Method and device for monitoring and positioning ultrasonic fault of cable

Abstract

The invention relates to a cable ultrasonic fault monitoring and positioning method and device, and the method comprises the steps: receiving an ultrasonic signal transmitted by an ultrasonic fault source through at least two fiber bragg gratings which are arranged in the direction of a cable, different fiber bragg gratings are made to distinguish fiber bragg grating parameters such as grating wavelength or reflectivity generated by the same ultrasonic fault source, and then the fiber bragg grating parameters such as different grating wavelength or reflectivity generated by different fiber bragg gratings are converted into ultrasonic parameters such as wavelength, frequency and intensity. And through known ultrasonic parameter information, position distances between different fiber gratings and ultrasonic attenuation characteristics, a fault point is accurately positioned, so that accurate positioning of a power cable, especially a long-distance cable, can be achieved. Compared with the prior art, the method and the device for monitoring and positioning the ultrasonic fault of the cable, disclosed by the invention, can achieve the purpose of accurately positioning the ultrasonic fault.

Description

Technical Field

[0001] The present invention relates to the technical field of cable detection, and in particular to a method and device for monitoring and locating ultrasonic faults of cables. Background Art

[0002] Whether in the industrial field or the research field, the monitoring and positioning of ultrasonic signals are crucial. The monitoring and positioning of ultrasonic signals have very important practical significance in the fields of fault diagnosis, power status monitoring and leakage detection. Fiber Bragg grating sensors are widely used in various engineering fields due to their advantages such as small size, wide dynamic range, anti-electromagnetic interference and high sensitivity. They are currently the most important sensor devices in distributed optical fiber sensor networks.

[0003] In the prior art, power cables are operated outdoors for a long time and are easily affected by the external environment, which leads to a decrease in insulation performance and partial discharge. Due to the narrow space and long transmission distance, it is impossible to power monitoring equipment and transmit signals over long distances. Many large-scale detection equipment cannot accurately locate the damaged position. Therefore, the localization and monitoring of partial discharge in power cables is a difficult problem that needs to be broken through and solved. Summary of the invention

[0004] In order to solve the defect that the detection equipment in the power cable cannot accurately locate the ultrasonic fault, the present invention proposes a monitoring and locating method and equipment for cable ultrasonic fault.

[0005] The technical solution adopted by the present invention is a method for monitoring and locating ultrasonic faults of cables, comprising:

[0006] At least two fiber Bragg gratings are arranged along the cable direction, and the fiber Bragg gratings receive ultrasonic signals emitted by ultrasonic fault sources to change the fiber Bragg gratings;

[0007] Receiving optical signals of the fiber Bragg gratings, and converting the optical signals of at least two fiber Bragg gratings arranged along the cable direction into ultrasonic parameters;

[0008] The fault point is monitored and located according to ultrasonic parameters, the position distance between different fiber gratings and ultrasonic attenuation characteristics.

[0009] Preferably, the fiber grating is a Bragg grating.

[0010] Preferably, the channel multiplexing mode of the Bragg grating is wavelength division multiplexing, time division multiplexing or wavelength division / time division mixed multiplexing.

[0011] Preferably, the ultrasonic parameter is an electrical signal curve.

[0012] The present invention also proposes a cable monitoring and positioning device based on fiber grating, comprising:

[0013] Fiber Bragg gratings, at least two fiber Bragg gratings arranged along the cable direction, the fiber Bragg gratings receive ultrasonic signals emitted by ultrasonic fault sources to change the fiber Bragg gratings;

[0014] A demodulation system receives optical signals of the fiber Bragg gratings and converts the optical signals of at least two fiber Bragg gratings arranged along the cable direction into ultrasonic parameters;

[0015] The computer monitors and locates the fault point according to ultrasonic parameters, the position distance between different fiber gratings and ultrasonic attenuation characteristics.

[0016] Preferably, the multiple fiber gratings are arranged along the cable direction and are arranged in series on the same optical fiber.

[0017] Preferably, the optical fiber is arranged inside the cable.

[0018] Preferably, the cable includes a power cell, the power cell is connected to a discharge host, and the discharge host is connected to a computer.

[0019] Preferably, the fiber grating is a Bragg grating, and a FP resonant cavity is provided at the Bragg grating.

