温度梯度场下同轴电缆中空间电荷测量波形的算法矫正

Correction of Algorithm for Coaxial Cable’s Space Charge Under Temperature Gradient

直流电场下电缆绝缘中的空间电荷积聚效应导致绝缘内电场严重畸变,直接影响电缆长期运行可靠性,因此对全尺寸长电缆空间电荷特性的实时测量显得尤为重要。然而,由于高压直流电缆运行时,内导体的发热会导致电缆绝缘中温度梯度效应,电缆绝缘材料密度变得不均匀。此外,电缆的同轴结构也会导致测量波形畸变。该文首先设计了一种改进的脉冲注入方式和波形信号检出的温度梯度下同轴电缆空间电荷测量装置;然后针对同轴电缆下电场分布的不均匀性和声波传播的发散性,对测量电荷波形进行了恢复;最后通过在声波传递方程虚部中引入二次项近似的方法,有效实现对声波衰减和时域平移现象的矫正。利用此算法,成功实现了温度梯度下同轴电缆的空间电荷测量波形的矫正。

The accumulation of space charge in coaxial cable under high voltage direct current（HVDC） may lead to the internal electrical field serious distortion,and thus extremely influence the long-term reliability of cable in service.Therefore,it is significant to measure the space charge characteristic in full size power cable real-timely.However,as the existence of temperature gradient across cable insulation under DC electrical stress,the density of dielectric will be inhomogeneous.Moreover,the influence of coaxial structure on the distortion of measuring waveforms has to be taken into consideration.An improved PEA system suited for full size power cable under temperature gradient was fulfilled through designing the units of pulse injection and signal detection.Then the charge density was corrected according to the non-uniform electric stress distribution and the divergent acoustic propagation.At last,the system transfer function was amended by adding the dispersion coefficient＇s quadratic approximation to the general solution of general wave propagation equation.With this new recovery algorithm,the distortion of the waveform can be recovered successfully.