Indoor high voltage load switch FZN21-12D/T630-20 and indoor high voltage load switch fuse brake composite apparatus FZN21-12DR/T125-31.5 can be used into distribution system of industry, mining, enterprise, residence district, high building and school, park etc. As indoor ac three phases 12kv, 50hz net ring electric supply and final terminal distribution device, that can make/break rated load current load current, make rated short-circuit current, and break transformer idle current, capacitor current of certain distance of overhead line, cable line and capacitor bank. Load switch fuse brake composite apparatus cabinet can break rated short circuit in one time. That can be the protection of distribution unit, distribution and control of electric energy in the electric system. This switch installed earthing knife and spring operating mechanism (operated by electric and/or manual) with the function of making capacity, and has the ability of far movement and control.