交流高压输电线工频电磁场精确计算与特性分析

交流输电线产生的工频电磁场及其谐波成分一方面会对传统电磁法的观测信号造成极大干扰, 另一方面也可将其利用进行大地电性结构探测.电力行业以及传统地球物理领域在计算输电线工频电磁场时都存在诸多近似和假设, 计算精度较低.本文同时考虑输电线实际排列形式和大地电导率, 给出了输电线工频电磁场的准确计算方式, 并对其特性进行分析.结果表明, 实际输电线产生的电磁场与传统上基于单条无限长导线获得的结果并不一致, 各相线空间位置会导致叠加后的电磁场在多处存在变号现象, 使得电磁场随距离增大并不是光滑衰减, 且实际输电线产生的电磁场随距离增大整体上衰减的速度更快, 但在几千米范围内其强度仍不可忽略.本文提出的特定输电线系统产生的工频电磁场计算方法对规避或利用该电磁场都具有重要意义.

Accurate calculation and characteristic analysis of power frequency electromagnetic field generated by AC high voltage transmission line

The electromagnetic fields generated by transmission lines, an essential factor to be considered in the electromagnetic (EM) exploration, not only can be regarded as the noise but can be used as the useful signal in field measurements. Hence, to avoid its interference or to make full use of it, it's of great significance to rapidly and accurately estimate its intensity and further learn its spatial distribution characteristics. However, previous researches were mainly based on field observations or calculations with a series of assumptions and approximations, thus did not form a precisely quantitative assessment method. In the article, we realize the calculation of the power-line frequency EM fields of the transmission lines under the condition of considering the earth's resistivity and the actual arrangement of the transmission lines. And results show that the EM fields produced by the actual transmission lines are of great difference from those generated by the traditional infinite current lines. Its attenuation is more rapid with the increase of the observation distance, and sign reversals may occur in many observation points which would lead to the abrupt change of the fields.