[0020] Preferably, the multiple fiber gratings are arranged along the cable direction and are set on at least two optical fibers.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present application discloses a monitoring and positioning method for ultrasonic faults of cables, comprising: at least two fiber gratings arranged along the cable direction, the fiber gratings receiving ultrasonic signals emitted by ultrasonic fault sources, causing the fiber gratings to change; receiving optical signals of the fiber gratings, converting the optical signals of the at least two fiber gratings arranged along the cable direction into ultrasonic parameters; monitoring and positioning the fault point according to the ultrasonic parameters, the position distance between different fiber gratings and the ultrasonic attenuation characteristics. By receiving the ultrasonic signals emitted by the ultrasonic fault source by at least two fiber gratings arranged along the cable direction, the fiber grating parameters such as grating wavelength or reflectivity generated by different fiber gratings for the same ultrasonic fault source are different, and then the fiber grating parameters such as different grating wavelengths or reflectivity generated by different fiber gratings are converted into ultrasonic parameters, such as ultrasonic parameter information such as wavelength, frequency and intensity, and then the fault point is accurately positioned according to the known ultrasonic parameter information, the position distance between different fiber gratings and the ultrasonic attenuation characteristics, thereby achieving accurate positioning of power cables, especially long-distance cables.

[0023] The present application also discloses a cable monitoring and positioning device based on fiber grating, including: fiber grating, demodulation system and computer. The fiber grating is used to receive ultrasonic signals so as to change fiber grating parameters such as grating wavelength or reflectivity of the fiber grating, the adjustment system is used to demodulate the fiber grating parameters and convert them into ultrasonic parameters, and the computer calculates the location information of ultrasonic fault points based on known information and accurately locates the fault points, thereby achieving accurate positioning of power cables, especially long-distance cables.

[0024] Compared with the prior art, the present application discloses a method and device for monitoring and locating ultrasonic faults of cables, which can achieve the purpose of accurately locating ultrasonic faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0026] Figure 1 A schematic flow chart of a method for monitoring and locating ultrasonic faults of cables provided in an embodiment of the present invention is shown;

[0027] Figure 2 A schematic diagram showing the connection relationship of a cable monitoring and positioning device based on fiber grating provided in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0029] The present invention discloses a method for monitoring and locating ultrasonic faults of cables. Figure 1 ,include:

[0030] S10, at least two fiber Bragg gratings are arranged along the cable direction, and the fiber Bragg gratings receive ultrasonic signals emitted by ultrasonic fault sources, causing the fiber Bragg gratings to change;

[0031] S20, receiving optical signals of fiber Bragg gratings, and converting the optical signals of at least two fiber Bragg gratings arranged along the cable direction into ultrasonic parameters;

[0032] S30, monitoring and locating the fault point according to ultrasonic parameters, the position distances between different fiber gratings, and ultrasonic attenuation characteristics.

[0033] At least two fiber gratings arranged along the cable direction receive ultrasonic signals emitted by ultrasonic fault sources, so that fiber grating parameters such as grating wavelength or reflectivity generated by different fiber gratings for the same ultrasonic fault source are different, and then the different grating wavelengths or reflectivity fiber grating parameters generated by different fiber gratings are converted into ultrasonic parameters, such as ultrasonic parameter information such as wavelength, frequency and intensity, and then the fault point is accurately located through the known ultrasonic parameter information, the position distance between different fiber gratings and the ultrasonic attenuation characteristics, thereby achieving accurate positioning of power cables, especially long-distance cables.

[0034] Specifically, the interior of a power cable is usually narrow and its transmission distance is long. When partial discharge occurs inside and ultrasonic signals are generated, conventional electrical sensors cannot supply power and transmit signals over long distances, and are susceptible to strong electromagnetic interference, making it difficult to achieve large-scale reuse. The collapse of an object or a structural fracture will be accompanied by the excitation of sound energy, which will radiate outward in the form of ultrasonic waves. Ultrasonic signals will be generated in cables, such as base station collapse, partial discharge, and cable fracture. Ultrasonic detection of ultrasonic fault sources is an effective and non-destructive detection method, especially for power cables that supply power over long distances.

[0035] It should be noted that the positioning detection of ultrasonic fault points in power cables is of great significance in fault diagnosis, power status detection and leakage detection. Power cables run outdoors for a long time and are easily affected by the external environment, which leads to a decrease in insulation performance and thus partial discharge. Partial discharge will cause equipment failure, affect power supply stability, and cause fires and explosions. Therefore, the positioning detection of such ultrasonic fault points is a difficult problem that needs to be broken through and solved at present.

