A Method and System for Detecting Partial Discharge in Cables Based on Photonic Lanterns and Few-Mode Fibers

Abstract

This invention discloses a cable partial discharge detection system based on a photonic lantern and few-mode optical fiber, comprising a few-mode optical fiber setting module, a multi-mode partial discharge detection module, a signal fusion module, and a partial discharge discrimination module. The few-mode optical fiber setting module winds the few-mode optical fiber onto the power cable to be tested with a predetermined number of turns. The multi-mode partial discharge detection module performs multi-mode partial discharge detection on the cable to obtain multi-mode partial discharge detection values. The signal fusion module weights and fuses the multi-mode partial discharge detection values ​​obtained from the multi-mode partial discharge detection module to obtain the final cable partial discharge detection data. The partial discharge discrimination module inputs the final cable partial discharge detection data into a predetermined partial discharge criterion to determine whether partial discharge has occurred at the current monitoring point. This invention also has significant advantages such as strong practicality and wide applicability.

Description

Technical Field

[0001] This invention relates to the field of partial discharge detection in cables, and specifically to a method and system for partial discharge detection in cables based on photonic lanterns and few-mode optical fibers. Background Technology

[0002] Due to their long distances and underground burial, power cables require continuous monitoring along their entire length to obtain real-time operational information. Distributed monitoring can quickly and accurately locate fault points, reducing the frequency of emergency repairs and replacements. Partial discharge is a significant problem encountered during power cable operation. It can lead to insulation aging, defects, and even failure, resulting in power outages. Effective detection of partial discharge is a crucial aspect of power cable operation and maintenance.

[0003] Fiber optic sensing is widely used in power equipment condition monitoring due to its advantages such as resistance to electromagnetic interference, high sensitivity, small size, high temperature and corrosion resistance, good insulation performance, and long-distance transmission capability. Phase-sensitive optical time-domain reflectometry (OTDR) is an important method for monitoring and locating the condition of power cables. In practical applications, phase-sensitive ODR may be affected by coherent fading, introducing detection errors and blind zones, leading to decreased detection accuracy and inaccurate fault location. Few-mode fiber, which supports the transmission of only a few modes, effectively reduces interference between modes compared to multimode fiber. Photonic lanterns can convert multiple modes in a few-mode fiber into a single mode in multiple single-mode fibers, improving signal quality and reducing the impact of coherent fading on detection results. Using few-mode fiber and photonic lanterns can significantly reduce the impact of coherent fading, thereby improving the measurement accuracy of phase-sensitive ODR.

[0004] CN116754910A discloses a method, system, and device for monitoring partial discharge in cables based on multi-path fiber differential. The method includes acquiring a time-series pulse signal and coherent light; modulating the coherent light into three pulses with different pulse widths based on the time-series pulse signal; using two optical signals from the pulsed light to detect partial discharge in a region of the cable to obtain N sets of pulse data; sequentially performing denoising, phase extraction, and smoothing / classification processing on the N sets of pulse data to obtain three corresponding sets of phase data; discretizing and performing dimension-shifting processing on each set of phase data to obtain three sets of one-dimensional arrays; and determining whether partial discharge has occurred in a region of the cable based on the three sets of one-dimensional arrays. This patent uses only one mode of light for detection. -OTDR detection, different modes - The OTDR signals are all different and independent. Since the fading locations of the different modes differ spatially, the three modes are fused. The use of OTDR to suppress coherent fading limits the practicality of this invention and restricts its application. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as limited practicality and narrow application scope, this invention provides a method and system for detecting partial discharge in cables based on photonic lanterns and few-mode optical fibers.

[0006] The present invention adopts the following technical solution.

[0007] The present invention discloses a cable partial discharge detection system based on a photonic lantern and a few-mode fiber, including a few-mode fiber setting module, a multi-mode partial discharge detection module, a signal fusion module, and a partial discharge discrimination module;

[0008] The few-mode fiber setting module winds the few-mode fiber onto the power cable to be tested according to a set number of turns;

[0009] The multi-mode partial discharge detection module performs multi-mode partial discharge detection on the cable based on the photonic lantern and the set few-mode optical fiber to obtain multi-mode partial discharge detection values.

