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What is Switchgear? What is Switchgear in hindi

The equipment used to switch, control and protect an electrical circuit and equipment is called switchgear.

Switchgear equipment essentially deals with switching and interrupting currents under normal or abnormal operating conditions. Tumbler switch with simple fuse is the simplest form of switchgear and is used to control and protect lights and other equipment in homes, offices etc.


use of switchgear

For circuits of higher ratings, a high-rupture capacity (HRC) fuse may be used in conjunction with a switch. Serve the purpose of controlling and protecting the circuit. However, such switchgear cannot be used advantageously on high voltage systems (3.3 kV) for two reasons. Firstly, when a fuse blows, it takes some time to replace it and consequently interrupts customer service. Secondly, the fuse may not successfully interrupt large fault currents resulting from faults on high voltage systems.

Switchgear in electrical department

With the progress of the power system, lines and other Device If the system operates at higher voltages and the current increases then a short circuit occurs, the heavy current flowing through the equipment can cause considerable damage. To interrupt such currents, automatic circuit breakers (or simply circuit breakers) are used.

Circuit breaker

A circuit breaker is a switchgear that can open or close an electrical circuit in both normal and abnormal conditions. Even in cases where a fuse is sufficient, with regard to breaking capacity, a circuit breaker may be preferable. This is because a circuit breaker can close circuits as well as break them without replacement and thus has a wider range of uses than a fuse.

Switchgear equipment

Switchgear covers a wide range of equipment related to switching and interrupting currents in both normal and abnormal conditions. This includes switches, fuses, circuit breakers, relays, and other equipment. A brief description of these devices is given below.


A switch is a device that is used to open or close an electrical circuit in a convenient way. It can be used under full-load or no-load conditions but it cannot impede contacts. This is especially true for circuits of high voltage and large current capacities. The contacts of the former are exposed to the air and the contacts of the latter to the oil. Switch can be divided into two parts –

  1. air switch
  2. oil switch

air-brake switch

This is an air switch and is designed to open a circuit under load, for quenching that occurs when such a switch is opened, special arcing horns are provided. Arcing holes are pieces of metal between which an arc is formed during the opening operation. As soon as the switch is opened, these horns spread far and wide. As a result, are long, cold and obstructed. Air-break switches are typically used externally for medium capacity circuits such as main transmission lines or lines supplying industrial loads from feeders.

isolator or disconnecting switch

It is essentially a knife switch and is designed to open a circuit without load. Its main purpose is to isolate one part of the circuit from another and is not intended to be opened when current flows in the line. Such switches are usually used on both sides of the circuit breaker so that repair and replacement of the circuit breaker can be done without any danger. They should not be open unless a circuit breaker is opened in the same circuit and must always be closed before the circuit breaker is closed.

oil switch

As the name suggests, the contacts of such switches open under oil. and large current carrying capacity. Form when the circuit is opened, these switches are used for high voltage circuits usually transformer oil. The effect of oil is their tendency to cool and extinguish those things.


A fuse is a small piece of wire or a thin strip of wire that melts when excessive current is passed for a sufficient amount of time. It is inserted in series with the circuit to be protected. Under normal operating conditions, the fuse gives it the element at a temperature below its melting point. Therefore, it carries normal load current without overheating.

However, when a short-circuit or overload occurs, the current through the fuse element increases beyond its rated capacity. This causes the temperature to rise and the fuse element melts (or blows out), disconnecting the circuit protected by it. In this way, a fuse protects the machine and equipment from damage caused by excessive current. It is worth noting that a fuse performs both detection and interruption functions.

circuit breaker

A circuit breaker is a device that can open or close a circuit under all conditions (no-load, full-load and fault conditions). It is designed in such a way that it can be operated manually (or by remote control) under normal conditions and automatically under fault conditions.

For the latter operation, a relay circuit with a circuit breaker is used. Figure (a) shows the parts of a typical oil circuit breaker while Figure (b) shows its control by a relay circuit. Circuit breakers essentially consist of moving and stationary contacts that are enclosed in sturdy metal tanks and immersed in oil, known as transformer oil.


Relay is a device which detects fault in the circuit and provides information to the breaker for circuit interruption.

It can be divided into three parts –

  1. The primary winding of a “current transformer (CT) which is connected in series with the circuit to be protected. The primary winding often consists of the main conductor itself.
  2. The second circuit is the secondary winding of the connected CT to the relay operating coil.
  3. Circuit Tripping Circuit – It consists of a source of supply, trip coil of circuit breaker and relay stationary contact.

Under normal load conditions, the secondary winding of the CT (current transformer) is shorted and the current flowing into the relay operating coil is insufficient to close the relay contacts. This keeps the circuit breaker’s trip coil without energizing. As a result, the contacts of the circuit breaker remain closed and this normal load current flows.

When a fault occurs, a high current flows through the primary of the CT. This causes a current to flow in the relay operating coil through the secondary Vvab, which closes the relay contacts and activates the trip coil of the circuit breaker to open the contacts of the circuit breaker.

What is switchgear?

The equipment used to switch, control and protect an electrical circuit and equipment is called switchgear.

Also read. What is a tachometer? What is Techometer in hindi.


Read in Hindi: What is Switchgear? What is Switchgear in hindi
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