Unlike IEC standards, which define different types of switchgear based on LSC (Loss of Operational Continuity) criteria, North American switchgear uses different standards for different cabinet types.

Would you be surprised if I said both are possible? Metal-clad switchgear is one of the three common types of metal-enclosed switchgear defined in ANSI standards. Before I further confuse you, let me give you a definition:

Metal-enclosed power switchgear: A switchgear assembly that is completely enclosed on all sides and top, with metal panels (except for ventilation holes and inspection windows), containing primary power circuit switching or breaking devices, or both, with busbars and connections. The assembly may include control and auxiliary devices, accessible through doors or removable covers, or both.

This definition appears in all three ANSI/IEEE standards covering the type of metal-enclosed power switchgear:

C37.20.1, Metal-enclosed low-voltage power circuit breaker switchgear;

Metal-enclosed low-voltage power circuit breaker switchgear is clearly applicable to low-voltage systems. C37.20.1 specifies a maximum rating of 635 V for AC switchgear and 3200 V for DC switchgear. A plug-in device is a low-voltage power frame circuit breaker, withdrawable or stationary. It can be manual or electric, with or without a fuse. Each circuit breaker is enclosed in a grounded metal compartment, but no additional isolation is required, such as between busbars and cable connections.

Metal-clad switchgear requires the main switch and breaking device to be withdrawn. It may be a circuit breaker (typically) or a load circuit breaker switch (less common). The circuit breaker is always selectively operated.

When the circuit breaker is withdrawn, numerous barriers, valves, and insulated busbars are required on the primary circuit elements.

The minimum rated voltage listed in C37.20.2 is 4.76 kV. This rating is typically used for 2400 V AC circuits, with ratings up to 38 kV, but rarely for lower voltages.

Metal-clad switchgear is generally considered the top-of-the-line product for medium-voltage metal-enclosed switchgear.

Metal-enclosed arc-extinguishing chamber switchgear has the same voltage range as metal-clad switchgear, but its structure is simpler. The main switch is a load switch, which is usually disconnected from the load; it may be stationary (usually) or withdrawable (less common).