[0010] The signal fusion module performs weighted fusion of the multi-mode partial discharge detection values ​​obtained by the multi-mode partial discharge detection module to obtain the final cable partial discharge detection data.

[0011] The partial discharge discrimination module inputs the final cable partial discharge detection data into the set partial discharge criteria to determine whether partial discharge has occurred at the current monitoring point.

[0012] More preferably,

[0013] In the multi-mode partial discharge detection module, the multi-mode includes the fundamental mode LP01 mode, the higher-order mode LP11a mode in the few-mode fiber, and the higher-order mode LP11b mode in the few-mode fiber.

[0014] More preferably,

[0015] The multi-mode partial discharge detection module includes a narrow-linewidth coherent laser (1); the output of the narrow-linewidth coherent laser (1) is connected to the input of a first optical coupler (2); the two outputs of the first optical coupler (2) are respectively connected to the first input of an acousto-optic modulator (4) and the input of a 1-to-3 coupler (13); the second input of the acousto-optic modulator (4) is connected to a waveform generator (3), and its output is connected to the input of an erbium-doped fiber amplifier (5); the output of the erbium-doped fiber amplifier (5) is connected to the input of an optical bandpass filter (6); the output of the optical bandpass filter (6) is connected to the input of a 1-to-3 coupler (7); the three outputs of the 1-to-3 coupler (7) are respectively connected to the first ends of a first fiber circulator (9), a second fiber circulator (10), and a third fiber circulator (11); the first fiber circulator (9), the second fiber circulator (10), and the third fiber circulator (11) are connected to the first ends of the first fiber circulator (9), the second fiber circulator (10), and the third fiber circulator (11). The second end of the circulator (11) is connected to the first, second and third ends of the photonic lantern (8); the fourth and fifth ends of the photonic lantern (8) are connected to the input and output ends of the few-mode fiber (12) respectively; the third end of the first fiber circulator (9) is connected to the second input end of the first balanced photodetector (14); the third end of the second fiber circulator (10) is connected to the second input end of the second balanced photodetector (15); the third end of the third fiber circulator (11) is connected to the second input end of the third balanced photodetector (16); the three output ends of the splitter (13) are connected to the first input ends of the balanced photodetector (14), balanced photodetector (15) and balanced photodetector (16) respectively; the output ends of the balanced photodetector (14), balanced photodetector (15) and balanced photodetector (16) are all connected to the data acquisition card (17).

[0016] More preferably,

[0017] The one-to-three coupler (7) divides the pulse filtered by the optical bandpass filter (6) into a first branch pulse, a second branch pulse, and a third branch pulse, for a total of three branch pulses; the spatial modes of the three branch pulses are LP01 mode, LP11a mode, and LP11b mode, respectively.

[0018] More preferably,

[0019] The first, second, and third ends of the photonic lantern (8) receive the first branch pulse, the second branch pulse, and the third branch pulse emitted by the second ends of the first fiber circulator (9), the second fiber circulator (10), and the third fiber circulator (11), respectively. The three modes corresponding to the branch pulses of the three modes are converted into multiple modes of the few-mode fiber, and the input end of the few-mode fiber is transmitted from the fourth end of the photonic lantern (8).

[0020] The fifth end of the photonic lantern (8) receives the output signal of the few-mode fiber and converts the multiple modes of the few-mode fiber into a single mode of the three single-mode fibers, and outputs the three signals from the first end, the second end and the third end respectively.

[0021] More preferably,

[0022] The few-mode fiber (12) receives the output signal from the fourth end of the photonic lantern (8) to sense the partial discharge signal of the power cable at the winding position, and outputs the signal with the partial discharge detection information of the cable at the detected position to the fifth end of the photonic lantern (8).

[0023] More preferably,

[0024] In the signal fusion module, the multi-mode partial discharge detection values ​​obtained from the multi-mode partial discharge detection module are weighted and fused to obtain the final cable partial discharge detection data as shown in the following formula:

[0025] S(t) = w 01 (t)S 01 (t)+w 11a (t)S 11a (t)+w 11b (t)S 11b (t);

[0026] Where S(t) is the final partial discharge detection value of the cable at time t; w 01 (t) is the partial discharge weight of LP01 mode at time t; S 01 (t) is the partial discharge detection value of LP01 mode at time t; w 11a (t) is the partial discharge weight of LP11a mode at time t; S 11a (t) is the partial discharge detection value of LP11a mode at time t; w 11b (t) is the partial discharge weight of the LP11b mode at time t; S 11b (t) is the partial discharge detection value of LP11b mode at time t.

