Flexible multi-optical-fiber-ring series acoustic sensor based on sagnac interferometer and application of flexible multi-optical-fiber-ring series acoustic sensor in power equipment partial discharge ultrasonic signal positioning detection

Abstract

The invention discloses a flexible multi-optical-fiber-ring series acoustic sensor based on a sagnac interferometer and application of the flexible multi-optical-fiber-ring series acoustic sensor in power equipment partial discharge ultrasonic signal positioning detection, and belongs to the technical field of partial discharge detection. According to the invention, the key problems of low detection sensitivity, poor anti-interference capability, limited application scene, poor multi-point detection capability, high integrated system manufacturing cost and the like of the existing electrical and optical ultrasonic sensors widely applied to partial discharge ultrasonic signal detection are solved. A plurality of planar flexible optical fiber ring sensing probes with different resonant frequencies are designed, the sensing probes are connected in series, the sensing probes with different resonant frequencies are distributed at different detection points, and the detection points are marked through the resonant frequencies, so that photoelectric conversion and signal acquisition of single-path optical fiber sensing are completed.

Description

Technical Field

[0001] The invention relates to a flexible multi-fiber ring series acoustic sensor based on a sagnac interferometer and its application in the positioning detection of partial discharge ultrasonic signals of electric power equipment, belonging to the technical field of partial discharge detection. Background Art

[0002] Partial discharge of power equipment is the main factor endangering insulation safety, which can easily cause operating accidents and huge economic losses. Therefore, the detection of partial discharge phenomenon is particularly important. Usually, the occurrence of partial discharge is accompanied by sound, light, electricity and chemical reactions. Among them, the detection of partial discharge ultrasonic signals has high real-time and anti-interference performance, and can quickly locate the partial discharge point through the output signal of the acoustic sensor. However, the existing electrical ultrasonic sensors and optical fiber ultrasonic sensors face the key problems of low detection sensitivity, poor quasi-distributed capability and extremely high cost of multi-point detection systems in the detection of partial discharge ultrasonic signals. Among them, electrical ultrasonic sensors are mainly piezoelectric ceramic sensors (PZT). Although this type of sensor has mature technology and a complete supporting demodulation and acquisition system, it has key problems at the detection end when used for partial discharge ultrasonic signal detection of power equipment, such as poor anti-electromagnetic interference ability, low detection sensitivity, and poor applicability of installation coupling methods (the sensor probe is a cylindrical rigid solid structure and can only be installed in the plane position of the power equipment. It is limited to surface installation on power equipment with tank structure characteristics such as GIS and GIL). At the same time, since this type of sensor cannot be interconnected in series and has a short signal transmission distance, it has poor quasi-distributed detection capabilities and each sensor probe needs to be equipped with a separate acquisition channel, which greatly increases the manufacturing cost of the detection system with the increase in the number of detection points.

[0003] In response to the many problems of PZT sensors, in recent years, more practitioners and researchers related to partial discharge detection of power equipment have turned their research focus to fiber optic ultrasonic sensing technology. This technology has the unique advantages of strong anti-electromagnetic interference ability and full insulation structure in partial discharge ultrasonic signal detection. Among the many fiber optic ultrasonic sensors, fiber grating ultrasonic sensors are rarely used for partial discharge ultrasonic signal detection due to their low detection sensitivity. Fabry-Perot, Mach-Zehnder, Michelson and Sagnac fiber optic ultrasonic sensors have been widely studied in partial discharge ultrasonic signal detection. Among them, the Fabry-Perot fiber optic ultrasonic sensor that detects based on the principle of multi-beam interference is only suitable for transformer oil insulation partial discharge ultrasonic signal detection. The sensor is greatly affected by environmental factors and has poor detection stability. In addition, there is a problem that the cost of the complete system increases significantly as the number of detection points of the PZT sensor increases. The main Mach-Zehnder, Michelson, and Sagnac fiber-optic ultrasonic sensors for partial discharge ultrasonic signal detection based on the principle of dual-beam interference, among which the Mach-Zehnder and Michelson fiber-optic ultrasonic sensors have the problem that the length of the measuring arm and the reference arm must be consistent, and phase adjustment is required to ensure high-sensitivity detection of partial discharge ultrasonic signals. The detection system is complex and has poor stability. At the same time, due to the use of phase demodulation, each sensor probe needs to be equipped with a photoelectric converter and a data acquisition channel. Therefore, the increase in detection points will lead to an increase in the cost of the detection system. The Sagnac fiber-optic ultrasonic sensor does not need to consider the problem of optical path length matching and phase modulation because the two beams of measurement and reference light form interference in a single closed-loop optical path. However, it needs to be driven by a low-coherence light source, resulting in low detection sensitivity, and each sensor probe also needs to be equipped with a photoelectric converter and a data acquisition channel. There is still a key problem of high cost of sensor system preparation. At the same time, the sensor probes of the above-mentioned dual-beam interference ultrasonic sensors are all solid multi-fiber winding ring structures, which limits the application scenarios of partial discharge ultrasonic signal detection. Summary of the invention

