This standard specifies the terms, symbols, codes, product models, specifications, signs, normal working and installation conditions, technical requirements, test methods and inspection rules for HK series switch-fuse groups (load switches). This standard is applicable to main switches in circuits with an AC frequency of 50Hz, rated voltage of single-phase 220V, three-phase 380V, and rated current up to 63A: branch switches and operating switches for lights, electric heaters, etc., as manual and infrequent switching Switches used for loaded circuits and small-capacity lines and moderate protection.