[0027] More preferably,

[0028] The partial discharge weight of LP01 mode at time t is shown in the following formula:

[0029]

[0030] Where max[·] represents finding the maximum value within the parentheses; min[·] represents finding the minimum value within the parentheses; It is the phase of partial discharge in LP01 mode at time t; δ is the partial discharge phase of LP01 mode at time t-1; δ is the phase correlation coefficient; t represents the t-th sampling point; N Z λ1 represents the total number of sampling points for multi-mode partial discharge; e represents the natural base; λ1 represents the first weighted correlation coefficient; and λ2 represents the second weighted correlation coefficient.

[0031] The partial discharge weight of LP11a mode at time t is shown in the following formula:

[0032]

[0033] in, It is the partial discharge phase of LP11a mode at time t; It is the partial discharge phase of LP11a mode at time t-1;

[0034] The partial discharge weight of LP11b mode at time t is shown in the following formula:

[0035]

[0036] in, It is the partial discharge phase of LP11b mode at time t; It is the partial discharge phase of LP11b mode at time t-1.

[0037] Another aspect of the present invention discloses a cable partial discharge detection method based on a cable partial discharge detection system, comprising:

[0038] The few-mode optical fiber is wound onto the power cable to be tested according to the set number of turns;

[0039] Multi-mode partial discharge detection of the cable is performed using a photonic lantern and a pre-set few-mode fiber to obtain multi-mode partial discharge detection values.

[0040] The multi-mode partial discharge detection values ​​obtained by the multi-mode partial discharge detection module are weighted and fused to obtain the final cable partial discharge detection data.

[0041] Input the final cable partial discharge detection data into the set partial discharge criterion to determine whether partial discharge has occurred at the current monitoring point.

[0042] Another aspect of this application discloses an electronic device, including a processor and a storage medium; characterized in that:

[0043] The storage medium is used to store instructions;

[0044] The processor is configured to operate according to the instructions to execute the aforementioned cable partial discharge detection method.

[0045] This application also discloses a computer-readable storage medium having a computer program stored thereon, characterized in that the program, when executed by a processor, implements the cable partial discharge detection method.

[0046] The beneficial effects of this invention are compared with those of the prior art:

[0047] Few-mode fiber is a type of fiber that supports the transmission of only a few modes. Compared to multimode fiber, it effectively reduces interference between modes. A photonic lantern can convert multiple modes in a few-mode fiber into a single mode in multiple single-mode fibers, improving signal quality. By fusing signals from different modes, it reduces the impact of coherent fading on detection results. Using few-mode fiber and a photonic lantern can significantly reduce the impact of coherent fading, thereby improving the measurement accuracy of phase-sensitive optical time-domain reflectometers.

[0048] This invention also has significant advantages such as strong practicality and wide applicability. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the detection principle based on photonic lanterns and few-mode optical fibers. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0051] This application discloses a cable partial discharge detection system based on a photonic lantern and a few-mode fiber, including a few-mode fiber setting module, a multi-mode partial discharge detection module, a signal fusion module, and a partial discharge discrimination module;

[0052] The few-mode fiber setting module winds the few-mode fiber onto the power cable to be tested with a set number of turns; in a preferred embodiment of the present invention, the few-mode fiber is uniformly wound onto the power cable 150 turns.

[0053] The multi-mode partial discharge detection module performs multi-mode partial discharge detection on the cable based on the photonic lantern and the set few-mode optical fiber to obtain multi-mode partial discharge detection values.

[0054] Preferably, the multi-mode includes the fundamental mode LP01 mode, the higher-order mode LP11a mode in the few-mode fiber, and the higher-order mode LP11b mode in the few-mode fiber.

