Introduction to Health and Safety at Work


The advantages and limitations of



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introduction to health safety at work

12.5.1
The advantages and limitations of 
protective systems
There are several different types of protective systems 
and techniques that may be used to protect people, plant 
and premises from electrical hazards, some of which, for 
example, earthing, have already been considered earlier 
in this chapter. However, only the more common types of 
protection will be considered here.
Fuse
A fuse will provide protection against faults and continu-
ous marginal current overloads. It is basically a thin strip 
of conducting wire which will melt when the rated cur-
rent passes through it, thus breaking the circuit. A fuse 
rated at 13 ampere (A) will melt when a current in excess 
of 13 ampere (A) passes through the fuse thus stopping 
the fl ow of current. A 
circuit breaker
throws a switch off 
when excess current passes and is similar in action to 
a fuse. Protection against overload is provided by fuses 
which detect a continuous marginal excess fl ow of cur-
rent and energy. This overcurrent protection is arranged 
to operate before damage occurs, either to the supply 
system or to the load which may be a motor or heater. 
When providing protection against overload, consider-
ation needs to be made as to whether tripping the cir-
cuit could give rise to an even more dangerous situation, 
such as with fi re-fi ghting equipment.
The prime objective of a fuse is to protect equipment 
or an installation from overheating and becoming a fi re 
hazard. It is not an effective protection against electric 
shock due to the time that it takes to cut the current fl ow.
The examination of fuses is a vital part of an inspec-
tion programme to ensure that the correct size or rating 
is fi tted at all times.
Insulation
Insulation is used to protect both people from electric 
shock, the short circuiting of live conductors and the 
dangers associated with fi re and explosions. Insulation 
is achieved by covering the conductor with an insulating 



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