An OPGW cable galloping monitoring noise reduction method based on matched grating sensing

Abstract

The application provides an OPGW cable galloping monitoring noise reduction method based on a matching grating sensor, comprising the following steps: using a matching grating array to perform distributed monitoring on a cable, and collecting a galloping signal on a monitoring line; selecting a sensing unit in the middle of a pair of gratings in the matching grating array as a reference sensor, using an interference demodulation algorithm to demodulate an optical phase change amount caused by environmental changes as an input end 1 of an adaptive noise cancellation algorithm; using the interference demodulation algorithm to demodulate an optical phase change amount caused by galloping as an input end 2 of the adaptive noise cancellation algorithm; and performing adaptive noise cancellation based on the input end 1 and the input end 2 signals through the adaptive noise cancellation algorithm. The application can obtain a sensing result with a better signal-to-noise ratio, improve the monitoring result, help to improve the technical progress of the optical fiber sensing technology in the power monitoring industry, and has important engineering value.

Description

Technical Field

[0001] This invention relates to the field of power systems, specifically to a method for noise reduction and monitoring of OPGW optical cable galloping based on matched grating sensing. Background Technology

[0002] Fiber optic sensing technology has developed rapidly in recent years, playing an increasingly important role in perimeter security, fire alarms, structural monitoring, and military applications. In the power industry, fiber optic composite overhead ground wires (OPGW) have also successfully incorporated fiber optic sensing technology for monitoring cable line conditions such as galloping, icing, and lightning strikes in complex environments. While fiber optic grating vibration and strain sensing technology has been successfully applied to OPGW line monitoring, the varying terrain and harsh external environments of OPGW lines often result in low signal-to-noise ratios in the monitoring systems. Summary of the Invention

[0003] The purpose of this invention is to provide a noise reduction method for OPGW optical cable galloping monitoring based on matched grating sensing. Applying this method to galloping monitoring yields sensing results with a better signal-to-noise ratio, improves monitoring results, and contributes to the technological advancement of optical fiber sensing technology in the power monitoring industry, thus having significant engineering value.

[0004] A noise reduction method for OPGW optical cable galloping monitoring based on matched grating sensing includes the following steps:

[0005] Distributed monitoring of optical cables is carried out using a matched grating array to collect galloping signals on the monitoring line. The matched grating array uses the optical fiber in the middle of the grating as the sensing unit.

[0006] In the matched grating array, a sensing unit between a pair of gratings is selected as a reference sensor. The amount of light phase change caused by environmental changes is demodulated using an interferometric demodulation algorithm. The amount of phase change of the reference sensor at this time is used as the input port 1 of the adaptive noise cancellation algorithm.

[0007] The other sensors in the matching grating array use an interferometric demodulation algorithm to demodulate the optical phase change caused by the dancing. The phase change of the other sensors is then used as the input port 2 of the adaptive noise cancellation algorithm.

[0008] Adaptive noise cancellation is performed based on the signals from input port 1 and input port 2 using an adaptive noise cancellation algorithm, wherein input port 1 is the reference input and input port 2 is the main input signal;

[0009] The adaptive noise cancellation algorithm continuously iterates and updates by setting weighting factors and filter order until the noise-reduced output signal is output.

[0010] Furthermore, the pulsed light emitted by the narrow linewidth laser passes through the first circulator and enters each grating of the matching grating array, where the grating spacing is L. After reflection by the gratings, it passes through the second circulator and coupler into the first and second Faraday rotators of different lengths. The difference in interferometer arm length is consistent with the grating spacing. The coupler, the first Faraday rotator, and the second Faraday rotator constitute an unbalanced interferometer. Adjacent light pulses achieve optical path matching through the unbalanced interferometer, thereby causing two-beam interference. At this time, each adjacent grating and the intermediate optical fiber constitute an FBG-FP cavity. By demodulating the vibration amplitude, the phase change of the reference sensor and the phase change of the monitoring sensor caused by the external environment are obtained. The phase change of the reference sensor is used as the reference input port of the adaptive noise cancellation algorithm, i.e., the input port 1, and the phase change of the monitoring sensor is used as the main signal input port, i.e., the input port 2.