[0055] The multi-mode partial discharge detection module includes a narrow-linewidth coherent laser 1; the output of the narrow-linewidth coherent laser 1 is connected to the input of a first optical coupler 2; the two outputs of the first optical coupler 2 are respectively connected to the first input of an acousto-optic modulator 4 and the input of a 1-to-3 coupler 13; the second input of the acousto-optic modulator 4 is connected to a waveform generator 3, and its output is connected to the input of an erbium-doped fiber amplifier 5; the output of the erbium-doped fiber amplifier 5 is connected to the input of an optical bandpass filter 6; the output of the optical bandpass filter 6 is connected to the input of a 1-to-3 coupler 7; the three outputs of the 1-to-3 coupler 7 are respectively connected to the first ends of a first fiber circulator 9, a second fiber circulator 10, and a third fiber circulator 11; the first fiber circulator 9, the second fiber circulator 10, and the third fiber circulator 11... The second end of the device 11 is connected to the first, second, and third ends of the photonic lantern 8, respectively; the fourth and fifth ends of the photonic lantern 8 are connected to the input and output ends of the few-mode fiber 12, respectively; the third end of the first fiber circulator 9 is connected to the second input end of the first balanced photodetector 14; the third end of the second fiber circulator 10 is connected to the second input end of the second balanced photodetector 15; the third end of the third fiber circulator 11 is connected to the second input end of the third balanced photodetector 16; the three output ends of the one-to-three coupler 13 are connected to the first input ends of the balanced photodetectors 14, 15, and 16, respectively; the output ends of the balanced photodetectors 14, 15, and 16 are all connected to the data acquisition card 17.

[0056] The narrow linewidth coherent laser 1 emits 1550nm laser light;

[0057] The first optical coupler 2 receives the laser emitted by the narrow linewidth coherent laser 1 and splits the laser into signal light and local oscillator light; the signal light is transmitted to the acousto-optic modulator 4 and the local oscillator light is transmitted to the 1-to-3 coupler 13.

[0058] Preferably, the first optical coupler can be a 90:10 optical coupler; in a preferred embodiment of the present invention, the 90:10 optical coupler 2 receives the laser emitted by the narrow linewidth coherent laser 1, and its output light is split into two branches by the 90:10 optical coupler 2, namely, signal light and local oscillator light. The signal light receives 90% of the power of the laser emitted by the laser 1, and the local oscillator light receives 10% of the power of the laser emitted by the laser 1.

[0059] The waveform generator 3 outputs a waveform for modulating the signal light to the acousto-optic modulator 4;

[0060] The acousto-optic modulator 4 modulates the received signal light with the waveform output by the waveform generator 3 to generate a detection pulse;

[0061] The erbium-doped fiber amplifier 5 receives and amplifies the detection pulses generated by the acousto-optic modulator 4.

[0062] The optical bandpass filter 6 performs bandpass filtering on the signal amplified by the erbium-doped fiber amplifier 5.

[0063] Those skilled in the art should know how to configure a bandpass filter to filter out noise signals and retain the amplified probe pulse signal;

[0064] The 1-to-3 coupler 7 divides the pulse filtered by the optical bandpass filter 6 into a first branch pulse, a second branch pulse, and a third branch pulse, for a total of three branch pulses.

[0065] Those skilled in the art will understand that the 1-to-3 coupler 7 can be used to enable different spatial modes. In a preferred embodiment of the present invention, the spatial modes of the three fiber branches are the fundamental mode LP01 mode in the fiber, the higher-order mode LP11a mode in the few-mode fiber, and the higher-order mode LP11b mode in the few-mode fiber, respectively. That is, the spatial modes of the three branch pulses are LP01 mode, LP11a mode, and LP11b mode, respectively.

[0066] The first ends of the first fiber optic circulator 9, the second fiber optic circulator 10, and the third fiber optic circulator 11 respectively receive the first branch pulse, the second branch pulse, and the third branch pulse;

[0067] The second ends of the first fiber optic circulator 9, the second fiber optic circulator 10, and the third fiber optic circulator 11 respectively output the branch pulse received at the first end to the first end, the second end, and the third end of the photonic lantern 8, and respectively receive the signals output from the first end, the second end, and the third end of the photonic lantern 8.