[0004] In view of the key problems of existing electrical and optical ultrasonic sensors widely used in partial discharge ultrasonic signal detection, such as low detection sensitivity, poor anti-interference ability, limited application scenarios, poor multi-point detection capability, and high manufacturing cost of complete systems, the present invention provides a flexible multi-fiber ring series acoustic sensor based on Sagnac interferometer and its application in the positioning detection of partial discharge ultrasonic signals of power equipment.

[0005] The technical solution of the present invention:

[0006] One of the purposes of the present invention is to provide a flexible multi-fiber ring series acoustic sensor based on sagnac interferometer, characterized in that it includes a driving light source 1, a 2*2 coupler 2, a plurality of sensing probes 3, a delay optical fiber 4, a photoelectric converter 5, a data acquisition module 6 and a data analysis and processing module 7;

[0007] The multiple sensing probes 3 are planar flexible optical fiber rings with different resonant frequencies;

[0008] The driving light source 1 is connected to a 2*2 coupler, and a plurality of sensor probes 3 and delay optical fibers 4 are connected in series in sequence and connected to the 2*2 coupler 2, and the 2*2 coupler 2 is also connected to a photoelectric converter 5, a data acquisition module 6 and a data analysis and processing module 7 in sequence.

[0009] It is further defined that the driving light source 1 is a C-band broadband light source.

[0010] It is further defined that the sensing probe 3 is formed by winding an optical fiber along a plane and curing it with epoxy resin.

[0011] It is further defined that the resonant frequency of the sensing probe 3 is selected within the range of 20-200 kHz.

[0012] Furthermore, the number of the sensing probes 3 is set to be 2 or more.

[0013] A second object of the present invention is to provide an application of the above-mentioned flexible multi-fiber ring series acoustic sensor based on sagnac interferometer, specifically for positioning and detecting partial discharge ultrasonic signals of power equipment.

[0014] The third object of the present invention is to provide a method for locating and detecting partial discharge ultrasonic signals, specifically, installing multiple sensor probes 3 with different resonant frequencies in the above-mentioned flexible multi-fiber ring series acoustic sensor based on sagnac interferometer at positions far away from the same power equipment or at different positions of non-same power equipment with spatial isolation.

[0015] It is further defined that the optical signal emitted by the driving light source 1 is divided into two paths by the 2*2 coupler 2, one path passes through multiple sensor probes 3 in sequence and then returns to the 2*2 coupler 2 through the delay optical fiber 4, and the other path first passes through the delay optical fiber 4 and then passes through multiple sensor probes 3 and returns to the 2*2 coupler 2. The two paths of light interfere in the 2*2 coupler, and enter the data acquisition module 6 after being received by the photoelectric converter 5. When local discharge occurs at the location of a sensor probe 3 or multiple sensor probes 3 of the power equipment, after the sensor probe 3 detects the local discharge ultrasonic signal, the data acquisition module 6 outputs a time domain waveform signal, and the data analysis and processing module 7 performs Fourier analysis on the signal to obtain frequency domain information of the time domain signal, and determines the local discharge position by comparing the characteristic frequency of the frequency domain information with the overlap of the resonance characteristic peak of one or more sensor probes 3.

[0016] The fourth object of the present invention is to provide a method for locating and detecting partial discharge ultrasonic signals of ABC three-phase lines in GIS, specifically, three sensor probes 3 with different resonant frequencies in the above-mentioned flexible multi-fiber ring series acoustic sensor based on sagnac interferometer are respectively installed on the ABC three-phase lines.

[0017] It is further defined that the resonance frequencies of the three sensing probes 3 are 25 kHz, 60 kHz and 115 kHz respectively.

