optic sensor fixture to ensure stability and reliability under live conditions.

[0063] The main body of the mandrel fiber optic sensor fixture is made of a piece of nickel alloy. Nickel alloy has excellent corrosion resistance and good electrical conductivity, and also has high mechanical strength, which can meet the requirements of the fixture in harsh environments. The alloy plate is 4cm long, 3cm wide and 1cm thick, ensuring the stability and durability of the fixture.

[0064] A cylindrical cover with a radius of 2.5 cm and a height of 1.5 cm is set in the middle of the alloy plate. The cylindrical cover is designed to facilitate the lead-out of the sensing optical fiber and prevent the optical fiber from being bent or squeezed unnecessarily during the lead-out process, thereby affecting the signal transmission quality.

[0065] Circular holes with a radius of 0.5 cm are provided at the four corners of the fixture cover 301. Two nylon rolling strips 302 can be passed through the circular holes. Nylon material has good insulation properties and sufficient strength, which can ensure that the cable connector 303 will not be damaged when the mandrel-type optical fiber sensor 304 is fixed, and the monitoring result will not be affected by electromagnetic interference. By adjusting the tightness of the rolling strip 302, the mandrel-type optical fiber sensor can be tightly and firmly fixed on the cable connector 303.

[0066] The use of nickel alloy body and the selection of nylon rolling belt together ensure the good insulation performance of the mandrel fiber optic sensor fixture in an electrically charged environment, ensuring the safety and reliability of the monitoring process. Through the carefully designed cylindrical cover and nylon rolling belt, the mandrel fiber optic sensor can fit tightly and stably on the cable connector, effectively avoiding the monitoring error caused by the loosening or displacement of the mandrel fiber optic sensor.

[0067] The cylindrical cover design not only protects the sensing optical fiber from interference from the external environment, but also facilitates the lead-out of the optical fiber, making the wiring and installation of the entire monitoring system easier and faster.

[0068] The sensing optical fiber is closely attached to the cable joint through an optical fiber ultrasonic mandrel optical fiber sensor to obtain the ultrasonic vibration signal generated by partial discharge of the cable joint.

[0069] One end of the mandrel fiber optic sensor is connected to the sensing fiber, and the other end is connected to the Faraday rotator. The Faraday rotator is used to rotate the reflected light signal to ensure that the light signal is not disturbed by the magnetic field during transmission.

[0070] When partial discharge occurs at the cable joint, the generated ultrasonic vibration signal is captured by the fiber optic ultrasonic mandrel fiber optic sensor and converted into strain or phase change in the fiber optic. This change modulates the single frequency laser in the sensing fiber and generates a laser detection signal containing partial discharge information.

[0071] S105 , the laser detection signal is reflected by a Faraday rotation mirror and returned to the coupler to interfere with the single-frequency laser in the reference optical fiber, thereby generating a laser interference signal.

[0072] After the optical signals in the sensing fiber and the reference fiber propagate to the end, they are reflected by the Faraday rotator and return to the coupler along the original path.

[0073] The returned optical signal interferes in the 3×3 coupler to form three beams of interference light with a phase difference of 120°. After being collected by a digital oscilloscope, it is recorded and analyzed by a computer to reflect the partial discharge ultrasonic signal of the cable joint.

[0074] S106, converting the laser interference signal into an electrical signal through a photoelectric converter.

[0075] Two of the interfering lights directly enter the photoelectric converters PD2 and PD3, and the other light enters the photoelectric converter PD1 through the circulator. The photoelectric converter converts the optical signal into an electrical signal (voltage signal).

[0076] S107. Determine the partial discharge state of the cable connector according to the electrical signal.

[0077] These voltage signals are collected by digital oscilloscopes and recorded and analyzed by computers. By analyzing the waveform and characteristics of the voltage signals, the state of partial discharge at the cable joint can be determined, including key parameters such as the intensity and frequency of the discharge.

[0078] The present application also provides a cable joint partial discharge monitoring device, comprising:

[0079] A laser unit emits a single frequency laser through a narrow linewidth laser;

[0080] The single frequency laser is transmitted to the unit, and the single frequency laser is transmitted to the coupler through the optical isolator and the circulator; the coupler divides the single frequency laser into two beams, which enter the sensing optical fiber and the reference optical fiber respectively;

[0081] An acquisition unit is used to acquire an ultrasonic vibration signal of partial discharge of a cable joint; the ultrasonic vibration signal is transmitted to the single frequency laser in the sensing optical fiber through an optical fiber ultrasonic mandrel optical fiber sensor to generate a laser detection signal of partial discharge of the cable joint;

[0082] An interference unit, which reflects the laser detection signal and the single-frequency laser in the reference optical fiber back to the coupler through a Faraday rotation mirror to generate a laser interference signal;

[0083] A conversion unit, converting the laser interference signal into an electrical signal through a photoelectric converter;

[0084] A determination unit determines a partial discharge state of the cable connector according to the electrical signal.

[0085] The present application also provides a cable joint partial discharge monitoring device, comprising:

[0086] Memory;

[0087] A processor is used to retrieve the computer executable program of the above-mentioned cable joint partial discharge monitoring method from the memory, and execute: emitting a single-frequency laser through a narrow-linewidth laser; the single-frequency laser passes through an optical isolator and a circulator and is transmitted to a coupler; the coupler divides the single-frequency laser into two beams, which enter a sensing optical fiber and a reference optical fiber respectively; obtaining an ultrasonic vibration signal of partial discharge of the cable joint; transmitting the ultrasonic vibration signal to the single-frequency laser in the sensing optical fiber through an optical fiber ultrasonic mandrel optical fiber sensor to generate a laser detection signal of partial discharge of the cable joint; reflecting the laser detection signal and the single-frequency laser in the reference optical fiber back to the coupler through a Faraday rotating reflector to interfere with each other and generate a laser interference signal; converting the laser interference signal into an electrical signal through a photoelectric converter; and determining the partial discharge state of the cable joint according to the electrical signal.

