CN-116465314-B - Method and device for monitoring ice coating of optical cable

CN116465314BCN 116465314 BCN116465314 BCN 116465314BCN-116465314-B

Abstract

The invention relates to the field of optical fiber sensing, in particular to a method and a device for monitoring ice coating of an optical cable. The method mainly comprises the steps of obtaining a first sensing data sequence in each sensing period, obtaining a phase data sequence in each period according to the first sensing data sequence, obtaining spectrum data corresponding to position phase change according to the phase data sequence, obtaining characteristic frequency according to the average value of the spectrum data in a plurality of sensing periods, and estimating the icing thickness of the optical cable according to the change of the characteristic frequency. The invention reduces interference fading of signals and random noise of environment, improves single-span distance of icing monitoring, and can improve icing monitoring precision.

Inventors

XIA XIAOMENG
DENG LI
BAI FUWEN
JIN WEI
LI YANG
CHEN FANG
SUN YUXIAO
WU GUANGZHE
DING JIAN
GUO YU
WANG TIANTIAN
CHEN TONG
LI FENG
QIN HAOTING
JIN JUAN
YUAN FANG
LIU YING
WU CHONG
BAI ZHIDAN
YANG YUE
WANG YING
DONG YONGKANG
LI SHUCHEN
DENG YUE
LI CAN
LI BOZHONG

Assignees

国家电网有限公司信息通信分公司
哈尔滨工业大学
电力规划总院有限公司
中国电力工程顾问集团西南电力设计院有限公司

Dates

Publication Date: 20260508
Application Date: 20230301

Claims (8)

1. The method for monitoring the ice coating of the optical cable is characterized by comprising the following steps of: The method comprises the steps of obtaining a first sensing data sequence in each sensing period, obtaining a phase data sequence in each period according to the first sensing data sequence, specifically, obtaining the first sensing data sequence in each sensing period, generating a circularly encoded detection light signal and a local oscillation light signal, receiving a backward Rayleigh scattering light signal corresponding to the detection light signal, collecting a beat signal between the local oscillation light signal and the backward Rayleigh scattering light signal, and demodulating the first sensing data sequence according to the beat signal, wherein the phase data sequence in each period is obtained according to the first sensing data sequence, specifically, the method comprises the steps of performing cyclic shift on the first sensing data sequence in each period for at least 3 times to obtain a corresponding number of compensation data sequences, combining the plurality of compensation data sequences in each period and the first sensing data sequence into a second sensing data sequence in the period through vector summation, and the vector summation method specifically comprises the steps of: ; Wherein, the For the vector sum at time t in the sampling period, Calculating the phase of each second sensing data in each period of the second sensing data sequence through arctangent, and taking the phases of all time points in each period as the phase data sequence of the period; and acquiring frequency spectrum data corresponding to the position phase change according to the phase data sequence, obtaining characteristic frequency according to the average value of the frequency spectrum data in the sensing periods, and estimating the icing thickness of the optical cable according to the change of the characteristic frequency.
2. The method for monitoring ice on an optical cable according to claim 1, wherein the generating the cyclically encoded probe optical signal and the local oscillator optical signal specifically comprises: Generating a cyclic code which changes periodically, wherein the change period is consistent with the sensing period, and the value of the cyclic code is between 1 and-1.
3. The method for monitoring ice on a fiber optic cable according to claim 2, wherein the demodulating the first sensing data sequence from the beat signal comprises: and performing correlation operation on the beat signal and the cyclic code at each time point, taking the result of the correlation operation as the sensing data of the time point, and taking a sensing data aggregate set at all time points as a first sensing data sequence of the period.
4. The method for monitoring ice-over-fiber optic cable according to claim 1, wherein the cyclic shift is performed at least 3 times on the first sensing data sequence of each period to obtain a corresponding number of compensating data sequences, specifically comprising: And when each time of cyclic displacement is carried out, on the basis of the previous cyclic displacement, circularly moving all the sensing data in the first sensing data sequence to a specified direction by a specified offset, and taking the data sequence obtained after each time of cyclic displacement as a compensation data sequence.
5. The method for monitoring ice coating on a fiber optic cable according to claim 1, wherein the combining the plurality of compensation data sequences and the first sensing data sequence for each period into the second sensing data sequence for the period by vector summation specifically comprises: and vector summation is carried out on the compensation data corresponding to the same time point in all the compensation data sequences and the sensing data corresponding to the same time point in the first sensing data sequence in each period to obtain second sensing data corresponding to each time point, and the second sensing data set of all the time points is used as a second sensing data sequence.
6. The method for monitoring ice coating on a fiber optic cable according to claim 1, wherein the calculating the phase of each second sensing data in each second sensing data sequence by arctangent comprises: The ratio of the real part and the imaginary part of each second sensing data is made to be an arctangent, and the value of the arctangent is taken as the phase of the second sensing data.
7. The method for monitoring ice coating on an optical cable according to claim 1, wherein the obtaining the characteristic frequency according to the average value of the spectrum data in the plurality of sensing periods specifically comprises: The spectrum data at all time points in all the phase data sequences are averaged, and the characteristic frequency is obtained from the average value of the spectrum data.
8. The device for monitoring the ice coating of the optical cable is characterized by comprising a laser, a polarization maintaining coupler, a code generator, an electro-optical modulator, an erbium-doped optical fiber amplifier, a filter, a circulator, a sensing optical fiber, an integrated coherent receiver, an acquisition card and a processor, and specifically comprises: The optical cable icing monitoring device comprises a laser, an electro-optical modulator, a code generator, an erbium-doped amplifier, a filter, a circulator, a3 rd port and a coherent receiver, wherein the laser is connected with the polarization-maintaining coupler, the polarization-maintaining coupler is connected with the electro-optical modulator, the polarization-maintaining optical coupler is connected with the coherent receiver through polarization-maintaining optical fibers, the code generator is connected with the electro-optical modulator through cables, the electro-optical modulator is connected with the erbium-doped amplifier, the erbium-doped amplifier is connected with the filter, the filter is connected with the circulator, the circulator is connected with the 3 rd port and the coherent receiver through single-mode optical fibers, the polarization-maintaining optical fiber coupler is used for generating sensing light and local oscillation light, the electro-optical modulator generates a specified cyclic code pulse optical signal under the modulation of the code generator, and the processor monitors the optical cable icing according to the method of any one of claims 1-7.

