In an electric power system, switchgears is compose of electrical disconnect switches, fuses or circuit breakers which is use to control, protect and isolate electrical equipment. Switchgear is use both to de-energize equipment to allow work done at clear faults downstream. This type of equipment is directly linke to the reliability of the electricity supply.
The switchgear system is directly link to the supply system. It is place in both the high and low voltage side of the power transformer. It is use for de-energizing the equipment for testing and maintenance and for clearing the fault.
When the fault occurs in the power system, heavy current flow through equipment due to which the equipment get damage, and the service also get interrupt. Moreover, To protect the lines, generators, transformers and other electrical equipment. From damage automatic protective devices or switchgear devices is require.
The automatic protective switchgear mainly consists of the relay and circuit breaker. When the fault occurs in any section of the system, the relay of that section comes into operation and close the trip circuit of the breaker which disconnects the faulty section. The healthy section continues supplying loads as usual, and thus there is no damage to equipment and no complete interruption of supply.
Types of Switchgears
The switchgear is mainly classified into two types, the outdoors type and the indoor type.
For voltages beyond 66 kV, we install outdoor switchgear equipment.
It is because, for such voltages, the clearances between conductors and the space required for switches, circuit breakers, transformers, and others equipment become so great that it is not economical to install all such equipment indoor.
The figure shows a typical outdoor sub-station with switchgear equipment. The circuit breakers, isolators, transformers, bus-bars, and all other substation equipment occupy considerable space on account of large electrical clearance associated with high voltages.
For voltages below 66 kV, switchgear is generally install indoor because of economic considerations.
It is generally of metal-clad type. In this type of construction, all live parts are completely enclose in an earthed metal casing. The primary object of this practice is the definite localization and restriction of any fault to its place of origin.