Short answer: OCS lightning protection uses metal-oxide (ZnO) surge arresters: nonlinear varistor blocks behave as insulators at operating voltage and conduct rapidly under lightning overvoltage. Four selection factors: system voltage (rating for the 25 kV traction system), nominal discharge current and energy capability (by lightning activity and line importance), installation point (anchor-section joints, neutral sections, tunnel portals, AT posts), and pressure relief and pollution class of the housing.
Installation essentials
Arresters work only with a sound earth path: meet the design grounding resistance and keep leads tight. Disconnector-type arresters detach visibly when blocks degrade; surge counters integrate into condition monitoring.
Related products
Surge arrester product family | Insulators (insulation coordination)