[0068] The third ends of the first fiber optic circulator 9, the second fiber optic circulator 10, and the third fiber optic circulator 11 respectively output the signals received at the second ends to the first balanced photodetector 14, the second balanced photodetector 15, and the third balanced photodetector 16.

[0069] The first, second, and third ends of the photonic lantern 8 receive the first branch pulse, the second branch pulse, and the third branch pulse emitted from the second ends of the first fiber optic circulator 9, the second fiber optic circulator 10, and the third fiber optic circulator 11, respectively. The branch pulses of the three modes are converted into multiple modes of the few-mode fiber, and the input end of the few-mode fiber is transmitted from the fourth end of the photonic lantern 8. The fifth end of the photonic lantern 8 receives the signal with partial discharge detection information of the cable at the detected location output from the few-mode fiber, and converts the multiple modes of the few-mode fiber into a single mode of the three single-mode fibers. The three signals obtained are output from the first, second, and third ends, respectively.

[0070] The few-mode fiber 12 receives the output signal from the fourth end of the photonic lantern 8, which is used to sense the partial discharge signal of the power cable at the winding position, and outputs a signal carrying the partial discharge detection information of the cable at the detected position to the fifth end of the photonic lantern 8. The photonic lantern multiplexes / demultiplexes the three modes of light to ensure good mode conversion between the single-mode fiber and the few-mode fiber.

[0071] The 1-to-3 coupler 13 splits the local oscillator light into a first branch local oscillator light, a second branch local oscillator light, and a third branch local oscillator light; the Rayleigh backscattered light of the output optical signals from the third ends of the first fiber circulator 9, the second fiber circulator 10, and the third fiber circulator 11 will be mixed with the first branch local oscillator light, the second branch local oscillator light, and the third branch local oscillator light, respectively.

[0072] The first balanced photodetector 14 performs photoelectric conversion on the mixed signal of the first branch local oscillator light and the Rayleigh backscattered light output from the third end of the first fiber optic circulator 9 to obtain the LP01 mode partial discharge signal.

[0073] The balanced photodetector 15 performs photoelectric conversion on the mixed signal of the second branch local oscillator light and the Rayleigh backscattered light output from the third end of the second fiber optic circulator 10 to obtain the LP11a mode partial discharge signal.

[0074] The balanced photodetector 16 performs photoelectric conversion on the mixed signal of the third branch local oscillator light and the Rayleigh backscattered light output from the third end of the third fiber optic circulator 11 to obtain the LP11b mode partial discharge signal.

[0075] Among them, the partial discharge signals of LP01 mode, LP11a mode, and LP11b mode are all electrical signals.

[0076] The data acquisition card 17 acquires the output signals of the first balanced photodetector 14, the second balanced photodetector 15, and the third balanced photodetector 16 respectively, and obtains the sampled values ​​of local discharge in LP01 mode, LP11a mode, and LP11b mode.

[0077] The pulses are transmitted to the three ports of the photonic lantern after passing through fiber optic circulators 9, 10, and 11, respectively. They then enter the few-mode fiber 12, which is uniformly wound 150 times around the power cable to sense the partial discharge signal of the power cable. The second branch, with a light ratio of 10%, serves as the local oscillator light and is split into three branches by a 1-to-3 coupler 13.

[0078] Since the OTDR waveforms of the three modes—the fundamental mode LP01, the higher-order mode LP11a, and the higher-order mode LP11b—are different and independent, and their fading locations differ spatially, fusing the signals from these three modes can effectively reduce the fading probability over both fiber length and time scale. Preferably, the three modes have the same function.

[0079] The signal fusion module performs weighted fusion of the multi-mode partial discharge detection values ​​obtained by the multi-mode partial discharge detection module to obtain the final cable partial discharge detection data.

[0080] The partial discharge detection signals measured by the data acquisition card 17 under the three modes are fused to obtain the final cable partial discharge detection data, so as to reduce the fading probability.

