Oil-less metalclad switchgear for medium-voltage alternating-current circuits up to 660 volts, 3-phase

This paper reviews the problems relating to medium-voltage switchgear and its application. Certain conclusions are arrived at as representing solutions to these problems, and the construction and design of appropriate air circuit-breakers and switch-fuse gear is described. The a.c. air circuit-breaker does not need magnetic blow-out coils, and test data are provided showing the effectiveness of design without such coils. High-rupturing-capacity fuses are also dealt with in so far as they affect the design of switchgear equipments. Finally, the paper considers complete switchboards built up, from the apparatus described earlier, into metal-enclosed units.