[0036] It should also be noted that the present application can locate and detect ultrasonic fault points at any position in the power cable in space. Since the cables between different base stations are sometimes not arranged along only one straight line in actual arrangement, it is often necessary to change the direction of the power cable according to the geographical location. The present application utilizes the difference in core mode reflectivity generated by the transverse vibration and the longitudinal vibration produced when the ultrasonic wave acts on the fiber grating. When the fiber grating is subjected to the ultrasonic wave to produce longitudinal vibration, reflection sidebands will appear on both sides of the central reflection wavelength of the grating; when the fiber grating is subjected to the ultrasonic wave to produce transverse vibration, reflection sidebands will appear in the short wavelength direction of the central reflection wavelength of the grating. In this way, it is possible to determine whether the ultrasonic fault point occurs in the direction of the power cable arranged along the fiber grating or in other directions, and then locate and detect the ultrasonic fault point at any position in space.

[0037] For fiber gratings, they can be divided into uniform period fiber gratings and non-uniform period fiber gratings. Uniform gratings can be divided into Bragg fiber gratings and long period fiber gratings. Non-uniform period gratings mainly include chirped fiber gratings, phase-shifted fiber gratings, and sampled fiber gratings. Among them, fiber gratings can be selected from Bragg fiber gratings, long period fiber gratings, chirped fiber gratings, phase-shifted fiber gratings, and sampled fiber gratings. It should be noted that the selection of different fiber gratings requires corresponding signal modulation according to the waveform change characteristics of the fiber grating, so as to identify the parameters of the fiber grating. Obviously, users can also choose other types of gratings according to specific usage requirements.

[0038] Preferably, at least three fiber gratings are arranged along the cable direction, one of which is a confirmation grating. After the ultrasonic fault point is confirmed by other fiber gratings, the ultrasonic parameters obtained by the confirmation grating, the position distance information between the ultrasonic fault point and the confirmation grating are fitted with the ultrasonic attenuation characteristic curve, so as to determine whether the determined ultrasonic fault point is reliable, and at the same time make the positioning accuracy higher.

[0039] In addition, the fault point is monitored and located based on the ultrasonic parameters, the position distance between different fiber Bragg gratings and the ultrasonic attenuation characteristics. Since the position distance between the fiber Bragg gratings is different, the changes in the fiber Bragg grating caused by the ultrasonic wave are also different. When the ultrasonic wave propagates in the medium, its energy will weaken with the increase of the propagation distance. Therefore, the ultrasonic fault source can be located based on the ultrasonic attenuation characteristics, ultrasonic parameters and the position distance between different fiber Bragg gratings.

[0040] In some embodiments, the fiber grating is a Bragg grating.

[0041] Fiber Bragg grating (FBG) is used for fiber grating. FBG is a fiber grating based on the principle of Bragg diffraction. Its structure is to make the middle part of an optical fiber have a periodic refractive index change to form a series of reflection gratings with periodic refractive index changes. FBG has the structural characteristics of being suitable for harsh environments, strong anti-electromagnetic interference ability, high stability, high durability and small size.

[0042] In some specific embodiments, the channel multiplexing mode of the Bragg grating is wavelength division multiplexing, time division multiplexing or wavelength division / time division hybrid multiplexing.

[0043] Specifically, by using wavelength division multiplexing, time division multiplexing or wavelength division / time division hybrid multiplexing, signals in different fiber gratings can be transmitted in one optical fiber without the need for multiple optical fibers. When used in power cables, it is less expensive and easier to install.

[0044] In some embodiments, the ultrasonic parameter is an electrical signal curve.

[0045] Specifically, the optical signal reflected from the fiber grating is received, and the received optical signal is converted into an electrical signal for demodulation, thereby obtaining an electrical signal curve. Compared with a single electrical signal, the electrical signal curve is more intuitive when used and can effectively reduce the amount of calculation in subsequent steps.

[0046] The present invention discloses a cable monitoring and positioning device based on fiber grating, please refer to Figure 2 ,include:

[0047] Fiber Bragg gratings, at least two fiber Bragg gratings arranged along the cable direction, the fiber Bragg gratings receive ultrasonic signals emitted by ultrasonic fault sources to change the fiber Bragg gratings;

[0048] A demodulation system receives optical signals of the fiber Bragg gratings and converts the optical signals of at least two fiber Bragg gratings arranged along the cable direction into ultrasonic parameters;

[0049] The computer monitors and locates the fault point according to ultrasonic parameters, the position distance between different fiber gratings and ultrasonic attenuation characteristics.

[0050] Fiber Bragg gratings are used to receive ultrasonic signals so that the grating wavelength or reflectivity of the fiber Bragg grating and other fiber Bragg grating parameters change. The adjustment system is used to demodulate the fiber Bragg grating parameters and convert them into ultrasonic parameters. The computer calculates the position information of the ultrasonic fault point based on the known information and accurately locates the fault point, thereby achieving accurate positioning of power cables, especially long-distance cables.

