In this topic, you study the Switchgear definition, Types, Components, & LT Switchgear.
Switchgear is like a protection device. Switchgear is needed by a power system network for its switching and or isolation under normal or abnormal operating conditions. In low voltage distribution circuits, a fuse may be used but for heavier electrical equipment and the majority of distribution and transmission networks, switchgear is used which is a combination of a circuit breaker and its control circuit.
Essential Features of Switchgear
The essential features of switchgear are:
- Complete reliability.
- Absolutely certain discrimination.
- Quick operation.
- Provision for manual control.
- Provision for instruments.
Components of Switchgear
Switchgear is a general term covering a wide range of equipment concerned with switching and protection. The main components of switchgear are bus-bars, switches, circuit breakers, relays, lightning arresters, instruments, and instrument transformers.
Types of Switchgear
Based on the voltage level, switchgear may be broadly classified into (i) outdoor type (ii) indoor type.
Outdoor type: For voltages more than 66 kV, switchgear equipment is installed outdoor, as shown in Figure 1.
Figure 1 Outdoor sub-station with switchgear equipment
Indoor type: For voltages below 66 kV, switchgear is generally installed indoor because of economic considerations.
Functions of switchgear
The two functions of switchgear in any power system are –
- To permit plant and distributors (transmission lines) to be conveniently put into and taken out of service.
- To enable the same plant and lines – when these become faulty to be rapidly and safely isolated by automatic means.
LT Switchgear
The LT (low tension) switchgear is used for circuits below rated voltage 1000 V A.C. or 1200 volts D.C.
Applications of switchgear
It has a very wide range of applications are –
- Switchgear is used to severe electrical and mechanical stresses related to specified applications.
- The low tension switchgear has to perform the specified duty over a long span of operating life within minimum maintenance.
- It occupied less space and available in a compact size. Its design is good, safe, and easy to install, maintain and operate.