What Is Switchgear?

Low Voltage Fixed-mounted Switchgear

Electrical switchgear is a centralized collection of circuit breakers, fuses, and switches (circuit protection devices) that act to protect, control, and isolate electrical equipment. The circuit protection devices are installed in a metal structure. A collection of one or more of these structures is called a switchgear family or assembly.

Switchgear is commonly found in electric utility transmission and distribution systems as well as in medium to large commercial or industrial facilities. Standards for electrical switchgear are defined by the IEEE in North America and the IEC in Europe and the rest of the world.

How does a switchgear work?

Electrical switchgear is a group of circuit protection devices (circuit breakers, fuses, or switches) installed in a common metal enclosure. Circuit protection devices distribute power to various parts of the facility and to the electrical loads within those parts. They also provide protection for individuals and equipment throughout the facility by limiting the current flowing through the system to safe levels.

The switchgear is connected directly to the power supply system and can be classified according to the voltage level as

Low voltage switchgear (LV).

Medium voltage switchgear (MV).

High voltage switches (HV).

Switchgear for lower voltages can be enclosed in the building, but higher voltages (approx. over 66 kV) usually require the switchgear to be mounted externally and insulated by air. 

【Read More about Switchgear Types】

High Voltage Switchgear

XGN2 type modular high-voltage switchgear cabinet is applied to receive and distribute the electrical energy in a three-phase AC power system with rated voltage 3, 6, 10KV and rated frequency 50HZ, especially for the frequently operated occasion. 

The switchgear cabinet is in line with the requirements of the National Standards GB3906 3-35KV AC Metal-enclosed Switchgear and the international Standard IEC298, also there are proposed "five anti" interlocking functions such as anti-breaking and closing by mistaken for circuit breaker, anti-breaking, and closing disconnector switch with load, anti-breaking and closing grounding wire/switch with load, anti closing circuit breaker/disconnector switch with grounding wire/switch, anti entering charged interval by mistaken.

Types of switchgear

There are two main types of switchgear: outdoor and indoor. For voltages above 66 kV, output switchgear is used. This is because, for higher voltages, construction work will unnecessarily increase installation costs due to the large spacing between conductors and the large size of the insulators.

Below 66kv there is no difficulty in providing construction work for switchgear at a reasonable cost. The indoor type switchgear is metal-clad and compact. Due to the compactness, the safety distance for operation is also reduced and therefore the required area is reduced. The switchgear can be a simple open-air disconnector or can be insulated with other substances such as oil, pressurized sulfur hexafluoride gas, or in a vacuum.

In the event of a fault in the power system, high currents flow through the equipment, thereby damaging it and interrupting service. For this reason, automatic protection devices or switchgear are required to protect lines, generators, transformers, and other electrical equipment from damage. Automatic protection switchgear consists mainly of relays and circuit breakers. When a fault occurs in any part of the system, the relay in that part will start to operate and close the tripping circuit of the circuit breaker, thus disconnecting the faulty part. The normally operating part will continue to supply power as normal, so no equipment will be damaged and the supply will not be completely interrupted.