Airborne Transient Electromagnetic Simulation: Detecting geoelectric structures for HVdc monopole operation

Geoelectric structures have great influence on the earth surface potential (ESP) induced by ground return currents (GRCs) in high-voltage dc (HVdc) monopolar operations. Traditional ground-detection methods are cumbersome due to the long distances between the grounding electrodes of substations. The airborne transient electromagnetic (ATEM) method has become a popular technique for exploring large-scale geoelectric structures. First, we analyze the influences of different 3D geoelectric models on the fluctuation in GRCs and propose a 3D model to evaluate ATEM simulations. Second, we present an efficient ATEM simulation method based on a finite-element (FE) algorithm to obtain the 3D geoelectric structure used to calculate the ESP. The stability and convergence rate of solving FE systems are improved by using an induced dimension reduction (IDR) solution algorithm. The detectability of the ATEM method is validated by an inversion case based on the Occam algorithm. The numerical results demonstrate that our robust ATEM simulation method is useful for detecting the 3D geoelectric structure used in ESP analysis.