[0081] The multi-mode partial discharge detection values ​​obtained from the multi-mode partial discharge detection module are weighted and fused to obtain the final cable partial discharge detection data as shown in the following formula:

[0082] S(t) = w 01 (t)S 01 (t)+w 11a (t)S 11a (t)+w 11b (t)S 11b (t);

[0083] Where S(t) is the final partial discharge detection value of the cable at time t; w 01 (t) is the partial discharge weight of LP01 mode at time t; S 01 (t) is the partial discharge detection value of LP01 mode at time t; w 11a (t) is the partial discharge weight of LP11a mode at time t; S 11a (t) is the partial discharge detection value of LP11a mode at time t; w 11b (t) is the partial discharge weight of the LP11b mode at time t; S 11b (t) is the partial discharge detection value of LP11b mode at time t.

[0084] The partial discharge weight of LP01 mode at time t is shown in the following formula:

[0085]

[0086] Where max[·] represents finding the maximum value within the parentheses; min[·] represents finding the minimum value within the parentheses; It is the phase of partial discharge in LP01 mode at time t; δ represents the partial discharge phase of LP01 mode at time t-1; δ is the phase correlation coefficient, with a preferred value range of 1 to 2.3; t represents the t-th sampling point; NZ λ1 is the total number of sampling points for multi-mode partial discharge; e is the natural base; λ1 is the first weighted correlation coefficient, with a preferred value range of 2.8δ~3.2δ; λ2 is the second weighted correlation coefficient, with a preferred value range of 0.55~0.7; where the total number of sampling points for multi-mode partial discharge = the total number of sampling points for LP01 mode partial discharge signals acquired by data acquisition card 17 = the total number of sampling points for LP11a mode partial discharge signals acquired by data acquisition card 17 = the total number of sampling points for LP11b mode partial discharge signals acquired by data acquisition card 17;

[0087] The partial discharge weight of LP11a mode at time t is shown in the following formula:

[0088]

[0089] in, It is the partial discharge phase of LP11a mode at time t; It is the partial discharge phase of LP11a mode at time t-1;

[0090] The partial discharge weight of LP11b mode at time t is shown in the following formula:

[0091]

[0092] in, It is the partial discharge phase of LP11b mode at time t; It is the partial discharge phase of LP11b mode at time t-1.

[0093] The amplitude and phase information of the final cable partial discharge detection data are calculated using the following method.

[0094]

[0095] In the formula, t represents the index of the sampling point, i.e., the t-th sampling point; Y I (t) represents the same-direction signal of the final partial discharge detection data of the cable at time t; Y Q (t) represents the orthogonal signal of the final partial discharge detection data of the cable at time t; E s (t) represents the light field intensity of the information light; E o (t) represents the light field intensity of the local oscillator beam; S(t) represents the phase of the final cable partial discharge detection data, which is also the phase of the external disturbance information; S(t) is the final cable partial discharge detection value at time t. Indicates same frequency information; Represents orthogonal information;

[0096] This represents the sum-frequency term in the same-frequency information. This indicates that the same-frequency information contains components of external disturbance information. This represents the sum-frequency term in orthogonal information. This indicates that the orthogonal information contains components of external disturbance information. The calculation formula is as follows:

[0097] Δω t =2πΔf / f s ;

[0098] Among them, f s This indicates the sampling rate of data acquisition card 17, and Δf represents the frequency of the waveform used for modulation signal emitted by waveform generator 3.

[0099] After orthogonal demodulation, the sum-frequency term is obtained from the same-direction and orthogonal information. and The second harmonic is filtered out using a low-pass filter to obtain information containing external disturbances.

[0100] The result Y of the same-direction signal after low-pass filtering of the final partial discharge detection data of the cable at time t. I Y, the result of low-pass filtering of the orthogonal signals of the final partial discharge detection data of the cable at time t (t), Q '(t) and and The relationship is as follows:

[0101]

[0102]

[0103] Y' obtained from low-pass filtering I and Y' Q The amplitude information of the final cable partial discharge detection data is shown below:

[0104]

[0105] Based on the amplitude information, obtain the sampling point number at the vibration point at the amplitude peak. Multiply the sampling point number by the sampling interval time and the speed of light, then divide by the refractive index of the optical fiber. Divide the calculated value by 2 to get the distance between the vibration point and the transmitting end.

[0106] The partial discharge discrimination module inputs the final cable partial discharge detection data into the set partial discharge criteria to determine whether partial discharge has occurred at the current monitoring point.

