Fault Response and Spatial Grounding Current Distribution Characteristics of Multipoint-Grounded GIL-Overhead Line Hybrid Transmission Systems Under High-Resistivity Soil Conditions

The transient responses of GIL-overhead line hybrid transmission systems during lightning and short-circuit faults directly affect insulation performance, equipment thermal stability, and grounding safety, particularly under high-resistivity soil conditions. However, research on enclosure fault current distribution and its spatial distribution of grounding currents along multipoint-grounded GIL systems under such conditions remains limited. To address this issue, an electromagnetic transient model of a 500 kV GIL-overhead line hybrid transmission system is established to investigate fault responses in high-resistivity soil conditions. The effects of short-circuit types, fault locations, and enclosure grounding spacing on grounding current distribution are analyzed. The results indicate that increased grounding impedance aggravates lightning-induced transient overvoltage. Under short-circuit faults, grounding currents along the GIL exhibit a U-shaped distribution, characterized by higher currents at both ends and lower currents in the middle. The peak local grounding current reaches 42.22 kA during a single-phase-to-ground fault in the middle section of the GIL. This study provides a basis for identifying critical grounding points, selecting adverse fault conditions, and comparing grounding configurations in hybrid transmission systems, as well as for grounding-lead thermal stability verification and grounding safety assessment.