All you need to know about switchgear and protection

Definition of Switchgear

Electrical metal-enclosed switchgear is a broad term which encompasses all the electrical equipments utilized for power system protection.

Acording to the voltage levels, it can be divided into high-voltage and lv switchgear.In addition, these devices oversee metering, controlling and regulating of electric power systems.

Assembling such components in an organized fashion creates switchgear.

In simpler terms, it is the system employed for switching, controlling and defending electrical energy circuits and multiple electrical apparatus.

Features of Switchgear

1.Complete reliability – Reliability refers to the dependability or consistency of a system. In other words, when a problem arises in some part of the power network, the switchgear should be able to disconnect the healthy portion from the faulty one. A less reliable system may not necessarily perform its duty in such an event; however, one that is highly reliable will always act instantly.

2.Quick operation – whenever a fault occurs on any part of the power system, the switchgear must operate very quickly to prevent various equipment of power system like transformers, and other electrical appliances.

3.Discrimination – It must be able to discriminate between the faulty section and healthy section accurately. A smart switchgear will discriminate automatically and accurately.

4.Provision for instruments and manual control– It must be able to adjust itself if any type of equipment. Like a voltmeter or an ammeter, needs to be installed. Furthermore, it should also include an option for manual manipulation of switching and regulation.

Switchgear and protection Equipments

There are various types of switchgear and differential protection devices in power system. See the following items also for detailed knowledge of these devices.

Switches:

A switch is a stationary device that is employed to conveniently open or shut off an electrical circuit. You may have noticed switches in residences, businesses, and so on. They all belong to the switchgear category. However, there are more types of switches of which you may not be aware; we will cover them all. Switches can be classified into

1.Air circuit breaker: It is activated without any medium, making it unnecessary to use a substance.

2.Oil circuit breaker: It runs in an oil-filled environment, which is utilized to terminate the arc that appears when the switch contacts are disconnected.

The application of a switch is confined to a specific voltage range, and it cannot be used for higher voltages.

Furthermore, its use is not automated. It needs to be operated manually in the event of an issue. In order to avoid any damage to delicate appliances or equipment. This manual action is an extensive downside as it may cause destruction to costly items.

Circuit breakers:

we want a equipment which can do switching automatically and manually when a fault occurs, and also able to connect the circuit automatically when a fault removed, hence indoor type circuit breakers gets introduced.

A circuit breaker is an equipment which can open or close a circuit under all conditions like no load, full load and fault conditions. A circuit breaker can operate both manually and automatically.

Manually under normal conditions for maintenance and other work, and automatically under fault conditions.

Circuit breaker can operate under high voltages. there are many type of circuit breakers like air circuit breaker, oil circuit breaker, vacuum circuit breaker, SF6.

Fuses:

A fuse is a slender strand of metal, which melts when too much electricity passes through it for an appropriate duration. It is typically positioned in the middle of the circuit which needs to be safeguarded.

Under normal condition, the fuse element is at a temperature below its melting point (it means that it will not melt upto that temperature) therefore, it carries the normal load current without over heating.

However, when a short circuit or any defect occurs the current passing through the fuse rises, causing the wire to heat up and melt. As a result, it triggers the circuit to shut down and shields the unharmed part from possible damage.

Once a fuse gets used in a fault, then we have to replace it with the new one. This is the big disadvantage of a fuse that it can not recover automatically.

Relays :

A relay is essentially a switch or device which identifies a fault in the system and then conveys this information to the circuit breaker, so that it can activate and protect any healthy parts from the affected area. The primary side of the relay is connected to a current transformer, with its secondary side linked to the operational coil of the relay.

When the malfunctioning current arrives, the magnitude of current in both the primary and secondary side of Current transformer grows. Therefore, the activating coil of Relay energizes and it concludes the trip circuit by dragging the rod downwards and thus completing the circuit.

The trip coil is now powered and will draw the rod attached to the circuit breaker, closing the circuit. However, this connection through the circuit breaker will be broken, interrupting the current flow.

Switchgear and Protection

Switchgear protection is of critical importance in today’s electrical power system, running the gamut from generation to transmission and distribution. The current interruption devices are known as circuit breakers. These circuit breakers can be manually operated when necessary. But they can also be set to work automatically if there is an over-current, short-circuits or any other malfunctions in the system. Due to sensing of unusual parameters.

The system can be measured by various parameters such as current, voltage, frequency and phase angle. The circuit breaker identifies any malfunctions by using protection relays. Which are triggered by faulty signals usually supplied from CT or VT.

The switchgear must operate as a switch, conveying, forming and severing the normal load current. Furthermore, it has to clear any faults in the power system. Moreover, it also provides measurements and controls various parameters of electrical power systems.

Thus the switchgear includes circuit breakers, CT, voltage transformers, protection relays, measuring instrument, electrical switches, electrical fuses, minature circuit breaker,lightning arresters or surge arresters, electrical isolators and other associated pieces of equipment.