by IP (Ingress Protection) class or NEMA enclosure type) Outdoor Industrial Utility Marine Draw-out elements (removable without many tools) Fixed elements (bolted fasteners) Live-front Dead-front Open Metal-enclosed (ME) — A switchgear assembly completely enclosed on all sides and the top with sheet metal. Metal-clad (MC) — A more expensive variety of metal-enclosed switchgear that has the following characteristics: the main switching and interrupting device of removable type; grounded metal barriers to separate compartments and enclose all major circuits and parts; mechanical interlocks; insulated bus conductors and other features. Arc-resistant By IEC degree of internal separation No Separation (Form 1) Busbars separated from functional units (Form 2a, 2b, 3a, 3b, 4a, 4b) Terminals for external conductors separated from busbars (Form 2b, 3b, 4a, 4b) Terminals for external conductors separated from functional units but not from each other (Form 3a, 3b) Functional units separated from each other (Form 3a, 3b, 4a, 4b) Terminals for external conductors separated from each other (Form 4a, 4b) Terminals for external conductors separate from their associated functional unit (Form 4b) By interrupting device: Fuses Air Circuit Breaker Minimum Oil Circuit Breaker Oil Circuit Breaker Vacuum Circuit Breaker Gas (SF6) Circuit breaker CO2 Circuit Breaker By operating method: Manually operated Motor/stored energy operated Solenoid operated By type of current: Alternating current Direct current By application: Transmission system Distribution By purpose Isolating switches (disconnectors) Load-break switches. Grounding (earthing) switches A single line-up may incorporate several different types of devices, for example, air-insulated bus, vacuum circuit breakers, and manually operated switches may all exist in the same row of cubicles. Ratings, design, specifications and details of switchgear are set by a multitude of standards. In North America mostly IEEE and ANSI standards are used, much of the rest of the world uses IEC standards, sometimes with local national derivatives or variations. Safety To help ensure safe operation sequences of switchgear, trapped-key interlocking provides predefined scenarios of operation. For example, if only one of two sources of supply are permitted to be connected at a given time, the interlock scheme may require that the first switch must be opened to release a key that will allow closing the second switch. Complex schemes are possible. Indoor switchgear can also be type tested for internal arc containment (e.g., IEC 62271-200). This test is important for user safety as modern switchgear is capable of switching large currents. Switchgear is often inspected using thermal imaging