[0018] Beneficial effects:

[0019] According to the characteristic that the intrinsic broadband characteristics of partial discharge ultrasonic signals are basically within the range of 20kHz-200kHz (the standard ranges given by IEC, IEEE, CIGRE, etc. are different, but basically within the range of 20kHz-200kHz), the present invention adopts the principle of sagnac interference, designs multiple planar flexible optical fiber ring sensor probes with different resonant frequencies, connects the sensor probes in series, distributes the sensor probes with different resonant frequencies at different detection points, and marks the detection points by the resonant frequency, thereby completing the photoelectric conversion and signal acquisition of single-channel optical fiber sensing, solving the problems of poor multi-point detection capability and high manufacturing cost of complete systems of sensors widely used in partial discharge ultrasonic signal detection. Compared with the prior art, it also has the following advantages:

[0020] (1) The sensor probe used in the present invention is formed by winding an optical fiber along a plane into a planar flexible optical fiber ring, and then cured and packaged using a low Young's modulus elastic epoxy resin. The sensitivity of the sensor probe is greatly improved by increasing the acoustic signal receiving area, and the applicability of the sensor probe for partial discharge ultrasonic signal detection in multiple scenarios is improved by designing a planar flexible cured packaging structure (for example, it can be installed and used in the oil area inside the transformer and on the outer surface of the transformer oil tank wall without performing additional operations, and can be directly used on the curved wall surface of power equipment with tank-type structural characteristics such as GIS and GIL), thereby solving the key problems of low sensitivity and poor applicability of partial discharge ultrasonic sensors.

[0021] (2) The present invention adopts an all-fiber sagnac interferometric sensor with extremely strong anti-electromagnetic interference capability, and the sensing and measuring optical paths share one optical fiber. The system structure is simple and has strong anti-environmental interference capability.

[0022] (3) The present invention adopts the form of flexible planar optical fiber ring sensor probes connected in series, which can detect partial discharge ultrasonic signals and determine the sensor probe that has detected the partial discharge through the characteristic peak value of the frequency domain information of the system output signal. At the same time, the location where the partial discharge occurs can be determined according to the location of the sensor probe, so as to realize the marking of the detection position through the resonant frequency of the sensor probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a flexible multi-fiber ring series acoustic sensor based on a sagnac interferometer provided in this application;

[0024] Figure 2 This is a physical photo of the sensor probe;

[0025] Figure 3 A partial discharge ultrasonic signal positioning detection system of a flexible multi-fiber ring series acoustic sensor based on a sagnac interferometer constructed in Example 1;

[0026] Figure 4 The time domain signal waveform obtained when partial discharge occurs at the isolation space 3 in Example 1;

[0027] Figure 5 The frequency domain signal waveform obtained when partial discharge occurs at the isolation space 3 in Example 1;

[0028] Figure 6 The time domain signal waveform obtained when partial discharge occurs at the positions of the isolation spaces 1 to 3 in Example 1;

[0029] Figure 7 The frequency domain signal waveform obtained when partial discharge occurs at the positions of the isolation spaces 1 to 3 in Example 1;

[0030] In the figure, 1-driving light source, 2-2*2 coupler, 3-sensing probe, 4-delay optical fiber, 5-photoelectric converter, 6-data acquisition module, 7-data analysis and processing module, 8-first isolation space, 9-second isolation space, 10-third isolation space. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", "top / bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" 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 indirectly connected 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 the present invention can be understood according to specific circumstances.