[0107] Those skilled in the art should understand that the partial discharge criterion can be set according to actual conditions. To improve calculation accuracy, the criterion setting proposed in this embodiment is only a preferred embodiment and is not a necessary limitation on implementing the cable partial discharge detection system and method based on photonic lanterns and few-mode optical fibers of this invention. Based on the final cable partial discharge detection data, the specific criterion setting is as follows:

[0108]

[0109] Where t0 represents the sampling time; S(t0) represents the final partial discharge detection value of the cable at time t0; For discharge judgment gain coefficient, its preferred value range is 0.13 to 1.54; Y' I (t) is the result of low-pass filtering of the same-direction signal of the final partial discharge detection data of the cable at time t; Y' Q (t) is the result of low-pass filtering of the quadrature signals of the final partial discharge detection data of the cable at time t; Y' I (t-1) is the result of low-pass filtering of the same-direction signal of the final partial discharge detection data of the cable at time t-1; Y' Q (t-1) is the result of low-pass filtering of the quadrature signal of the final partial discharge detection data of the cable at time t-1; where time t is the first sampling time, Y' is set. I (t-1)=Y' I (t); Y' Q (t-1)=Y' Q (t);

[0110] If the partial discharge criterion is met at time t, then it is determined that no partial discharge occurred at time t; otherwise, it is determined that a partial discharge occurred at time t.

[0111] This application also discloses a cable partial discharge detection method based on a cable partial discharge detection system, characterized in that it includes:

[0112] The few-mode optical fiber is wound onto the power cable to be tested according to the set number of turns;

[0113] Multi-mode partial discharge detection of the cable is performed using a photonic lantern and a pre-set few-mode fiber to obtain multi-mode partial discharge detection values.

[0114] The multi-mode partial discharge detection values ​​obtained by the multi-mode partial discharge detection module are weighted and fused to obtain the final cable partial discharge detection data.

[0115] Input the final cable partial discharge detection data into the set partial discharge criterion to determine whether partial discharge has occurred at the current monitoring point.

[0116] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0117] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0118] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0119] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A cable partial discharge detection system based on a photonic lantern and few-mode optical fiber, characterized in that, It includes a few-mode fiber setup module, a multi-mode partial discharge detection module, a signal fusion module, and a partial discharge discrimination module; The few-mode fiber setting module winds the few-mode fiber onto the power cable to be tested according to a set number of turns; The multi-mode partial discharge detection module performs multi-mode partial discharge detection on the cable based on the photonic lantern and the set few-mode optical fiber to obtain multi-mode partial discharge detection values. The signal fusion module performs weighted fusion of the multi-mode partial discharge detection values ​​obtained by the multi-mode partial discharge detection module to obtain the final cable partial discharge detection data as shown in the following formula: ； in, This is the final partial discharge detection value of the cable at time t; It is the partial discharge weight of LP01 mode at time t; This is the partial discharge detection value of LP01 mode at time t; It is the partial discharge weight of LP11a mode at time t; This is the partial discharge detection value of LP11a mode at time t; It is the partial discharge weight of LP11b mode at time t; This is the partial discharge detection value of LP11b mode at time t; the partial discharge weight of LP01 mode at time t is shown in the following formula: ； in, This indicates finding the maximum value within the parentheses; This indicates finding the minimum value within the parentheses; It is the phase of partial discharge in LP01 mode at time t; It is the partial discharge phase of LP01 mode at time t-1; The phase correlation coefficient is denoted by t; t represents the t-th sampling point. The total number of sampling points for multi-mode partial discharge; e is the natural base; The first-weighted correlation coefficient; The second-weighted correlation coefficient; The partial discharge weight of LP11a mode at time t is shown in the following formula: ； in, It is the phase of partial discharge in LP11a mode at time t; It is the partial discharge phase of LP11a mode at time t-1; The partial discharge weight of LP11b mode at time t is shown in the following formula: ； in, It is the partial discharge phase of LP11b mode at time t; It is the partial discharge phase of LP11b mode at time t-1; The partial discharge discrimination module inputs the final cable partial discharge detection data into the set partial discharge criteria to determine whether partial discharge has occurred at the current monitoring point.

