Electrical Switchgear Classification

Switchgear is the apparatus used for switching, controlling, and protecting electrical circuits and equipment.

Switchgear can be classified as low voltage (LV) switchgear (up to 1KV), medium voltage (MV) switchgear (3 KV to 33 KV), and high voltage (HV) switchgear (above 33 KV).

Components of LT switchgear include low voltage circuit breakers, switches, off load electrical isolators, HRC fuses, earth leakage circuit breaker, miniature circuit breakers (MCB), and molded case circuit breakers (MCCB).

A fuse is used for interrupting an electrical circuit under short circuit or excessive overload current magnitudes.

A fuse has inverse time-current characteristics.

The current that an electrical device can carry, under specified conditions, without resulting in overheating or mechanical overstress

It is the minimum current at which the fuse element melts and thus disconnects the circuit protected by it.

1. It is the cheapest form of protection available. 2. It needs no maintenance. 3. Its operation is inherently completely automatic. 4. It interrupts enormous short circuit currents without noise, flame, gas, or smoke.

1. Considerable time is lost in rewiring or replacing a fuse after operation. 2. Discrimination between fuses in series cannot be obtained unless there is considerable differences in the relative sizes of the fuse concerned. 3. The current-time characteristics of a fuse cannot always be correlated with that of the protected device.

1. Round type fuse unit. 2. Kit-kat type fuse unit. 3. Cartridge type fuse unit. 4. HRC (High Rupturing Capacity) fuse units. 5. Semiconductor fuse units.