Fault Locating And Analysis Of Power Overhead Cable Based On Brillouin Optical Fiber Sensing

Brillouin optical fiber sensing technology has many advantages such as distributed,long distance,anti-electromagnetic interference,high pressure resistance,and fiber core measurement without additional sensors.It has important application value in the field of structural health monitoring of large-scale infrastructure constructions such as power systems,bridges,integrated pipeline corridors,and petroleum pipelines.In view of the technical bottlenecks and limitations in the maintenance process of overhead power cable,this paper combines theory with practice and puts forward fault locating and analysis of overhead power optical cable based on Brillouin optical fiber sensing.This paper studies the Brillouin optical timedomain reflectometer（BOTDR）technology using single-ended measurement and the Brillouin optical fiber time-domain analysis（BOTDA）adopting loop measurement,and applies them to the fault detection and location of optical fiber composite overhead ground wire（OPGW）and carbon fiber composite core（ACCC）respectively,aiming to realize power overhead wire and optical cable identify the fault point and locate it quickly and accurately.It is of great significance for improving the fault monitoring capability of the power communication network,ensuring the efficiency of operation and maintenance,and the stable and safe operation of the power system.The specific research content is as follows:Firstly,the principle of time-domain Brillouin optical fiber sensing is systematically explained,and the differential pulse pair technology to improve the spatial resolution of BOTDA and the principle of Raman amplification to increase the measurement distance are introduced.Secondly,the long-distance BOTDR system is used to collect the Brillouin frequency shift data of multiple optical fibers in the OPGW cable in operation.According to the different characteristics of Brillouin frequency shift at different locations,the physical positioning of all 25 connecting towers between two communication stations was successfully achieved,and the positioning accuracy was100%.On this basis,the identification and location analysis of fault points such as broken fiber,abnormal loss points and abnormal strains are further realized,which provides a guarantee for the safe and stable operation of OPGW optical cable.At last,in view of the limitations of the current ACCC nondestructive testing methods,the high-spatial-resolution BOTDA technique was proposed to detect the defects of ACCC optical cables,and the indoor simulation and outdoor distributed strain measurement experiments were carried out respectively.The experimental results show that at a spatial resolution of 5 cm,four defects were identified in the indoor simulation experiment,and two defects were identified in the outdoor wirehanging experiment.In the outdoor wire-hanging experiment,when the tensile force was increased from 1.5T to 3T,the strain difference between the two identified defects increased from 74.8με to 114.4με,and from 135.6με to 251.8με,which verified the principle based on stress concentration.The feasibility of using high-spatial-resolution BOTDA to detect defects in ACCC optical cables based on the principle of stress concentration is verified,which provides a new technical scheme for effective detection of ACCC defects.