中国空间电力线谐波辐射现象关键问题研究

The power line harmonic radiation (PLHR) events in the near-Earth space above China were increased year by year. Their frequency coverage has already far exceeded the range studied by foreign scholars. The most special finding was that PLHR could be detected continuously above several specific regions of China. As a widely recognized man-made pollutant to the near-Earth space environment, PLHR’s formation mechanism, correlation with power system on the ground and impacts on the space lack systematic and thorough investigation in recent years. Based on PLHR events detected from both satellite and ground observations this project will study the relationship between PLHR and harmonic radiators in power system by on-site investigation, experiments and testing. The project will verify the propagation altitude of PLHR and its real impacts on the earth radiation belt and ionosphere by analyzing the observation data of the quasi-synchronized satellite with the sun and the earth equatorial plane satellite together. The 3-D model of electromagnetic wave produced by harmonic currents through overhead transmission lines and propagating in the earth, atmosphere and anisotropic ionosphere and its solution will be studied. Also the possibilities of PLHR and PLHR-triggered emissions caused by nonlinear effects of ionosphere will be discussed theoretically. This project has characteristics of multidisciplinary crossing and synthesis and will further promote the solving of issues related to PLHR. The project is of great value in understanding the various kinetic processes and special electromagnetic effects in the ionosphere and magnetosphere.

我国近地空间电力线谐波辐射(PLHR)事件逐年增多，其频率覆盖范围已远超国外所讨论的范围。最特别的是，在我国某些地方上空可持续探测到这种现象。作为已被国外认可的近地空间环境人为污染源，这种现象的形成机理、与地面电力系统的关联以及对空间环境的影响，近年缺少系统而深入的论证。本项目拟结合卫星探测实例与地基探测实例，通过实地调研和实验测试的方法，研究PLHR与地面电力系统谐波辐射源之间的关系；联合太阳准同步卫星与地球赤道平面卫星探测数据，论证PLHR传播的高度，以及对地球辐射带及电离层的影响；研究地面架空线中的谐波电流在地球、大气层、各向异性电离层构成的空间中的三维传播模型及其解；从理论上探讨PLHR由电离层非线性效应导致的可能性及其触发其他辐射的可能性。本项目具有多学科交叉和综合研究的特点，将进一步推动与PLHR有关问题的解决，对于认识电离层和磁层中的动力学过程以及特殊的电磁效应具有重要价值。

卫星观测结果表明近地空间存在电网工频及其谐波辐射，并且在电力消耗较强的地区上空，这些辐射更容易被观测到。然而，目前这种辐射的形成机理及对近地空间的电磁效应仍不确知。本项目的主要研究内容及重要结果有：(1)研究了准太阳同步卫星飞过我国上空时探测到的电网谐波辐射现象，结果表明我国上空的谐波辐射比国外已报道的更加复杂，存在8~10kHz范围内的高频谐波辐射，与12脉换流器特征谐波频率一致的辐射，与地磁感应电流相关的零序谐波辐射，以及工频与甚低频发射站频率交叉调制的辐射等，并且穿过这些辐射的地磁场线与北半球地表面的交点多位于超高压/特高压输变电站工程的首端。(2)研制了20Hz~150kHz频带内噪声水平低于10pT/Hz^0.5的三维弱磁场测量系统，对我国多个超高压/特高压交直流输变电工程的磁场辐射进行了测量，结果表明在变电站附近确存在(3~5)kHz、(8~9)kHz范围内较强的稳态谐波辐射，具体成因尚不明确。(3)研究了电网谐波辐射在近地空间产生的电磁效应，结果表明电网谐波辐射可以在南北磁共轭空间来回传播，在传播中强度并无太大衰减，并且与辐射波发生波粒共振的高能电子存在沉降的可能，最为重要的是在地磁平静期发现的电网谐波辐射事件多与电离层局部等离子体电子密度的梯度变化有关。(4)研究了地面电网谐波辐射在各向异性电离层中的传播特征，利用时域有限差分方法研究了电磁波在地球、中性层、各向异性电离层中传播的二维模型和三维模型求解程序，它们在一定程度上可解释卫星探测到的谐波辐射现象特征。(5)基于卫星探测及电离层非线性理论，探讨了近地空间电网谐波辐射由电离层非线性效应导致的可能性，特别是分析了我国上空由电离层非线性效应导致的磁层线辐射与电网谐波辐射的区别，结果表明前者更像是一种自然辐射。本项目提供了一种新的角度来认识电网电磁辐射问题，对于完善电网电磁环境评估体系，认识电离层-磁层的能量交换过程，拓宽电网在极低频和甚低频领域的潜在应用价值等具有重要意义。