Description

Method and device for monitoring ice coating of optical cable Technical Field The invention relates to the field of optical fiber sensing, in particular to a method and a device for monitoring ice coating of an optical cable. Background An optical fiber composite overhead ground wire (Optical Fiber Composite Overhead Ground Wire, abbreviated as OPGW) optical cable, the optical fiber of which is placed in the ground wire of overhead high-voltage transmission line, is used for forming an optical fiber communication network of the transmission line, and provides communication channels for protecting, dispatching telephone, administrative communication, office automation, dispatching automation and the like for the power network. The OPGW optical cable is positioned at the uppermost end of the power line, and is not convenient to carry out inspection, maintenance and overhaul of the OPGW optical cable due to the fact that the position specificity is affected by factors such as line power failure and safety. Therefore, how to make OPGW optical cable maintenance, inspection and detection, make OPGW optical cable fault prevention in advance, discover OPGW optical cable faults in time, promote safe and reliable operation of a communication network, provide more powerful communication guarantee support for safe, reliable and stable operation of the power network, and have great significance. The reasons for the faults of the OPGW optical cable mainly include damage such as icing, lightning strike, tower falling, wind dance, discharge, gunshot, explosion, theft and the like. Wherein, ice coating formed around OPGW cable due to freezing rain, rime, snow and the like and galloping phenomenon caused by the ice coating are most common and most harmful. Therefore, the icing detection is carried out on the bookstore line, and even if fault hidden dangers are found and processed, the requirement of ensuring safe and stable operation of the power grid is urgent. The traditional electronic icing detection technologies such as a weighing method based on a tension sensor and an image monitoring method based on a camera have the defects of difficult power supply networking, poor electromagnetic interference resistance, weak environmental adaptability, high cost, difficult high-density deployment and the like. In recent years, part of OPGW optical cables are provided with full-distributed optical fiber sensors to realize on-line monitoring of the optical cables, and the full-distributed optical fiber sensor adopts the whole optical fiber as a sensing element and a signal transmission medium of external parameters, and has the advantages of high sensitivity, strong electromagnetic interference resistance, no blind area in continuous measurement and multiple measurable parameters. Especially, the sensing optical fiber can multiplex idle fiber core resources in the OPGW optical cable, and the defect of the traditional icing detection technology is overcome. However, the distributed Optical fiber vibration sensor represented by phase-sensitive Optical Time-domain reflectometry (PHASE SENSITIVE Optical Time-Domain Reflectometry, abbreviated as phi-OTDR) can only detect the galloping phenomenon, and cannot judge whether or not ice is covered or not. On the other hand, the traditional phi-OTDR sensing system has inherent phase fading. The phi-OTDR coherent detection distributed optical fiber sensing system using the single-mode optical fiber as a sensing medium can improve the physical quantity measurement precision of phase demodulation to a certain extent, but the signal to noise ratio of the system is still limited due to the inherent low backward Rayleigh scattering coefficient and the problem of signal attenuation, and the system is difficult to adapt to long-distance phi-OTDR sensing, and has a larger difference in performance compared with the traditional discrete optical fiber sensor based on reflection points. The laying distance of the OPGW optical cable often exceeds 50 km, the phase of the traditional single-mode optical fiber signal at the fading position is difficult to demodulate correctly, and the reliability of the phi-OTDR distributed optical fiber sensing system is also affected. Therefore, how to improve the signal-to-noise ratio of the sensing signal of the phi-OTDR distributed optical fiber sensing system during ice coating thickness estimation, so as to improve the accuracy of the phi-OTDR distributed optical fiber sensing system during ice coating estimation, is a technical problem which needs to be solved in the field. Disclosure of Invention Aiming at the defects or improvement demands of the prior art, the invention solves the problem that the existing distributed optical fiber vibration sensor cannot calculate the icing thickness. The embodiment of the invention adopts the following technical scheme: The invention provides a method for monitoring ice coating of an optical cable, which comprises the steps of o