Introduction to Health and Safety at Work

Electrical hazards and control
193
dissipated in a short time in a limited space with a 
varying degree of damage. The current produced in the 
vast majority of strikes exceeds 3000 amps over a short 
period of time. Before a strike, the electrical potential 
between the cloud and earth might be about 100 million 
volts and the energy released at its peak might be about 
100 million watts per metre of strike.
The need to provide lightning protection depends on 
a number of factors, which include:
➤
the risk of a strike occurring
➤
the number of people likely to be affected
➤
The location of structure and the nearness of other 
tall structures in the vicinity
➤
the type of construction, including the materials 
used
➤
the contents of structure or building (including any 
fl ammable substances)
➤
the value of the building and its contents.
Expert advice will be required from a specialist company 
in lightning protection, especially when fl ammable sub-
stances are involved. Lightning strikes can also cause 
complete destruction and/or signifi cant disruption of 
electronic equipment. 
12.3.6 Portable electrical equipment
Portable and transportable electrical equipment is 
defi ned by the Health and Safety Executive as ‘not part 
of a fi xed installation but may be connected to a fi xed 
installation by means of a fl exible cable and either a 
socket and plug or a spur box or similar means. It may 
be hand held or hand operated while connected to the 
supply, or is intended or likely to be moved while con-
nected to the supply’. The auxiliary equipment, such as 
extension leads, plugs and sockets, used with portable 
tools is also classifi ed as portable equipment. The term 
‘portable’ means both portable and transportable.
Almost 25% of all reportable electrical accidents 
involve portable electrical equipment (known as portable 
appliances). While most of these accidents were caused 
by electric shock, over 2000 fi res each year are started 
by faulty cables used by portable appliances, caused by 
a lack of effective maintenance. Portable electrical tools 
often present a high risk of injury, which is frequently 
caused by the conditions under which they are used. 
These conditions include the use of defective or unsuit-
able equipment and, indeed, the misuse of equipment. 
There must be a system to record the inspection, 
maintenance and repair of these tools.
(a)
(b)
(c)
Figure 12.6
Portable hand-held electric power tools.

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