8.1.2 - Why do we need inspection and testing?
There is little point in setting up Regulations
to control the way in which electrical installations are
designed and installed if it is not verified that they have
been followed. For example, the protection of installation
users against the danger of fatal electric shock due to
indirect contact is usually the low impedance of the earth-fault
loop; unless this impedance is correctly measured. this
safety cannot be confirmed. in this case the test cannot
be carried out during installation, because part of the
loop is made up of the supply system which is not connected
until work is complete.
In the event of an open circuit in a protective
conductor, the whole of the earthed system could become
live during the earth-fault loop test. The correct sequence
of testing {8.3}
would prevent such a danger, but the tester must always
be aware of the hazards applying to himself and to others
due to his activities. Testing routines must take account
of the dangers and be arranged to prevent them. Prominent
notices should be displayed to indicate that no attempt
should be made to use the installation whilst testing is
in progress.
The precautions to be taken by the tester
should include the following:
1.
- make sure that all safety precautions are observed
2. - have a clear understanding
of the installation, how it is designed and how it has been
installed
3. -
make sure that the instruments to be used for the
tests are to the necessary standards (BS 4743 and BS 5458)
and have been recently recalibrated to ensure their accuracy
4. - check that the test leads to
be used are in good order, with no cracked or broken insulation
or connectors, and are fused where necessary to comply with
the Health and Safety Executive Guidance Note GS38
5. -
be aware of the dangers
associated with the use of high voltages for insulation
testing. For example, cables or capacitors connected in
a circuit which has been insulation tested may have become
charged to a high potential and may hold it for a significant
time.
The dangers associated with earth-fault
loop impedance testing have been mentioned in {5.3}.
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