Low voltage switchgear is used to control, protect, switch, and isolate electrical equipment. Switchgear is composed of different circuit breakers, disconnectors, load switches, and switch disconnectors. Each has slightly different applications and functions that serve the primary role of low voltage switchgear in electrical engineering. Edvard Csanyi, the founder of Electrical Engineering Portal, does a great job of outlining the essential functions of disconnectors, load switches, switch disconnectors, and circuit breakers concerning the requirements laid out by IEC 60947.
The breakdown of the different elements of Switchgear can be read below.
Disconnectors: A disconnector is used to isolate electrical equipment when it needs to be repaired or inspected as part of a regular maintenance schedule. This is necessary for safety reasons. According to Csanyi, a disconnector must be completely guaranteed "from pole to pole and from input to output." Disconnectors can be automatic or manually operated, depending on the specific device.
Load Switches: On the other hand, load switches can make or break currents under normal circuit conditions. They can also be used for time currents in the event of short-circuit or some other abnormality. Load switches have short-circuited making capacity, but lack short-circuits breaking capacity as per IEC 60947‐1 and ‐3. Load switches cannot be switched off, but they can be conducted.
Switch Disconnectors: As you can probably guess by the name, a switch disconnector combines properties of the disconnector and the load switch. This means that it can be used to isolate electrical equipment for the safety feature, but it can also be used to make and break normal currents. Csanyi says that there are many different types of switch disconnectors in low voltage switchgear as well, including normal switch disconnectors, fuse switch disconnectors, and circuit breakers.
Circuit Breakers: Circuit breakers can fulfill the requirements of a load switch or a disconnector. Circuit breakers make, carry, and break currents, and they can also be used to carry or break short circuits as well for a specified time period. Circuit breakers can provide the isolation function as well for low voltage switchgear if necessary, too.
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