The ZN85-40.5KV indoor vacuum circuit breaker is primarily used in a 3-phase AC 50Hz power system for opening and closing load currents, overload currents, and short-circuit currents in rural, urban, and small-scale power systems. The product features a 3-phase common box structure, with the 3-phase vacuum interrupters housed in a metallic box, utilizing SMC insulating materials for phase-to-phase and phase-to-ground insulation, ensuring high insulation strength.