Study on high-altitude tunnel-catenary positive impulse breakdown voltage correction by rod-plane discharge characteristic

• Proposes a novel gap correction coefficient k c for tunnel-catenary insulation design in high-altitude areas. • Develops two voltage correction methods with 5.83% lab and 1.95% field test errors, ensuring cost-effective insulation. • Validates methods via artificial climate chamber and 1500 m field tests under extreme humidity and temperature. • Reveals altitude-driven air pressure and gap length effects on insulation breakdown performance. • Guides safe and economical electrified railway tunnel construction in harsh high-altitude environments. The insulation design of tunnel-catenary in high-altitude areas primarily affects the excavation of railway tunnels. In engineering, the discharge breakdown voltages of the rod-plane gaps at low altitudes are commonly used as a correction criterion for high-altitude areas. However, the breakdown performance relationship between tunnel-catenary and rod-plane has not been thoroughly studied. In this paper, the high-altitude tunnel-catenary positive impulse tests are simulated in an artificial climate chamber. A novel gaps correction coefficient k c is defined to quantify the breakdown voltage difference between tunnel-catenary and rod-plane. The discharge breakdown voltages, influenced by gaps length and air pressure/altitude, are discussed in detail. Based on the test results of k c , two positive impulse breakdown voltage correction methods are originally derived. The accuracy of the proposed methods is demonstrated by comparing the calculative values with those from the artificial climate chamber, as well as through field tests. The results show an average error of 5.83% for the climate chamber and 1.95% for the field tests. This work provides valuable theoretical guidance for the design and construction of electrified railroad tunnels in high-altitude areas.