2. The cable partial discharge detection system according to claim 1, characterized in that: In the multi-mode partial discharge detection module, the multi-mode includes the fundamental mode LP01 mode, the higher-order mode LP11a mode in the few-mode fiber, and the higher-order mode LP11b mode in the few-mode fiber.

3. The cable partial discharge detection system according to claim 1, characterized in that: The multi-mode partial discharge detection module includes a narrow-linewidth coherent laser (1); the output of the narrow-linewidth coherent laser (1) is connected to the input of a first optical coupler (2); the two outputs of the first optical coupler (2) are respectively connected to the first input of an acousto-optic modulator (4) and the input of a 1-to-3 coupler (13); the second input of the acousto-optic modulator (4) is connected to a waveform generator (3), and its output is connected to the input of an erbium-doped fiber amplifier (5); the output of the erbium-doped fiber amplifier (5) is connected to the input of an optical bandpass filter (6); the output of the optical bandpass filter (6) is connected to the input of a 1-to-3 coupler (7); the three outputs of the 1-to-3 coupler (7) are respectively connected to the first ends of a first fiber circulator (9), a second fiber circulator (10), and a third fiber circulator (11); the first fiber circulator (9), the second fiber circulator (10), and the third fiber circulator (11) are connected to the first ends of the first fiber circulator (9), the second fiber circulator (10), and the third fiber circulator (11). The second end of the circulator (11) is connected to the first, second and third ends of the photonic lantern (8); the fourth and fifth ends of the photonic lantern (8) are connected to the input and output ends of the few-mode fiber (12); the third end of the first fiber circulator (9) is connected to the second input end of the first balanced photodetector (14); the third end of the second fiber circulator (10) is connected to the second input end of the second balanced photodetector (15); the third end of the third fiber circulator (11) is connected to the second input end of the third balanced photodetector (16); the three output ends of the splitter (13) are connected to the first input ends of the balanced photodetector (14), balanced photodetector (15) and balanced photodetector (16); the output ends of the balanced photodetector (14), balanced photodetector (15) and balanced photodetector (16) are all connected to the data acquisition card (17).

4. The cable partial discharge detection system according to claim 3, characterized in that: The one-to-three coupler (7) divides the filtered pulse of the optical bandpass filter (6) into a first branch pulse, a second branch pulse and a third branch pulse, for a total of three branch pulses; the spatial modes of the three branch pulses are LP01 mode, LP11a mode and LP11b mode, respectively.

5. The cable partial discharge detection system according to claim 4, characterized in that: The first, second, and third ends of the photonic lantern (8) receive the first branch pulse, the second branch pulse, and the third branch pulse emitted by the second ends of the first fiber circulator (9), the second fiber circulator (10), and the third fiber circulator (11), respectively. The three modes corresponding to the branch pulses of the three modes are converted into multiple modes of the few-mode fiber, and the input end of the few-mode fiber is transmitted from the fourth end of the photonic lantern (8). The fifth end of the photonic lantern (8) receives the output signal of the few-mode fiber and converts the multiple modes of the few-mode fiber into a single mode of the three single-mode fibers, and outputs the three signals from the first end, the second end and the third end respectively.

6. The cable partial discharge detection system according to claim 5, characterized in that: The few-mode fiber (12) receives the output signal from the fourth end of the photonic lantern (8) to sense the partial discharge signal of the power cable at the winding position, and outputs the signal with the partial discharge detection information of the cable at the detected position to the fifth end of the photonic lantern (8).

7. A method for detecting partial discharge in a cable using the cable partial discharge detection system according to any one of claims 1-6, characterized in that, include: The few-mode optical fiber is wound onto the power cable to be tested according to the set number of turns; Multi-mode partial discharge detection of the cable is performed using a photonic lantern and a pre-set few-mode fiber to obtain multi-mode partial discharge detection values. The multi-mode partial discharge detection values ​​obtained by the multi-mode partial discharge detection module are weighted and fused to obtain the final cable partial discharge detection data. Input the final cable partial discharge detection data into the set partial discharge criterion to determine whether partial discharge has occurred at the current monitoring point.

8. An electronic device, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the cable partial discharge detection method according to claim 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the cable partial discharge detection method as described in claim 7.

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