Objectives
• To understand switch gear types
• To understand protection types
• To understand the basics of power distribution.
Introduction
To open or close an electrical circuit, a switch device is required. In addition, to protect an electrical circuit, a protection device is required.
Low-voltage switches with HRC ceramic enclosed fuses are used commonly in industries though the present trend is to use circuit breakers with overload and short-
circuit protection in place of the fuse switch. There are various types of switches and protection devices used in the industry for different applications. All these devices are generally called Switchgear.
Apart from switching on or off any section of an electrical installation, the switchgear must include the necessary protective devices. These protective devices automatically
isolate a particular section of the installation under fault conditions.
The switchgear must withstand short-circuit faults without thermal or mechanical damage and are therefore given a short time withstand rating (usually 1 s in LV), Though this rating is mainly applicable to the bus bars and other conductors, control devices such as switches and circuit breakers must also have such rating (either short time or dynamic withstand for prospective short-circuit current) appropriate to their function.