DC Grounding Electrode Potential Based on a Kriging Geoelectric Structure Model

The inaccuracy of the geoelectric structure model is the main reason for the low accuracy of the evaluation of the impact of the ground-return current (GRC) of ultra-high voltage direct current (UHVDC) on the AC power grid. Given insufficient raw data of soil resistivity, the Kriging method combined with the original data of magnetotelluric sounding (MT) is proposed to predict the soil resistivity in the unknown area and form the Kriging soil electrical structure model. In view of the high cost and slow speed of large-scale earth surface potential (ESP) calculation, it is proposed to separate the small-scale resistivity mutation region in the Kriging soil electrical structure model from the large-scale model, and use the Dirichlet Neumann (DN) iterative algorithm to calculate the ESP in parallel for multiple sub-regions. Based on the measured data of the bias current of each substation around the Zhalute grounding electrode of ± 800 kV Zhalute-Qingzhou UHVDC transmission project, it is proved that the accuracy of using the data obtained by Kriging method to establish the soil electrical structure model.