[0011] Furthermore, the reference sensor consists of a set of FBG-FP cavities and is located at the front end of the monitoring array.

[0012] Furthermore, adaptive noise cancellation is performed based on the signals from input port 1 and input port 2 using an adaptive noise cancellation algorithm, specifically including:

[0013] The noisy useful signal demodulated by the sensing part is taken as the overall input port 2, denoted as x(n), and the noise signal demodulated by the reference part is taken as the system noise input port 1, denoted as y(n). The specific expression is as follows:

[0014]

[0015] In the formula: x(n) is the signal of the sensing part; noise(n) is the noise contained within the sensing part; s(n) is the useful signal of the sensing part; y(n) is the signal of the reference part; noise c z(n) represents the noise contained within the reference section; z(n) represents the error signal; p(n) represents the filter output signal; w i (n) is the i-th value in the filter weight coefficient vector; y(n-1) is the i-th sample value of y(n) before time n.

[0016] This invention utilizes a coherent detection method in a sensing system to demodulate phase difference; it selects sensor phase differences at each transmission tower node to extract reference signals; the reference signal phase difference serves as one input, and the original signal phase difference from the sensor array serves as another input, both being fed into an adaptive noise canceller to achieve adaptive noise cancellation in the galloping monitoring system; finally, it outputs high signal-to-noise ratio galloping monitoring results, achieving better signal-to-noise ratio sensing results compared to existing technologies, improving monitoring results, and contributing to the technological advancement of fiber optic sensing technology in the power monitoring industry, thus possessing significant engineering value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the OPGW optical cable galloping monitoring and noise reduction system based on matched grating sensing of the present invention;

[0018] Figure 2 This is a comparison of the time-domain results of adaptive filtering based on the reference sensor;

[0019] Figure 3 This is a comparison of adaptive filtering frequency domain results based on a reference sensor. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a method for noise reduction and monitoring of OPGW optical cable galloping based on matched grating sensing, comprising the following steps:

[0022] Distributed monitoring of optical cables is carried out using a matched grating array to collect galloping signals on the monitoring line. Since the interferometry principle is matched interference, the grating unit does not generate a sensor. Instead, the optical fiber in the middle of the grating is used as the sensing unit. The sensing spacing is variable and the sensing sensitivity is adjustable, which is more suitable for the monitoring requirements of OPGW optical cables.

[0023] In the matched grating array, a sensing unit between a pair of gratings is selected as a reference sensor. The amount of light phase change caused by environmental changes is demodulated using an interferometric demodulation algorithm. The amount of phase change of the reference sensor at this time is used as the input port 1 of the adaptive noise cancellation algorithm.

[0024] The other sensors in the matching grating array use an interferometric demodulation algorithm to demodulate the optical phase change caused by the dancing. The phase change of the other sensors is then used as the input port 2 of the adaptive noise cancellation algorithm.

[0025] Adaptive noise cancellation is performed based on the signals from input port 1 and input port 2 using an adaptive noise cancellation algorithm, wherein input port 1 is the reference input and input port 2 is the main input signal;

[0026] The adaptive noise cancellation algorithm continuously updates the weighting factor and filter order until the noise-reduced output signal is output.

[0027] OPGW fiber optic sensing galloping monitoring system with noise suppression based on reference sensors, such as Figure 1 As shown, pulsed light emitted from a narrow-linewidth laser (Laser) enters the various gratings (FBGs) of the OPGW line through a circulator (CIR1), where the grating spacing is L. After reflection from the gratings, the light passes through circulator 2 (CIR2) and couplers to Faraday rotator mirrors 1 (FRM1) and 2 (FRM2) of different lengths. The difference in interferometer arm length is consistent with the grating spacing. The couplers, Faraday rotator mirrors 1 (FRM1) and 2 (FRM2) constitute an unbalanced interferometer. Adjacent light pulses achieve optical path matching through the unbalanced interferometer, resulting in two-beam interference. At this point, each adjacent grating and the intermediate fiber form an FBG-FP cavity. By demodulating the vibration amplitude, the phase change of the reference sensor and the phase change of the monitoring sensor caused by the external environment are obtained. The phase change of the reference sensor is used as the reference input of the adaptive noise cancellation algorithm, and the phase change of the monitoring sensor is used as the main signal input. By setting the weighting factor and the filter order, the output signal is continuously referenced to the noise results contained in the input, and finally the adaptive noise cancellation of the monitoring signal is realized, and the noise-reduced monitoring signal is obtained. Then, the optical cable galloping characteristics are further inverted with high precision.

