Lightning Coupling Induced Voltage of Secondary Cables in Substation With Different Terminal Load and Grounding Dissipation Paths

Lightning strike on a power substation always brings severe coupling effects in the secondary cables. Research on the influence of cable terminal load and grounding-grid dissipation on the lightning-induced coupling of secondary cables, especially through experimental methods, remains limited up to now. We investigate the impact of four terminal load configurations and two grounding-grid dissipation paths on the cable-port induced voltage, by applying a simulated lightning surge current into the substation grounding grid. Results indicate that the high-amplitude overvoltage exists in the cable port when the cable equipment is unloaded near the lightning strike point, reaching twice the voltage compared to the scenario where both ends of the cable are connected to the equipment. The surge-current dissipation paths of the grounding grid significantly affect cable-induced voltages, particularly in scenarios of near-end grounding through load and double-ended ungrounded conditions. Following the change of the surge current injection points from the right side to the central grounding point, there is an overall reduction of approximately 10–30% in the cutoff frequency of induced voltages. Underground cables are more affected by the dispersion paths of grounding-grid currents than ground surface cables. This investigation provides data and guidance for future numerical modelling of substation grounding systems and lightning protection design in secondary substation systems.