[0034] like Figure 1As shown, the present invention provides a kind of flexible multi-fiber ring series acoustic sensor based on sagnac interferometer, the sensor includes a driving light source 1, a 2*2 coupler 2, a plurality of sensor probes 3, a delay optical fiber 4, a photoelectric converter 5, a data acquisition module 6 and a data analysis and processing module 7; specifically, the driving light source 1 is connected to the 2*2 coupler, and the plurality of sensor probes 3 and the delay optical fiber 4 are connected in series in sequence and then connected to the 2*2 coupler, and the 2*2 coupler is also connected in sequence to the photoelectric converter 5, the data acquisition module 6 and the data analysis and processing module 7. Among them, the plurality of sensor probes 3 are planar flexible optical fiber rings with different resonant frequencies, which are formed by winding optical fibers along a plane and curing them with epoxy resin. The driving light source 1 is a C-band broadband light source. In this way, by installing the plurality of sensor probes 3 at different positions of the same power equipment that are far away and the ultrasonic signal cannot be transmitted, or at different positions of non-same power equipment with spatial isolation (for example, the ABC three-phase line in GIS has a clear spatial isolation feature). A C-band broadband light source is used as the driving light source 1. The optical signal emitted by the driving light source 1 is divided into two paths by the 2*2 coupler 2. One path first passes through multiple sensor probes 3 and then continues to propagate through the delay optical fiber 4 and then returns to the 2*2 coupler 2. The other path first passes through the delay optical fiber 4 and then continues to propagate through multiple sensor probes 3 and then returns to the 2*2 coupler 2. The two paths of light interfere at the 2*2 coupler 2, and are received by the photoelectric converter 5 and then enter the data acquisition module 6.When partial discharge occurs at a certain position of the sensor probe 3, the ultrasonic signal generated by the partial discharge acts on the sensor probe 3 at that position in the form of a mechanical wave. Since the sensor probe 3 is made of an optical fiber ring, the acoustic signal causes the optical fiber to vibrate, and the optical signal passing through the optical fiber ring changes, thereby causing the interference light signal in the 2*2 coupler 2 to change (assuming that there is no partial discharge, the interference light signal output from the 2*2 coupler 2 and incident on the photoelectric converter should remain constant, and the electrical signal output by the photoelectric conversion should also remain constant). This changing interference light signal becomes a changing electrical signal after passing through the photoelectric converter. At this time, a high level with a rising edge appears, and the data acquisition module 6 outputs a time domain waveform signal, which triggers the data analysis module 7 to perform data acquisition, processing and analysis. Module 7 performs Fourier analysis on the signal to obtain frequency domain information of the time domain signal. Since the sensor probes 3 used are all detected with narrowband resonance characteristics, the sensor probes 3 naturally output frequency domain information with resonance frequency characteristic values. At this time, by performing characteristic frequency comparison on the frequency domain information of the detection system output signal, it can be determined which sensor probe 3 detected the local discharge ultrasonic signal. For example, if the frequency domain characteristic peak of the output signal of the detection system overlaps with the resonance characteristic peak of the sensor probe 3 at the first installation position, it can be determined that local discharge occurs in the area of ​​position 1. If the output signal of the detection system has two frequency domain characteristic peaks, and they overlap with the resonance frequency peaks of the sensor probe 3 at the first installation position and the second installation position, it can be determined that local discharge occurs at both the first installation position and the second installation position.

[0035] The sensor probe 3 designed by the present invention is as follows Figure 2 As shown, it is made of optical fiber wound along a plane and cured by low Young's modulus epoxy resin. It has good flexibility and can fit tightly to the surface of the non-planar power equipment housing to detect partial discharge ultrasonic signals. Because the sensor probe 3 is planar, its sound receiving area is greatly improved compared to the traditional optical fiber ring used in the EFPI sensor and the double-beam interferometer, thereby improving its detection sensitivity, and the sensor probe can change the inherent resonant frequency by adjusting the plane result size and the number of winding layers.

[0036] Preparation of sensor probe: The sensor probe consists of two parts, one is made of optical fiber, and the other is a coupling substrate that modulates the resonant frequency of the sensor probe. The optical fiber ring is a planar single-layer optical fiber. Figure 2As shown, the fiber ring has an inner diameter of 20mm and an outer diameter of 60mm. It is wound with a single-mode optical fiber of 10m in length and quickly cured and shaped by ultraviolet curing glue. Its base structure for modulating the resonant frequency is cast by flexible epoxy resin. The inner diameter and outer diameter of the structure are consistent with those of the fiber ring. The resonant frequency is modulated by changing the thickness. The thickness of the resonant frequency modulation base of the sensor probe 3 with a resonant frequency of 25kHz is 1mm, the thickness of the resonant frequency modulation base of the sensor probe 3 with a resonant frequency of 60kHz is 5mm, and the thickness of the resonant frequency modulation base of the sensor probe 3 with a resonant frequency of 115kHz is 12mm. In the preparation process, the preparation of the fiber ring is first completed, and then a mold with matching size is fixed on the fiber ring, and epoxy resin is poured on the mold for curing, so that the flexible epoxy resin and the fiber ring become an integrated structure.