[0028] In the OPGW optical cable adaptive noise reduction system based on matched grating interferometry, the reference sensor consists of a set of FBG-FP cavities located at the front end of the monitoring array. The interference signal coupled to the environment mainly consists of two parts: the signal coupled to the sensor interference; and other similar link noise, with the matched interferometer as the main noise source. Combining the unique dual-beam common-path structure of the FBG-FP interferometer, since all array sensors share a reference interferometer and other links, the noise signal characteristics coupled through the interferometer are theoretically completely identical. The reference section can then form the input terminal for the adaptive noise suppression signal.

[0029] The vibration monitoring and noise reduction system primarily relies on an adaptive noise cancellation algorithm to achieve low signal-to-noise ratio signal output. Unlike fixed-parameter digital filters, adaptive filters adjust filter parameters through different adaptive algorithms to achieve digital filtering. By adjusting the step size, they iteratively update to obtain the desired denoised signal. For the OPGW optical cable vibration monitoring system, the adaptive noise suppression system uses the noisy useful signal demodulated by the sensing part as the overall input port 2, denoted as x(n), and the noise signal demodulated by the reference part as the system noise input port 1, denoted as y(n). The specific expression is as follows:

[0030]

[0031] In the formula: x(n) is the signal of the sensing part; noise(n) is the noise contained within the sensing part; s(n) is the useful signal of the sensing part; y(n) is the signal of the reference part; noise c z(n) represents the noise contained within the reference section; z(n) represents the error signal; p(n) represents the filter output signal; w i (n) represents the i-th value in the filter weight coefficient vector; y(n-1) represents the i-th sampled value of y(n) before time n. Due to the difference between the noise (n) in the sensing part and the noise in the reference part of the system... c (n) has a strong correlation. After the adaptive algorithm is processed, the filter output signal p(n) will continuously approach the real noise (n), so that the output error signal z(n) will be iteratively calculated to approach the desired output.

[0032] To reduce computational load, the fastest descent iterative algorithm is used to update the adaptive filter weight coefficients. This is adjusted using the negative slope value of the mean square error, resulting in:

[0033]

[0034] The least squares estimate is calculated using stochastic gradient descent. By estimating the value of E[z(n)×(n)] in the above equation using the instantaneous value of the error signal z(n)×(n), the iterative calculation formula for the adaptive filter weight coefficients can be obtained.

[0035] W(n+1)=W(n)+2uz(n)×(n) (3)

[0036] In the formula: W(n+1) and W(n) are the n+1 and n-order weight coefficient vectors of the filter, and n is the filter order; u is the iteration step size, which must be greater than 0. The smaller the step size, the less distortion of the front-end time-domain signal; the larger the step size, the smoother the filtering, but it is also more prone to distortion. After adaptive noise processing, the common noise of the signal can theoretically be eliminated, the phase difference caused by line galloping can be obtained, and finally a low-noise OPGW optical cable galloping monitoring signal is output.

[0037] from Figure 2 The mid-time domain monitoring results show that the sensor detected periodic vibration signals, indicating slight low-frequency galloping of the line. The signal-to-noise ratio of the time-domain signal waveform was significantly suppressed after data processing. It is worth noting that at the beginning of monitoring, due to system instability or other interference, sudden changes in local data may produce erroneous results. However, our proposed algorithm based on the reference sensor can reasonably handle these sudden changes while reducing noise, resulting in more stable output results.

[0038] like Figure 3Comparing the frequency domain results of adaptive filtering based on the reference sensor, the dominant dancing frequency is approximately 1.2Hz. Although the overall signal-to-noise ratio in the time domain is not high due to significant noise, the signal quality is still noticeably improved, with clear time-domain characteristics. Figure 3 The comparison shows the frequency domain results of adaptive filtering based on the reference sensor. It can be observed that while the dancing signal is output without distortion, noise in the high-frequency portion of the signal is significantly suppressed, with a noticeable noise reduction effect above 10Hz. The signal-to-noise ratio is improved by approximately 5dB, representing a significant technological advancement compared to existing OPGW optical cable monitoring systems without noise processing.