[0051] In some embodiments, multiple fiber gratings are arranged along the cable direction and are set in series on the same optical fiber.

[0052] It should be noted that in the laying of long-distance power cables, laying one more cable will significantly increase the cost. In order to reduce the cost and simplify the structure, multiple fiber gratings are set on the same optical fiber for communication.

[0053] In some specific embodiments, the optical fiber is arranged inside the cable.

[0054] Specifically, in order to further reduce costs and enable power cables to have the function of locating ultrasonic fault points in addition to transmitting electricity, optical fibers are arranged inside the cables. In addition to the above advantages, if the ultrasonic fault point and the fiber grating are set in the same section of the cable without separation, the ultrasonic signal will propagate along the medium in the cable, thereby making the positioning of the ultrasonic fault point more accurate.

[0055] In some more specific embodiments, the cable includes a power cell, the power cell is connected to a discharge host, and the discharge host is connected to a computer.

[0056] It should be noted that the discharge host and the positioning of ultrasonic fault points are controlled by computers, which optimizes the relevant structures used in power cables.

[0057] In some embodiments, the fiber grating is a Bragg grating, and a FP resonant cavity is provided at the Bragg grating.

[0058] Specifically, the FP resonant cavity is a semiconductor light-emitting device that emits multi-longitudinal mode coherent light. It has the characteristics of high output light power, small divergence angle, narrow spectrum and high modulation rate. Therefore, the FP resonant cavity at the Bragg grating can play a more significant role in long-distance power cables, with lower signal packet loss rate and more accurate positioning detection results.

[0059] In some embodiments, the plurality of fiber gratings are arranged along the cable direction and are disposed on at least two optical fibers.

[0060] It should be noted that in order to make the positioning result more accurate, the positioning accuracy can be improved by setting multiple optical fibers.

[0061] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0062] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0063] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0064] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. A method for monitoring and locating ultrasonic cable faults. It is characterized in that include: At least two fiber Bragg gratings are arranged along the cable direction, and the fiber Bragg gratings receive ultrasonic signals emitted by ultrasonic fault sources to change the fiber Bragg gratings; Receiving optical signals of the fiber Bragg gratings, and converting the optical signals of at least two fiber Bragg gratings arranged along the cable direction into ultrasonic parameters; The fault point is monitored and located according to ultrasonic parameters, the position distance between different fiber gratings and ultrasonic attenuation characteristics.

2. A method for monitoring and locating ultrasonic cable faults according to claim 1, It is characterized in that Fiber Bragg grating is a fiber grating.

3. A method for monitoring and locating cable ultrasonic faults according to claim 2, It is characterized in that The channel multiplexing mode of the Bragg grating is wavelength division multiplexing, time division multiplexing or wavelength division / time division hybrid multiplexing.

4. A method for monitoring and locating ultrasonic cable faults according to claim 1, It is characterized in that Ultrasonic parameters are electrical signal curves.

5. A cable monitoring and positioning device based on fiber grating, It is characterized in that include: Fiber Bragg gratings, at least two of which are arranged along the cable direction, wherein the fiber Bragg gratings receive ultrasonic signals emitted by ultrasonic fault sources, causing the fiber Bragg gratings to change; A demodulation system receives the optical signal of the fiber Bragg grating and converts the optical signals of at least two fiber Bragg gratings arranged along the cable direction into ultrasonic parameters; The computer monitors and locates the fault point according to ultrasonic parameters, the position distances between different optical fiber gratings and ultrasonic attenuation characteristics.

6. A cable monitoring and positioning device based on fiber grating according to claim 5, It is characterized in that The plurality of fiber gratings are arranged along the cable direction and are arranged in series on the same optical fiber.

7. A cable monitoring and positioning device based on fiber grating according to claim 6, It is characterized in that The optical fiber is arranged inside the cable.

8. A cable monitoring and positioning device based on fiber grating according to claim 7, It is characterized in that The cable includes a power cell, the power cell is connected to a discharge host, and the discharge host is connected to the computer.

9. The cable monitoring and positioning device based on fiber grating according to claim 5, It is characterized in that The fiber grating is a Bragg grating, and a FP resonant cavity is arranged at the Bragg grating.

10. The cable monitoring and positioning device based on fiber grating according to claim 5, It is characterized in that The plurality of fiber gratings are arranged along the cable direction and are set on at least two optical fibers.

Images