[0037] The above-mentioned flexible multi-fiber ring series acoustic sensor based on sagnac interferometer is used to build a partial discharge ultrasonic signal positioning detection system, such as Figure 3 As shown, three sensing probes 3 with resonance frequencies of 25kHz, 60kHz and 115kHz are placed in the first isolation space 8, the second isolation space 9 and the third isolation space 10 respectively, and high-voltage pulse signal generators are also placed in the first isolation space 8, the second isolation space 9 and the third isolation space 10 respectively.

[0038] First, a high-voltage pulse signal generator in the third isolation space 10 is used to generate a partial discharge ultrasonic signal. The time domain signal waveform and its frequency domain signal captured by the detection system are as follows: Figure 4 and Figure 5 As shown in FIG. 1 , it can be clearly seen from the frequency domain signal that the frequency domain signal collected by the detection system has a 115kHz resonance characteristic peak. Subsequently, the high-voltage pulse generators in the first isolation space 8, the second isolation space 9 and the third isolation space 10 are discharged at the same time. The time domain signal waveform and its frequency domain signal captured by the detection system are shown in FIG. Figure 6 and Figure 7 As shown, the frequency domain collected by the detection system has obvious resonance characteristic peaks of 25kHz, 60kHz and 115kHz. It can be seen that the above-mentioned form of connecting the flexible planar optical fiber ring sensor probes in series can simultaneously detect partial discharge ultrasonic signals, and the sensor probe that detects the partial discharge can be judged by the characteristic peak value of the frequency domain information of the system output signal. At the same time, the location where the partial discharge occurs can be determined according to the position of the sensor probe, so as to realize the marking of the detection through the resonance frequency of the sensor probe.

[0039] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A flexible multi-fiber ring series acoustic sensor based on sagnac interferometer, characterized in that: It includes a driving light source, a 2*2 coupler, multiple sensor probes, a delay optical fiber, a photoelectric converter, a data acquisition module and a data analysis and processing module; The multiple sensing probes are planar flexible optical fiber rings with different resonant frequencies; The driving light source is connected to a 2*2 coupler, a plurality of sensor probes and delay optical fibers are sequentially connected in series and then connected to the 2*2 coupler, and the 2*2 coupler is also sequentially connected to a photoelectric converter, a data acquisition module and a data analysis and processing module.

2. The flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to claim 1 is characterized in that: The driving light source is a C-band broadband light source.

3. The flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to claim 1 is characterized in that: The sensor probe is made of an optical fiber wound along a plane and cured by epoxy resin.

4. The flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to claim 1 is characterized in that: The resonant frequency of the sensing probe is selected within the range of 20-200kHz.

5. The flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to claim 1, characterized in that: The number of sensor probes is 2 or more.

6. An application of a flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to any one of claims 1 to 5, characterized in that: Used for positioning and detecting partial discharge ultrasonic signals of power equipment.

7. A method for locating and detecting partial discharge ultrasonic signals, characterized in that: A plurality of sensing probes with different resonant frequencies in the flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to any one of claims 1 to 5 are respectively installed at positions far away from the same power equipment or at different positions of non-same power equipment with spatial isolation.

8. The method for locating and detecting partial discharge ultrasonic signals according to claim 7, characterized in that: The optical signal emitted by the driving light source is divided into two paths by a 2*2 coupler. One path passes through multiple sensor probes in sequence and then returns to the 2*2 coupler through a delay optical fiber. The other path first passes through a delay optical fiber and then returns to the 2*2 coupler through multiple sensor probes. The two paths of light interfere in the 2*2 coupler and enter the data acquisition module after being received by the photoelectric converter. When local discharge occurs at the location of a sensor probe or multiple sensor probes of the power equipment, the sensor probe detects the local discharge ultrasonic signal, and the data acquisition module outputs a time domain waveform signal. The data analysis and processing module performs Fourier analysis on the signal to obtain frequency domain information of the time domain signal. The local discharge location is determined by comparing the characteristic frequency of the frequency domain information with the resonance characteristic peak overlap of one or more sensor probes.

9. A method for locating and detecting partial discharge ultrasonic signals of ABC three-phase lines in GIS, characterized in that: The three sensing probes with different resonance frequencies in the flexible multi-fiber ring series acoustic sensor based on sagnac interferometer according to any one of claims 1 to 5 are respectively installed on the ABC three-phase line.

10. The detection method according to claim 9, characterized in that: The resonant frequencies of the three sensor probes are 25kHz, 60kHz and 115kHz respectively.

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