Circuit Breakers
The definition of switchgear includes circuit breakers that interrupt a circuit when there is an electric fault. The circuit breakers protect the electric system from overloads when a short circuit occurs. They are a key part of most switchgear installations because technicians can re-close them after repairing a fault.
Load Break Switches
Load break switches can't interrupt a short circuit but they can switch loads on and off. Often used in substations to connect transformers to power lines, or in industry to manually disconnect loads, they are the inexpensive work horses of the switchgear family.
Disconnect Switches
Disconnect switches can't switch any currents, but can isolate loads and power supplies for maintenance or in case of failure. They are a key safety element in switchgear assemblies because the technicians must be certain that the circuit they are working on can't be connected to power. They attach locks to the disconnect switches to lock them open and make sure their circuits remain safely voltage-free.
Fuses
For less critical switchgear applications, fuses are much less expensive than circuit breakers, and perform the same protective functions. A switch often carries a fuse in a fused disconnect switch combination. Technicians open the switch after the fuse blows, permitting them to work safely. After repairs, they have to replace the fuse.
Contactors
When switchgear has to switch loads on and off frequently, it includes contactors. These parts of the switchgear have heavy contacts that are rated for millions of switching cycles under load. The contacts move when an operator remotely activates a magnetic coil that is attached to them, closing the circuit.
Enclosures
All switchgear elements carry dangerous voltages and currents. For outdoor substations, fences and signs restrict access. For switchgear in commercial and industrial buildings, metal enclosures and metal cabinets prevent the public and technical staff from coming into contact with live parts. The definition of switchgear always includes such enclosures when dealing with indoor equipment.