Theoretical Study and Resistance Reduction Performance of a Pipeline-Type Grounding Grid in Seepage-Proof Pumped Storage Power Stations

Pumped storage power stations commonly adopt impermeable linings at reservoir bottoms to reduce seepage losses. However, these linings significantly weaken the current dissipation capability of grounding grids, particularly in high-resistivity bedrock areas. To address this problem, a pipeline-type grounding grid (PTGG) with seepage holes is proposed for installation beneath impermeable reservoir basins. By enabling controlled water seepage, the PTGG increases bedrock moisture content and reduces its electrical resistivity, thereby improving grounding performance. A coupled seepage–resistivity–grounding model is established by integrating multiphase flow simulation in porous media with grounding impedance calculations using CDEGS. Simulation results indicate that controlled seepage can reduce the effective resistivity of initially dry bedrock from approximately 38,000 Ω·m to about 500–2000 Ω·m within the primary current-dissipation zone. For a typical pumped storage power station, the proposed PTGG reduces the overall grounding resistance by approximately 11.3–14.0% within 0.5–2 years of operation. Parametric analyses show that decreasing the spacing of seepage holes from 10 m to 1 m significantly enhances resistance reduction, whereas the influence of hole diameter (5–20 cm) on grounding resistance is relatively minor when the spacing is fixed. These results demonstrate that the PTGG provides an effective and site-specific resistance reduction solution for impermeable basin pumped storage power stations, where conventional grounding measures exhibit limited effectiveness.