基于不同大地模型的接地极入地电流分布规律研究

Research on Distribution of Grounding Current Based on Different Earth Models

大地电性结构是否反映真实的地下各种介质的分布情况决定了特高压直流输电(Ultra-high Voltage Direct Current,UHVDC)接地极近区交流厂站变压器中性点电位计算的准确程度。研究分层大地电性结构模型、大地电磁测深(Magnetotelluric Sounding,MT)剖面延拓模型和三维Kriging大地电性结构模型对计算地电位、直流电流透入深度以及直流电流在大地中的分布规律的影响。结果表明,对于不同的大地电性结构模型都会有3%左右的入地电流进入地下300 km的深层大地;比较三种模型计算得到的直流偏磁电流(DC Biasing Current,DCBC)与锡盟-泰州±800 kV特高压直流输电工程系统调试数据,可知利用三维大地电性结构模型计算得到的地电位准确度更高,且岩性不均匀会导致稳定的电流场的空间分布发生变化。

Whether the geoelectric structure reflects the real distribution of various underground media determines the accuracy of the calculation of neutral point potential of AC station transformer near the grounding pole of ultra-high voltage direct current(UHVDC).The effects of layered geoelectric structure model,magnetotelluric sounding(MT)profile extension model and three-dimensional Kriging geoelectric structure model on the calculation of ground potential,penetration depth of DC current and distribution law of DC current in the earth are studied.The results show that for different geoelectric structure models,about 3%of the earth entry current will enter the deep earth 300 km underground.Compared the DC bias current(dcbc)calculated by the three models with the system commissioning data of Ximeng Taizhou±800 kV UHV DC transmission project,it can be seen that the ground potential calculated by the three-dimensional geoelectric structure model has higher accuracy,and the uneven lithology will lead to the change of the spatial distribution of the stable current field.