8.3  Equipment and the area around 
it 
Electrical installation: 
An assembly of electrical leads and the appliances to 
which the leads are connected. 
Switching and distribution unit, switchgear 
A unit to protect or switch on or off, in one place, two or 
more parts of an electrical installation. 
Switch room: 
The area in which the switchgear is set up. 
Working area: 
A clearly indicated part of the operating area in which 
work on the installation can be carried out safely. 
Switch: 
An apparatus designed to switch electrical currents on 
and off. 
Load-break switch: 
A switch capable of safely switching on a short-circuit 
current and switching off a nominal current. 
Circuit-breaker: 
A switch capable of operating safely under abnormal 
circumstances, and in particular capable of switching a 
short-circuit current on and off safely. 
Fuse: 
An electrical appliance that is connected in series with a 
circuit, and can interrupt the circuit safely by the melting 
of an internal conductor immediately the current in the 
circuit exceeds a specified value for a specified time. 
Cartridge fuse: 
The replaceable part of a fuse that contains the (melting) 
conductor. 
Busbar insulating bushings: 
Insulators for running busbars through the sidewalls of 
switch panels so as to be proof against arcing. 
Tapered bushings: 
Insulators for running insertion contacts through the 
partition walls between the switch compartment and the 
busbar and cable compartments, so as to be proof 
against arcing 
Witdrawable Unit: 
A unit on a withdrawable carriage designed to be 
inserted into the switchgear compartment and can be a 
circuit breaker, contactor, metering truck, disconnector 
truck, VT truck for example.