基于斜坡法的智能化架空线路应变快速感知

A fast strain sensing for intelligent overhead line based on slope-assisted technique

为了提高输电线路状态感知实时性,将单斜坡法和基于伪Voigt模型的最小二乘谱拟合法用于架空线路复合光纤应变的测量,基于实测布里渊谱系统,研究了工作点增益的信噪比和布里渊频移对单斜坡法准确性的影响。结果表明,随着工作点增益信噪比增加,布里渊频移误差近似成指数规律减小;随着布里渊频移与工作点频率之差的增加,布里渊频移误差先快速下降,然后略有增加;当工作点处布里渊增益的信噪比不小于25 dB且工作点频率始终小于(或大于)布里渊频移时,单斜坡法应变误差小于60με;根据不同布里渊频移下60με对应的临界信噪比,可插值获得不同情况下对应的临界信噪比;单斜坡法的谱测量时间和计算时间分别为谱拟合法的1/161和1/600左右。该工作为提高智能化光纤复合架空线路态势感知实时性奠定了基础。

In order to improve the real-time performance of state sensing, the slope-assisted techniqueand the least-squares spectrum fit method based on the pseudo-Voigt model were introduced into the strain measurement of optical fiber composite overhead lines. The programs about the least squares spectrum fitting method and the slope-assisted technique based on the pseudo-Voigt model were written and applied to the strain measurement along an optical fiber composite overhead line. Based on the measured Brillouin spectra, the influence of the signal-to-noise ratio(SNR) of the working point gain and the Brillouin frequency shift(BFS) on the accuracy of the slope-assisted technique was systematically investigated. The results reveal that the BFS error decreases exponentially with SNR. The BFS error decreases rapidly and then increases slightly with the difference between BFS and working point frequency. The strain error of the slope-assisted technique is less than 60 με when the SNR of Brillouin gain at the working point is not less than 25 dB and at the same time, the frequency at the working point is always less or larger than the BFS. In addition, the corresponding critical SNR of 60 με is presented for different BFSs, and the critical SNR corresponding to different cases can be obtained by interpolation. The measurement time and computation time of the slope-assisted technique are about 1/161 and 1/600 of that of the spectrum fitting method, respectively. The work provides a reference for improving the real-time performance of sate sensing of intelligent optical fiber composite overhead lines.