面向电力管廊外破监测的分布式光纤传感技术研究

Research on distributed optical fiber sensing technology for power pipe corridor breakdown monitoring

电力管廊是城市里重要的基础设施,对其结构和状态进行监测及评估备受关注。本文针对电力管廊外力破坏监测的问题,提出一种基于衰减补偿的光时域差分曲线方差阈值定位振动事件的方案,并通过实验论证了其定位外破事件的准确性。该方案基于相敏型光时域反射系统架构,根据管廊外破事件引起的光纤振动导致光时域反射曲线在该事件位置处混乱度急剧增加的现象,对不同测量序列得到的光时域反射曲线作差,然后对光纤各位置对应的差值向量数据求方差,设定方差阈值定位外破事件。同时,考虑到光纤衰减导致方差阈值随距离增加而降低的问题,采用衰减补偿算法使光纤上任意散射位置对应相同的脉冲功率水平,从而修正光纤衰减对方差阈值的影响。实验搭建了分布式光纤振动传感系统,采用脉宽为30 ns、峰值功率为30 dBm的光脉冲,在约25 km的光纤范围,获得±3 m的定位精度。电力管廊外力破坏事件,具有低频、大扰动、持续长的特点,所提出系统方案通过曲线平均抑制瑞利散射衰落噪声,结合光纤衰减补偿校正散射信号幅值,从而将振动事件引起的光信号相位变化作为探测曲线波动的主导因素,以确保对外力破坏事件不漏报、不误报。

The power pipe corridor is an important infrastructure in the city,and the monitoring and evaluation of its structure and state have attracted much attention.Aiming at the problem of external failure monitoring of power pipe corridor,this paper proposed a scheme for locating vibration events based on attenuation compensation and variance threshold of optical difference time domain curve,and proved its accuracy by experiments.This scheme was based on the phase-sensitive optical time domain reflectometry system architecture.According to the phenomenon that the optical fiber vibration caused by the broken event outside the pipe corridor leaded to a sharp increase in the confusion of the optical time domain reflectometry curve at the location of the event,the optical time domain reflectometry curve obtained from different measurement sequences was differentiated,and then the difference vector data corresponding to each position of the optical fiber was evaluated and the variance threshold was set to locate the broken event.At the same time,considering the problem that the variance threshold decreased with the increase of distance due to fiber attenuation,the attenuation compensation algorithm was used to make any scattering position on the fiber correspond to the same pulse power level,so as to correct the influence of fiber attenuation on the difference threshold.A distributed fiber-optic vibration sensing system was set up in the experiment.Optical pulses with a pulse width of 30 ns and a peak power of 30 dBm were used to obtain a positioning accuracy of±3 m in the optical fiber range of about 25 km.The external force damage event of the power pipeline gallery has the characteristics of low frequency,strong disturbance,and long duration.The proposed system scheme suppresses Rayleigh scattering fading noise through trace averaging,and combines fiber optic attenuation compensation to correct the amplitude of the scattering signal.Therefore,the phase change of the optical signal caused by vibration events is the dominant factor in trace fluctuations to ensure that external force damage events are not missed or misreported.