[0088] The present application also provides a storage medium, comprising a computer executable program stored therein, wherein the computer executable program is used to be called by a processor to execute the steps of the above-mentioned cable joint partial discharge monitoring method.

[0089] Although the present invention is disclosed as above by the embodiments, it is not intended to limit the protection scope of the present invention. Any changes and modifications made by any technician familiar with the technology without departing from the concept and scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for monitoring partial discharge of a cable joint, characterized in that: include: Single frequency laser light is emitted through narrow line width laser; The single frequency laser is sequentially transmitted through the optical isolator and the circulator to the coupler; The coupler divides the single frequency laser into two beams, which enter the sensing optical fiber and the reference optical fiber respectively; The optical fiber ultrasonic mandrel optical fiber sensor interferes with the single frequency laser entering the sensing optical fiber to generate a laser detection signal for partial discharge of the cable joint; The laser detection signal is reflected by a Faraday rotation mirror and returned to the coupler to interfere with the single-frequency laser in the reference optical fiber, thereby generating a laser interference signal; Converting the laser interference signal into an electrical signal through a photoelectric converter; The partial discharge state of the cable joint is determined according to the electrical signal.

2. A cable joint partial discharge monitoring method according to claim 1, characterized in that: The laser interference signal is converted into an electrical signal through a photoelectric converter, comprising: In the coupler, the laser interference signal is divided into three laser interference signals. The first laser interference signal and the second laser interference signal enter the first photoelectric converter and the second photoelectric converter respectively to be converted into the first electrical signal and the second electrical signal. The third laser interference signal is transmitted toward the narrow linewidth laser and is transferred to the third photoelectric converter at the circulator to be converted into the third electrical signal.

3. A cable joint partial discharge monitoring method according to claim 1, characterized in that: The optical fiber ultrasonic mandrel type optical fiber sensor comprises: a mandrel and a wound optical fiber; The wound optical fiber is wound on the core shaft, and the core shaft is made of carbon fiber composite material.

4. A cable joint partial discharge monitoring method according to claim 3, characterized in that: The winding angle of the wound optical fiber wound on the core shaft is 30 degrees obliquely downward.

5. A cable joint partial discharge monitoring method according to claim 3, characterized in that: The number of winding layers of the wound optical fiber wound on the core shaft is 10 layers.

6. A cable joint partial discharge monitoring method according to claim 1, characterized in that: The optical fiber ultrasonic mandrel optical fiber sensor comprises: a mandrel optical fiber sensor fixture, The mandrel-type optical fiber sensor fixture comprises: a cover plate and a rolling strip; Both ends of the cable tie are connected to the cover plate; The mandrel optical fiber is arranged on the cover plate, the optical fiber ultrasonic mandrel optical fiber sensor is close to the cable connector, and the side of the cable connector away from the optical fiber ultrasonic mandrel optical fiber sensor is tightly clamped by the fixed rolling belt.

7. A cable joint partial discharge monitoring method according to claim 6, characterized in that: The fixture cover plate is made of nickel alloy.

8. A cable joint partial discharge monitoring device, characterized in that: include: A laser unit emits a single frequency laser through a narrow linewidth laser; The single frequency laser is transmitted to the unit, and the single frequency laser is transmitted to the coupler through the optical isolator and the circulator; the coupler divides the single frequency laser into two beams, which enter the sensing optical fiber and the reference optical fiber respectively; An acquisition unit, according to the effect of the ultrasonic vibration signal of the partial discharge of the cable joint on the optical fiber ultrasonic mandrel optical fiber sensor, the optical fiber ultrasonic mandrel optical fiber sensor interferes with the single frequency laser entering the sensing optical fiber, and generates a laser detection signal of the partial discharge of the cable joint; An interference unit, which reflects the laser detection signal and the single-frequency laser in the reference optical fiber back to the coupler through a Faraday rotation mirror to interfere with each other, thereby generating a laser interference signal; A conversion unit, converting the laser interference signal into an electrical signal through a photoelectric converter; A determination unit determines a partial discharge state of the cable connector according to the electrical signal.

9. A cable joint partial discharge monitoring device, characterized in that: include: Memory; A processor, for retrieving from the memory a computer executable program of a cable joint partial discharge monitoring method as described in any one of claims 1 to 7, and executing: emitting a single-frequency laser through a narrow-linewidth laser; the single-frequency laser is transmitted to a coupler through an optical isolator and a circulator; the coupler divides the single-frequency laser into two beams, which enter a sensing optical fiber and a reference optical fiber respectively; according to the effect of an ultrasonic vibration signal during partial discharge of the cable joint on an optical fiber ultrasonic mandrel-type optical fiber sensor, the optical fiber ultrasonic mandrel-type optical fiber sensor interferes with the single-frequency laser entering the sensing optical fiber to generate a laser detection signal for partial discharge of the cable joint; the laser detection signal is reflected back to the coupler through a Faraday rotating reflector to interfere with the single-frequency laser in the reference optical fiber to generate a laser interference signal; the laser interference signal is converted into an electrical signal through a photoelectric converter; and the partial discharge state of the cable joint is determined according to the electrical signal.

10. A storage medium, characterized in that: The invention comprises a computer executable program stored therein, wherein the computer executable program is used to be called by a processor to execute the steps of a cable joint partial discharge monitoring method as claimed in any one of claims 1 to 7.

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