Low-voltage switchgear is a commonly used name for metal-enclosed or
metal-clad low-voltage power circuit breaker switchgear rated for 600 V
alternating current (AC) and below. The metal-enclosed switchgear assembly
is completely enclosed on all sides and top with sheet metal (except for ventilating
openings and inspection windows) and contains stationary primary
power circuit switching or interrupting devices, or both, with buses and connections.
The metal-clad low-voltage switchgear contains circuit breakers of
removable (rack-out) types which are housed in individual grounded metal
compartments. The construction features of metal-enclosed and metal-clad
switchgear were described previously in Chapter 7. The service conditions
for the design and performance of low-voltage switchgear are based upon
ambient temperature from −30°C to +40°C, altitude not to exceed 6000 ft,
and switchgear installed in nonexplosive atmosphere.