[0039] This invention relates to an OPGW (Optical Power Wire) cable galloping monitoring system based on a grating sensor array. Adjacent gratings are combined with an unbalanced interferometer to achieve matched interference. The phase difference is demodulated using a coherent detection method of the sensor system. The phase difference of the sensor is selected at each transmission tower node to extract the reference signal. The reference signal phase difference is used as one input, and the original signal phase difference of the sensor array is used as another input. Both are input to an adaptive noise canceller to achieve adaptive noise cancellation of the galloping monitoring system. Finally, a high signal-to-noise ratio galloping monitoring result is output. Compared with existing technologies, this system achieves a better signal-to-noise ratio, improves monitoring results, and contributes to the technological advancement of fiber optic sensing technology in the power monitoring industry, thus possessing significant engineering value.

[0040] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for noise reduction and monitoring of OPGW optical cable galloping based on matched grating sensing, characterized in that, Includes the following steps: Distributed monitoring of optical cables is carried out using a matched grating array to collect galloping signals on the monitoring line. The matched grating array uses the optical fiber in the middle of the grating as the sensing unit. In the matched grating array, a sensing unit between a pair of gratings is selected as a reference sensor. The amount of light phase change caused by environmental changes is demodulated using an interferometric demodulation algorithm. The amount of phase change of the reference sensor at this time is used as the input port 1 of the adaptive noise cancellation algorithm. The other sensors in the matching grating array use an interferometric demodulation algorithm to demodulate the optical phase change caused by the dancing. The phase change of the other sensors is then used as the input port 2 of the adaptive noise cancellation algorithm. Adaptive noise cancellation is performed based on the signals from input port 1 and input port 2 using an adaptive noise cancellation algorithm, wherein input port 1 is the reference input and input port 2 is the main input signal; The adaptive noise cancellation algorithm continuously iterates and updates the weighting factor and filter order until the noise-reduced output signal is output. The pulsed light emitted by the narrow linewidth laser enters each grating of the matching grating array through the first circulator. The grating spacing is L. After reflection by the gratings, the light passes through the second circulator and coupler to the first and second Faraday rotators of different lengths. The difference in interferometer arm length is consistent with the grating spacing. The coupler, the first Faraday rotator, and the second Faraday rotator constitute an unbalanced interferometer. Adjacent light pulses achieve optical path matching through the unbalanced interferometer, resulting in two-beam interference. At this time, each adjacent grating and the intermediate fiber constitute an FBG-FP cavity. By demodulating the vibration amplitude, the phase change of the reference sensor and the phase change of the monitoring sensor caused by the external environment are obtained. The phase change of the reference sensor is used as the reference input port of the adaptive noise cancellation algorithm, i.e., input port 1, and the phase change of the monitoring sensor is used as the main signal input port, i.e., input port 2.

2. The method for noise reduction and monitoring of OPGW optical cable galloping based on matched grating sensing as described in claim 1, characterized in that: The reference sensor consists of a set of FBG-FP cavities and is located at the front end of the monitoring array.

3. The method for noise reduction and monitoring of OPGW optical cable galloping based on matched grating sensing as described in claim 1, characterized in that: Adaptive noise cancellation is performed based on the signals from input port 1 and input port 2 using an adaptive noise cancellation algorithm, specifically including: The noisy useful signal demodulated by the sensing part is taken as the overall input port 2, denoted as x(n), and the noise signal demodulated by the reference part is taken as the system noise input port 1, denoted as y(n). The specific expression is as follows: (1)； where x(n) is the sensor portion signal; noise(n) is the noise contained in the sensor portion; s(n) is the useful signal of the sensor portion; y(n) is the reference portion signal; noiseC(n) is the noise contained in the reference portion; z(n) is the error signal; p(n) is the filter output signal; w i (n) is the i-th value in the filter weight vector; y(n-1) is the value of the i-th sampling point of y(n) before the n time.

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