to the 16th Edition IEE Regulations
   
   
   
 
 

chapter 5
Earthing

chapter 6
Circuits

Installation control and protection
  3.1 - Introduction 3.5 - High temperature protection
  3.2 - Switching 3.6 - Overload currents
  3.3 - Isolation 3.7 - Protection from faults
3.4 - Electric shock protection

3.8 - Short circuit and overload
------- protection
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3.4.6 -  Indirect contact protection

There are three methods of providing protection from shock after contact with a conductor which would not normally be live:

1. - making sure that when a fault occurs and makes the parts live, it results in the supply being cut off within a safe time. In practice, this involves limitation of earth fault loop impedance, a subject dealt with in greater detail in {5.3}.

2. - cutting off the supply before a fatal shock can be received using a residual current device {5.9}.

3. - applying local supplementary equipotential bonding which will ensure that the resistance between parts which can be touched simultaneously is so low that it is impossible for a dangerous potential difference to exist between them. It is important to stress that whilst this course of action will eliminate the danger of indirect contact, it will still be necessary to provide disconnection of the supply to guard against other faults, such as overheating.

It is important to appreciate that in some cases a dangerous voltage may be maintained if an un-interruptible power supply (UPS) or a standby generator with automatic starting is in use.

 

 

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Extracted from The Electricians Guide Fifth Edition
by John Whitfield
Published by EPA Press Click Here to order your Copy

Click here for list of abbreviations